Manual AO.pdf

Michael Ehrenfeld | Paul N Manson | Joachim Prein

Principles of Internal Fixation of the Craniomaxillofacial Skeleton Trauma and Orthognathic Surgery

PCMF_Book_R08.indb 1

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01.06.12 15:13

Michael Ehrenfeld | Paul N Manson | Joachim Prein

Principles of Internal Fixation of the Craniomaxillofacial Skeleton Trauma and Orthognathic Surgery 275 Illustrations, 13 tables


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Library of Congress Cataloging-in-Publication Data is available from the publisher.

Hazards Great care has been taken to maintain the accuracy of the information contained in this publication. However, the publisher, and/or the distributor, and/or the editors, and/or the authors cannot be held responsible for errors or any consequences arising from the use of the information contained in this publication. Contributions published under the name of individual authors are statements and opinions solely of said authors and not of the publisher, and/ or the distributor, and/or the AO Group. The products, procedures, and therapies described in this work are hazardous and are therefore only to be applied by certified and trained medical professionals in environments specially designed for such procedures. No suggested test or procedure should be carried out unless, in the user‘s professional judgment, its risk is justified. Whoever applies products, procedures, and therapies shown or described in this work will do this at their own risk. Because of rapid advances in the medical sciences, AO recommends that independent verification of diagnosis, therapies, drugs, dosages, and operation methods should be made before any action is taken. Although all advertising material which may be inserted into the work is expected to conform to ethical (medical) standards, inclusion in this publication does not constitute a guarantee or endorsement by the publisher regarding quality or value of such product or of the claims made of it by its manufacturer.

Legal restrictions This work was produced by AO Foundation, Switzerland. All rights reserved by AO Foundation. This publication, including all parts thereof, is legally protected by copyright. Any use, exploitation or commercialization outside the narrow limits set forth by copyright legislation and the restrictions on use laid out below, without the publisher‘s consent, is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, scanning or duplication of any kind, translation, preparation of microfilms, electronic data processing, and storage such as making this publication available on Intranet or Internet. Some of the products, names, instruments, treatments, logos, designs, etc. referred to in this publication are also protected by patents and trademarks or by other intellectual property protection laws (eg, “AO”, “ASIF”, “AO/ ASIF”, “TRIANGLE/GLOBE Logo” are registered trademarks) even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name, instrument, etc. without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain. Restrictions on use: The rightful owner of an authorized copy of this work may use it for educational and research purposes only. Single images or illustrations may be copied for research or educational purposes only. The images or illustrations may not be altered in any way and need to carry the following statement of origin ”Copyright by AO Foundation, Switzerland”. Check hazards and legal restrictions on www.aofoundation.org/legal

Copyright © 2012 by AO Foundation, Switzerland, Clavadelerstrasse 8, CH-7270 Davos Platz Distribution by Georg Thieme Verlag, Rüdigerstrasse 14, DE-70469 Stuttgart and Thieme New York, 333 Seventh Avenue, US-New York, NY 10001 Layout: nougat GmbH, CH-4056 Basel Illustration: nougat GmbH, CH-4056 Basel, and AO Education ISBN: 978-3-13-171481-7 e-ISBN: 978-3-13-171491-6

Principles of Internal Fixation of the Craniomaxillofacial Skeleton—Trauma and Orthognathic Surgery Michael Ehrenfeld, Paul N Manson, Joachim Prein


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Preface

Michael Ehrenfeld, MD, DDS, PhD

Paul N Manson, MD

There are no facial fracture textbooks in any of the involved specialties that deal with introductory principles in the same amount of detail as the Principles of Internal Fixation of the Craniomaxillofacial Skeleton for Trauma and Orthognathic Surgery. Traditionally, each specialty has had its own areas of interest and expertise. This textbook is different in that it combines and focuses the expertise and competence of different specialties on the entire craniofacial skeleton, resulting in a comprehensive work of considerable breadth. It serves as a tribute to the many individuals who have taught as faculty in AO courses and symposia over the last 50 years. Their efforts and individual hard work are summarized in this volume. They have sought to make operative sense of the complexity of the craniofacial skeleton and its related soft tissues by describing the principles of clinical applied anatomy and surgical technique.

Joachim Prein, MD, DDS, PhD

Having spent our lives developing and teaching algorithms for the efficient and successful reconstruction of the face following trauma, congenital deformities, and tumor removal, we are keenly aware of the Manual’s contribution, and what it represents in terms of work, effort, and surgical experience. We cannot help wondering what it would have meant to have such a textbook at the beginning of our careers! It has been a privilege to serve as editors for this new CMF Manual, and to suggest ideas for the masterful artwork which illustrates this textbook. We hope it will enrich the knowledge of the current and future generations of CMF surgeons and assist them in mastering the intricate anatomical details and techniques that lead to exemplary results in surgery. Sincerely, Michael Ehrenfeld Paul N Manson Joachim Prein

V


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Introduction

Fourteen years after the publication of the Manual of Internal Fixation in the Cranio-Facial Skeleton*, an update is now available. Representing the multidisciplinary spirit of AOCMF, the Principles of Internal Fixation of the Craniomaxillofacial Skeleton for Trauma and Orthognathic Surgery includes contributions from oral and maxillofacial surgeons, plastic surgeons, otolaryngologists, as well as researchers: The 41 chapter authors represent a truly international authorship spanning three continents. This Manual is not only meant to provide an overview on current concepts of craniomaxillofacial trauma care and orthognathic surgery, but also to serve as a resource textbook for AOCMF Principles Courses, which are an important part of the education of residents and fellows around the world. The Manual is divided into seven sections. The first section covers general aspects of bone, types and materials of implants, and principles of CMF trauma care. Sections two to six describe the treatment of fractures in all areas of the craniomaxillofacial skeleton and section seven presents

fixation techniques of standard osteotomies of the facial skeleton. The principles described in this textbook represent the evolution of CMF buttress reconstruction over the last 60 years. In addition to standard procedures, techniques representing recent surgical advances and new developments are presented as well. Principles and techniques are highlighted by clear, accurate illustrations, images, and tables. The combination of text and figures helps the reader to understand the relationship between the anatomy and the principles of surgical reconstruction, and to appreciate the difficult challenge of obtaining consistently superior results. Key references and suggested readings are provided for each section. Much effort was made to make the new CMF Manual a consistent book and to avoid overlapping content across the chapters. It is now up to the readers to judge whether this task has been accomplished. Zürich, April 2012

*Prein J (1998) Manual of Internal Fixation in the Cranio-Facial

Skeleton. 1st ed. Berlin Heidelberg New York: Springer-Verlag.

VI



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Acknowledgement

The editors wish to express their gratitude to the 38 authors for contributing chapters to this book and sharing their knowledge and experience with the reader. We are convinced that this effort will contribute significantly to the education of craniomaxillofacial residents and fellows. We also thank the authors for understanding that the editors needed to make changes to the original manuscripts in order to prohibit overlap and ensure consistency throughout the book. We would also like to thank all surgeons who provided additional ideas and material such as images or photographs. Special thanks go to Almuth Nussbaumer who has been of invaluable help to the editors in the coordination of this book project. Over the last 5 years she has very patiently been in constant contact with the chapter authors. The AO Education team has provided resources and expertise without which this book would not have been possible. We thank Urs Rüetschi, Kathrin Lüssi, and Renate Huter for the overall planning and management of this project. Kathrin also provided invaluable assistance in overseeing

the incorporation of changes and corrections. Carl Lau, Vidula Bhoyroo, and Claire Jackson helped with language editing and proofreading. Thanks go to all illustrators, in particular Stefan Auf der Maur from nougat GmbH, Basel, as the main illustrator and Jecca Reichmuth. Stefan Auf der Maur also did a tremendous job in typesetting the book. Samuel Leuenberger from Synthes Switzerland proved tireless in providing details about instrumentation and a number of graphics for the illustration of chapter 1.4.3 Design and function of implants. We thank Synthes for their kind permission to include this illustrative material in our textbook. Further thanks go to Börje Müller, Basel, for the excellent photographs of a number of implants and instruments displayed in chapter 1.4.3 Design and function of implants. Finally, we thank our families for their help and support during the production of this book. Michael Ehrenfeld Paul N Manson Joachim Prein

VII


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Contributors

Editors Michael Ehrenfeld, MD, DDS, PhD

Professor and Chairperson Department of Oral and Maxillofacial Surgery Ludwig-Maximilians University Lindwurmstr. 2a 80337 München Germany Paul N Manson, MD

Professor Department of Plastic Surgery Johns Hopkins University School of Medicine 8152 R. McElderry Wing 601 North Caroline Str Baltimore, MD 21287-0981 USA Joachim Prein, MD, DDS, PhD

Professor emeritus Department of Oral and Cranio-Maxillofacial Surgery University Hospital Basel Spitalstr. 21 4031 Basel Switzerland

VIII



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Authors

Rudolf RM Bos, DMD, PhD

John A Disegi, FASTM

Professor and Deputy Head

Group Manager Materials Development

Brian Alpert , DDS

Department of Oral and Maxillofacial Surgery

Synthes USA

Professor and Chairperson

University Medical Center Groningen

Synthes Technical Center


PO Box 30.001

1301 Goshen Park Way

University of Louisville School of Dentistry

9700 RB Groningen

West Chester, PA 19380

Preston Str, Suite 334

The Netherlands

USA

Louisville, KY 40292 Jon B Chadwell, MD

Edward Ellis III , DDS, MS,

Chadwell Facial Plastic Surgery


Oleh Antonyshyn, MD, FRCSC

6301 University Commons


Professor

Suite 380

University of Texas Health Science Center at San Antonio

Plastic Surgery, Head Adult Craniofacial Program

South Bend, IN 46635

7703 Floyd Curl Dr, MC 7908

University of Toronto

USA

San Antonio, TX 78229-3900

USA

M1-520 Sunnybrook Health Sciences Centre

USA

2075 Bayview Ave

Ricardo Cienfuegos, MD, FACS

Toronto, Ontario M4N 3M5

Head

Marcelo F Figari, MD, FACS

Canada

Department of Plastic, Reconstructive and

Head Section of Head and Neck Surgery

Maxillofacial Surgery

Department of General Surgery

Leon A Assael, DMD

Plastic and Reconstructive Surgeon, American British

Hospital Italiano


Cowdray Medical Center

Perón 4199


Hospital de Traumatología y Ortopedia Lomas Verdes

1181 Buenos Aires

Oregon Health & Science University, School of Dentistry

IMMS

Argentina

611 SW Campus Dr

Tlacotalpan 59-310, Colonía Roma

Portland, OR 97239

Mexico, D.F., 06760

Nils-Claudius Gellrich, MD, DDS, PhD

USA

Mexico


Laurent Audigé, DVM, PhD

Douglas J Colson, MD

Medical University Hannover

Methodology and Statistics Manager

Clinical Instructor Brown University

Carl-Neuberg-Str. 1

AO Foundation

Rhode Island Ear, Nose, and Throat Physicians

30625 Hannover

AO Clinical Investigation and Documentation

333 School Str

Germany

Stettbachstr. 6

Suite 302

8600 Dübendorf

Pawtucket, RI 02860

Beate Hanson, MD, MPH

Switzerland

USA

Clinical Epidemiologist, Assistant Professor

Robert Bentley, BDS,FDS, RCS, MB BCh, FRCS,

Carl-Peter Cornelius, MD, DDS, PhD

AO Foundation

FRCS (OMFS)

Professor

Stettbachstr. 6

Consultant Cranio-Oral and Maxillofacial Surgery


8600 Dübendorf

Kings College Hospital

Ludwig-Maximilians University

Switzerland

Denmark Hill, Camberwell

Lindwurmstr. 2a

SE5 9RS London

80337 München

Richard H Haug , DDS

United Kingdom

Germany

Section Head


Director AO Clinical Investigation and Documentation

Oral and Maxillofacial Surgery Carolinas Medical Center 1601 Abbey Place Suite 220 Charlotte, NC 28209 USA

IX

Contributors

Robert M Kellman, MD

Thiam-Chye Lim, MD

Carlos Ries Centeno, MD, DMD


Professor, Senior Consultant, and Head

Professor

Department of Otolaryngology and

Division of Plastic, Reconstructive and Aesthetic Surgery

Department Head & Neck/CMF Surgery

Communication Sciences

National University Hospital

Hospital “I Pirovano”

SUNY Upstate Medical University

Lower Kent Ridge Rd

Don Bosco 2736

750 East Adams Str

Singapore 119074

1642 San Isidro, Prov. Buenos Aires

Syracuse, NY 13210

Singapore

Argentina

USA Christian Lindqvist , MD, DDS, PhD, FDSRCS

Randal Rudderman, MD, FACS

Tanja Ketola-Kinnula, MD, DDS


Adjunct Professor

Oral and Maxillofacial Surgeon

Department for Oral and Maxillofacial Surgery

Department of Civil Engineering

Mickelsinkuja 8A

Helsinki University Central Hospital

Case Western University

02770 ESPOO

PO Box 263

Department of Plastic Surgery

Finland

00029 HUS Helsinki

Northside Hospital, Atlanta

Finland

3400C Old Milton Parkway, Suite 365

Peter J Koltai, MD, FACS, FAAP

Alpharetta, GA 30005

Professor and Chief

Gerson Mast , MD, DDS

Division of Pediatric Otolaryngology


USA

Stanford University School of Medicine

Ludwig-Maximilians University

Ralf Schoen, MD, DDS, PhD

Lucile Packard Children’s Hospital

Lindwurmstr. 21

Professor and Head

801 Welch Rd

80337 München


Stanford, CA 94305

Germany

St. Josefshospital Uerdingen Kurfürstenstr. 69

USA Jiska M Meijer, MD, DMD, PhD

47829 Krefeld

Paul Krakovitz , MD

Associate Professor

Germany

Assistant Professor of Surgery


Vice Chairperson, Surgical Operations, Section Head

University Hospital Groningen

Kevin A Shumrick , MD, FACS

Pediatric Otolaryngology

PO Box 30.001

Facial Plastic Surgery

Head and Neck Institute Cleveland Clinic

9700RB Groningen

Group Health Associates

9500 Euclid Ave

The Netherlands

Anderson Towne Center Rd, 7810 Five Mile Rd Cincinnati, OH 45230

Cleveland, OH 44195 Robert L Mullen, PhD, PE, F.ASCE

USA

USA

Professor and Chairperson Christoph Kunz , MD, DDS, PhD

Department of Civil and Environmental Engineering

Robert B Stanley Jr, MD, DDS

Associate Professor

University of South Caroline

Professor

Department of Oral and Cranio-Maxillofacial Surgery

300 Main Str, Room C231

Department of Otolaryngology, Head and Neck Surgery

University Hospital Basel

Columbia, SC 29208

University of Washington

Spitalstr. 21

USA

325 Ninth Ave, Box 359894

4031 Basel

Seattle, WA 98104 Berton A Rahn, MD, DDS, PhD † (28.03.2008)

Switzerland

USA

Professor of Maxillofacial Surgery George M Kushner, DMD, MD

AO Research Institute Davos, Switzerland

Professor

Adrian Sugar, DDS, FRCS, Dr hc

Consultant


Robert G Richards, PhD, FBSE

Maxillofacial Unit

University of Louisville

Professor

Morriston Hospital

501 South Preston Str

Director AO Research Institute (ARI) Davos

W Glamorgan

Louisville, KY 40202

AO Foundation

Swansea, SA6 NL, Wales

USA

Clavadelerstr. 8

United Kingdom

7270 Davos Switzerland

X


Brett Ueeck , DMD, MD

Oral and Maxillofacial Surgery 11786 SW Barnes Rd, Suite 110 Portland, OR 97225 USA Nicolaas B Van Bakelen, MD

Department of Oral and Maxillofacial Surgery University Medical Center Groningen Hanzeplein 1 PO Box 30.001 9700 RB Groningen The Netherlands Joseph E Van Sickels, DDS

Professor and Assistant Dean of Hospital Dentistry Department of Oral and Maxillofacial Surgery University of Kentucky College of Dentistry Chandler Medical Center D-508, 800 Rose Str Lexington, KY 40536-0297 USA Anders Westermark , DDS, PhD

Associate Professor Maxillofacial Surgery Medimar AX 22100 Marieham Aland Finland

XI


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Table of contents

XII



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Table of contents Preface

V

Introduction

VI

Acknowledgements

VII

Contributors

1

VIII

General aspects

1.1 Introduction 1.1.1 AO Foundation Mission Statement

Joachim Prein, Michael Ehrenfeld

1.1.2 Research and development within AO Foundation 1.1.3 TK system CMF 1.1.4 Education

Berton Rahn

3

4 5

Edward Ellis III

Michael Ehrenfeld, Joachim Prein

1.1.5 Clinical investigation and documentation

6

Beate Hanson

1.1.6 AO classification of craniomaxillofacial fractures 1.2 Bone

3

7

Carl P Cornelius, Laurent Audigé, Joachim Prein

Berton Rahn

17

1.3 Fractures in the craniomaxillofacial skeleton

21

1.3.1 Biomechanics of the craniomaxillofacial skeleton 1.3.2 Fracture and blood supply

Randal Rudderman, Robert Mullen

21

Berton Rahn

1.3.3 Biological reaction and healing of bone

27 31

Berton Rahn, Joachim Prein

1.4 Implant materials and types 1.4.1 Metals, surfaces, and tissue interactions

39

Robert G Richards, John A Disegi

1.4.2 Biodegradable osteosynthesis: past, present, and future 1.4.3 Design and function of implants

9

39

Nicolaas B van Bakelen, Jiska M Meijer, Rudolf RM Bos

45

Richard H Haug

53

1.5 Principles of craniomaxillofacial trauma care

83

1.5.1 Goals of CMF trauma care


83

1.5.2 Indications for surgical, nonsurgical, or no treatment of craniomaxillofacial fractures 1.5.3 Presurgical and postsurgical considerations, treatment planning 1.5.4 Principles of surgical fracture management 1.5.5 Biomechanics of the bone-implant-unit



1.5.8 Teeth in the fracture line

85 87 89

Adrian Sugar, Robert Bentley

1.5.6 Principles of stabilization: splinting, adaptation, compression, lag screw principle 1.5.7 Dental and alveolar trauma


91 Adrian Sugar, Robert Bentley

95

Anders Westermark

103

Anders Westermark

109

1.5.9 Implant removal and stress protection

Gerson Mast, Michael Ehrenfeld, Joachim Prein

1.5.10 Techniques of mandibulomaxillary fixation (MMF) 1.6 References and suggested reading

Gerson Mast

111 115 125 XIII


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Table of contents

2

Mandibular fractures

2.1 Symphyseal and parasymphyseal fractures 2.2 Body and angle fractures of the mandible


137

Leon Assael, Brett Ueeck

2.3 Condyle, ascending ramus, and coronoid process fractures 2.4 Fractures in bone of reduced quality

Brian Alpert, George M Kushner

147

Nils-Claudius Gellrich, Ralf Schoen

169

2.5 References and suggested reading

3

177

Midfacial fractures

3.1 Lower midface (Le Fort I and palatal fractures) 3.2 Upper midface (Le Fort II and III)

Ricardo Cienfuegos

183

193

Marcelo Figari, Thiam-Chye Lim

3.3 Zygomaticomaxillary complex (ZMC) fractures, zygomatic arch fractures 3.4 Orbital fractures

Carl-Peter Cornelius

Christoph Kunz

3.5 Nasoorbitoethmoidal (NOE) fractures 3.6 Fractures of the nasal skeleton

205 223

Oleh Antonyshyn

Kevin A Shumrick, Jon B Chadwell

235


4

159

247 255

Skull and skull base fractures

4.1 Frontal sinus, frontal bone, and anterior skull base 4.2 Lateral skull base fractures 4.3 Cranial vault fractures

Robert B Stanley, Robert M Kellman

261 271

Douglas J Colson, Robert M Kellman

281

Paul N Manson


287

5

Panfacial fractures

293

6

Fractures in the growing skeleton

XIV


Paul N Manson

Paul Krakovitz, Peter Koltai

309


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7

Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery)

7.1 Definitions, diagnosis, and treatment planning 7.2 Standard osteotomies in the mandible 7.3 Standard osteotomies in the maxilla 7.3.1 Le Fort I

Joseph E Van Sickels, George Kushner

Christian Lindqvist, Tanja Ketola-Kinnula

Gerson Mast

357

7.3.2 Surgically assisted rapid palatal expansion (SARPE)

Michael Ehrenfeld

7.3.3 Subapical (block) and segmental maxillary osteotomies

Gerson Mast

7.4 Special considerations and sequencing in 2-jaw osteotomies

7.6 Complications and pitfalls

Gerson Mast

335 353

Carlos Ries Centeno, Gerson Mast

7.5 Perioperative and postoperative management

321

Gerson Mast

Carlos Ries Centeno

363 369 377 381 385


391

Credits

395

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1.1 Introduction 1.1.1 AO Foundation Mission Statement 1.1.2 Research and development within AO Foundation

3 3

4

1.1.3 TK system CMF

5

1.1.4 Education

6

1.1.5 Clinical investigation and documentation

7

1.1.6 AO classification of craniomaxillofacial fractures

9

1.2 Bone

17

1.3 Fractures in the craniomaxillofacial skeleton

21

1.3.1 Biomechanics of the craniomaxillofacial skeleton

21

1.3.2 Fracture and blood supply

27


31

1.4 Implant materials and types 1.4.1 Metals, surfaces, and tissue interactions

39

1.4.2 Biodegradable osteosynthesis: past, present, and future

45

1.4.3 Design and function of implants

53

1.5 Principles of craniomaxillofacial trauma care

83


83

1.5.2 Indications for surgical, nonsurgical, or no treatment of craniomaxillofacial fractures

85

1.5.3 Presurgical and postsurgical considerations, treatment planning

87

1.5.4 Principles of surgical fracture management

89

1.5.5 Biomechanics of the bone-implant-unit

91

1.5.6 Principles of stabilization: splinting, adaptation, compression, lag screw principle

95

1.5.7 Dental and alveolar trauma

103


109


111

1.5.10 Techniques of mandibulomaxillary fixation (MMF)

115



39

125

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1 General aspects


01.06.12 15:13

1 General aspects 1.1 Introduction

1

AO Foundation Mission Statement

5

2

Research and development within AO Foundation

6

3

TK system CMF

7

4

Education

8

5

Clinical investigation and documentation

9

5.1 AOCID mission and strategy

9

5.2 Doing clinical research

9

5.3 Using clinical research

10

5.4 Summary

10

6 AO classification of craniomaxillofacial fractures

11

6.1 General concept and objectives of a fracture classification

11

6.2 A brief history of CMF classifications

12

6.3 Evolution of a modern AO craniomaxillofacial fracture classification 6.4 Future perspectives

2


13 16


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1 General aspects

Authors Joachim Prein, Michael Ehrenfeld

1.1 Introduction 1 AO Foundation Mission Statement

1.1 Introduction

1

AO Foundation Mission Statement

The AO Foundation is a medically guided nonprofit organization led by an international group of surgeons specialized in the treatment of trauma and disorders of the musculoskeletal system. It was founded in 1958 as a study group by 13 visionary Swiss surgeons and transformed into a foundation in 1984. The vision of the AO Foundation is excellence in the surgical management of trauma and disorders of the musculoskeletal system.

The mission is to foster and expand the AO network of healthcare professionals in education, research, development, and clinical investigation to achieve more effective patient care worldwide. To adapt to the specific needs of each anatomical region as well as differences in human and animal surgery, AO has established autonomous speciality areas for trauma, spine, craniomaxillofacial, and veterinary surgery. All AO specialties continually redefine the state of the art in their field, maintaining activities in research, development, clinical investigation, and education. In addition, AO has set up an entity to educate operating room personnel (ORP) and achieve the best possible interaction between specialties and between surgeons and ORP.

3


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1 General aspects

Author Berton Rahn

1.1 Introduction 2 Research and development within AO Foundation

2

Research and development within AO Foundation

One of the goals of the AO Foundation is to promote research and development within the scope of the AO Foundation's activities. Research within the AO Foundation is conducted and promoted through different channels. • The AO Research Institute Davos (ARI) is dedicated to basic and applied research and development in the area of trauma, disorders of the skeletal systems, and related topics. The institute employs specialists in surgery, biology, materials, science, veterinary medicine, dentistry, biomechanics, and biomedical engineering, among others. Defined research groups specialize in trauma-related topics (more information at: www.aofoundation.org). • Research grants are available in the clinical priority programs (CPPs). The CPPs are specialty-based research programs which promote research in fields of major interest to each specialty. The principal topic of the craniomaxillofacial CPP is currently “Imaging and Planning in Surgery” (www.aofoundation.org). This program is led by a program committee which reports to the AOCMF Research and Development Commission. It issued its first open calls for grant applications in 2009. Details of these calls and of the studies being funded can be found on the AOCMF website. • The AO Research Fund (AORF) has since 1983 issued open calls twice a year for start up grants, especially to support young researchers. These grants cover the broad areas of interest of the AO. They will continue to be available from the successor to the AORF, the AO Research and Review Commission (AORRC), on the same basis but will be funded by the AO Academic Council.

4


• Between 2005 and 2009, the AO Research Fund also issued open calls twice a year for larger focus grants. These were specifically in the focus fields of the specialities and designed to be applied by experienced researchers. Since 2010, these grants are now available from the specialty research and development commissions. • The AO Exploratory Research Board (AOERB), on which all specialties and the ARI are represented, has the principal responsibility for oversight and funding of basic research in the AO Foundation. Currently much of that is focused on the reconstruction of large bone defects. The AOERB also approves and provides project funding for collaborative research centers worldwide which work with the AO and its researchers on specific research goals. • Development work can also be done at the ARI. Increasingly, this is collaborative with outside researchers. However, most product development today is done in close cooperation with industrial partners. Usually every marketable product goes into the TK System (see chapter 1.1.3) and is subject to intensive clinical trials before it is released for marketing through the respective industrial partner. The research and development environment within AOCMF may change while this book is on the market. For current information search the AO website at: www.aofoundation.org.


01.06.12 15:13

1 General aspects

Author Edward Ellis III

1.1 Introduction 3 TK system CMF

3

TK system CMF

The AO Foundation has a long history of close collaboration with industrial partners. Surgeon control over the design of implants and instruments was and still is one of the fundamental principles of the AO. Within the AO Foundation, the responsibility for the development and clinical testing of new devices is the TK (“Technische Kommission” or technical commission). The German abbreviation “TK” was kept even after the AO Foundation became a global organization. The TK is an organization of committees consisting of surgeons, product development staff, and engineers. In the specialty of craniomaxillofacial surgery, there is an overall Technical Commission with various Expert Groups (EGs) in which approximately 40 surgeons work with the engineers on solutions for clinical problems. From the beginning, the aim of the TK was to ensure that all implants and instruments that were manufactured according to AO standards have a proven record of safety, simplicity, and universality in application. There are three EGs working with the AO industrial partners on the development of new instruments, implants, and techniques in CMF surgery. Ad-hoc committees such as task forces or working groups focussing on new technologies, ie, computer assisted surgery and biomaterials, were also established to support the efforts of the TK and EGs where necessary.

Without prior approval of the TK, almost no Synthes implant or instrument becomes available to the surgical community. However, there is more to the TK System than the decision on the final product approval. All EGs work in close collaboration with the engineers from the first idea to clinical use, and all instruments and implants go through several stages of evaluation with the independent medical members of the EGs making the final decision whether or not the respective project is pursued. Special care is taken to ensure that Expert Groups evolve in line with changing requirements and react promptly to the needs of the medical community. Thus, new research insights are considered, new possibilities for development are evaluated, and new needs and trends are studied. Further tasks of the Expert and Working Groups are to evaluate devices and methods identified by surgeons or any other interested party and to define and approve a clinical evaluation process. They also monitor the clinical success of approved devices and methods once they have been on the market for a while. Each group within the TK System consists of five medical members as well as engineers, researchers, and other representatives of the AO industrial partners. Despite defined membership terms, the TK System is anything but a closed circle and remains open to ideas from the outside. Everybody is invited to participate and present his or her ideas to the TK Chairman (see TK innovation form available on the Web: http://courses.aocmf.org/files/editor/documents/TK_Idea_ Form_CMF_2009.pdf).

5


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1 General aspects

Authors Michael Ehrenfeld, Joachim Prein

1.1 Introduction 4 Education

4

Education

Worldwide education is probably the most important mission of the AO Foundation with regard to improving healthcare. Educational activities were traditionally coordinated through AO International (AOI), and then later through AO Education (AOE) in a supra-specialty manner. Today education is organized by the four specialties (AOTrauma, AOSpine, AOCMF, and AOVET) and is delivered through different educational channels:

6


• Face-to-face education through courses, workshops, seminars, and symposia • Printed media, such as journals (ie, Journal of Craniomaxillofacial Trauma and Reconstruction) and books • Audiovisual media (eg, videos and DVDs) • Internet • Fellowships: The AO Fellowship program offers fellowships to both surgeons and operating room personnel in designated approved AOCMF Fellowship Centers. Interested surgeons and ORP can apply for fellowships on the AO Foundation website (www.aofoundation.org/fellowships).


01.06.12 15:13

1 General aspects

Author Beate Hanson

1.1 Introduction 5 Clinical investigation and documentation

5

Clinical investigation and documentation

5.2 Doing clinical research

5.1 AOCID mission and strategy

AO Clinical Investigation and Documentation (AOCID) conducts multicenter clinical studies to document safety, effectiveness, and outcome of fracture treatment, thus promoting the application of evidence-based surgery. Its worldwide activities are increasing steadily. AOCID’s strategy is to promote the science of applied clinical research. Applied clinical research involves both doing and using clinical research. AOCID directs and assists surgeons in the conduct of clinical studies. It assists surgeons to search and critically appraise the available literature to answer clinical questions (Tab 1.1.5-1).

Design and conduct of a clinical trial can be a daunting task. The key to designing and conducting research successfully is being creative and careful. Researchers must correctly articulate the study question, choose the correct study design, and ensure that data are extracted, recorded, managed, and analyzed carefully. The accuracy of the results is dependent on internal and external validity. Internal validity refers to the effects obtained in a study due to the intervention under evaluation. Internal validity is attained through sound study methods. If there are alternative explanations for the data (eg, selection bias), the study may not have internal validity. External validity refers to whether the results can be generalized outside of the specific participants and situations of the study. Careful selection of study subjects ensures that study findings are generalizable. Five major steps are involved in successfully conducting a clinical study that possesses both internal and external validity: 1. Developing a study idea 2. Careful crafting of a study plan 3. Ensuring that detailed standard operating procedures are followed during study implementation 4. Performing careful data analysis 5. Publishing the results with careful thought and attention (Tab 1.1.5-2).

DOING Clinical research

USING Clinical research

• H ow to design and conduct clinical trials.

• H ow to search the literature to answer a clinical question. • H ow to critically appraise a medico-scientific article.

Tab 1.1.5-1 AOCID is committed to doing and using clinical research.

Publication Data analysis Study implementation Study plan Study idea

Step 5

Step 4

Step 3

Step 2

Step 1 Tab 1.1.5-2 The five major steps in successfully conducting a clinical study.

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Author Beate Hanson

1.1 Introduction 5 Clinical investigation and documentation

5.3 Using clinical research

5.4 Summary

The study and understanding of basic mechanisms of injury and healing alone are not sufficient guides for clinical practice. In addition, clinical experience, while valuable, may be misleading in solving clinical problems. There is a growing agreement in the field of surgery that surgeons need to move beyond physiological principles and clinical experience toward evidence-based medicine and its rigorous evaluations of the consequences of clinical actions. Knowing how to use clinical literature (ie, literature search, literature review, and critical appraisal) is imperative in ensuring that surgeons are providing optimal patient care. Surgeons need to focus on a specific clinical question, know where to look for pertinent articles that address the question, and select only the information that is likely to provide results with the best evidence. The final skill of critical appraisal allows surgeons to weigh the evidence against published conclusions.

AOCID is dedicated to assist clinicians in achieving success in clinical research. AOCID provides useful services and tools for surgeons to evaluate their devices and interventions. Detailed information on AOCID and its services is available online at: www.aofoundation.org/cid

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Authors Carl P Cornelius, Laurent Audigé, Joachim Prein

1.1 Introduction 6 AO classification of craniomaxillofacial fractures

6 AO classification of craniomaxillofacial fractures 6.1 General concept and objectives of a fracture classification

In biosciences and medicine classifications are omnipresent. Almost every advent of new technologies and novel diagnostic or therapeutic regimens is publicized together with the urge to rethink former systematization and conceptions. This is reflected in headlines and titles containing vocabulary such as grouping, coding, rating, grading, scaling, scoring, typifying, which is indicative for a classifying process. Fractures of the human skeleton come in many variations rendering it difficult to identify appropriate parameters and to assign a clinical series of unique cases into a fixed number of possible categories. Today the least common denominator for a formal fracture classification is the description of the fracture topography and its morphology based on the analysis of diagnostic x-rays or CT imaging. There are multiple other variables and factors to fully portray a patient and his injury such as etiology, severity of the trauma, bone quantity and quality, associated soft-tissue damage, functional impairment, age, physical or psychic comorbidities, and social integration. In theory it may seem reasonable to include all conceivable variables and patient

Phase 1 Development phase

Phase 2 Reliability and accuracy in clinical setting

Classification proposal

Multicenter agreement study

Pilot agreement studies

details into a fracture classification; however, this would lead to a diversification into small subcategories, which would be unmanageable in routine clinical use. What really matters in the treatment of an individual patient is firstly, usefulness for and ease of communication, and secondly, the therapeutic relevance of classifying. For this reason the hierarchy of categories and groups in a fracture classification system should best correlate to the injury severity and/or the difficulty of treatment. A set of agreed rules and definitions is mandatory to identify the groups within an ascending order of injury severity. A classification model should be minimalistic. Thus, preselection of pertinent parameters by virtue of a rigorous methodological validation concept is crucial. An inherent problem in the development of a concise fracture classification m odel is to delineate the cut-off criteria between groups from the very onset to predict treatment outcomes. In the first development stages, a fracture classification proposal should exclusively refer to the biological substratum (nature) of an injury, such as anatomical location, fragmentation, and so on. Necessary modifications are to follow in an iterative process of exploratory trial phases in pilot and agreement studies (Fig 1.1.6-1). Only after successful validation, the outcome of differential treatment procedures and the potential risk for complications can be analyzed prospectively in evidenced-based studies.

Phase 3 Association with patient outcome(s)

Clinical studies

Fig 1.1.6-1 Methodological development and validation along a 3-phase pathway (Audigé et al 2005). The classification proposal and the pilot agreement study are looped repetitively until acceptable reproducibility and consensus are reached.

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Empirical information gained from specific treatment paths should not be implemented in the initial version of a fracture classification. Such treatment-based criteria result in bias rather than yielding a rational base for the prospective evaluation of any targeted therapy. Apart from providing guidelines for individual patient care, a fracture classification serves further purposes. A consistent and reproducible classification provides a universal language and coding that facilitates communication and collaboration. Coding and indexing are prerequisites for using present-day information and computing media for web-based exchange and storage of records on fractures in trauma databases. It enables large-scale documentation, inter-institutional comparisons, quality surveillance of clinical outcomes, the adoption of benchmarking methods in order to possibly optimize the surgical procedures, and last but not least, economic analysis. In 1986 the AO Foundation officially adopted “The Comprehensive Classification of Fractures of the Long Bones” developed by Maurice Müller and his group as a groundwork for its activities in documentation. This forerunner of today’s AO classification endeavors has introduced a standardized alphanumeric code to indicate the affected bone, the fracture type, and its morphological complexity. Topographic identification analogous to this initial coding is still in use, eg, in the CMF region: 91 for mandible, 92 for midface, 93 for skull base, and 94 for cranial vault. The fracture codes (or classes) were assembled according to the so-called AO tripartition concept, which was a ranking scale for fracture severity into 27 different degrees with a hierarchical tree-like architecture. For many years the idea was to apply the tripartition concept universally to all fracture locations in the human skeleton. Interestingly enough, the AO classification manuals have ever since relied on wide-scope diag rammatic representations. Still a visually based, more or less non-verbal, self-explaining, and intuitive coding procedure is regarded as essential to developing a user-friendly, internationally accepted fracture classification scheme and its successful implementation in the routine workflow of clinicians.

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6.2 A brief history of CMF classifications

To date central midface fractures with a potential impact on the occlusion are referred to worldwide by the name of Le Fort. The simple distinction of three Le Fort type fractures is considered as a prototype of a classification system for facial fractures. The experimental cadaver studies of the French physician and pathologist René Le Fort (1901) dating back to the very beginning of the 20th century led to an understanding of the honeycomb construction of the midfacial skeleton and, in turn, of the major lines of weakness. This bony architecture explains why the fractures may follow a predictable course that can be divided into a limited number of well-defined patterns. Over more than a century a multitude of classifications were created to detail site-specific fracture entities for craniofacial fractures: • Midface (Guérin 1866, Le Fort 1901, Wassmund 1927, Donat et al 1998) • Zygoma, zygomaticomaxillary complex fractures (Zingg et al 1992) • Orbito-zygomatic and orbitoethmoid region (Jackson 1989) • Nasoorbitoethmoid (NOE) region (Markowitz et al 1991) • Orbit (Hammer 1995, Carinici 2006, Jacquiéry et al 2007) • Medial orbital wall (Nolasco and Mathog 1995) • Palate (Chen et al 2008) • Midface in conjunction with skull base (Buitrago-Téllez et al 1992, 2002, Bächli et al 2009) • Anterior skull base (Madhusdan et al 2006) • Temporal bone (Rafferty et al 2006) • Mandible (Spiessl 1989, Roth et al 2005, Buitrago-Téllez et al 2007) • Condylar process of the mandible (Spiessl, Schroll 1972, Loukota et al 2005) • Panfacial injuries and avulsions (Clark et al 1995) Various attempts were made to build up fracture severity scores for the CMF region by Cooter and David 1989, Joos et al 1999, Bagheri et al 2006, Zhang et al 2006, based on categorical (ordered or ordinal) scales.


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6.3 Evolution of a modern AO craniomaxillofacial fracture classification

Several years ago the AO Foundation started to create an up-to-date classification of craniofacial injuries. The project was launched by the work of Buitrago-Téllez, who initially designed a CT-based diagnostic algorithm for craniomidfacial fractures to establish a hierarchical classification of increasing severity. The elementary concept was to split craniofacial fracture patterns analogous to the AO tripartition system. The innovation of this first generation CMF classification was the incorporation of accompanying anterior and lateral skull base fractures and fracture line courses deviating from the Le Fort levels. In 2008, a classification model for the mandible differentiating vertical mandibular compartments and a horizontal subdivision of the body and parasymphyseal region was conjoined. Persistent inconsistencies in interobserver reliability of this first generation CMF system as well as a second generation model accomplished in several classification sessions by the members of an international group of CMF traumatologists did not comply with the upcoming methodological standards. The complexity of the models enabling a comprehensive mapping of each and every conceivable fracture line and possible combinations was revealed as the main reason for the limited performance of the classification proposals. The plausible solution was a paradigm shift moving to a streamlined classification model considered as practical, clinically meaningful, and scientifically sound.

In order to keep up with the request for simplification, the road map for the development of the current third generation CMF AO classification takes the following aspects into account: • To address trauma of: mandible (91), midfacial skeleton (92), skull base (93), and cranial vault (94) • To use imaging information as common basis for all levels and modules: (91–94: CT scans/supplementary MRIs, 91 alternatively: Panorex, conventional x-rays in two planes) • To include topographical description of fracture location • To integrate the Le Fort Classification in the midfacial skeleton (92) • To describe fracture morphology • To incorporate a rigorous methodological pathway (interobserver reliabilty, validity) • Stepwise development of the system in three levels with progression of accuracy and clinical significance: - Level 1: Elementary system for gross fracture location (mandible, midface, skull base, cranial vault) - Level 2: Basic system for refined fracture location in the CMF skeleton (outlining the topographic boundaries of the anatomical regions within the fundamental units of the CMF skeleton as a basis for an accurate localization) - Level 3: Focused modular system assessing fracture morphology (ie, fragmentation and displacement) - Levels 1 and 2 serve as anatomical localizers, while level 3 describes the fracture morphology in an array of modules representing anatomical regions and subregions. • To build up a hierarchical classification system that allows grading of fracture severity • To provide a rational basis for prospective (functional and patient reported) treatment outcome studies, from which algorithms for clinical decision making can be derived

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Anatomical units of the craniofacial skeleton yield the templates (Figs 1.1.6-2–3) on which the overall system is gradually built up in a series of modules. A module is representing circumscript anatomical regions, either in concert (eg, mandibular body, parasymphyseal region and angle) or alone (eg, condylar process). Each of the modules is developed in a step-by-step manner to define different levels of precision related to the necessities of documentation and varying scopes of clinical application. Such a staged approach with pilot testing of the items ensures the elimination of all ambiguities and verifies the reliability and appropriateness before any progression to the next level is permitted.

The final proposal for levels 1 to 3 for the entire craniofacial skeleton have been recently completed by the CMF Classification Group. This is considered as a sign that the current development process of a modular CMF fracture classification is on the right track, though the long and arduous way to generate measures reflecting the fracture severity is yet to come.

F

P

P S

S

T

T

U

Z

I

I

Z

L

a

b

Fig 1.1.6-2a–b Third generation AOCMF classification. a Level 1: Mandible, midface, skull base, and cranial vault. b Level 2: C lassification proposal: skull frontal view. Differentiation of anatomical regions: zygoma (Z), upper central midface (U), intermediate central midface (I), lower central midface (L), frontal (F), parietal (P), sphenoidal (S), temporal (T).

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In the level 2 classification the mandibular body is subdivided by vertical lines into horizontally oriented subdivisions (Fig 1.1.6-3). Neither the dental state nor the vertical bone height or any degree of atrophy is an explicit item at level 2. Nonetheless, it is necessary to acknowledge the dentition since the tooth roots are used to provide baseline markings to divide the mandible into regions. Therefore, a full set of permanent teeth is plotted in the level 2 graphic charts of the mandible. Four transition zones were interposed between the mandibular regions to procure corridors in the approximate width of the canine or the third molar for the unequivo cal allocation of fracture courses running at the borderline or passing obliquely across the boundaries of adjacent regions.

stacked one above the other alongside the pillars of the central midface (Fig 1.1.6-2a–b): lower central midface (LCM), intermediate central midface (ICM), and upper central midface (UCM). Obvious deficiencies of the Le Fort classification are offset: fracture pattern scenarios beyond the monotonous lowenergy impact skeletal disruptions produced in his experiments (ie, direct blows with a wooden club or banging of the head against the round edge of the autopsy table) with comminution, inclusion of multiple midfacial units, extension into the adjacent cranial base and vault, or involvement of the mandible in terms of pancraniofacial fractures are taken into account by the all-inclusive cartography.

It is not pure nostalgia that the level 2 midface fracture classification module integrates the classic Le Fort fracture pattern. The Le Fort scheme is popular in the medical community and should not be replaced because it ideally fits into the present-day requirements for a fracture classification. It is easily intelligible, relies on visual programs, and precludes language or semantic problems. The level 2 m idface fracture classification delineates the Le Fort levels (except the zygoma) with the help of three horizontal partitions

P

Each area-specific classification module will be explained in detail and illustrated with case examples in particular instructional brochures and in a special issue of the Craniomaxillofacial Trauma and Reconstruction journal. To facilitate fracture classification and coding in routine clinical settings, software has been released and can be downloaded, ie, the AO Comprehensive Injury Automatic Classifier (AO COIAC), (http://www.aofoundation.org/aocoiac).

C

C

A

P

A

2

B

B

S 1

2

1

Fig 1.1.6-3 3rd generation AOCMF level 2 classification proposal: Panoramic view of the mandible. Body regions = 1 (anterior transitional zones) Ramus regions = 2 (posterior transitional zones) Condylar process (P), coronoid (C), angle/ramus (A), body (B), symphysis/parasymphysis (S).

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6.4 Future perspectives

It takes time to gain expertise in fracture classifications and the current versions certainly will not represent the end of the development process. Although the existing level 2 CMF classification software provides an almost non-verbal visual logic allowing for effortless documentation, it seems overly ambitious to generate an intuitive software user interface to characterize the fracture morphology at the next level. Level 3 has to deal with an enormous number of variables (injuries of teeth and parodontium, bone atrophy, number and spatial distribution of fracture lines), which can be hardly displayed in the form of symbols, icons or thumb nails, that can be checkmarked by simple pointing and clicking. Another unsolved issue is the aggravating time constraints of clinicians. Image fusion of CT scans and classification charts followed by automatic analysis might be a technical answer to the problem. Technological advances will not only enhance the precision of evaluation and diagnosis but will continuously detect imperfections unknown to previous classification endeavors.

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1 General aspects 1.2 Bone

1

Origin of skull bones

17

2

Structure

17

3

Chemical composition

19

4

Mechanical properties

19

5

Mechanical glossary

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Author Berton Rahn

1.2 Bone

1

Origin of skull bones

During embryogenesis two different mechanisms of bone formation take place in the skull. In the dermatocranium (exocranium) the ossification occurs by direct mineral deposition into the organic matrix of mesenchymal or connective tissue, resulting in a process called membranous bone formation, which is the major ossification process in the skull. Frontal, parietal and nasal bones, maxilla, zygoma, and the mandible are all formed by this mechanism. Endochondral bone formation is the mechanism in the chondrocranium (endocranium). Here a cartilaginous template is formed, which becomes mineralized and then replaced by bone. In the skull the cartilaginous origin of bone is confined to the skull base, occipital bone, nasal septum, and internal components of the nose. Further growth in membranous as well as in bone of endochondral origin occurs by the membranous mechanism. Thus, barely any bone of cartilaginous origin can be detected after completion of all modeling and remodeling processes which take place during growth. Although there seem to be differences in the phenotype of bone cells from sites of different origin, repair processes follow the same membranous patterns, regardless of the embryological origin of the bone.

2

Structure

Depending on functional demands, bone appears as a light weight construct, cancellous bone, or in a compact form, cortical bone. This appearance is not directly related to microscopic composition and origin of the bone tissue. The mandible mainly consists of compact bone, with cancellous portions in the condyle, angle, and body. The cranial vault is a tri-layered construct with an internal and an external table made of compact bone, separated by the cancellous diploe region. The bones of the midface mainly consist of thin compact layers, supported by a more stable bony frame, while the bones of the skull base have a more compact appearance. Bone as a tissue is first formed as a relatively loose material, woven bone, in a process which proceeds relatively fast. Later it is reinforced by additional bone deposition into the meshes of this loose network and on its surfaces (Fig 1.2-1). This latter type of bone, lamellar bone, is formed more slowly, layer by layer, at a speed of about 1 to 2 mm per day. As a result, this bone is more organized and more compact. Once bone is formed, it undergoes continuous modeling and remodeling to adapt to functional demands (Fig 1.2-2).

O Dead bone Hc Hc

Dle

Hc Bv

Bv Dle Remodelled bone

O

Fig 1.2-1 Bone tissue first formed as a woven bone scaffold, later reinforced by lamellar bone deposition. Green is the original woven bone; red indicates newly deposited woven bone; yellow indicates osteoid; arrows indicate osteocytes; and circles indicate blood vessels.

Bv

Fig 1.2-2 Bone undergoes continuous remodeling to adapt to functional demands. O: living bone osteocytes stained pink within lacunae Dle: dead bone lacunae, empty Bv: blood vessels (red) Hc: Haversian canal

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1 General aspects 1.2 Bone

Osteoclasts are responsible for these structural changes (Fig 1.2-3), which are large multinuclear cells, which locally decalcify and remove bone. Osteoblasts (Fig 1.2-4) are responsible for the synthesis of the organic matrix and the mineralization of new bone. Osteoclasts are derived from the hematopoetic system, where monocytes and macrophages are considered to be precursors. Osteoblasts have a local origin from osteoprogenitors and mesenchymal precursor cells. During bone deposition, single osteoblasts are buried in the new bone. They become osteocytes, which are connected to each other by thin cell processes, cana-

liculi (Fig 1.2-5). Through this fine canalicular network a rapid exchange of calcium ions becomes possible. Occasionally this exchange becomes visible as osteocytic osteolysis or periosteocytic mineralization. To keep the net bone mass constant, the function of osteoclasts and osteoblasts has to be well balanced. A disturbed balance can be observed under pathological conditions. If osteoclast function dominates over osteoblastic bone formation, a net bone loss will result (osteoporosis). A higher bone density results when osteoclast function is disturbed, as for instance in osteopetrosis or by the influence of therapeutic agents (osteoclast inhibitors).

Bone

N

N

N

Fig 1.2-3 Osteoclasts, large multinuclear cells, are able to decalcify bone and then remove the organic matrix. At its periphery (zone between arrows) the osteoclasts are intimately attached to the bone surface, creating a subcellular zone between bone and base of osteoclast. Within this hyperacidic resorption compartment (pH 4,5), demineralization takes place. N indicates nuclei.

Canalicular network Bone

Bv

Osteoid O

O

O

Bv

Lacuna with osteocyte Fig 1.2-4 Osteoblasts (O) are responsible for formation and mineralization of new bone. In between arrows, mineralization front.

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Fig 1.2-5 Nutrition of bone occurs through a fine canalicular network connecting osteocytes. Bv indicates blood vessels.


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Author Berton Rahn

3

Chemical composition

Bone is composed of an organic matrix loaded with inorganic substances. The sum of the inorganic components amounts to approximately 65% of the total mass. Bone tissue is the most important reservoir of calcium ions which allows rapid release in the case of high demand, or rapid storage in the case of high supply. This is especially important for maintaining the serum level of calcium strictly within narrow boundaries. Hydroxyapatite [Ca10(PO4)6(OH)2], together with other calcium and phosphorus salts, is the major inorganic constituent. Besides the calcium, bone salts contain relevant amounts of magnesium, potassium, chlorine, iron, and carbonate. The organic component of bone consists of about 90% collagen, primarily type I. The remaining 10% are non-collagenous proteins and lipids. These proteins include 23% osteonectin, 15% osteocalcin, 9% sialoprotein, 9% phosphoproteins, 5% α2-HS-glycoproteins, 4% proteoglycans, 3% albumin, and further proteins in minor amounts. In recent years, a whole group of bone proteins have been identified which have important functions in bone turnover and bone repair when they are released.

4

Mechanical properties

Bone as a material is a composite, comparable to technical materials like steel-reinforced concrete or fiber-reinforced polymer. Primarily the collagen fibers are responsible for taking over tensile forces, while the mineral phase absorbs compressive forces. The microstructure determines the mechanical characteristics of the materials. It has been demonstrated that fibers show specific orientation depending on the specific loading situation. This results in anisotropic material characteristics which means that the properties are different in different directions. Similar to technical materials, fiber length influences the mechanical properties. An intense remodeling, which interrupts existing structures, leads to a change in material properties. This is probably less important for compressive forces, but it might play a role in tension or shear forces. Bone is rather brittle; it only tolerates an elongation of 2% before it breaks. The “material” bone has an ultimate strength of about 1 MPa, whereby tensile strength only amounts to two-thirds of compressive strength. This explains why bone

usually fails on the tension side first when it is bent. The mechanical properties of dead bone are not dramatically different to those of living bone, but a continuous remodeling is necessary to avoid accumulation of microtrauma injuries which finally may result in a fatigue fracture. Bone as an organ has design characteristics that are adapted to the local mechanical requirements. The design normally includes ample reserve for peak loads. Depending on the local demands, bone appears as beams, compact or hollow, or as a light weight construct, as cancellous bone. The mechanical properties of cancellous bone depend on the amount of material, orientation, thickness, and connectivity of trabeculae. The strength of cancellous bone thus covers a wide range but is typically less than one tenth of cortical bone.

5

Mechanical glossary

Technical terminology is encountered when dealing with skeletal biomechanics related to fracture treatment. A small selection is explained here in a simplistic way, and more details can be found in corresponding textbooks. When a force (Newton, N) acts on a body it produces an internal stress (σ, force per unit area, N/m2). A moment is force acting with a lever arm, its unit being Newton times meters (Nm). Under such a force a body is deformed. The deformation ratio, change of length per original length is called strain (ε=δL/L). It is unitless, and describes the change of the original dimension as a percentage. The relationship between a force and the resulting deformation is called stiffness. The lower the stiffness is the higher is the deformation. A load may consist of up to three vectors of force and three components of moment. It can be static or dynamic, and it can be produced by tension, compression, bending, torsion, or shear, or by a combination thereof. Strength describes the load a body can bear, and it is usually given as ultimate strength, the maximum that the body can bear. The word “stability” is frequently used in context with fracture fixation. This term is technically not well defined. It is used to describe a certain degree of fixation considered adequate to permit undisturbed fracture healing in a specific situation. Thereby the personality of the patient, the type of fracture, the expected loading situation, soft-tissue conditions, expected healing time, and many other parameters are all important in the clinical situation.

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1 General aspects 1.3 Fractures in the craniomaxillofacial skeleton

1.3.1 Biomechanics of the craniomaxillofacial skeleton

21

1

Introduction

21

2

Mandible biomechanics in detail

25

3

Midface biomechanics in detail

25

4

Repair of structures

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Authors Randal Rudderman, Robert Mullen

1.3.1 Biomechanics of the craniomaxillofacial skeleton 1

Introduction

The craniomaxillofacial skeleton provides a frame for the protection of soft organs including the eyes and the brain. In addition, it contains important functional entities such as airway and the masticatory apparatus. The bones of the facial skeleton, the skull, and the skull base form a bony, structurally stable frame, on which muscles insert at defined locations that allow suspension and controlled movements of muscles and skin. The hemispherical design and the layered structure of the cranial vault make it especially suited to protect the brain against direct impact. The cellular structure in the midface, reinforced by the orbitozygomatic frame, is able to function as a shock-absorbing structure, absorbing energy as fractures occur. The mandible acts mechanically like a curved beam in the axial plane and is supported by the major muscles that insert in the area of the angle and the ascending ramus, and by joints at each end. This curved structure has a pair of sup-

port slings, one on each side, called the pterygo-masseteric sling. Consistent with the natural laws of physics, all curved beams or supports will develop regions of strain in compression or tension relative to a load location. A midline mandible load will generate tension opposite the load (along the lower surface) and compression at the bite location when viewed in the coronal plane. A posterior load will develop a similar pattern at the bite position viewed in the sagittal plane, with a relative reversal of strain at the contralateral position. It remains inconsistent with the laws of physics to define the alveolar surface as a tension zone for all bite force scenarios. This description continues to be used erroneously in reference literature in conflict with basic science. During mastication the mandible moves relative to the rest of the skull. Forces act at the attachment sites of the masticatory musculature and in the occlusal plane at the bite location. These latter bite forces are transmitted via the teeth to the alveolar bone and from there to the structures of mandible and maxilla. The maxilla is connected by six main vertical trajectories to the orbitozygomatic frame, which is then connected to the neurocranium (Fig 1.3.1-1).

Fig 1.3.1-1 The vertical buttresses of the facial skeleton (nasomaxillary, zygomaticomaxillary, and pterygomaxillary).

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1 General aspects 1.3 Fractures in the craniomaxillofacial skeleton 1.3.1 Biomechanics of the craniomaxillofacial skeleton

Loading of the occlusal plane may reach high force values. Maximum bite forces in an average population are found in an order of magnitude of 200 to 300 N in the incisor area, 300 to 500 N in the premolar region, and 500 to 700 N in the molar area. The values found during normal mastication are usually much smaller, amounting only to a fraction of the maximum biting forces. These regular masticatory forces cause micro-deformations of the facial bones as a result of strain conditions, but functional forces never cause any fractures in a healthy skeleton.

a

At the time of deformation of the facial bones, pressure-, tension-, shearing- and neutral zones are observed. During the complex and physiological masticatory loadings the areas for the various forces change rapidly over time and according to the individual loading situation. Similar deformations are observed when external forces act on the facial bones, however, with strain conditions that may exceed load carrying capabilities of the structures. In this case the areas of tension, compression, or shearing depend on the vector of the external forces (Figs 1.3.1-2a–b, 1.3.1-3a–b).

b

Fig 1.3.1-2a–b a E xternal force anteriorly with resulting tension forces superiorly and compression forces inferiorly within the mandible. b E xternal force posteriorly with resulting tension forces inferiorly and compression forces superiorly within the mandible.

a

b

Fig 1.3.1-3a–b a As a result of lateral forces acting against the mandible the compression zone is lateral and the tension area is medial. b Fracture dislocation as a result of forces acting from the lateral aspect against the mandible.

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The biomechanical behavior of the mandible has been studied using finite element analysis (FEA). These studies confirm that areas of compressive, tensile, shear, and neutral forces dynamically change with the load vector and the absolute amount of load (Fig 1.3.1-4a–c).

a

An osteosynthesis must be performed with devices of the appropriate size and placed in such a way that the physiological forces are distributed in a manner consistent with the normal patterns of strain.

b Fig 1.3.1-4a–c a Finite element model of a mandible, midline load, and midline view. Note the relative region of tension at the lower lingual surface. b Finite element model of a mandible, molar region load. Midline posterior view. c Finite element model of a skull. Partially edentulous. Pressure via frontal teeth. Tension zone in lower left mandible area as well as paranasally left.

c

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The mandible consists mainly of solid bone. The midface includes both, shell-like thin bones and stronger vertical and horizontal buttresses surrounding the orbits, the nasal cavity, and the paranasal sinuses.

Located within this complex compartmental system are several buttresses which can tolerate higher forces (Fig 1.3.1-5).

Fig 1.3.1-5 Transversal (blue), vertical (red), and sagittal (green) buttresses of the facial skeleton.

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2

Mandible biomechanics in detail

• The mandible displays behavior consistent with a curved beam supported by a sling at each end (muscles). • The load surface (superior surface) functions as the contact point with the midface (teeth, dentures). • Load points vary in location from posterior to midline to posterior (contralateral) and, being consistent with natural physics, the locations of stress (tension and compression) vary depending on the load (bite) location. • There is no muscle (dynamic) support at the midline during loading. Functional loads in this immediate region develop primarily compressive stresses at the upper margin and tensile stresses at the lower margin. • The geometry of the mandible, being consistent with curved beams, develops the majority of stress at any load site at the superior and inferior margin of the structure. When structural bone is separated by injury (eg, fracture, osteotomy), devices used to restore geometry are most efficient in functional support when placed in areas of maximal tensile natural stress. Stresses are typically minimized at the mid-section of a curved suspended beam (neutral zone) depending on the load pattern. Increased stress develops in tension or compression zones. • However, because the change between compression and tensile zones occurs rapidly during function, the placement of osteosynthesis material in the so-called neutral zone is an established technique, especially to treat fractures in the lateral body of the mandible, and is often very effective because the “neutral zone” is mislabelled and is not “neutral.” • Devices used to repair a damaged mandible will have the most predictable long-term observable results if, following application, the original pre-injury stress distribution is re-established. Devices, regardless of size (strength, stability), that significantly alter the stress patterns may present with failure. Biology also requires that a fracture site has a “quiet” environment for cellular healing (lack of disruptive motion). • Areas of the mandible (mid-body) that have experienced fracture and plate application for repair will experience alternating stresses depending on bite location. Loads posterior to the fracture site will result in compression at the superior margin at the fracture site and tension at the inferior margin. Loads anterior to the site will lead to the opposite stress patterns. Only as healing progresses can tensile stresses be conveyed at the fracture area. Compressive stress, however, can present by contact of the fracture segments.

3

Midface biomechanics in detail

Midface biomechanics are less understood due to significantly more complicated geometry and loading conditions. However, basic tenants of mechanics must apply. • The midface occlusal surfaces experience load conditions of equal magnitude and opposite direction to those of the mandible. • The areas of the structure which are the stiffest due to material properties and geometry have the lowest probability of deformation when loaded and experience the greatest forces during function. In the midface, medial and lateral vertical components of the maxilla and zygoma (medial and lateral buttresses by convention) support force flow preferentially through these structures during load application at the occlusal surface. • Soft-tissue contraction of the masseter sling (muscle groups) develops equal forces at the origin and insertion with stresses distributed differentially due to significant differences in geometry of the midface and mandible. • Soft-tissue attachments including fascia contribute to overall stability of components (ie, temporal fascia), and, when damaged during injury or repair, will alter stress distributions of local structures.

4

Repair of structures

• Systems that most accurately re-establish the uninjured state (including geometry and material properties) and result in the least damage to biological structures and mechanisms will be most predictable in observable outcomes. • Damage to a system may occur with repair techniques least sensitive to the contributions of soft tissue (blood supply) for function and cellular healing. When treating a fracture, it should be understood that bone and the material for osteosynthesis build a complex interacting system. The stability of an osteosynthesis is not only dependent on the size of a plate or screw but also on its placement, material properties, application technique, and the condition of the bone (size, density, cellular orientation). Under favorable conditions and with proper device application, the bone serves as a buttress and provides a path for functional forces to act on each side of the fracture, developing strain patterns while remaining stable enough for mastication without failure and uneventful healing. The weaker the bone is, the less it can add to the stability of an

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osteosynthesis construct. In this case the material used for osteosynthesis must be stronger (in essence must remain stable under functional loading while serving as a pathway for forces to develop patterns of strain). The most predictable approach in repairing any dynamic and complex system is to create a solution that mimics the natural functional state and minimizes additional damage to the system when engaging in repair (respect the soft tissue, delicately apply devices that are consistent with the material requirement of the natural structure, and return force distribution to normal, allowing for uneventful healing).

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Author Berton Rahn


A fracture disrupts not only the mechanical but also the biological continuity of bone. The circulatory situation after a fracture influences to a large extent the subsequent healing process, whereby the level at which circulation is disturbed has a major impact on the outcome. If afferent vessels are injured outside the bone, or if the fracture includes larger vessels like a nutrient artery, then main bone areas are compromised. In all cases intracortical vessels like those in Haversian and Volkmann canals are interrupted along the fracture plane. The intracortical circulation is a low-pressure system. Following injury, clotting occurs inside the interrupted vessels, which stops the bleeding. Moreover the inhibition of efflux leads to congestion, followed by further clotting. This leaves the fragment ends without proper blood

supply. If a reconnection to circulation is not gained within a few hours, the occlusion of vessels becomes irreversible and the osteocytes in the compromised bone undergo necrosis. A functioning circulation is a prerequisite for a successful healing process. While vascular recovery occurs relatively fast in soft tissues, the situation is more complex inside bone, especially compact bone, because space for new vessels has first to be opened. After 2–3 weeks a recanalization of existing but thrombosed vascular pathways starts (Fig 1.3.2-1). The areas of dead bone are removed by osteoclastic activity, starting from the perfused bone and gradually entering the necrotic area along the reopened vascular canals (Fig 1.3.2-2), removing dead bone. New vessels follow the osteoclasts;

Intact circulation

Oc

Oc

Oc Oc

Oc

Oc Ob

Oc

Ob

Oc

Dead bone

Fig 1.3.2–1 Disturbed perfusion of compact bone. The blue marker stains the region of intact circulation. At the border to the disturbed area (dotted line) the vessels regain access to circulation (arrows).

Ob Oc

Fig 1.3.2–2 Intracortical remodeling in an area of disturbed perfusion. Osteoclasts (Oc) “drill” canals into the old bone, osteoblasts (Ob) fill these canals with new bone. Arrows indicate direction of osteon growth.

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1 General aspects 1.3 Fractures in the craniomaxillofacial skeleton 1.3.2 Fracture and blood supply

subsequently, osteoblasts fill the widened canals with new bone (Fig 1.3.2-3). Usually this remodeling is limited to the zone in which circulation was jeopardized. Since old, nonperfused bone has to be removed before new bone can be built, there is a transitional period in which a healing bone, especially in the fragment ends, appears less dense on x-rays. The trauma of the fracture leaves a hematoma between the fragment ends. There is some evidence that this hematoma could be a source of precursor cells involved in tissue differentiation. Vascular invasion of the fracture hematoma is a prerequisite for the start of the differentiation cascade (see chapter 1.3.3 Biological reaction and healing of bone), which finally leads to a bony bridging of the fracture. During this process the interfragmentary space remains without vessels across the fracture plane as long as there is significant interfragmentary motion. A reconstruction of major intracortical and medullary vessels only becomes possible after the

fracture has united and remodeling toward the original shape of the bone has started. A disadvantage is that a hematoma offers excellent conditions for bacterial growth. This increases the susceptibility to infection, since natural defence mechanisms do not get access to the nonperfused areas. An osteitis will result, and osteoclasts attempt to remove the dead bone, resulting in the formation of sequestra (Fig 1.3.2-4). Operative treatment interferes with bone blood supply in addition to the damage produced by the initial trauma. Manipulation for alignment and the drilling of screw holes directly damage cortical circulation, and plates disturb the efflux on the periosteal side. On the other hand primary operative stabilization offers certain advantages. Rapid recovery of the intramedullary circulation becomes possible, and a direct crossing of capillaries from one fragment end to other permits a union in exactly the position in which the fragments were aligned.

Bv

Fig 1.3.2–3 Partially remodeled compact bone. Black indicates old bone; green indicates new bone; and red indicates blood vessels (Bv). Fig 1.3.2–4 Sequestration of nonperfused areas (status after wire osteosynthesis of an experimental mandibular fracture in a sheep). The circulation is disturbed in the fragment ends and the area where the operative procedure took place. Osteoclasts attempt to remove the dead bone, resulting in the formation of sequestra.

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Author Berton Rahn

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1 General aspects 1.3 Fractures in the craniomaxillofacial skeleton 1.3.3 Biological reaction and healing of bone

1

Primary bone healing

31

2

Secondary bone healing via callus formation

33

3

Steps of differentiation cascade

33

4

Nonunion

37

5

Delayed union

37

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Authors Berton Rahn, Joachim Prein


A sufficient blood supply, presence of specific cells, and adequate mechanical conditions are the prerequisites for undisturbed fracture healing. Fracture healing may occur under different degrees of interfragmentary motion, ranging from absolute immobilization of the fracture zone, ie, no opening and closing of the fracture plane under functional loading, to moderate excursions of fragment ends when no or nonstable fixation is performed. The range of motion, which is dependent on whether or not a fracture is treated, and in which way, determines the healing pattern. Dependent on the biological and biomechanical environment, three basic scenarios can be differentiated: 1. Primary bone healing (contact or gap healing) 2. Secondary bone healing via callus formation 3. No bone healing

a

1

Primary bone healing

In cases where interfragmentary motion can be completely avoided, a healing pattern results which is characterized by an increased amount of intracortical remodeling, inside and in between the fragment ends. Bony contact between the fragments is necessary to maintain stability. This is the case in compression osteosynthesis, buttressing conditions, or load-bearing osteosynthesis. Contact areas and gap zones of different widths characterize the morphological situation between the fragment ends. In contact zones, the Haversian remodeling proceeds through the fracture plane. This leads to a direct bony bridging by a structure which is already mature bone and is oriented in the preinjury axial direction (Fig 1.3.3-1a–b). In the neigh-

b

Fig 1.3.3-1a–b a Functionally stable fixation of a mandibular fracture with excellent repositioning as a precondition for primary bone healing. b Enlarged section of (a): primary bone healing contact area, direct bony bridging showing osteons crossing the fracture area.

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boring non-loaded areas (gaps) a minimal amount of motion is possible, but it is limited by the elastic deformability of the neighboring contact zones. As long as there is no destruction of bone in the contact areas, the motion in the gap is small enough to keep interfragmentary strain below 2%. This process allows for the direct formation of bone as well. Within these gaps, granulation tissue appears first, bringing in new blood supply. While loose connective tissue can be observed only briefly in the center of the gap, the deposition of lamellar bone starts early on the surface of the bone fragment ends. This lamellar bone deposition continues until the whole gap is filled. After the complete filling of the gaps with lamellar bone in a direction parallel to the fracture surface, osteons originating in the fragment ends cross the filled gap and enter the other fragment. Thus, the fragments are united by lamellar bone structures that are arranged parallel to the long axes of the bone (Fig 1.3.3-2a–b). This process is called primary or direct bone healing, since it does not proceed through the entire tissue differentiation cascade

a

that one observes in the secondary healing process via callus formation. The process of primary healing leads to a gradual disappearing of the fracture line on the x-ray. Since this healing pattern is characterized by an absence of callus formation, it is difficult to judge the progress of healing on x-rays. The intracortical remodeling of a fracture zone is a slow process, and such a fracture needs protection by the plate over a prolonged period. The time span during which a fracture plate needs to be in place is dependent on individual factors like loading patterns, bone quality, fracture patterns, eg, comminuted vs simple fractures, and patient compliance. On average, a period of 6 months is sufficient for all possible scenarios. The pattern of direct healing per se is not a goal to strive for, but the absence of this pattern, ie, the formation of periosteal callus under conditions of plate fixation is an indicator that complete immobilization was not achieved. Too much motion, often combined with a jeopardized circulation and eventually an infection, may result in a delayed healing or even nonunion.

b

Fig 1.3.3-2a–b a Stable fixation, load sharing with contact area superiorly and gap area inferiorly. b Enlarged section of (a): primary healing gap area: complete filling of the fracture gap with lamellar bone in a direction parallel to the fracture surface.

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2

Secondary bone healing via callus formation

In cases when no fracture fixation or just loose adaptation fixation is done, macromotion between the fragment ends occurs. Under these conditions direct bone healing is not possible. The strain in between the fragments exceeds what bone can tolerate, and new bone developing between the fracture ends would be destroyed before it is formed. The disruption of the bone’s integrity is not the only damage caused during a fracture. The trauma also causes an interruption of circulation of larger vessels and especially of microcirculation within the bone. The vessels of the Haversian and Volkman canals are occluded over a distance of a few millimeters from the fragment ends within the first few hours following an injury. This is the cause for resorption at the fracture ends. During the course of secondary healing, periosteal and endosteal callus is formed. In between the fracture ends a tissue differentiation cascade takes place, during which stiffness and strength increases and strain tolerance gradually de-

a

creases. The differentiation cascade starts with a hematoma, thereafter granulation tissue develops which proceeds through connective tissue, fibrocartilage, and mineralized cartilage to woven and finally to compact bone. During this tissue-differentiation process, the stiffness and strength increases until the end when the interfragmentary space is totally reossified.

3

Steps of differentiation cascade

Hematoma

Initially a hematoma is found between the fragment ends (Fig 1.3.3-3a–b). The function of the hematoma in the course of fracture healing is still controversial. There is some evidence that the leukocytes within the blood may transform into fibroblasts and other cells of the supporting tissue system. The hematoma might as well act as a guiding structure, which, as a spacer, determines the size and shape of the callus. Then fibroblasts occur within the hematoma.

b

Fig 1.3.3-3a–b a Secondary bone healing under the condition of motion between the fracture ends. b Enlarged section of (a). Secondary bone healing, phase 1: hematoma filling the fracture gap.

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Granulation tissue/connective tissue

Next the hematoma changes to granulation tissue, and then connective tissue develops from the granulation tissue (Fig 1.3.3-3c). The maturation of this granulation tissue results in increased stiffness. The elongation to rupture is found to be between 5% and 17%. Fibrous tissue is found in areas where tensile forces act, while, according to Pauwels, cartilage is formed in zones of hydrostatic pressure.

Hematoma

Granulation tissue

Interfragmentary connective tissue

Fig 1.3.3-3c Same section of (a) as in (b). Secondary bone healing, phase 2: granulation tissue and connective tissue replacing the hematoma in the fracture gap.

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Fibrocartilage

The next step is the development of fibrocartilage (Fig 1.3.3-3d) which, with further development, becomes mineralized cartilage which then is replaced by woven bone and finally

Fig 1.3.3-3d Same section of (a) as in (b). Secondary bone healing, phase 3: fibrocartilage replacing the connective tissue in the fracture gap.

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by compact bone (Fig 1.3.3-3e). The mineralization of fibrocartilage progresses from the fragment ends toward the center of the fracture gap. This pattern of fracture healing results in a rapid gain of mechanical strength that can be attributed to the increasing amount of bone material formed. In cases of too much motion, this healing cascade can be interrupted and may then end in nonunion or pseudarthrosis.

Fig 1.3.3-3e Same section of (a) as in (b). Secondary bone healing, phase 4: woven bone replaced by lamellar bone through Haversian remodelling.

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4

Nonunion

Nonunion exists when repair is primarily not possible and surgery is required to bring about union. In those cases in which either the distance in between the fragment ends is too wide, or there is too much unfavorable motion in between the fragment ends, or biological factors like vascularization are unfavorable, or infection occurs, complete healing may be impossible and nonunion will occur. Unphysiological mobility will then be the result. Nonunion and pseudarthrosis (in German terms) are the same, while in the English literature a pseudarthrosis is only the condition which shows a true false joint and therefore is considered as the end point of a nonunion.

5

Delayed union

Delayed union is primarily a clinical term describing a prolonged healing period, while the histological healing cascade is similar to regular healing. Delayed union can result from a biologically difficult environment (eg, reduced blood supply, irradiation).

Nonunions in the craniofacial area are rare. In most instances the correct treatment is sufficient stabilization with a plate.

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1 General aspects 1.4 Implant materials and types

1.4.1 Metals, surfaces, and tissue interactions

39

1

Metals

39

2

Surfaces

40

3

Tissue interactions

41

4

Summary

43

1.4.2 Biodegradable osteosynthesis: past, present, and future

45


53

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Authors Robert G Richards, John A Disegi

1.4.1 Metals, surfaces, and tissue interactions

Implant requirements

1

The selection of implant material depends predominantly on the function to be accomplished and also on the manner in which the implant will be applied. Materials applied for internal fixation must fulfill various fundamental mechanical requirements. Of the potential biomaterials available, only metal can currently provide the stiffness and strength required as well as ductility and, importantly, biopassivity for the majority of craniomaxillofacial (CMF) fracture fixation applications. Resorbable and nonresorbable polymers are also used for specific CMF applications when the implants are subjected to relatively low stress. In terms of bone fracture fixation and eventual bone healing, material stiffness is essential since it functions to avert buckling at the injury site as well as reducing fracture-site movement so that tissue repair will occur correctly. The ductility of a material determines the degree to which a device can be deformed or contoured. As titanium (Ti) has a lower ductility compared with stainless steel (SS), Ti provides less warning and can be a cause of handling issues resulting in breakage for the surgeon. The strength of a device (level of load that can be tolerated by the implant before failure) is also a consideration as it is required to maintain reduction and stability of the fracture site. Even more significant is a material resistance to fatigue brought on by repetitive load. Although SS has a better resistance to static load compared with Ti, Ti and its alloys prove superior under high cycle fatigue–loading conditions.

Metals

Type 316L SS meeting ISO 5832-1 and ASTM F 138/139 material standards has been used for AOCMF implants for more than 20 years. The trend in the last 20 years has been a replacement of SS by Ti for CMF applications because removal is not suggested. The driving force behind this change is primarily related to the superior corrosion resistance, lower stiffness, and enhanced diagnostic imaging compatibility associated with Ti and its alloys. Implant-quality 316L is an iron-base alloy with approximately 62.5% iron, 18% chromium, 14% nickel, 2.5% molybdenum, and minor elemental additions. Titanium is essentially pure Ti which is available in five grades according to ISO 5832-2 with different ultimate tensile strength, 0.2% yield strength, and elongation or ductility combinations. Minimum tensile properties for annealed Ti grade 1 extra low interstitial, grades 1–4, Ti-6Al-7Nb alloy, and Ti-15Mo alloy are compiled in Table 1.4.1-1 for bar product. Titanium15Mo alloy can be provided in either the b or the a + b condition depending on the heat treating temperature that is selected. Titanium alloys, such as Ti-6Al-7Nb or Ti-15Mo, may be selected when a higher stress resistance is required. Ti-6Al7Nb tends to exhibit higher tensile strength but lower ductility compared with Ti. Ti-15Mo is a relatively new Ti alloy that offers some improved implant design opportunities

Alloy

Ultimate tensile strength, MPa

0.2% yield strength, MPa

Elongation, %

Standards

Ti grade 1 extra low interstitial

200

140

30

ISO 5832-2

Ti grade 1

240

170

24

ISO 5832-2 ASTM F67

Ti grade 2

345

275

20

ISO 5832-2 ASTM F 67

Ti grade 3

450

380

18

ISO 5832-2 ASTM F67

Ti grade 4

550

483

15

ISO 5832-2 ASTM F67

(b) Ti-15Mo

690

483

20

ASTM F 2066

(a + b) Ti-15Mo

900

800

12

ASTM F 2066

Ti-6Al-7Nb

900

800

12

ISO 5832-11 ASTM F1295

Table 1.4.1-1 Minimum tensile properties for annealed titanium (Ti) implant materials.

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1 General aspects 1.4 Implant materials and types 1.4.1 Metals, surfaces, and tissue interactions

because of superior notch sensitivity and reverse-bending properties compared with Ti. The density of Ti is about 57% of SS density. This decrease in density equates to a weight reduction of approximately 50% when comparing materials of similar volumes. The lower implant weight compared with an identical SS implant is not a major patient comfort factor for relatively small CMF implants. The modulus of elasticity for Ti is about 55% of SS, and for an equivalent cross-sectional area, the stiffness of a Ti implant is 55% of an SS implant. Physical properties are shown in Table 1.4.1-2 . The general corrosion and fretting corrosion properties of Ti and Ti alloy plates and screws are superior to SS. A reduction in the amount of in vivo corrosion products minimizes the foreign body reactions to maintain a satisfactory biocompatibility response. Titanium and Ti alloy implants may be mixed without causing any objectionable galvanic corrosion effects. Implant quality SS and Ti materials are completely nonmagnetic and will not cause torque or displacement during magnetic resonance (MR) imaging. MR heating is a separate issue that is related to implant geometry. Long and thin implants, like K-wires, cables, and so on, with specific lengthto-diameter ratios may show a temperature rise due to ½ wavelength resonance heating effects. ASTM F 2182 states that metal structures less than 2 cm in dimension are not expected to exhibit clinically significant radio frequencyinduced temperature rise during MRI. Compared with SS, MR visualization of Ti is significantly improved because less artifact or starburst is created. Approximately 40% less MRI interference is experienced with Ti devices compared with SS devices due to the lower magnetic susceptibility of Ti, giving Ti implants a distinct advantage over SS in the CMF region. Turbo spin-echo and fast spin-echo MR pulse sequences tend to provide the lowest amount of artifact for all metal biomaterials.

Alloy

Density, gm/cc

Modulus of elasticity, GPa

All Ti grades

4.51

103

Ti-6Al-7Nb

4.52

105

(b) Ti-15Mo

4.96

78

(a + b) Ti-15Mo

4.96

105

2

Surfaces

Allergic reactions to nickel have been identified in about 3–5% of the general patient population and can approach 15% or higher in selected patient subsets. The 14.5% nickel content in SS is sufficient to cause nickel sensitivity reactions in patients who already have a history of metal allergies. Titanium does not contain nickel as an intentional addition and the typical nickel content is less than 0.02%. An advantage of Ti is its ability to readily form a naturally occurring oxide layer on its surface which provides additional corrosion protection. Therefore, when subjected to deformation damage during surgery, the oxide layer will spontaneously re-form as long as oxygen is present and will protect the material. This layer ranges between 5 and 6 nm in thickness but anodizing can increase this thickness. Final surface treatments for Ti implants include standard nitric acid immersion or electrochemical anodizing reactions that increase the thickness of the protective Ti oxide (TiO2) or mixed oxide (ie, TiO2 + Al2 03 + Nb2 O5) film. Titanium implants are immersed in a chemical solution and a known electrical voltage is applied for a specified time. The thickness of the oxide film determines the color that is observed due to visible light diffraction within the oxide film. No pigments or organic-coloring agents are present in the anodized Ti film. Titanium anodizing is capable of producing a variety of colors that permit the design of color-coded implant systems. Various studies indicate that anodizing removes objectionable surface contaminants, improves the corrosion resistance, has minimal effect on fatigue properties, and provides excellent biocompatibility. Multiple steam sterilization cycles will not significantly change the appearance of anodized Ti. Modified anodized films with unique properties and specialized organic coatings are under development to provide specific implant surface modifications. The anodized layer readily repassivates if the oxide becomes damaged, making Ti an extremely corrosion-resistant material. The oxide layer is capable of protecting cells from toxic-alloying elements and ultimately it is the oxide layer that produces a

Table 1.4.1-2 Physical properties of titanium (Ti) alloys.

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cellular response and not that of the bulk material composite. Thermal and electrochemical anodization of Ti surfaces does not have any deleterious effect on fibroblast cell cytocompatibility in vitro. Moreover, there appears to be an absence of allergic reaction to Ti attributed to the absence of appreciable quantities of chromium, cobalt, and nickel, a distinct advantage over SS. Titanium dioxide is often used as a basis for many cosmetics because of the lack of allergic response experienced. In 1997, Rogers et al showed that wear debris generated by Ti-6Al-4V incited an increase in inflammatory response factors, such as PGE2 and IL-1, in comparison with TAN (Ti-6% aluminum-7% niobium) and Ti. X-ray photoelectron spectrometry for surface chemical analysis reveals that an oxide film consisting of TiO2 , Al2 O3 , and NbO5 occurs on the surface of TAN. The insolubility of this stable oxide layer is responsible for the excellent biopassivity reported, and the assorted oxide film demonstrated by TAN is chemically more stable compared with the oxide layer formed on Ti.

3

Tissue interactions

When inserting a wire, screw, pin, plate, or any other fracture fixation device into the body, regardless of the material or materials used, the implant is coated with a proteinaceous film within seconds of contact with the blood. Blood contains over 2,000 proteins which can interact with the surface of an implant. The proteins provide a provisional matrix for the cells to adhere to and represent the primary matrix in which cells interact. Platelets from the blood arrive at the scene from the blood and upon adherence to a surface the platelets contract, resulting in a process known as degranulation. This involves the release of intracellular contents, such as potent platelet activators, which in turn recruits additional platelets to the wound site. Macrophages and other inflammatory cells (granulocytes, lymphocytes, and monocytes) also infiltrate the hematoma and function to prevent infection and to secrete cytokines and growth factors. The growth factors possess chemotactic activity, thus serving as migratory signals for repair cells, such as osteoblasts, fibroblasts, monocytes, neutrophils, and leukocytes.

The cells arrive at the scene within minutes from the blood and can adhere to the protein matrix which has adsorbed to the surface (determined by the properties of that surface). However, the cells never interact directly with the bare implant surface (the oxide). Cells bind to Ti and its alloys through a series of adhesive molecules, such as vitronectin and fibronectin. Increased cell attachment is directly proportional to the amount of pre-adsorbed protein. Implant surface microtopography is important in osteoblast-mediated adhesion. Integrin-mediated binding to pre-adsorbed proteins on an implant is substrate dependent, eg, α5β1, the receptor for fibronectin, increases on micro-rough Ti surfaces. At the same time as the cell migration to the implant starts, the hematoma retracts. The ability of an implant surface to retain fibrin attachment during this retraction phase is crucial in determining if migrating cells will reach the device surface. The complexity of a micro-rough Ti surface oxide provides a 3-D topography so that fibrin remains sufficiently attached to the implant to withstand retraction, allowing for cell migration to the surface. Cell adhesion is often followed later by either soft-tissue adhesion or eventual bony integration, depending on the implant surface and implantation site. The molecular events at the implant surface/tissue interface are controlled by the surface properties (the oxide, not by the underlying bulk material properties). The oxide surface properties include charge, chemistry, heterogeneity, hydrophobicity, and topography. Topography has the utmost significance for interaction with the surrounding tissues of currently used clinical metal implants. All the properties help determine which proteins adsorb to the surface, their orientation, and the types of intermolecular forces that occur between the surface and adsorbed proteins. These surface properties are not directly visible to the surgeon but are fundamental controllers of the biological success of an implant and all interrelate with each other, eg, changing surface chemistry alters the surface charge and can influence hydrophobicity and topography at the nano level (but the effects of the associated changes can be minimized). Early soft-tissue integration with associated vascularization at the tissue-implant interface, without liquid-filled capsule

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1 General aspects 1.4 Implant materials and types 1.4.1 Metals, surfaces, and tissue interactions

formation is generally desirable for many areas of the body. Without protein adsorption and cell adhesion, under the presence of micromotion, fibrous capsule formation occurs often surrounding a liquid-filled void at the interface. Under aseptic conditions encapsulation is not problematic but becomes difficult when bacteria are present, since the vascular system is prevented from access to the liquid-filled void, which protects the bacteria. Clinically, this situation is more prevalent with SS implants compared with anodized Ti implants. Increasing micro-discontinuities of SS internal fixation plates prevents formation of liquid-filled fibrous capsules at the soft-tissue interface. Increasing surface micro-discontinuities on the undersurface of SS internal fixation plates also increases bony integration. Unfortunately increasing SS implant micro-roughness with current industrial methods can reduce corrosion resistance of the implant and has also been observed to initiate a macrophage response to the implant. Developments are underway to increase SS implant micro-roughness without reducing corrosion resistance, which could have major benefits for percutaneous implants by allowing soft-tissue integration and vascularization directly at the implant surface which would close a route for bacterial invasion. In special areas the presence of a plate can produce friction for gliding tissues, such as muscles, and in orbital fixation where the plate is liable to become a site for tissue adhesion and inflammation. In such areas encapsulation may be desired to prevent adhesion to the implant surface and possible inflammation. These applications require the development of surfaces that prevent soft-tissue attachment and resultant irritation, and allow free gliding of the overlying tissues. It is extremely unlikely that a liquid-filled void could arise within the space between a plate and the overlying gliding tendon or muscle due to the large tissue displacements during normal use and these movements would also be too large to allow fibrous encapsulation of the plate to occur. This can be achieved by using either SS implants or Ti with good surface polishing to reduce the presence of microdiscontinuities, while maintaining biocompatibility of the metal, since the surface chemistry should not be altered by the correct method of polishing. Mechanical polishing has been applied with success in hand surgery with the Ti alloy Ti-15Mo to prevent tendon adhesion and subsequent rupture. A general review of the use of Ti and SS in fracture fixation with regards to the above aspects has recently been published by Hayes and Richards.

42


Currently clinically used micro-rough Ti implants exhibit unique biocompatibility properties which include soft tissue and bone adhesion to their surfaces. Surfaces with many micro-discontinuities support osteoblast differentiation. An advantage of tissue integration at the surface has been the possibility of less bacterial colonization and reduced infection. Recently it has been shown in vivo that for locked implants where minimal periosteal damage occurs, both material and topography were found not to influence susceptibility to infection, with SS and Ti. The same result that both material and topography were found not to influence susceptibility to infection was found with an intramedullary (non-locked) pin model in the rabbit. However, a point to bear in mind is that the in vivo rabbit models included in the studies did not comprise a fracture, nor was there major trauma to the adjacent soft tissues. Another disadvantage of tissue integration onto Ti and TAN surfaces (alongside prevention of damage to gliding tissues, eg, nerves, tendons, muscles) appears during implant removal. Indications exist to suggest that device retention is not ideal. Studies over the years have shown that, subsequent to fulfilling its function, a device can negatively affect the host by evoking foreign body responses. These can produce complications, such as delayed infections, implant breakage, device migration, hindrance of skeletal maturity and growth, nonunions, nonstable fixations, protrusion/intrusion into joint, cosmetic issues, pain, and discomfort including protrusion under the skin or even optically. Exposure of the implant in the oral cavity also can necessitate removal. In craniomaxillofacial surgery implant removal is sometimes indicated to allow insertion of dental implants and prosthesis. Bone growth through and between the empty spaces of a device, such as into a screw head or between the thread of a screw and a plate, significantly increases the difficulty of implant removal. In children alone, approximately 13% of complications encountered during scheduled osteosynthesis material removal are related to the occurrence of excessive bony overgrowth on the device. Reduction in surface micro-topography resulting from surface polishing can potentially affect differentiation of osteoblast cells through genotypic regulation. In vitro work assessed the potential of surface polishing of the clinically available materials Ti, TAN, and Ti15Mo for alleviating excessive bony overgrowth. Polishing reduces surface microdiscontinuities that can be “seen” by the cells producing


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surfaces of high smoothness (Ra less than 0.2 µm) which thereby reduce expression and function of genes specific for osteoblast differentiation and maturation, compared with standard micro-rough counterparts. Surface polishing appears to target the events relating to terminal differentiation as osteocalcin mRNA levels were markedly reduced for polished Ti and Ti alloy samples. Osteocalcin is to date the only ‘osteoblast specific’ marker as it is synthesized, secreted, and deposited by differentiated osteoblasts during mineralization. Translation of the in vitro results to the in vivo situation has been observed with surface polishing of TAN and Ti screws reducing removal torque and the percentage of bone contact in cortical and cancellous bone. Ease of polished locked plate removal from cortical bone and of polished nails has also been shown in vivo. These results cause postulation that bone apposition is not negatively affected by surface polishing, but is accelerated by micro-rough surfaces and that polished devices prevent long-term strong bone adherence. Thus, the combination of the reduced strength of matrix adhesion to polished samples with slower rate of remodeling/apposition relative to standard micro-rough devices would directly influence the occurrence of bony overgrowth and ease removal.

4

Summary

For internal fracture fixation metal presently remains the material of choice since it provides strength for bone fragment support, good ductility for presurgical contouring, and it is generally bio-passive. The large use of metal internal fixators has proven successful; however, more challenging applications for metal internal fixators are emerging. For instance, given the large increase in the occurrence of these procedures in children and the different mechanical and biological requirements based on anatomical site, the requirements of metal implants have become more demanding. Therefore, current metal internal fixator–related research is based on defining specific cell and tissue responses to material surfaces both in vitro and in vivo, as well as ways to direct these site-specific tissue responses through implant surface modification. Upon integration with the surrounding soft and hard tissue, CMF implants have different requirements within different anatomical areas. Permanent implants, such as mandibular joints, need permanent direct osseointegration. External percutaneous fixators should benefit from soft-tissue adhesion to close the entry route for potential microbiological pathogens. It is extremely important that plates in the CMF region should minimize adherence of tissue (nerves, muscles, bone). Fracture fixation implants that are to be removed after fracture healing should prevent direct osseointegration to their surface, since this is not required for their stability. Research is therefore focused on attempting to alleviate the occurrence of removal-related morbidity through surface design. Implant characteristics to control the integration with the surrounding soft or hard tissue include surface roughness, hydrophobicity, and chemistry. Polished surfaces with minimal average roughness of less than 0.2 µm are able to prevent direct osseointegration and reduce extraction torque of screws to ease implant removal. When polishing is performed optimally, it does not change the surface chemistry, hydrophobicity, or biocompatibility. Polishing does not increase susceptibility to infection in mechanically stable osteosynthesis (eg, locked plates).

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1 General aspects 1.4 Implant materials and types 1.4.2 Biodegradable osteosynthesis: past, present, and future

1

Introduction

45

2

History

45

3

Polymer chemistry

47

3.1 Polymer types

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3.2 Molecular weight

47

3.3 Microstructure

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3.4 Isomerism

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3.5 Glass transition temperature

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3.6 Creep

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3.7 Self-reinforcement

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3.8 Processing methods

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3.9 Sterilization

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4

49

Ideal material and mechanical properties

4.1 Ideal material

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4.2 Biomechanical demands

49

4.3 Degradation

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4.4 Handling properties

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5

Present situation

50

6

Future perspectives

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6.1 From clinical demand to implant

51

6.2 Future aims

51

7

51

Conclusion

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Authors Nicolaas B van Bakelen, Jiska M Meijer, Rudolf RM Bos

1.4.2 Biodegradable osteosynthesis: past, present, and future 1

Introduction

Today, most orthognathic procedures and facial skeletal fractures are fixed by using titanium plates and screws. Titanium fixation systems can be used safely and effectively, are easy to handle, and the intrinsic mechanical properties ensure that the device dimensions are kept within acceptable limits. However, these metal systems have some disadvantages. Potential adverse effects associated with metal implants are hot and cold sensitivities, plates palpable under the skin, possible mutagenic effects, interference with later diagnostic or therapeutic radiological investigations, and interference with function and/or growth. Consequently, a second operation to remove the implants is performed after bone healing in 5–40% of patients. Biodegradable plates and screws, degrading after healing time and with gradual transfer of functional forces to the healing bone during disintegration of the biodegradable devices, seem to be the perfect solution for most of the above-mentioned potential disadvantages. There is no need for another surgical intervention to remove the plates and screws. This implies reduction of additional discomfort, risks, operation time, and associated socioeconomic costs.

2

History

Biodegradable devices have been used in the medical field for more than four decades. In 1962, polyglycolic acid (PGA) (Dexon™) was developed by the American Cyanamid Co. as the first absorbable synthetic suture. It has been commercially available since 1970. A copolymer of 92% PGA and 8% polylactic acid (PLA) (Vicryl®) entered the market in 1975 as a competitive resorbable suture. Since 1966 different research groups have been developing resorbable osteosynthesis systems. In 1966, Kulkarni published an article on the implantation of poly(L-lactide) (PLLA) films and membranes. The polymeric films disappeared from the subcutaneous implantation sites in guinea pigs within 6 weeks, causing only a mild inflammatory reaction. A fibrous tissue layer was formed around the implants. Several other animal experiments with PLLA implants followed in the next few years. Mandibular and blowout fractures were repaired with PLLA implants. Although good biocompatibility and bone healing were reported in these experiments, they did not result in any clinical trial. This may be due to the fact that the implants were neither strong enough nor small enough for clinical use. Clinical trials were first performed in the 1980s. Rokkanen, Tormälä, and others from Finland have produced numerous reports on biodegradable PLLA and PGA implants for fracture fixation. They performed clinical implantations in both children and adults. Törmälä et al developed the first commercially available biodegradable PGA/PLA rods (Biofix®) that were suitable for fracture fixation.

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Bos et al fixed zygomaticomaxillary fractures in humans with PLLA plates and screws and reported good early results (Fig 1.4.2-1). However, all patients displayed an unfavorable tissue reaction three years after implantation. Swelling at the site of implantation was clinically detectable (Fig 1.4.2-2). This swelling seemed to be related to massive disintegration of the PLLA implants into many lamellar crystals (Fig 1.4.2-3), as a histological survey after removal indicated. Bergsma et al performed a number of animal experiments and were able to demonstrate this effect again. They concluded that a semi-crystalline PLLA polymer can induce a late and probably persistent swelling when used in a subcutaneous implantation site. Although experiments had been done with other materials, for example polydioxanon, most of them were performed with pure PLLA because it has the best strength properties. However, the late unfavorable tissue reaction induced the development of additives to pure PLLA and/or other biodegradable materials for medical implants. Also non-chemical modifications like self-reinforcement were developed in the next decades.

Tormälä and Rokkanen developed the self-reinforcing technique in 1985. Extensive research (experimental and clinical studies) has been done on the self-reinforced PLLA plates and screws by different research groups. Short-term results were positive; the devices retained their strength long enough for the fractures to heal. However, degradation of self-reinforced PLLA resulted in the same crystals that can cause swelling after a few years. Self-reinforced (70L:30DL) PLA plates and screws were described by Haers and Sailer. In clinical trials rigid fixation was obtained in internal fixation of the mandible and the maxilla. Other materials that have been developed in the last few decades are all still based on PLLA but with additives like polyglycolide and D-lactide. Degradation is faster with these additives, however pure PLLA is still stronger. Clinical trials performed with these materials all resulted in rather good short-term outcomes and acceptable stability was obtained. Buijs et al systematically reviewed the available literature and concluded that the implications for the clinical applicability of biodegradable osteofixation systems in the long term remain inconclusive. There is evidence available from

Fig 1.4.2-2 Swelling at the lateral orbital rim 3 years after implantation of a PLLA plate and screws for fixation of a left zygomaticomaxillary fracture.

Fig 1.4.2-1 Fixation of a right zygomaticomaxillary fracture with a 4-hole PLLA plate and PLLA screws in the lateral orbital rim.

PL P

P R

46


N

Fig 1.4.2-3 Electron microscopical image, 3.7 years after implantation, of membrane-bound (triangles) phagosomes (P) enclosing crystallites and a combination of a phagosome and a non–crystal-bearing vacuole, designated together as phagolysosome (PL). R indicates swollen rough endoplasmic reticulum; N indicates cell nucleus; bar, 400 μm. Uranyl acetate/lead citrate staining.


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randomized controlled trials to support the conclusion that there is no significant difference between biodegradable and titanium osteofixation devices with regard to short-term clinical outcome, complication rate, and infections in the area of orthognathic surgery. Reoperation rates do not significantly differ in the biodegradable and titanium groups. The numerous studies with biodegradable osteofixation devices that have been published hereafter still remain inconclusive; they did not include titanium as a control group, there was no randomization, or only small, unmatched groups of patients were included.

3

Polymer chemistry

Metals, ceramics, and polymers are the three major groups of engineering materials. There are polymers of natural origin (eg, polysaccharide, cellulose, silk, natural rubber, cotton, wool, and leather) and synthetic polymers (eg, polyethylene, polystyrene, polyvinylchloride, polyesters, polycarbonates, polyurethanes, and polytetrafluorethylene). Synthetic polymers are, in general, strong, not too expensive to produce, and have good mechanical properties compared with their natural counterparts. The resorbable synthetic polymers used for manufacturing osteosynthesis devices are certain poly(urethanes), certain poly(esters), and poly(carbonates) like poly(lactide), poly(glycolide), poly(dioxanone), poly(trimethylene carbonate), poly‑ (ε-caprolactone), and their copolymers. 3.1 Polymer types

A polymer is a large molecule consisting of covalently bound smaller units, called monomers. These repeating units resemble the links in a chain and therefore the molecules are often referred to as polymer chains. If only a single type of monomer is used, a homopolymer is formed (-AAAAA-). If two or more types of monomers are used, it is called a copolymer. In a random copolymer the different subunits of a copolymer are arranged randomly (-AAAABBAABBBABABAA-). In a block copolymer the subunits are arranged in alternating long regions (-AAAABBBBAAAABBBBAAAA-). The properties of a copolymer differ significantly from the properties of the homopolymers consisting of one of the monomers of the copolymer.

Polymer chains may be linear or form a branched, crosslinked, or 3-D network. Linear polymers are those in which the monomer units are joined together end-to-end in single chains. These long chains are flexible. Branched polymers are polymers in which the side-branch chains are connected to the main ones. The branches, considered to be part of the main-chain molecule, result from side reactions that occur during the synthesis of the polymer. The chain-packing efficiency is reduced with the formation of side branches, which results in lowering the polymer density. In cross-linked polymers, adjacent linear chains are joined one to another at various positions by covalent bonds. The process of cross-linking is achieved either during synthesis or by an irreversible chemical reaction that is usually carried out at an elevated temperature. Often this cross-linking is accomplished by additive atoms or molecules that are covalently bonded to the chains. Many of the rubber elastic materials are cross-linked. Trifunctional units, having three active covalent bonds, form 3-D networks creating polymers called network polymers. Actually, a polymer that is highly cross-linked may be classified as a network polymer. 3.2 Molecular weight

Forming a polymer, the chemical reactions do not result in the same molecular weight for every single molecule but rather a bell-shaped distribution is present. Mostly the mean molecular weight is cited to describe this—the higher the mean molecular weight and the narrower the bell-shaped curve, the better the mechanical properties of the polymer. Or, the fewer low molecular weight polymer chains in a sample the better the properties. 3.3 Microstructure

A polymer can have an amorphous or a crystalline microstructure. An amorphous microstructure means that the polymer chains are randomly orientated and therefore can easily slip past each other (Fig 1.4.2-4). The result is a relatively weak polymer. Crystalline polymers are ordered polymers in which the chains lie parallel in close proximity to each other and are densely packed and strong. Repeatability along the length of the polymer is a condition for crystallization. Thus, random polymers have little crystalline parts and are amorphous in character. Even crystalline homopolymers are not totally crystalline and will always contain

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both crystalline and amorphous parts (semicrystalline) (F ig 1.4.2-4). When a polymer specimen is loaded, there will be a tendency for the polymer chains to slip and move, resulting in a distortion of the specimen. The longer the polymer chains, the greater the chance that they will entangle. This makes slipping more difficult and increases strength. Finally, under the action of an applied load, a finite amount of time is required for these macromolecules to rearrange and move. A polymer will appear stronger if the load is applied rapidly than if the load is applied slowly. This property of time dependence is called viscoelasticity.

Crystalline regions

Amorphous regions

3.6 Creep

Creep is a time-dependent plastic deformation of materials subjected to a constant temperature and/or load or stress. This means a reorientation of the polymer molecules by which an implant is deformed. In practice, this could result, eg, in loosening of a screw. No literature can be found on the combination of biodegradable implants and creep. 3.7 Self-reinforcement

Self-reinforcement is a process during which randomly orientated crystals are reorganized into highly orientated fibrils. Hereby the mechanical properties enhance and the elements are stiffer and stronger in the direction of their long axis. These devices must be bent at room temperature with pliers, contrary to non-self-reinforcement devices that require heating. The desired shape retains after bending. The plates can also be cut with scissors and an additional hole can be drilled in. 3.8 Processing methods

The processing methods used at present for preparation of experimental or commercial resorbable internal devices, eg, screws, plates, rods, pins, and fibers usually involve meltprocessing and/or machining, extrusion or compression mold of polymeric material. All these methods are far from optimal as they significantly affect the molecular and, hence, mechanical properties of the resulting implants. Fig 1.4.2-4 Schematic drawing of the microstructure of a polymer with crystalline and amorphous domains.

3.4 Isomerism

Two or more compounds with the same molecular formula but with a different atomic arrangement are called isomers. For example, lactic acid has two isomers: D-lactide and L-lactide. 3.5 Glass transition temperature

Metals are often categorized by their melting point. Polymers exhibit a glass transition temperature (Tg) that can be used to classify the thermal behavior of many plastics. Below this temperature the polymer is stiff and hard and above the Tg it is soft, flexible, and rubbery. The Tg is characteristic of the amorphous domains of a polymer. Because a polymer implant will be able to sustain greater loads when its temperature is below the Tg, the Tg of polymeric fixation implants should be above body temperature.

48


3.9 Sterilization

Steam, high-energy (gamma, beta) irradiation, and ethylene oxide (ETO) alone or in mixture with other gases are the media used commonly for sterilization of polymers. Ideally, the medium used for sterilization should adequately sterilize the device without affecting its shape, physical, or chemical properties. In practice this is never the case with biodegradable polymeric devices. Steam and heat treatment at temperatures up to 190° C cause extensive plastic deformation and degradation of resorbable implants and therefore cannot be used at all. High-energy irradiation can result in semicrystalline polymers due to depolymerization, chain scissioning, and cross-linking. Color alterations can appear, caused by a diminished purity. Consequently, material characteristics like tensile strength and elasticity can change by using irradiation. Sterilization with ETO might leave residues in harmful quantities in the implants and on their surface. ETO is mutagenic and carcinogenic. However, when carefully performed, no residues are left. In practice only ETO or high-energy irradiation is used for sterilization of resorbable materials, although both have drawbacks.


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4

Ideal material and mechanical properties

4.1 Ideal material

An ideal biodegradable implant is made of a material that meets the following criteria (some of which are discussed in this chapter): • Can be fabricated and designed with appropriate initial strength to meet the biomechanical demands • Degrades in a predictable fashion and allows safe progressive loading during each stage of bone healing • Causes no tissue responses necessitating device removal • Disappears completely • Easy to use • Cost-effective • Compatible with diagnostic or therapeutic radiation 4.2 Biomechanical demands

The biomechanical demands depend on the maxillofacial area where the device will be used and on the kind of fracture or osteotomy. Generally, a biodegradable osteosynthesis system is exposed to tensile forces, bending forces, shear forces, and compression forces. The screws are especially exposed to torsional forces during insertion. The intrinsic mechanical properties of biodegradable osteofixation systems are less favorable than those of titanium. During screw tightening, large torsional forces develop along its long axis, which can shear off the screw head. In case of a screw breakage, a new hole can easily be drilled through the broken screw and a new screw inserted. 4.3 Degradation

Biodegradable materials usually degrade in vivo through a two-phase process. During phase 1, water molecules hydrolytically attack the chemical bonds, cutting long polymer chains to many short chains. Enzymes can possibly enhance this process. Other factors that can influence degradation are, for example, molecular weight, orientation, isomerism, and crystallinity. The most important effect during phase 1 is a reduction in molecular weight and because it is easier for short chains to slip past each other than for long chains, polymer strength also diminishes. As this process continues, the polymer implant loses its integrity and is fragmentized. Phase 2 involves the cellular response whereby macrophages and giant cells metabolize the products of phase 1 degradation into substances, such as water and carbon dioxide. The mass of the implant rapidly disappears. Thus, the implant will have lost its strength long before it loses its mass. Soon after implantation there is an initial inflammatory response by the body, as normally occurs during wound healing. This is followed by encapsulation of the implant in

a thin, fibrous membrane, which occurs in response to implants made of any material (eg, stainless steel, titanium, polyethylene). At least a residue of the fibrous membrane will remain after total resorption. Therefore, biodegradable materials are also called bioresorbable or bioabsorbable materials, but in the literature there is no evidence of total in vivo resorption, at least on an electronic microscopic level, of any biodegradable osteosynthesis material. Bergsma et al have concluded that complete resorption of PLLA does not occur after 5.7 years. Amorphous 50:50-poly(D,L)lactide (PDLLA, ResorbX®) and 82:18-poly(L-lactide-co-glycolide) (PGLA, Lactosorb®) completely resorbed after 12 and 14 months on a fluorescence microscopic level. An electronic microscope was not used. Edwards et al also showed complete resorption of PLLA-PGA fixation devices by 18 to 24 months after surgery. Evaluation consisted of x-rays and light microscopy. Residual implant material of amorphous 82:12:6-poly(lactide-co-glycolideco-trimethylene carbonate) (Inion CPS® baby) was found on gross and histological examination (light miscroscopy) at 18 months. Nieminen et al could not detect Inion CPS (composed of L-lactide, D-lactide, and trimethylene carbonate in varying proportions per product) in light microscopy after 2 years. 4.4 Handling properties

Although the biomechanical properties and biocompatibility are a precondition in using biodegradable osteosynthesis systems, handling characteristics are also aspects of a wellconsidered selection and application of osteosynthesis systems (Fig 1.4.2-5).

Fig 1.4.2-5 Two different-sized titanium plates and two differentsized biodegradable plates. From left to right: MatrixMIDFACE strut plate, pure titanium; RapidSorb strut plate 1.5; RapidSorb adaptation plate 1.5; MatrixMIDFACE adaptation plate, pure titanium. Above: titanium screw 1.5; rapid resorbable screw 1.5.

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Surgeons appreciate good handling properties, such as malleability of plates at room temperature and avoidance of bone tapping. Jain et al stated that contouring resorbable plates is easier than metallic plates. With few extra tools (ie, heating bath) resorbable plate systems could be easily handled and adapted. However, biodegradable screws can be inserted only after predrilling and pretapping. Unlike titanium screws, which can be inserted directly after drilling a pilot hole (self-tapping screw) or even without drilling a pilot hole (self-drilling screw). Biodegradable plate bending and screw insertion are time-consuming and still far more complicated compared to titanium plates.

5

Present situation

More than ten different biodegradable osteosynthesis systems are commercially available today. All are copolymers still based on PLLA. Despite the supposed advantages of biodegradable osteofixation devices, these systems have not yet replaced titanium systems and are currently applied in only limited numbers. The intrinsic mechanical properties of biodegradable osteofixation systems are still less favorable than the intrinsic mechanical properties of titanium. Application is therefore especially recommended for the stabilization of sections of the face that are not excessively loaded (midface and cranium). Also, biodegradable systems are much more accepted nowadays in orthognathic and craniofacial surgery than in traumatology. This is probably due to the contaminated, atypical, frequently comminuted fractures in traumatology and the clean, simple, and predictable osteotomy lines in orthognathic and craniofacial surgery. The time-consuming acts of pretapping, screw insertion, and possible screw breakage can be avoided by using the relatively new technique of SonicWeld®. The application of this osteosynthesis system is based on two components: the already well-established resorbable plate and mesh system, ResorbX®, in combination with a new special configured pin system, SonicWeld®. The pin (which replaces the screw known from other systems) is inserted by means of an ultrasonic handpiece. Due to the ultrasound application, the pin is welded into the corticospongy microstructure of the bone and melts together with the plate. The combination of plate-pin provides a more stable complex than can be accomplished by the combination of plate and screws. The thermal stress caused by the ultrasound-aided pin insertion does not lead to a foreign body reaction or induced necrosis. The major drawback to the general use of biodegradable devices is the lack of clinical evidence that they dissolve completely without complications or remnants while biomechanically performing similar to titanium implants.

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6

Future perspectives

6.1 From clinical demand to implant

The complete process of the development of a new biodegradable osteosynthesis system can easily take 15 years. First, a surgeon identifies a clinical demand or need. A technologist and material scientist develops the material and prototype. This material has to be evaluated in a laboratory, for example, by a biologist and a material scientist for toxicity. Thereafter, animal studies have to be performed by a surgeon and a cell biologist. An industrial designer will take care of the manufacturing, sterilization, and packaging. Finally, the surgeon can clinically evaluate the product. 6.2 Future aims

Some aims for future research can be formulated. The potential mechanical properties are still untapped, and stronger and stiffer biodegradable plates and screws could be developed. With a stronger material the dimensions could be reduced to microplate dimensions which would generate more indications. The degradation mechanism is not yet fully understood and more research on this topic could enhance the safety of using biodegradable implants, especially in children. Adverse reactions could be observed in more detail. New sterilization methods that do not cause degradation should be a big advantage in the practical use of the materials.

7

Conclusion

Despite extensive study for more than 40 years, biodegradable materials have not replaced metallic osteosynthesis devices except for some limited indications. Current and future research will have to solve problems like limited mechanical properties, appropriate degradation, biocompatibility, sterilization, shelf life, and comfortable handling before biodegradable devices will be as safe and effective as metallic ones. The socioeconomic and psychological advantages of resorbable osteosyntheses over metallic ones make it valuable to develop them. Considering the intrinsic properties of polymers, it is questionable if biodegradable polymeric osteosyntheses will ever fully banish metallic osteosyntheses from the market.

Besides these aims for further research on the existing materials, new materials could be developed for osteosynthesis. There is also an urgent need for sufficiently powered, highquality, and appropriately reported randomized controlled trials with respect to biodegradable osteofixation devices vs nondegradable osteofixation devices for well-defined maxillofacial fractures and osteotomies. Future studies should include a cost-effectiveness analysis in which hospital admission costs, surgical costs (material and operating room time), and the costs associated with sick leave of the patients should be analyzed.

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1 General aspects 1.4 Implant materials and types 1.4.3 Design and function of implants

1

Introduction

53

2

Implants

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2.1 Screws

54

2.2 Function of screws

58

2.3 Types of screws

58

2.4 Technique and instruments for screw insertion

59

3

60

Plates

3.1 Function of plates

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3.2 Craniofacial plates

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3.3 Mandibular plates

67

4

External fixators

70

5

Distraction devices

71

6

Instruments

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7

Power tools

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Author Richard H Haug


1

Introduction

High-quality implants and instruments are essential for successful internal fixation and reconstruction. Implants must come with defined and reliable mechanical and biological properties. They must be biocompatible, non-toxic, and corrosion resistant. Meticulous quality control during the production process is required. Implants and instruments require in most countries official certification of their safety and effectiveness based on legislative compliance regulations such as the European Medical Device Directive (93/42/EEC) or the Code of Federal Regulations (21 CFR 860) in the United States of America.

The gold standard material for craniofacial implants is titanium and its alloys, however, for some applications biodegradable implants may be considered. In the past, stainless steel and vitallium implants were used (Table 1.4.3-1). Most instruments are made from stainless steel, but instruments made of non-ferrous materials are also available for use within open magnetic resonance imaging.

Implant material

Specification

Composition

Commercially pure titanium

Grade 1

Ti (99%), N (0.03%), C (0.08–0.10%), H (0.015–0.0125%), O (.18%), Fe (.20%)

Grade 2

Ti (99%), N (0.03%), C (0.08–0.10%), H (0.0125%), O (.25%), Fe (.30%)

Grade 3

Ti (99%), N (0.05%), C (0.08–0.10%), H (0.0125%), O (.35%), Fe (.30%)

Grade 4

Ti (99%), N (0.05%), C (0.08–0.10%), H (0.0125%), O (.40%), Fe (.50%)

Stainless steel alloy

316 L

F e (approximately 65%), Cr (17–19%), Ni (13–15%), Mo (2.25–3.0%), N (0.1%), C (0.03%), Mn (2%), P (0.025%), Si (0.75%), Cu (0.50%)

Cobalt-chromium alloy

Vitallium

Co (58–65%), Cr (27–30%), Mo (6.0%), C (0.4%), Mn (1.0%), Si (1.0%), Fe (5.7%)

Titanium aluminum niobium alloy

TAN

T i (approximately 87%), Al (5.5–6.5%), Nb (6.5–7.5%), N (maximum 0.05%), C (maximum 0.8%), H (maximum 0.009%), O (maximum 0.20%), Fe (maximum 0.25%), Tn(maximum 0.5%),

Titanium molybdenum alloy

Ti-15Mo

T i (approximately 85%), Mo (14–16%), N (maximum 0.05%), C (maximum 0.10%), H (maximum 0.015%), O (maximum 0.20%), Fe (maximum 0.10%)

Poly L-lactic acid (PLLA) and Poly D, L-lactic acid (PDLA) combination

70% PLLA/30% PDLA

Poly (L-lactide-co-glycolide)

85% L-lactide/15% Glycolide

Table 1.4.3-1 Plate and screw materials (examples).

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2

Implants

2.1 Screws

The basis for current rigid internal fixation is the interaction between screws, plates, and bone. To understand this interaction, the surgeon must first understand the screw, its components, and intended functions. To simplify the description of the screw components, the glossary of screw terminology should be reviewed (Table 1.4.3-2) along with

a schematic representation of a typical screw (Fig 1.4.3-1). The first basic component of the screw is the core. This is generally the same diameter as the drill required to create the receptacle site within the bone that receives the screw. The outer diameter is the thread width. The threads engage the bone and provide resistance to pullout forces. It is this outer thread diameter that is the name-determinant of the particular screw or screw/plate system (for instance, 1.0 mm, 1.3 mm, 1.5 mm, 2.0 mm and so on) in conventional systems.

Head

The superior portion or cap of the screw that is attached to the core. It contains a recess for the screw driver.

Core

The center substantive portion of the screw to which the head and threads are attached.

Thread

That portion of the screw attached to the core that engages the bone. Thread diameter describes the width of the screw measured from the edge of the thread on one side to the other side. The outer thread diameter is associated with the description of the screw or plate system (eg, 1.0, 1.3, 1.5) in conventional systems, not in the Matrix systems.

Pitch

The distance between threads.

Flutes

The channels cut through the outer threads and into the core of the tip of a screw intended to collect bone debris.

Self-tapping

A screw that has been designed to be used without tapping. This requires at least two flutes at the tip of the screw that extend superiorly for at least two threads.

Self-drilling

A screw that has been designed to be used without drilling and tapping. This is a screw that is tapered to a point and possesses at least two flutes at the tip of the screw that extend superiorly for at least three threads.

Cruciform head

A screw head that has a flat cross-like recess with centered dimple that fits intimately with the corresponding screwdriver.

PlusDrive head

Optimized cruciform drive • Easy to pick up the screws • Improved retention in comparison to the conventional cruciform drive • Easy to re-engage the screwdriver in situ

Matrix head

Optimized PlusDrive

Emergency screw

When the threads in bone have stripped, or the hole was driven too large, then the next largest outer thread diameter screw is called an emergency screw in clinical terminology. A more accurate term would be a salvage screw.

Table 1.4.3-2 Glossary of terms for screws.

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The Matrix plating systems for the craniomaxillofacial skeleton have a different denomination according to the areas of application (midface, mandible, orthognatic) and the plate sizes. The head of the screw engages the plate or bone to maintain stability, and is also used by the screwdriver to insert the screw. The different types of screw heads correspond to the varying screwdriver types. For Synthes titanium screws, these are cruciform, PlusDrive, or Matrix. The distance between the threads is the pitch.

Intermaxillary fixation (IMF) screws have two holes underneath the head in a 90 degree angle to each other. RapidSorb screws are made of 85% L-lactide/15% glycolide. They are available as 1.5, 2.0, and 2.5 mm (emergency screw) with a cruciform recess head. For insertion of resorbable screws, drilling and tapping is mandatory. As an alternative to screws, resorbable tags with a diameter of 1.5 mm are available. After drilling, a tag is pressed through the plate into the drilled hole thus fixing the plate to the bone (Table 1.4.3-3a–c).

Head diameter

Cruciform recess

Thread pitch

Outer thread diameter

PlusDrive

Flute Core diameter

Self-drilling tip

Self-tapping tip

Matrix recess

Fig 1.4.3-1 Craniomaxillofacial screws are fully threaded. Self-drilling or self-tapping screws are available.

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Resorbable screws

Matrix system

Compact system

Screw (midface)

Thread (mm)

Core (mm)

Pitch (mm)

Head ø (mm)

Length (mm) *

Drive

1.0 mm, self-tapping or self-drilling

1.0

0.7

0.25

1.6

(1.2 mm Emergency)

(1.2)

(0.9 )

(0.25)

1.6

Self-tapping: 2, 3, 4, 5, 6, 7, 8 Self-drilling: 2, 3 Emergency: 2, 3, 4, 5, 6, 7, 8

Cruciform and PlusDrive. (Self-drilling screws with PlusDrive only)


1.3

0.9

0.5

2.4

(1.7 mm Emergency)

(1.7)

(1.1)

(0.6)

1.4

Self-tapping: 3, 4, 5, 6, 8 Self-drilling: 4, 5, 6 Emergency: 3, 4, 5, 6, 8



1.5

1.1

0.5

3.0

(2.0 mm Emergency)

(2.0)

(1.4)

(0.6)

3.0

Self-tapping: 4, 6, 8, 10, 12, 14,18 Self-drilling: 4, 6, 8 Emergency: 6, 8, 10, 12



2.0

1.4

0.6

3.5


(2.4 mm Emergency)

(2.4)

(1.7)

1.0

3.5

Self-tapping: 4, 6, 8, 10, 12, 14, 16, 18 Self-drilling: 4, 6, 8 Emergency: 6, 8, 10, 12:

MatrixMIDFACE, self-tapping or self-drilling

1.5

1.2

0.6

2.6

Matrix

MatrixMIDFACE, emergency

1.8

1.5

0.6

2.6

Self-tapping: 3, 4, 5, 6, 8, 10, 12 Self-drilling: 3, 4, 5, 6, 8 Emergency: 3, 4, 5, 6, 8, 10, 12

MatrixOrthognatic screw, self-drilling MatrixOrthognatic screw, self-tapping Emergency screw

1.85

1.5

0.6

2.6

4, 5, 6, 8

Matrix

1.85

1.5

2.1 2.1

1.7 1.7

0.6 1.0 0.6 1.0

2.6 3.0 2.6 3.0

4, 5, 6, 8 10, 12, 14, 16, 18 4, 5, 6, 8 10, 12, 14, 16, 18

Rapid resorbable screw 1.5 mm

1.5

1.15

0.6

2.5

3, 4, 5, 6, 8

Cruciform

Rapid resorbable screw 2.0 mm Rapid resorbable screw 2.5 mm (emergency)

2.0 2.5

1.6 2.0

0.75 0.75

3.2 3.2

4, 6, 8 4, 6, 8

Cruciform

Table 1.4.3-3a Craniofacial screws: midface (Compact and Matrix systems). * Underlined numbers indicate the length of the screws shown in this table.

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Matrix system

Compact system

Screw (mandible)

Thread (mm)

Core (mm)

Pitch (mm)

Head ø (mm)

Length (mm) *

Drive

Cortex screw 2.0 mm, self-tapping or self-drilling

2.0

1.35

0.75 (4–6 mm length) 1.0 (8–18 mm length)

3.5

PlusDrive (TAN) and Cruciform (TiCp)

Emergency screw 2.4 mm

2.4

1.7

1.0

3.5

Self-drilling and self-tapping: 4, 6, 8 Self-tapping only: 10, 12, 14, 16, 18 Emergency: 6, 8, 10, 12

2.4 mm TM Trauma, self-tapping

2.4

1.7

1

4.0

Cruciform

Emergency screw 2.7 mm, self-tapping

2.7

1.9

1

4.0

6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40 Emergency: 8, 10, 12, 14, 16, 18

LOCK 2.0 mm, (locking), self-tapping or self-drilling

2.0

1.35

0.75

3.3

Self-tapping: 5, 6, 8, 10, 12, 14, 16, 18 Self-drilling: 5, 6, 8

PlusDrive

UniLOCK screw 2.4 mm, self-tapping UniLOCK screw 2.7 mm, self-tapping UniLOCK screw 3.0 mm, self-tapping

2.4

1.7

1

4.0

Cruciform

2.7

1.7

1

4.0

3.0

2.4

1

4.0

8, 10, 12, 14, 16, 18, 20, 22 8, 10, 12, 14, 16, 18 8, 10, 12, 14, 16, 18

2.0 mm, self-tapping

2.0

1.4

1

3.5

5, 6, 8, 10, 12, 14, 16, 18

Matrix

2.4 mm, self-tapping 2.7 mm, self-tapping (emergency)

2.4

1.8

1

3.5

Matrix

2.7

2.1

1

3.5

5, 6, 8, 10, 12, 14, 16, 18 5, 6, 8, 10, 12, 14, 16, 18

2.0 mm locking, self-tapping

2.0

1.4

1

3.3

5, 6, 8, 10, 12, 14, 16, 18

Matrix


2.4

1.8

1

3.3

8, 10, 12, 14, 16, 18

Matrix


2.9

2.3

1

3.3

8, 10, 12, 14, 16, 18

Matrix

PlusDrive and Cruciform

Table 1.4.3-3b Mandible screws (Compact and Matrix systems). * Underlined numbers indicate the length of the screws shown in this table.

Screw (IMF) IMF screw

Thread (mm)

Core (mm)

Pitch (mm)

Head ø (mm)

Length (mm) *

Drive

2.0

1.35

0.75

4.0

8, 12

Cruciform

Table 1.4.3-3c Screw for intermaxillary fixation (IMF). * Underlined number indicates the length of the screws shown in this table.

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2.2 Function of screws

The purpose of screws is to stabilize bone, to secure a bone to a plate or a plate toward bone, to compress bone, or to fix special appliances such as distractors. Stabilization of bone can be accomplished by screws only (positional or compression technique) or by securing the bone to a plate. Compression can be accomplished via the lag screw principle or by the spherical gliding principle with a dynamic compression plate. While the concept of compression is currently controversial regarding its necessity for bone healing, compression does help to increase the stability of the reduction. 2.3 Types of screws

The nomenclature for screws (and the entire plate/screw system) in conventional systems follows the measurement of the outer thread diameter and the screw type. The outer thread diameter is measured in millimeters. Thus, 2.4 refers to a 2.4 mm outer thread diameter. Two basic types of metal screws are in clinical use, conventional screws with a single thread and locking head screws. All Matrix Midface screws have an identical diameter of 1.5 mm and emergency screws of 1.8 mm. However, Matrix Mandible screws come in different outer thread diameters (2.0, 2.4, 2.7 emergency, and 2.9 mm) and can be used with all Matrix Mandible plates.

Three subtypes of conventional screws exist. The first screw generation needed pretapping with a tap of corresponding size. Today only biodegradable screws need pretapping to avoid shearing-off of screw heads during insertion. A selftapping screw eliminates the need for preparing the bone with a tap. This inevitably saves steps in the procedure and therefore time. The tapping procedure removes select amounts of bone and creates an intimate receptacle for the screw. The flutes at the end of the self-tapping screw act as a tap and collect bone debris as the screw is advanced. A self-drilling and self-tapping screw eliminates the need for a drill, thus saving time by eliminating steps. The tapered edge of this type of screw acts as a drill, but is only used in limited circumstances based on the bone quality. Locking head screws are screws with two threads, one to anchor the screw in the bone and a second thread to lock the screw to the plate. For locking head screws, the pitch along the core must be proportional in ratio to the pitch along the head (Fig 1.4.3-2). This permits engagement of both the bone and the plate. A disproportional pitch would not permit engagement of the plate.

Thread for the plate

Thread for the bone

Locking head screw recess

Fig 1.4.3-2 Locking head screw.

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Locking head screws are a considerable advancement in plate/screw technology. Whereas conventional screws act by pressing the plate to the bone, locking head screws are locked into the plate (Fig 1.4.3-3a–b). Locking plate-screw combinations thus become a form of internal “external fixator.” They do not depend upon the integrity of the outer table of bone to keep the plate/screw/bone interface intact and stable. They are particularly advantageous in bone of reduced quality. Moreover, because the screw is locked to both the plate and bone, relative movements between the plate, screw, and bone will not occur. This reduces fretting (movement between plate, screw, and adjacent or overlying tissues) and ultimately, fretting corrosion as well as screw loosening.

a

2.4 Technique and instruments for screw insertion

While the placement of screws might at first seem relatively simplistic, there are certain caveats that assure greater stability, better healing, and less breakage of the screw. The drill corresponding to the screw to be inserted is the same diameter as the core of the screw (Fig. 1.4.3-4). The drill should be used with the appropriate power tool described in the sections to follow. It should be stabilized adjacent to the bone or plate with the corresponding drill guide. This permits concentricity of the receptacle hole and screw during placement. Without such, there is a greater chance of the screw head shearing off the screw core. The drill guide and bone should be cooled while drilling to assure that the bone remains at a temperature of less than 47°C. This minimizes bone damage and necrosis.

b

Fig 1.4.3-3a–b a Conventional screw pressing the plate against the bone. b Locking head screw stabilizing the plate without direct bone/plate contact.

Fig 1.4.3-4 The drill bit diameters correspond with the core diameter of the corresponding screws.

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The drill should be removed from the bone while it is still rotating. If the drill is allowed to stop rotating while in bone, it may become lodged in the bone and break. Once the drill is removed, for bicortical screw fixation, a depth gauge is used to measure the length for the screw to be placed. Finally, the screw is placed. When securing plates with screws, the plate is first secured to the bone with the appropriate clamp. A drill guide is placed within the plate hole to maintain concentricity (neutral screw) or eccentricity (compression screw). For placement of locking head screws special drill guides that are screwed into the plate hole before drilling are recommended.

3

Plates

Since the initial application of rigid fixation to the mandible, numerous plate designs, differing in size, shape, dimension, and purpose have been developed and introduced for use in craniomaxillofacial fixation. Since the initial application four decades ago, continuous modifications of materials and design were made to improve implants, and therefore, patient care. Developments this past decade include the design of plates specific to particular anatomical regions, locking technology, and mesh, to name just a few. 3.1 Function of plates

The basic functions of a plate are to stabilize bone and/or bridge a void or gap, temporarily or permanently. Stabilization of bone can be performed by the most diverse forms and types of plates and by using different techniques (Table 1.4.3-4). According to plate design, plates can be classified into adaptation plates, compression plates, and locking plates.

Adaptation plate

A 1.0 to 2.0 mm plate or Matrix plate with a chain-link design that permits linking of bone segments.

Dynamic compression plate (DCP)

A plate using the gliding-hole principle to compress the fragments.

Locking plate

A plate with a threaded hole. This plate is engaged by and therefore locked to the screw creating one stable unit.

Limited-contact dynamic compression plate (LC-DCP)

A compression plate with channels removed from the underside to permit less bone surface contact and more soft tissue ingrowth.

Reconstruction plate

A wide plate with a higher profile and therefore strong enough to provide the effects of buttressing.

Universal fracture plate

A plate with a chain-link design. While it looks like a reconstruction plate it is not as wide or as thick and therefore not as strong. It is a form of stabilization plate.

Plate profile

The height of the plate as measured from the undersurface (the portion which contacts bone) and the outer surface.

Intersection bar

The connection between two holes of a plate.

Strut plate

A plate composed of two plates linked together with interconnecting bars.

Table 1.4.3-4 Glossary of terms for plates.

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Adaptation plates have round plate holes. Screws are typically placed into the center of each hole (Fig 1.4.3-5). Compression plates have specifically designed oval-shaped plate holes with an oblique inner surface, that allow eccentrically placed screws to glide down the oblique inner surface of the hole to finally be centered within the plate

hole (Fig 1.4.3-6). During this process the screw, which is firmly anchored into one fragment, takes the underlying bone with it. This facilitates a defined movement of the fragment toward the fracture line. If this procedure is performed on both sides of a fracture ultimately the two fragments are compressed, and the procedure is described as a compression osteosynthesis (Figs 1.4.3-7a–f, 1.4.3-8a–c).

Fig 1.4.3-5 Section of an adaptation plate, titanium, thickness: 0.8 mm.

LC-DCP surface

LC-DCP undersurface

MatrixMANDIBLE DCP plate surface

Oval-shaped plate hole

Fig 1.4.3-6 Limited contact dynamic compression plates (LC-DCP). Limited contact design for minimal contact with the bone without impairing the implant strength.

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a

d

b

c

e

f

Fig 1.4.3-7a–f Compression with a plate. a The screw head moves in the oval-shaped plate hole like a ball in an angled cylinder. b The screw hole can be seen as a section of an inclined and a horizontal cylinder. c The screw head can be interpreted as a section of a ball gliding down in the DC hole of the plate because of its spherical undersurface. d The eccentrically placed screw arrives at the rim of the plate hole. e–f As the screw is driven in, it glides within the plate hole to its final, centered position.

a

b

c

Fig 1.4.3-8a–c Compression with a plate. a The two innermost screws should be placed eccentrically within the DC holes. b As these screws are driven in, they approximate the fragments. c With final tightening of the screws, compression is achieved. The remaining screws are placed in neutral position.

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Locking plates have threaded plate holes. Since a locking screw will always lock centrically into the plate hole, it should be inserted strictly perpendicular to the plate in the 2.4 system. The Matrix Mandible locking plates allow for a screw angulation up to 15 degrees. However, it must be noted that conventional screws may also be used with a locking plate (Fig 1.4.3-9), but in this case the plate will not be locked to the screw. Apart from that plates do come in different sizes (height, width, length), but in conventional plate systems they are typically described by the outer core diameter of the screws that are used along with a plate. Therefore, the term "plate 2.0" means that the plate is used together with 2.0 mm screws. This denomination does not say anything about plate dimensions and has been chosen to make communication between operating room personal and surgeons easier.

Plates have different sizes according to their purpose. Plates used to bridge defects in loaded areas such as the mandible (load bearing plates) need to be bigger in size compared with plates used for fixation in non-loaded areas, such as the frontal bone. Plates do also come in different designs, which have evolved through many years of product development and clinical research. Whereas the first plates had a relatively simple bar-like design, newer plate designs have lateral groves to facilitate 3-D bending or undercuts to reduce the contact area between plate and bone thus allowing for soft-tissue ingrowth and better vascularization of the underlying bone. Other plate designs include special plates for defined anatomical regions, such as orbital plates. Their function is not so much fixation of bone fragments but reconstruction of orbital or facial walls.

2.5 mm

a

b

c

Fig 1.4.3-9 Locking reconstruction plate with threaded holes. 2.4 mm cortex screw (can be placed in an angled position) (a). 2.4 mm locking head screw (b). 3.0 mm locking head screw (c).

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3.2 Craniofacial plates

The greatest offering in terms of diversity in size, shape, and application are for craniofacial plates. Craniofacial plates are available in the Matrix and conventional 1.0, 1.3, 1.5, and 2.0 mm plating systems. The plates offered vary greatly

in length, width, and profile (Fig 1.4.3-10). Straight plates, multiple link adaptation plates, curved orbital rim plates, and strut plates make up the majority of the plates offered. The strut plate has the advantage of increased stability due to its cross-linked design. L-plates, oblique L-plates, X-plates,

Micro or mini plates (silver)—plate thickness: 0.4 mm Comparable to 1.0 craniofacial fixation system

Mini plates (blue)—plate thickness: 0.5 mm Comparable to 1.3 craniofacial fixation system

Medium plates (pink)—plate thickness: 0.7 mm Comparable to 1.5 craniofacial fixation system

Large plates (gold)—plate thickness: 0.8 mm Comparable to 2.0 craniofacial fixation system

Fig 1.4.3-10 Craniofacial plates from the MatrixMIDFACE plating system are color coded according to plate thickness (0.4 mm–0.8 mm). All plates are used with one screw dimension.

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Y-plates, Z-plates, T-plates, H-plates, double Y-plates, and box plates of multiple sizes and lengths complement the systems (Fig 1.4-11). Eight different internal orbital plates

exist for custom reconstruction of internal orbital injury. Among other fixation devices are cranial burr hole covers, cranial clamps, and a multitude of mesh types (Fig 1.4.3-12).

Titanium H-plate

Titanium oblique L-plates, available in different sizes, and left and right

Titanium Y and double-Y-plate

Titanium box plates

Titanium strut plate

Titanium X-plate

Titanium T-plate

Titanium orbital rim plate

Titanium adaptation plate (straight)

Fig 1.4.3-11 Matrix craniofacial plates are designed for MatrixMIDFACE screws. These plates are used mainly for the midface and cranial areas. They are available in different sizes, ranging from 0.4 mm to 0.8 mm.

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Titanium orbital floor plate, anatomic, small

Titanium orbital floor plate, anatomic, large

Titanium universal orbital floor plate

Titanium universal medial wall plate (available as left or right)

Titanium orbital mesh plate

Titanium MatrixNEURO contourable mesh plate, malleable

SynPOR titanium reinforced fan plate with exposed fixation holes

Titanium preformed orbital plate (available small and large, left and right versions)

Burr hole cover with and without shant

Two different types of meshes and burr hole covers in place (contourable mesh, mastoid plate, burr hole cover, double Y-plate).

Fig 1.4.3-12 Craniofacial plates: MatrixMIDFACE orbita plates, burr hole covers, and meshes.

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3.3 Mandibular plates

Numerous forms of mandibular plates have been developed for varying conditions and circumstances. Miniplates are available when indicated for fractures requiring minimal or moderate resistance to three-dimensional deforming forces,

1.0

for so-called load-sharing situations (see chapter 1.5.6 Principles of stabilization). These may or may not use locking technology (Fig 1.4.3-13a–b). More rigid mandibular plates are fabricated in various forms. These include the universal fracture plate and limited contact dynamic compression plate

4.8 Small

1.3

5.0 Medium

1.5

6.5 Large

2.0

6.7 Extra-large

a

1.0 mm, malleable

1.0 mm

1.25 mm

1.0 mm, 1.0 mm, 1.25 mm, 1.5 mm malleable

2.0 mm, 2.5 mm

2.8 mm

Plate strength gradient

1.5 mm

2.0 mm

2.5 mm

2.8 mm

b Fig 1.4.3-13a–b Mandibular plates. a 2.0 Compact LOCK plates. b MatrixMANDIBLE plate system.

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(LC-DCP). The universal fracture plate has a chain-link design that allows for easy bending and limited bone contact that permits periosteal ingrowth (Fig 1.4.3-14). The undersurface of the LC-DCP also allows for limited bone contact, again permitting periosteal ingrowth.

Reconstruction plates have been developed for fixation of atrophic edentulous mandibles, multifragmentary fractures, or reconstruction requiring the load-bearing effects of a larger plate. These may or may not utilize locking technology (Fig 1.4.3-15). Additionally, four condylar head add-ons

Fig 1.4.3-14 Universal fracture plate.

Fig 1.4.3-15 UniLOCK reconstruction plates 2.4.

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are available for reconstruction plates, whose height can be adjusted in increments of 2 millimeters (0–6 mm) (Fig 1.4.3-16). Similar mandibular plates are available from the Matrix Mandible system. A newer development are the preformed reconstruction plates. These plates were designed after

analysis of 1,000 CT-scans of human mandibles and come in three different sizes (Fig 1.4.3-17a–b). Special anatomically shaped plates have been designed for the subcondylar region (Fig 1.4.3-18).

Fig 1.4.3-16 MatrixMANDIBLE reconstruction plate with condylar head add-on.

Small

Medium

Large

a

b

Fig 1.4.3-17a–b Preformed MatrixMANDIBLE reconstruction plates (a) and corresponding bending templates (b).

Fig 1.4.3-18 MatrixMANDIBLE subcondylar plates.

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4

External fixators

External fixators are available for the mandible. External fixators are used for immediate stabilization in emergency situations (gun shot injuries, high-energy trauma) and for temporary defect bridging in oncology. The components are Schanz screws, mandible rods, and clamps (Fig 1.4.3-19a–d).

a

b

c

d

Fig 1.4.3-19a–d External fixation. a External fixator fixed to the left mandible. b Prebent rods. c Schanz screws. d Clamp.

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5

Distraction devices

Decades after the development of distraction osteogenesis, a resurgence of interest has taken place within the surgical community. While initially a focus of attention for orthopaedic surgeons, much enthusiasm now exists among craniomaxillofacial surgeons for this technology. The first of the distractors to gain popularity was the single-vector distractor for mandibular application. While the first distractors of this type were applied externally, internal single-vector distractors are currently also available (Fig 1.4.3-20a–b). As technology has advanced and our understanding of the complexities of osteogenesis has matured, multivector distractors were developed. These multivector distractors have the ability to permit body and ramus elongation simultane-

ously (Fig 1.4.3-20c). The contours of the mandible and thus the esthetics of the face are more accurately established. Segmental distractors for ridge augmentation have also been developed (Fig 1.4.3-20d). The combination of experience with mandibular distraction and orthognathic surgery has permitted the development and refinement of external (Fig 1.4.3-20e) and internal maxillary distractors (Fig 1.4.3-20f ). These distractors permit controlled advancement of the maxilla despite the challenging contours of the midface. For craniomaxillofacial deformities, osteotomies in combination with external distraction appliances and traction are alternatives to osteotomies, fragment positioning, and bone grafts. Internal midface distractors (Fig 1.4.3-20g) allow controlled advancement without the psychosocial effects of an external appliance.

a

b

c

d

e

f

Fig 1.4.3-20a–g Distraction. a Single-vector mandible internal distractor. b Single-vector mandible internal distractor with flexible rod. c Multivector mandible external distractor. d Two-vector alveolar ridge distractor. e Multivector external midface distractor. f Single-vector internal lower midface distractor. g Single-vector internal midface distractor.

g

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6

Instruments

Drill bits: A selection of drill bits is used with the corresponding screws. These are twist drills that are standard (without stop), or with stop, and have shaft ends compatible with any power tool. These include hexagonal coupling, J-latch, and quick coupling (Fig 1.4.3-21a–b). The drill bit diameters correspond with the core diameter of the corresponding screws (Fig 1.4.3-4). The drill bits come in varying lengths for use with or without a trocar.

the bone while the flutes gather bone debris. These should be advanced three turns clockwise and then back once counterclockwise, and then advanced again three turns clockwise. This permits the flutes to adequately collect the bone debris, rather than the debris collecting along the threads and thereby preventing precise cutting of the screw receptacle site. Tapping should always be done by hand and not with power tools to avoid stripping and distraction of the thread within the bone.

Taps: When tapping is preferred or needed (this is especially true for resorbable systems), a variety of taps are available. These are fluted and come with diameters that correspond to the outer thread diameter of the screws and are of varying lengths (Fig 1.4.3-22). The taps have quick coupling, hex coupling, or J-latch couplings that correspond to the appropriate handle. The sharp edges of the tap threads cut

Coupling

J-Latch

Dental Mini Quick With stop

Without stop

Quick

Drilling length

Jacobs chuck

Hexagonal coupling

a

b Drilling depth

Fig 1.4.3-21a–b a The various couplings for drill bits and screwdrivers. b Drill bits consisting of shaft with coupling, drilling length, and drill d iameter which corresponds to the core of the screw and cuts the pilot hole. The tips of the drill bits may be with or without stop.

Drill diameter

Fig 1.4.3-22 Tap.

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Handles: Handles may be required for taps, countersinks, or screw driver blades. These handles may be stationary without a rotating palm grasp, a jeweler’s handle that permits rotation, or ratcheting (Fig 1.4.3-23a–d). Screwdrivers: A number of different screwdrivers are available. Screw driver blades are available that fit into corresponding handles. These come in an array of variations that

fit with cruciform, PlusDrive, and Matrix screws. They are either self-retaining or are used with a sleeve that holds the screw. The most unique is the 90° or right angle screwdriver which is useful for transoral ramus approaches, or for endoscopic approaches. This particular screwdriver possesses a handle, main body, head piece, extension arm, and screw holder (Fig 1.4.3-24a–c).

a

b

c

d

Fig 1.4.3-23a–d Handles. a Small handle with hexagonal coupling. b Medium handle with hexagonal coupling. c Large handle with hexagonal coupling. d Ratcheting screwdriver handle with hexagonal coupling.

a

b

c Fig 1.4.3-24a–c Screwdrivers. a Screwdriver shaft MatrixMIDFACE, self-holding, with hexagonal coupling. Short; length 52 mm. Medium; length 76 mm. Long; length 96 mm. b Screwdriver shaft MatrixMIDFACE , with holding sleeve and hexagonal coupling. Medium; length 79 mm. Long; length 95 mm (shown here). c 90° angled screwdriver.

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Drill guides: Drill guides are available for numerous specific purposes. The internal diameter corresponds to the appropriate drill to be used. They come in lengths for standard drill bits, or for use with a trocar. Neutral drill guides are designed to insert a screw centrally (neutral) into a plate hole. Eccentric drill guides are designed to place a screw eccentrically into a compression plate hole (see Fig 1.4.3-7). Threaded drill guides are available for use with locking plate and screw systems. They are threaded into the plate before the drill is introduced. The drill guides are intended to maintain concentricity of the drill hole and screw core and for soft-tissue protection (Fig 1.4.3-25a–e). Depth gauges: While numerous types of depth gauges are available for different applications, they have the same basic design. The shaft of the instrument contains the graduated markings. The blade has a tip that catches the underside of the bone. The blade is attached to a separate handle

that is adjusted by the thumb of the dominant hand. Different lengths of shaft are provided to permit use through a trocar (Fig 1.4.3-26). Countersink: When using the lag screw technique, countersinking the outer cortex of bone assures the appropriate receptacle site for the screw head. They are provided with centering pins that correspond to the appropriate core diameter. These are provided with a coupling that fits with the appropriate screwdriver handle (Fig 1.4.3-27). Countersinks should not be used with power tools. Templates: Aluminum templates are available for plates. These templates are easily bendable in three dimensions permitting the recreation of the complex contours of the craniofacial skeleton. They can also be cut to fit the dimensions to be recreated. The plates can then be contoured using the template as a guide. These templates can be sterilized and re-used (Fig 1.4.3-17b).

a

b

c

d

e

Fig 1.4.3-25a–e Drill guides. a Nonthreaded double drill guide 2.4/1.8 b Nonthreaded double drill guide 2.0/1.5 c Threaded drill guide 1.5 (silver) d Threaded drill guide 1.8 (blue) e Threaded drill guide 2.4 (gold)

Fig 1.4.3-26 Depth gauge.

Fig 1.4.3-27 Countersink.

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Bending irons and pliers: The bending of plates can be accomplished with three basic forms of instruments. The first and most simple are bending irons. They are single-unit instruments with a handle and stainless steel plate receptacle that are used to bend and contour mandibular plates. While simplistic, they are capable of engaging the plate to provide contouring in three dimensions (Fig 1.4.3-28a–c). Bending pliers come in two basic forms. The first is a single hinge and is useful for contouring miniplates and microplates (Fig 1.4.3-29). The second type of pliers uses the mechanical advantage of a fulcrum. This additional mechanical advan-

tage permits easier contouring of miniplates or large mandibular plates (Fig 1.4.3-30a–b). The contoured anvil within the pliers’ tips permits the creation of gentle curves. Plate cutters: Three different forms of plate cutters are available for titanium plates. The simple shears construction works effectively for mesh and craniofacial plates (Fig 1.4.331a–b). The same shears concept is used with the shortcut plate cutter, yet without the fulcrum within the instrument (Fig 1.4.3-31d). The two separate and individual shears engage the plate which then acts as the fulcrum. This is designed

a

b

c

d

e

f

a Fig 1.4.3-29 Bending plier for MatrixMIDFACE plates.

Fig 1.4.3-28a–f Bending irons and plier for MatrixMandible plates. a Bending iron: In plane bending. b Bending iron: Out of plane bending. c Bending iron: Bending the last segment of the plate and twisting. d Bending plier: In plane bending. e Bending plier: Out of plane bending. f Bending the last segment of the plate.

b

Fig 1.4.3-30a–b Three point bending plier with nose for MatrixMIDFACE plates (fulcrum). a In plane bending. b Out of plane bending.

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for cutting mandibular reconstruction or universal fracture plates. The third form is that of a plier with fulcrum and uses this additional mechanical efficiency to cut larger plates (Fig 1.4.3-31c). Forceps: Forceps are designed for grasping screws and plates, for securing plates to bone, for plate contouring, and for pre-stressing bone. Plate and screw forceps for microplates and miniplates take the form of a hemostat or Castroviejo design. These fine-locking forceps are designed for the secure transfer and stabilization of smaller plates and screws. They

a

c

b

d

can also be quickly released afterwards. For the mandible, plate-holding forceps with either a ball or foot are used to secure the plate to the bone (Fig 1.4.3-32a). The pointed tip of the forceps engages the bone, while the ball engages the receptacle for the screw, or the foot engages the shaft of the plate. Reduction forceps with points are essentially towel clamps with a more oblique angle of the tips (Fig 1.4.3-32b). The tips are inserted directly onto the bone surface, or into holes created in the outer cortex. As the ratchet is engaged, the bone is pre-stressed.

Fig 1.4.3-31a–d Plate cutting instruments. a Plate cutter for MatrixMIDFACE plates. b Cutting scissors for mesh plates, long. c Cutting pliers for MatrixMANDIBLE plates 1.0 to 1.5, length 175 mm. d ShortcutTM for MatrixMANDIBLE plates, thickness 1.5 to 2.8 mm, with rasp, required in pairs.

a

b

Fig 1.4.3-32a–b Forceps for the mandible. a Bone holding forceps. b Reduction forceps.

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Transbuccal instruments: To avoid open transcutaneous approaches, especially for the ramus of the mandible, transcutaneous trocars have been developed. The basic components are the trocar handle (Fig 1.4.3-33a), the cannula (Fig 1.4.3-33b), and the drill sleeves (Fig 1.4.3-33c). The internal diameter of the cannula is slightly larger than the outer diameter of the drill sleeve and screwdriver that are in-

serted through it. Some designs permit interchangeable cannulas and drill sleeves of differing internal diameters, permitting multiple uses for the trocar handle and cannula. Various forms of cheek retractors may be applied to the cannula (Fig 1.4.3-33d–f ). A trocar fits through the cannula to permit entrance and passage through skin, soft tissues, and mucosa. The transbuccal technique is illustrated in Fig 1.4.3-34a–c .

a

d

b

e

c

f

Fig 1.4.3-33a–f Transbuccal instruments. a Handle. b Cannula with obturator. c Drill sleeve. d-f Cheek retractors.

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b

a

c Fig 1.4.3-34a–c Transbuccal fixation technique. a Transbuccal drilling. b Depth measurement. c Transbuccal screw insertion.

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Resorbable plate instrumentation: In the majority of available systems they can only be contoured if they are heated first. Placing the plate into a water bath permits heating of the plate to the point that it can be contoured. While the water bath heater is not sterile, the water bath tray and water bath sterility cover are. Sterile water is placed into the tray and the heater turned on (Fig 1.4.3-35a–b).

a

Graphic cases: The organization of plates, screws, and instruments into graphic cases is a substantial improvement. The current graphic cases are so numerous in variety and versatile in their modular capability that there is a “place for everything and everything in its place” no matter how large or small the operating room or hospital. Moreover, the modular design permits adaptability or customization of storage for virtually every surgeon, procedure, or space problem (Fig 1.4.3-36a–b).

b

Fig 1.4.3-35a–b Resorbable plate instrumentation. a Water bath. b Resorbable plates.

a

b

Fig 1.4.3-36a–b Instrument and implant sets. a MatrixMIDFACE international set. b MatrixMIDFACE US set.

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7

Power tools

Power tools are used to drill and cut bone. The power instruments of the past have been improved, with a more lightweight, compact, and efficient air-driven rotary power source, as well as the introduction of self-contained (battery) power sources for both drills and screwdrivers (Fig 1.4.3-37a–b).

a

b

Fig 1.4.3-37a–b Power tools. a Colibri. b E-Pen.

Acknowledgements

Thanks to Regan Barber, Valerie Biggers, Ralph Zwirnmann, Bryan Griffiths, Chuck Goudy, Paul Ciccone, and Samuel Leuenberger for their efforts in drafting the tables for plates, screws, and equipment.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care


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1.5.2 Indications for surgical, nonsurgical, or no treatment of craniomaxillofacial fractures

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1.5.3 Presurgical and postsurgical considerations, treatment planning

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1.5.4 Principles of surgical fracture management

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1.5.5 Biomechanics of the bone-implant-unit

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1.5.6 P rinciples of stabilization: splinting, adaptation, compression, lag screw principle

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1.5.10 Techniques of mandibulomaxillary fixation (MMF)

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The ultimate goal of modern craniomaxillofacial trauma care is immediate or early restoration of both form and function of all structures of the face and cranium, with complete, predictable, and complication-free healing. This also applies to corrective bone surgery of the facial and cranial skeleton as well as for ablative and reconstructive tumor surgery. Depending on the type and extent of craniofacial injuries or pathology, this goal cannot always be achieved. For instance, when specific tissues are severely damaged or lost, like eyeballs, teeth, and nerves, anatomy or function cannot be restored. However, even in these severe cases, the patients should be treated as completely as possible; always keeping the ultimate goal in mind which is to reach the best possible result. The crucial goal of modern craniomaxillofacial surgery is to achieve the highest possible quality of life by returning the patients to the best possible condition.

Modern trauma care as well as corrective bone surgery and tumor surgery are based on a number of prerequisites: • Interdisciplinary approach involving all specialties needed according to the specific injuries of the patient • Adequate imaging • Individual treatment planning based on science and individual experiences • Adequate timing of surgery • Treatment, especially surgery, should be performed according to the highest standards, involving modern techniques and equipment. In craniofacial traumatology, this implies use of modern internal fixation systems, tissue (bone) replacement materials, tissue transfer, and resuspension of soft tissue to bone as standard components. However, endoscopy and navigation may be used in special circumstances. • Case-adapted aftercare and follow-up. All of the above-mentioned points are almost equally important to realize a state-of-the-art treatment outcome.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.2 Indications for surgical, nonsurgical, or no treatment of craniomaxillofacial fractures

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1.5.2 Indications for surgical, nonsurgical, or no treatment of craniomaxillofacial fractures Craniomaxillofacial fractures may be treated in different ways. In many instances there is more than one option for dealing with a given clinical situation or problem. In principle, three treatment options exist for managing CMF fractures. They are:

Generally all treatment options for facial fractures can be associated with specific complications and adverse effects. A surgeon must be familiar with these and be able to communicate them to a patient in an appropriate manner via the informed-consent process.

• No treatment • Nonsurgical treatment • Surgical treatment

The primary goal of CMF fracture care is a predictable, safe, undisturbed, and complication-free healing. Sometimes this goal can be reached with more than one treatment option. There are situations when the patient’s comfort is a major factor with dominant impact on the treatment decision; for instance, in a situation in which a patient can choose between a nonsurgical treatment of a mandible body fracture with arch bars and four weeks of MMF or a surgical treatment. The latter may have more specific surgical complications but allows function immediately or soon after surgery. In addition, the ability for cooperation is a factor in the decision, especially in elderly patients.

Within each of the three treatment options there are subgroups with different treatment algorithms, for example, within the surgical group, rigid versus nonrigid fixation. No treatment means no active treatment and no structured follow-up. Nonsurgical treatment for many years was also called conservative treatment or closed treatment. It means fracture treatment without opening skin or mucosa and without direct visualization of fragments. Within this group there is a wide range of treatment possibilities, such as soft diet and observation, functional treatment with orthodontic appliances, mandibulomaxillary fixation (MMF) with wires, arch bars, or other MMF devices, sometimes with subsequent functional therapy. It is important to note that “observation only” and follow-up, for example in a greenstick-fracture in a child, or in nondisplaced fractures, is regarded as treatment and not as no treatment. The terms surgical treatment, open treatment, and operative treatment are interchangeable. Surgical fracture treatment typically involves these steps: • Exposure of the fracture site • Reduction of the fragments • Internal fixation Open reduction and internal fixation (ORIF) always involves soft-tissue surgery and may involve tissue transplantation and the use of grafts or alloplastic tissue (bone) replacement.

It is critically important to always remember that surgeons do not only treat fractures but patients with fractures. Therefore, decision making on treatment choices involves more than the type and the severity of the fracture. The general health status, intercurrent diseases, age, estimated compliance, social status of patients, and their wishes and expectations all need to be considered. Of various treatment options, the ones selected are those most likely to provide the best possible outcome. In the mandible, no treatment and observation only may be considered for incomplete and/or undisplaced fractures without malocclusion, pain, or other functional disturbances with no additional pathology, such as dentigerous cysts, at the fracture site. In the midface this applies for lateral midface (zygoma) fractures with minimal or no displacement, undisplaced zygomatic arch and orbital wall fractures. In the central midface the same is true for nasal fractures and nasoorbitoethmoid (NOE) fractures with little or no displacement. Frontal sinus fractures, cranial vault fractures, and skull base fractures without displacement or with

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.2 Indications for surgical, nonsurgical, or no treatment of craniomaxillofacial fractures

inimal displacement and without additional pathology also m do not require surgery. Mobile or displaced (impacted or incomplete) Le Fort type midface fractures should always be treated surgically in adults. Here nonsurgical treatment should be limited to children with greenstick fractures. Nonsurgical treatment with short-term MMF and/or orthodontic treatment should be considered in adults for undisplaced condyle and condylar head fractures associated with malocclusion, pain, or functional deficits. Undisplaced fractures of the mandibular body with pain and/or functional problems can also be successfully treated with MMF and sometimes subsequent functional therapy. Nonsurgical treatment of body fractures in adults requires longer immobilization, approximately 4–6 weeks. Therefore, many patients request open surgery and internal fixation for comfort and improved function. For children younger than 12 years, nonsurgical management with MMF for undisplaced and displaced condyle fractures with functional problems and/ or pain is still considered the treatment of choice, although recently attempts have been made toward surgical treatment especially for dislocated fractures.

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For central midface fractures with malocclusion, mobility, pain, and/or other functional problems there is no possibility for fracture treatment with MMF alone in either adults or children, except for isolated alveolar process fractures. In both the mandible and the midface, surgical treatment is indicated for all fractures with more than minimal displacement. They require open reduction, internal fixation, and/or reconstruction of bony subunits of the face, such as orbital walls, nose, and zygoma. For all fractures with a potential impact on the occlusion, it is of paramount importance to apply MMF in proper occlusion before performing internal fixation. An internal fixation with plates and screws should be three-dimensionally stable. Malocclusion resulting from an improperly reduced osteosynthesis cannot be corrected by keeping a patient in MMF postoperatively or using elastic traction. Antibiotic prophylaxis is indicated in major injuries, especially for those with compromised soft tissues, such as avulsive crush or gunshot injuries. In less severe injuries antibiotic prophylaxis is optional. Antibiotics are routine in the treatment of all fractures with signs of infection.


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1.5.3 Presurgical and postsurgical considerations, treatment planning Meticulous preparation and treatment planning is essential to achieve the best possible results in trauma care as well as in corrective and reconstructive surgery of the musculoskeletal systems. It involves: • Detailed clinical examination • Adequate preoperative imaging • Data analysis and development of a treatment plan including alternatives • Communication with the patient • Informed consent These steps need to be documented and the data needs to be archived according to local legal regulations. Preoperative checklists have been introduced to simplify and standardize the process. Not only severity and type of fractures, defects or malformations, but also the individual patient's personality, age, sex, and general condition are major factors for treatment planning. Thus an osteosynthesis or reconstruction technique has to address both the characteristics of a fracture and the characteristics of a patient. Personality of the patient: Highly educated and intelligent patients tend to have a better compliance with therapeutic measures and advice while those with a lower education level and social standard may be negligent in their postoperative behavior. These patients require closer supervision and more reliable techniques, for instance a more rigid fixation in a trauma case.

Age and sex of the patient: Healing, especially bone repair is usually better in younger patients. In addition, the bite forces of young dentate men are higher compared to young dentate females. Bite forces in general tend to be smaller in older individuals. Bite forces tend to be higher in dentate compared with partially dentate or edentulous individuals. As a consequence, internal fixation should be more rigid in young fully dentate patients. Medically compromised patients: Patients with metabolic diseases such as diabetes, allergies, bleeding disorders, and those with substance abuse must be treated with particular caution. Metabolic diseases, disturbances of liver function, and excessive hematoma formation may effect postoperative soft-tissue and bone healing. Psychiatric and neurological diseases (such as epilepsy) and substance abuse are contraindications for postoperative mandibulomaxillary fixation (MMF). Postoperative aftercare includes clinical controls and adequate imaging. Intra- or postoperative imaging needs to be performed and documented to prove the quality of reduction and the adequacy of hardware placement (quality control). This may be done with 2-D imaging, usually x-rays, in two planes for simple fracture scenarios, such as simple fractures of the mandible. For more complex fracture and reconstruction scenarios, including all orbital fractures with orbital wall repair, 3-D imaging, usually with CT or cone beam CT, has become almost the therapeutic standard.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.4 Principles of surgical fracture management

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1.5.4 Principles of surgical fracture management Besides meticulous planning, surgical fracture repair involves four sequential surgical steps: • • • •

Adequate exposure Fragment reduction Adequate internal fixation Meticulous wound closure

Adequate exposure: The surgical approach is chosen according to localization and severity of fractures. In general, a surgical approach should be as small and hidden as possible, but must give adequate access for bone handling and placement of osteosynthesis material. Fragment reduction: The goal of fragment reduction is establishing preinjury bone anatomy prior to internal fixation. Indirect fragment reduction is possible, for instance through applying arch bars and putting the patient into occlusion. Direct fragment management with the help of reduction forceps, bone hooks, or bone-anchored devices such as a Caroll-Girard device, and combinations of these

are possible as well. The fragments are held in place while internal fixation is performed. For all fractures with a potential impact on the occlusion, such as mandibular or Le Fort type fractures, temporary intraoperative mandibulomaxillary fixation (MMF) is recommended. Adequate internal fixation: Adequate hardware first must be selected, according to the personality (severity) of the injury and the personality of the patient. In addition it includes appropriate hardware placement and fixation according to the expected biomechanical stresses and forces in the fracture areas. Meticulous wound closure: This includes wound closure in layers, including muscle and periosteal resuspension. The need for meticulous soft-tissue resuspension increases with the amount of soft-tissue stripping for exposure, reduction, and fixation. The indication for wound drainage should be considered, but is always an individual surgical decision. In cases with soft-tissue defects, such as gun-shot injuries, immediate vs delayed soft-tissue reconstruction needs to be discussed.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.5 Biomechanics of the bone-implant-unit

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Authors Adrian Sugar, Robert Bentley

1.5.5 Biomechanics of the bone-implant-unit To obtain appropriate stability in fracture treatment it is essential to consider not only the factors pertinent to the type of fracture and the soft-tissue environment in which it has occurred but also patient related factors. These factors include the build of the patient, intercurrent illness (comorbidity), smoking and alcohol habits, occupation, personality, and compliance of the individual patient, all of which affect the appropriate choice of implant. The chosen implant must accommodate the expected magnitude and duration of load for each specific case (Fig 1.5.5-1). The specific danger is underestimation of certain loading conditions such as fractures of the mandibular condyle and the atrophic mandible. While miniplates in the body of the mandible can perform perfectly if loaded in tension, their stabilizing func-

tion may be insufficient if placed at a site subjected to various kinds of load. In addition, the requirements that the fixation device must meet change in function and bone anatomy over time. During a physiological and undisturbed healing process bone gradually takes over the load across the fracture site and the implant becomes unloaded. If the healing process is delayed, for example by patient related factors such as smoking, poor oral hygiene, or compromised healing in immuno-compromised cases, the estimated biomechanical situation may be different due to prolonged loading condition. As a consequence, a small implant may undergo fatigue failure. Such an osteosynthesis, in which implant and bone need to share the load, is called a loadsharing type of fixation.

Patient factors

Fracture factors • • • • • •

• General health: Diabetes etc • Habits: Smoking Alcohol Drugs • Compliance: Oral hygiene Attendance

Fixation factors

Simple / complicated Soft-tissue injury Tissue loss Time since injury Presence of infection Presence of teeth in fracture line

• Adequate reduction • Adequate stabilization • Atraumatic technique

Fig 1.5.5-1 Interrelationship of patient, fracture, and fixation factors in fracture healing.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.5 Biomechanics of the bone-implant-unit

The fracture fragments and implants should be considered as one single unit which must be able to deal with the type and degree of load exerted across the fracture. A relatively undisplaced well-reduced fracture, for example, is able to transmit some of the compressive forces across the fracture plane. The implant, however, must substitute for the lost tensile properties across the fracture plane. This ability to share the load between the bone and the implant allows implant dimensions to be used on a much smaller scale than those necessary for a fully loaded situation (Fig 1.5.5-2). The aim is therefore to use an implant system that provides sufficient stability for the fracture to heal in a predictable way but at the same time it adequately stabilizes the fracture preserving blood supply and reducing the associated morbidity of implant insertion. The current trend is to use more biologically-friendly fixation techniques where additional exposure would result in iatrogenic disturbance of blood supply. The hope is that a certain compromise on the mechanical side is compensated by a gain on the biological side by preserving vascular connection to the bony fragments. In addition, damage to associated structures such as nerves may be reduced by using minimally invasive techniques as opposed to large open procedures.

Fig 1.5.5-2 Miniplate fixation of the mandibular angle. Simple linear fracture. Load sharing osteosynthesis.

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In case of reduced bone quality and quantity (defects, infection, atrophy, multifragmentation) the fixation device has to bear the majority if not all of the load. If sufficient bone is not present or healing does not progress in a satisfactory manner, further active intervention such as bone grafts may be required as even the largest plates will eventually fail in fatigue. In some situations the bone fixation system must be able to bear the total load. Ideally, the majority of the load is borne by the fragments allowing the smallest fixation to be inserted. However, a range then exists whereby less support can be provided by the fragments due either to mechanical or biological conditions (eg, atrophy, defects). Then it becomes necessary for more load to be taken by the implant unit. In these cases the implant has to be of sufficient stiffness and strength to perform this function completely and we shift from a simple load sharing scenario, such as a simple linear fracture in the body of the mandible at one end of the spectrum, to a load bearing scenario such as a grossly comminuted or defect fracture at the other end of the spectrum (Fig 1.5.5-3).

Fig 1.5.5-3 Reconstruction plate at the mandibular angle. Reduced buttress with bone defect. Load bearing osteosynthesis and bone graft.


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The decision which implant to use is based on the surgeon’s experience and the relative emphasis that he or she places on the relevant factors such as fracture type and dislocation and patient related factors. Fixation systems rarely fail if used appropriately. Failure is usually due to the surgeon not assessing the situation correctly and the underestimation of the loading conditions which exceed those required for the bone-implant unit to permit uninterrupted healing.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.6 Principles of stabilization: splinting, adaptation, compression, lag screw principle

1

Splinting

95

2

Adaptation

95

3

Compression

96

4

Compression with a plate

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5

Compression with lag screws

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6 Compression with a plate in combination with a lag screw

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1.5.6 P rinciples of stabilization: splinting, adaptation, compression, lag screw principle 1

Splinting

External splinting is the application of a device that reduces the mobility of bone fragments in one or both jaws. The fractured bones are not exposed and manipulated under direct vision, therefore this technique to treat fractures is also commonly called closed or indirect management. External splinting in the craniomaxillofacial area may be applied internally to the teeth (in dentate patients) with arch bars, wires, or custom made splints. It may also be applied to the mucosa and underlying bone (for example in edentulous patients) by fixing a prosthesis or Gunning splint directly to one or both jaws. Devices for indirect fracture management can be applied directly to the bone transmucosally using IMF screws or similar devices, or transcutaneously using pins and an external fixator. Accurate fracture reduction is not always possible using these indirect methods of fixation and absolute stability of the fracture is rarely achieved. Provided that the reduction and stability are adequate and the mobility does not interfere with the healing process, these methods may be sufficient to achieve bony union if movement and forces on the fracture are minimized. However, external splinting is often an unreliable method of maintaining good fracture alignment while the bone unites.

a

The fixation of osteosynthesis implants directly to the fracture fragments after exposure and reduction is internal splinting. However, to avoid confusion with external splinting, the better terms are osteosynthesis or internal fixation. The internal splint may still allow some interfragmentary motion, but in general this tends to be less than with external splints. The degree of stability produced by osteosynthesis material in general varies considerably, from osteosynthesis with wire, to fairly flexible plates, and then more rigid devices.

2

Adaptation

In the application of internal fixation devices to a fracture, some brace the fragments together and others actually force the fracture edges into close approximation under pressure. Yet in the majority of uncomplicated simple fractures of the mandible and in most situations in the midface and cranium, the fixation device merely holds the fragments together after reduction without any attempt to apply forces to the fragments to compress them. Adaptation can be achieved with intraosseous wires or adaptation plate and screw combinations. The typical adaptation plate contains round holes allowing only central screw placement (Fig 1.5.6-1a–b). Locking

b

Fig 1.5.6-1a–b a Fracture fixation of the lateral mandible with an adaptation plate. Load sharing situation. b Close-up of the round hole of an adaptation plate.

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plate and screw combinations are also typical adaptation plates. Adaptation plate osteosynthesis can be performed with microplates, miniplates, or stronger plates such as 2.4 reconstruction or Matrix mandible plates. Adaptation osteosynthesis with wires has limited threedimensional stability. For mandibular fractures, wire osteosynthesis is only indicated in combination with a period of mandibulomaxillary fixation (MMF). It also has defined drawbacks in midface fixation and is rarely used in modern fixation methods. Especially in dentate mandible areas, adaptation plates are usually fixed with monocortical screw anchorage. For monocortical screw placement, precise drilling in one direction is essential to maintain good screw-bone contact (Fig 1.5.6-2). Today, adaptation plate osteosynthesis with micro-, mini- or stronger plates, (depending on the biomechanical situation), is the technique of choice for most craniomaxillofacial fractures.

3

Compression

Compression is a means of preventing interfragmentary movement by pressing two surfaces together. In a fractured bone, the effect is to increase interfragmentary friction and to preload the fracture. Compression permits undisturbed healing by guaranteeing stability even during function. It allows the sharing of load between the bone and the implants (plates and/or screws). Plates in this load sharing situation need not be as large and strong as those in a load bearing situation (eg, a mandibular resection defect) when the plates and screws have to support the entire load. Compression is not a requirement for fixation of fractures of the craniomaxillofacial skeleton but is a method which, in the right circumstances, will increase stability and healing. Provided that the fragments are well reduced and held in direct approximation, compression osteosynthesis may permit primary (osteonal) bone healing in which osteons directly cross the fracture gap (Fig 1.3.3-1b, page 31). It is applicable in the mandible in simple, uncomminuted fractures only, and occasionally elsewhere in the facial skeleton. It is not applicable with a defect at the fracture, or when the bone ends are resorbed (eg, infection), nor usually in the maxilla where the bones are commonly too thin to support compression. Here adaptation osteosynthesis is appropriate. Situations in which compression osteosynthesis may be considered are: • Linear fractures of the mandible • Zygomaticofrontal suture • Root of the zygomatic arch • Repositioning small fragments (with lag screws) • Fixation of bone grafts (with lag screws) Both plates and screws, and screws alone (see next section) may be used to achieve compression.

Fig 1.5.6-2 Unprecise drilling leads to a widening of a screw hole and results in undesired limited screw-bone contact.

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4

Compression with a plate

A compression plate is a plate with special oval-shaped holes which together with a screw forms the dynamic compression unit (DCU) (Fig 1.4.3-8 , page 62). To allow for compression, it is necessary for the fractured bone ends to be well approximated before the implants are placed. Compression plates in general must be placed perpendicular to the fracture line. Interfragmentary compression can be achieved by designing elliptical plate holes (as in a section of an inclined and horizontal cylinder), such that when the screw hole is drilled laterally (distant) from the fracture, the screw as it is inserted tries to achieve a more central position in the plate hole (Fig 1.4.3-8 , page 62). The undersurface of the screw head is shaped in the cross-section of a ball which will move in the plate hole down the inclined plane of the angled cylinder. In doing so, it moves the bone–screw unit in the direction of the fracture line. When performed on both sides of the fracture, the compressive load is doubled. No more

a

Fig 1.5.6-3a–c a Correctly overbent plate above a fracture. b The inner screws must be placed first eccentrically and be driven home. As a result of the overbending of the plate the fracture gap at the opposite side is closed. c Thereafter all other screws are placed in a neutral position within the plate holes.

than one screw on each fracture side should be inserted in this way because the forces applied then may damage the bone. All other screws should be placed neutrally, ie, in the center of the plate hole (the part of the hole closest to the fracture line). Compression plates are designed somewhat stronger and more rigid than adaptation plates as compression is only possible as long as the plate does not deform under the forces applied. Because of the resulting forces, bicortical screw insertion is mandatory in compression plate osteosynthesis. This creates a problem in the treatment of fractures in the lateral mandibular body. Due to the inferior alveolar canal and the tooth roots, compression plates may only be applied to the inferior border of the mandible. Consequently, when compression is applied on one side of a fracture, the opposite sides tend to open up. In case of the mandible these are the lingual side and the superior border. Opening of a lingual gap can be avoided by overbending the plate before it is fixed, and opening of a superior border gap by tension banding (Fig 1.5.6-3a–c). Tension banding can either

b

c

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be performed with a tension band splint or a tension band plate, which is typically a monocortically fixed miniplate. Tension band splints or plates must be applied before the compression osteosynthesis is performed (Fig 1.5.6-4a–b). Compression plating has little place in fracture treatment in the midface. Due to reduced buttressing capacity of the relatively thin midfacial bones, it may change the occlusion because of telescoping or cause bone necrosis at the fracture gap.

5

Compression with lag screws

Lag screw fixation is particularly applicable to any situation in which two broad flat surfaces need to be approximated. It therefore has particular application to: • Oblique fractures • Symphyseal fractures • Fixation of bone grafts • Sagittal split osteotomies It has been shown that lag screw fixation of bone grafts produces better graft take and less graft resorption than most commonly used alternatives. Some manufacturers have produced special lag screws. They are characterized by an unthreaded shaft, which is smooth and close to the head, while the tip is threaded. However any screw can be used in the lag screw technique. Most screws encountered in maxillofacial sets will be fully threaded.

a

b

Fig 1.5.6-4a–b a Tension banding performed with an arch bar reinforced with acrylic. In addition a universal fracture plate 2.4 is placed at the inferior border. b Double-plate fixation with a miniplate as a tension band above the mandibular nerve, and a universal fracture plate 2.4 at the lower border of the mandible. Protection of the inferior alveolar nerve has to be considered.

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In order to use a fully-threaded screw as a lag screw the proximal cortex of the bone must be drilled to a diameter as wide or wider than the width of the outer thread diameter. This is called a gliding hole because the screw will glide through it without gripping the bone. Into this gliding hole a special drill guide needs to be inserted, which then enables the distal cortex of the bone on the opposite side of the fracture to be centrally drilled to a diameter less than the width of the screw threads, typically the core diameter of the screw. This is called the threaded hole which the screw will grip as it is inserted. Depending on the situation (eg, how thick and strong the bone is) and the type of screw being used, this threaded hole may or may not be tapped before screw insertion. As the screw thread grips the distal threaded hole and the screw head engages the outer cortex adjacent to the gliding hole, the two fragments are squeezed together and interfragmentary compression results across the fracture. Lag screws always need to be placed exactly perpendicular to the fracture line to avoid secondary dislo-

cation (Fig 1.5.6-5). If the cortex underlying the screw head is thick and strong enough, a countersink hole should be drilled to receive the screw head and prevent it becoming prominent and palpable. Countersinking allows for full contact between screw head and bone thus minimizing the risk of microfractures of the cortex, which otherwise may be seen in situations with minimal contact and subsequent overloading (Fig 1.5.6-6a–b). Care must be taken not to penetrate the cortex. An alternative, though slightly less precise, way of inserting a lag screw is to drill all the way through both proximal and distal cortices of bone and then overdrill a gliding hole in the proximal cortex. This is less precise because the two holes are not necessarily centrally located and there is increased risk of drilling the gliding hole too deep. If only one lag screw is inserted, the fragments can easily rotate making a reduction unstable. Therefore a minimum

a

b Fig 1.5.6-5 Interfragmentary compression exerted with two lag screws. Note: the outer holes are gliding holes which do not engage the thread, the inner holes are lag holes which engage the thread.

Fig 1.5.6-6a–b a Oblique insertion of a lag screw leads to a point-to-point eccentric force when the screw hits the bone and this may induce microfractures in the external cortex. b Countersinking leads to a full surface contact between screw and bone. The risk of microfractures is minimized.

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of two lag screws should always be inserted. If only one screw can be inserted (as is sometimes possible, for example, at the root of the zygomatic arch), some other form of fixation should be used in addition (eg, a plate). Interfragmentary compression across a sagittal split osteotomy may squeeze and thus damage the inferior alveolar nerve. It is also uncommon for the split surfaces of a sagittal split osteotomy to fit together completely and precisely in the new position of the mandible. Usually, there are areas of contact and areas of gap. Consequently, the use of interfragmentary compression across a gap usually displaces the fragments and thus disturbs the position of the occlusion and the condyle. As a result, the use of so-called position screws has become popular (Fig 1.5.6-7).

6 Compression with a plate in combination with a lag screw

Another way of achieving interfragmentary compression across a fracture is to use a screw which passes through the plate and then across the fracture (Fig 1.5.6-8). This screw has to be placed as a lag screw, so that the screw threads grip only the distal fragment and the head grips the proximal fragment, drawing the two together. When a lag screw is inserted through a plate in this way, all other screws in the plate need to be inserted secondarily and placed neutrally. This type of fixation is particularly applicable to oblique mandibular fractures.

In order to place a position screw, a hole is drilled through both cortices which corresponds to the diameter of the screw shaft. The screw that is then inserted grips on both sides of the fracture and only holds the fragments in relative position to each other. It does not squeeze the fragments together, rotate, or move them.

Fig 1.5.6-7 Fracture fixation with a position screw, this way the fracture or osteotomy gap is kept. Note: the inner and outer holes both engage the threads of the screw.

100


Fig 1.5.6-8 Compression with a lag screw and a plate. The lag screw must be placed first. Thereafter, the remaining screws must be placed in a neutral position.


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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.7 Dental and alveolar trauma

1

Introduction

103

2

Tooth fracture

103

3

Tooth luxation

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4

Tooth avulsion

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5

Alveolar trauma

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6

Primary dentition

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Author Anders Westermark


1

Introduction

Dental and alveolar trauma may occur either as an isolated injury or as part of a more complex craniomaxillofacial trauma. Minor dental and alveolar injuries usually result from direct forces in accidents like falls, fist-fights, or sports related collisions. In more severe injuries, the impact of the trauma can be direct, but also indirect, as when the mandible is forced against the maxilla with such a force that teeth and alveolar tissues are injured. There is a contradiction in the treatment of dental trauma. Certain isolated dental injuries will most often receive immediate treatment, while more severe dentoalveolar injuries, especially when they occur in combination with severe facial bone or soft-tissue injuries and in patients with a compromised general condition, may get delayed treatment. Thus, an isolated crown fracture with pulp exposure will require root canal treatment to relieve pain, and an avulsed tooth must be replanted immediately to improve the prognosis. In more complex injuries, however, life saving measures will take priority over dental procedures. The obvious treatment modalities for dental injuries may have to be postponed. In such cases one should still remember that the pain from exposed pulp may contribute to the restlessness in an unconscious patient. It falls outside the scope of this text to give a detailed classification of all types of dentoalveolar injuries and their treatment. Such information can be found in specialist publications on the subject. The following will focus on tooth fracture, tooth luxation or avulsion, and alveolar trauma.

2

Tooth fracture

Isolated tooth fractures, needless to say, are most common in the maxillary incisor region. In a direct trauma resulting in a horizontal crown fracture, usually the periodontal tissues are unharmed. Then, the prognosis for tooth vitality will depend on the pulp status and how deep the fracture goes into the tooth. In a young tooth with an open apex, there is a good chance that pulp vitality will remain. The narrower the pulp is, the more likely it is that the pulp may undergo necrosis due to secondary circulatory collapse. If the pulp is not exposed, the dentin should be treated with calcium hydroxide cements covered with acid-etch restoration of the tooth. Acid-etch techniques may also be used to reattach a crown fragment to the tooth. Close follow-up with x-rays is recommended. It should be mentioned that immediately after injury, and even some time later, pulp testing with an electrical pulp stimulator or ice is of limited value as a sensitivity test. The trauma may have disturbed the nerve function so that the test is false negative. A nonsensitive tooth may still be vital. If the crown fracture is deep enough to expose the pulp, the tooth will be very painful to all kinds of stimuli. Usually, pulpectomy at varying levels (depending on root development) must be carried out, followed by calcium hydroxide dressing, and later filling of the root canal. A relatively common type of tooth fracture is one where the fracture line is oblique, extending subgingivally. In deep fractures, such a tooth must be extracted. Apart from the depth of the fracture, other factors may also influence the decision whether to save or extract the tooth. Such factors may include endodontic and prosthodontic considerations, the rest of the patient’s dentition, and economic factors. Tooth fractures with missing fragments in association with soft-tissue lacerations require thorough examination, including x-rays, to confirm that tooth fragments are not embedded in the soft tissues. The same precaution must be taken if a tooth or tooth fragment might have been inhaled. Then a chest x-ray must be obtained.

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3

Tooth luxation

Tooth luxation may involve intrusive and extrusive luxations as well as lateral luxations. They may be combined with fractures of the alveolar bone. Tooth luxation with simultaneous buccal fracture of the alveolar process usually affects the maxillary incisors. Frequently, in such cases, the tooth/bone complex will be superiorly displaced. Upon repositioning, it is important, first to pull down the tooth, then to replace it in its place adjacent to the remaining alveolar bone (Fig 1.5.7-1a–c). Once the tooth or group of teeth have been properly repositioned, they should be splinted with some kind of stabilization. Reliable, rigid or semirigid fixation can be designed either with acid-etch techniques, or in combination with orthodontic wires, plain steel wires, or similar appliances

a

b

(Fig 1.5.7-2a–c). For isolated tooth luxations semirigid fixation is preferred over rigid fixation with stable splints or arch-bars. Rigid devices are used in patients with facial fractures in combination with tooth luxations. In order to improve the patient’s ability to maintain good oral hygiene, one should make the fixation devices as small as possible. The duration of fixation varies with type and extent of the injury. Extrusion injuries should have semirigid fixation for 7–10 days; lateral luxation injuries should have semirigid fixation for 2–3 weeks; luxation injuries with simultaneous fracture of the buccal or lingual bone plate should have semirigid fixation for 4–6 weeks. After luxation injuries, root canal treatment is indicated for all involved teeth with a closed apex. It is usually done shortly after initial treatment when primary wound healing is completed. During follow-up one should pay special attention to possible signs of root resorption.

c

Fig 1.5.7-1a–c a A part of the buccal bone is fractured along with a luxated upper incisor. The tooth/bone complex is superiorly displaced. b Before the tooth can be replaced, it must be pulled down over the bone margin. c After the tooth has been properly positioned, it can be fixed with semirigid fixation appliances.

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4

Tooth avulsion

Many factors will have an impact on the decision whether or not to replant an avulsed tooth. Most avulsion injuries involve the upper incisors, which in itself creates compelling esthetic indications for replantation. Root development, periodontal status, and general condition of the remaining dentition are other factors to consider. The most important factor, however, is the length of time the avulsed tooth was allowed to dry. After a dry period exceeding 30 minutes, the cells of the periodontal ligament will have dried to an extent where the chance of success after replantation will be very low. Thus, immediate or very early replantation must be the treatment most of the time, although immediate replacement is not possible. The viability of the periodontal cells is supported if the tooth is kept in a suitable transport fluid. The periodontal cells can maintain their viability up to two

hours in the patient’s saliva and up to six hours in fresh milk. Water should not be used since the cells will die from osmolytic lysis. Before the tooth is replanted, it should be gently rinsed with saline until free of all debris. Scrubbing or trauma to the periodontal cell layer must be avoided. If there is a reason to suspect foreign material in the tooth socket, the socket should be gently cleaned by suction. Otherwise, no special attention is needed for the socket. The tooth is firmly replanted in the socket by firmly gripping the crown. One should pay attention to possible injury to bony margins as after tooth luxations. When the tooth has been replanted in proper position, it can be fixed with methods similar to those employed after luxation. After tooth avulsion, a semi-rigid fixation for 7–10 days should be applied. Usually, antibiotic treatment is recommended following replantation of avulsed teeth.

a

b

c

Fig 1.5.7-2a–c a The two central incisors have been luxated and displaced. b After repositioning, one can inspect the reduced fracture and the buccal bone plate through the preexisting mucosal laceration. In cases without soft-tissue lacerations, small bone fragments should not be denuded. Semirigid fixation has been created with acid-etch techniques in combination with thin, plain steel wire, covered with light cured resin. c The condition after closure of the mucosal lacerations.

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The postoperative treatment will be similar to that after luxation injuries. An avulsed tooth with a closed apex should undergo early pulpectomy and root canal treatment. Even so, the risk for root resorption will be higher in proportion to the length of the “dry” period. Often, the prognosis may be regarded as so poor that it is tempting not to replant the avulsed tooth. Even then however, there may be things to gain from a replantation. The alveolar bone may be preserved to a much larger degree with the tooth in position in the socket, if only for a limited period of time, than if the tooth had not been replanted. Thereby, the conditions for future dental implant installation may be greatly improved.

5

Alveolar trauma

Obviously, alveolar trauma seldom occurs alone, almost invariably a tooth or group of teeth are involved. Typically fractures of the alveolar process are stabilized through indirect management by splinting of the dentition. Only in rare indications and in the presence of larger bone blocks is microplate or rarely miniplate fixation of alveolar segments indicated. Care must be taken to maximally preserve the blood supply and thus the viability of the segments. A fracture of a dentate block of the alveolar process should be treated longer with more rigid arch bars or splints than mentioned for other isolated conditions in this chapter. Such a fixation should be maintained for 6 weeks. In high-energy trauma the mandible is sometimes forced towards the maxilla with a force that splits both the teeth and alveolar process (Fig 1.5.7-3a–b). Such injuries may require extraction of a large number of teeth. Due to the crush type injury, large amounts of alveolar bone may have to be removed. Care should be taken to preserve any bone that might have a chance to survive. The success of future reconstruction efforts will be greatly improved if as much of the original bone structure as possible can be saved.

a

b

Fig 1.5.7-3a–b a High-energy trauma sustained in a fall from high altitude. The mandible has hit the maxilla and the upper and lower dentition each have impacted the other. Severe axial fractures of teeth were sustained in combination with corresponding fractures of supporting alveolar bone. b CT scan of the injury.

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6

Primary dentition

In general, trauma in the primary dentition seldom should have sophisticated treatment. Extraction is the treatment of choice for most fractured or luxated teeth in the primary dentition. Replantation of avulsed primary teeth should be avoided due to the risk of damage to underlying permanent teeth and the poor prognosis of replanted teeth. Intrusion injuries most often can be left untreated, since most primary teeth will have the potential to reerupt spontaneously.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.8 Teeth in the fracture line

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The fate and consequences of teeth involved in the fracture line have been debated for a long time. It is almost exclusively a matter of concern in mandibular fractures. The controversy is whether they should be extracted or preserved and what the risk of infection will be to the fracture. Fear of infection was the main reason to extract a tooth in the fracture line. This fear has to a large extent been inherited from the past, especially in the pre-antibiotic era. In those days, it was more or less mandatory to remove a tooth from the fracture line. Otherwise it was presumed that the communication from the oral cavity through a disrupted periodontal membrane into the fracture line would create an infection resulting in delayed healing, non-union, or even osteomyelitis. Other sources of infection from a tooth in the fracture line might include the devitalized tooth, which could be secondarily infected, and then infect the fracture. Today, with rigid fracture stabilization and antibiotics available, many teeth in fracture lines are preserved and not extracted during primary fracture care. Although many scientific studies have offered information on the issue, the controversy persists. In one study, Ellis studied 402 patients with fractures in the mandibular angle. Teeth were removed in 75% of the fractures that contained teeth. Postoperative complications occurred in 19% of the sample, versus 19.5% when the tooth was retained. Fractures not containing teeth had postoperative infection rate of 15.8% compared to 19.1% for those which had teeth in the fracture. The differences, however, were not significant. Similar findings have been demonstrated by others. Thus, we find ourselves without strong scientific evidence to support either side of the controversy. Other factors must also be considered. The patient’s general oral hygiene and

cooperation always influence the decision. The site of the fracture may be important. The mandibular angle is more prone to fracture infection than other locations in the mandible. An impacted third molar with little prospect of normal eruption should be removed at the time of open fracture treatment if it would not make the fracture treatment more complex. In any area, needless to say, the presence of periapical, periradicular, or pericoronal infection around a tooth in the fracture is an indication for removal. The same goes for badly fractured teeth, or teeth dislocated from their sockets. On the other hand, a healthy tooth, surrounded by healthy periodontal membrane and good gingival conditions, should be retained. Sometimes, but not always, a tooth in the line of fracture may make the fracture reduction easier. If such a tooth needs to be removed, it may still be advisable to delay extraction until the fracture has been stabilized by internal fixation. Surgical removal of an impacted tooth may lead to a reduced bone buttress, and as a consequence may make a stronger and more rigid internal fixation necessary or may reduce the remaining bone’s potential for healing. Finally, the prognosis for teeth left in the line of mandibular fractures needs to be discussed. Kahnberg and Ridell studied 185 teeth in the line of mandibular fractures. Clinical and radiological findings revealed complete recovery in 59% of those teeth. Obviously 41% did not do so well. Therefore, if teeth are left in mandibular fracture lines, they should be followed both clinically and radiologically, with emphasis on both marginal and periapical conditions. All in all, the management of teeth in mandibular fracture lines should continue to be an individual clinical judgement, taking case by case and considering all aspects of the injury.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.9 Implant removal and stress protection

1

Removal before completion of fracture healing

111

2

Removal after fracture healing

111

3

Stress protection

112

4

Implants and secondary trauma

112

5

Adverse side effects from titanium implants

112

6

Effects on medical imaging and radiotherapy

113

7

Summary

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Authors Gerson Mast, Michael Ehrenfeld, Joachim Prein


Along with the development and first clinical use of modern internal fixation materials, which started with metallic implants first made of stainless steel and cobalt-chromiummolybdenium (vitallium), later of titanium, questions about the necessity for implant removals were raised. These questions are closely related to the biologic behavior of those materials in the human body, namely corrosion resistance, behavior in presence of infection, and the potential to create other adverse phenomena such as allergies. In addition, questions about the long-term performance of relatively stiff implants were discussed, because obviously there is no need for an implant to be in place after a fracture has healed. Above that, an implant may have long-term adverse effects on bone stability, because the presence of the implant may prevent the bone from returning to maximum strength under a given physiological situation. A considerable amount of scientific and clinical research was invested over the years with the result that all materials mentioned above interfere with the biologic environment to some extent. However, the interpretation of those results and their clinical relevance is still controversially discussed. In addition, implant removal always means an additional surgical intervention with associated risks resulting from surgery and/or anaesthesia, and with additional costs. The intention of scientists was to find a biocompatible material without the need for removal, ideally a biodegradable implant that would completely disappear after a fracture has healed. Early experiences with corrosion of internal fixation devices made from stainless steel and reports about allergic reactions have driven the practice of implant removal. The development and worldwide distribution of pure titanium implants for craniomaxillofacial applications, which have shown biocompatibility without evidence of any adverse side reactions, and which are widely used as permanent implants for dental rehabilitation, has overcome the necessity for implant removal as a principle technique. Therefore, every decision for the removal of a nonresorbable implant should have a clear individual indication depending on the material and also on the clinical situation.

1

Removal before completion of fracture healing

Indications to remove and replace implants during fracture healing are mainly problems caused by fractured plates, malpositioned plates, or loose hardware (like loose screws) with or without consecutive infection. Infection alone with osteosynthesis material adequately in place is not an indication for implant removal. Fracture healing in an infected area is possible, but only if there is no interfragmentary motion and adequate stability, usually under the condition of load-bearing fixation.

2

Removal after fracture healing

Absolute indications to remove metallic implants after a fracture has healed are mostly related to fractured or loose plates and screws, problems with infection, and/or penetration of the hardware through the soft-tissue envelope. Relative indications for implant removal are potential interferences of implants with additional surgical interventions, such as sinus operations following midface fractures, bone augmentation procedures, or dental rehabilitation, for instance placement of dental implants. In children, removal of metallic implants is still recommended. Expanding and growing bones have a tendency to overgrow metallic implants, which leads to a relative change in position of an implant, which finally may be incorporated into the bone or even appear on the opposite side. This phenomenon has falsely been called “plate migration,” which is a misnomer because there is no active movement (migration) of the implant, but a passive translation. Nevertheless, in craniofacial surgery this translation may lead to an intracranial displacement of metallic fixation devices. Some surgeons believe that leaving implants in the midface and the mandible may have a negative impact on further growth, even if there are controversial reports about growth problems following trauma care in children.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.9 Implant removal and stress protection

Additional relative indications arise from individual patient’s concerns, such as palpable plates, visible plates through layers of overlaying skin, sensitivity to the cold, or uncharacteristic and unspecified disturbances. However, the vast majority of nonresorbable pure titanium fixation devices do not cause any problems during or after fracture healing. Therefore, there is usually no objective indication for their removal.

3

Stress protection

Plates for internal fixation reduce the load in the fracture site to prevent interfragmentary motion and support fracture healing. The terms “stress protection” or “stress shielding” were first used in long-bone healing to describe unfavorable structural changes in the form of porosis under the respective plates in the fractured areas after healing. This effect was believed to be the result of the stress (load) reduction caused by the plates. Meanwhile it became evident that cortical porosis in long bones was mainly the result of impaired periosteal blood supply due to pressure of the plates against the bone surface. Low contact plate profiles helped to overcome this problem. In the craniomaxillofacial area the overwhelming majority of data published show that there is no good evidence for a negative effect of so-called stress protection neither in the mandible nor in the midface. Experimental findings, supported by clinical observations, show that there are no signs for osteoporosis or bone atrophy in patients with nonresorbable implants of any available size in place. Prevention of “stress protection” today is not a valid argument for implant removal.

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4

Implants and secondary trauma

The structure and biomechanical properties of the facial skeleton help to protect the functional units, like eye balls and brain, in case of injury. Internally placed fixation devices, which are left in place after bone healing, can change the biomechanical behavior of the part of the facial skeleton where they are located. It is being discussed, if this change of biomechanical behavior can lead to atypical and perhaps more complex fracture patterns in the case of secondary trauma, which may present higher risks for injuries of functional units. However, a secondary trauma with secondary fractures in an identical area is very rare and there are no relevant data available up to now to support the thesis that more complex fracture patterns may be observed in these cases.

5

Adverse side effects from titanium implants

The majority of approved metallic implants for trauma and reconstruction today are made of pure titanium. The human body is saturated with titanium, no additional soluable titanium can thus become active. Titanium implants, as used in the craniomaxillofacial area, are fully biocompatible and no adverse health effects are known up to now.


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Authors Gerson Mast, Michael Ehrenfeld, Joachim Prein

6

Effects on medical imaging and radiotherapy

X-rays and computed tomography (CT)

The attenuation and backscatter of diagnostic medical x-rays is a function of the energy of the x-ray, thickness and density of the object, and atomic numbers of constituents. Stainless steel and cobalt-chrome-molybdenium alloys, which have densities twice that of titanium, decrease x-ray penetration by three orders of magnitude more than titanium, and four orders of magnitude more than calcium. Thus, compared to stainless steel, the degree of artifact creation with titanium implants is not relevant in almost all clinical situations. Magnetic resonance imaging (MRI)

MRI is based on the response of substances to static and dynamic magnetic fields of significant magnitudes. Basic concerns arising with metallic objects in a magnetic field are the introduction of artifacts in the diagnostic image, movements of the implant within the magnetic field, or production of heat or electrical current at the implant site. Ferromagnetic materials are of greatest concern. Different from stainless steel, the capacity of ferromagnetism of titanium is very low. Therefore it causes only minimal imaging artifacts or backscatter.

showed elevated doses by 10–15% with titanium at the plate-tissue interface, and 15–25% with stainless steel due to backscatter effects. Recent studies did not find a significant increase of radiation doses in the vicinity of titanium implants. As a consequence a routine plate removal is not recommended prior to postoperative radiotherapy. Increased associated risks with late implant removal at a higher age

An argument to promote early implant removal after fracture healing or reconstruction is the fact that late implant removal may become necessary after many years because of secondary changes, for instance plate exposure following alveolar crest atrophy. After an interval of many years the patient’s general condition may have changed for the worse, thus creating an unnecessary risk scenario that would not have been present in early implant removal. However, indications for late implant removal are very rare, and there is no statistical evidence that an overall increased risk for complications in those cases presents a clinical problem which is statistically more significant than potential problems associated with routine early implant removal.

7

Summary

Radiation therapy

Due to the backscatter phenomena the distribution of radiation around plates and screws is of concern, when postoperative radiation is required. Compared to diagnostic x-rays, external beam radiation therapy has much greater penetration and different absorption characteristics. Reports

In summary, besides the above mentioned absolute indications no general recommendation for removal of metallic osteosynthesis material can be given. It must be noted that it is first of all the patient’s decision, whether he or she wants to have the implants removed or not.

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1 General aspects 1.5 Principles of craniomaxillofacial trauma care 1.5.10 Techniques of mandibulomaxillary fixation (MMF)

1

Basic considerations

115

2

Mandibulomaxillary fixation options

115

3

Tooth-borne devices

115

3.1 Wire fixation

115

3.2 Arch bars

117

3.3 Brackets

120

4

120

Bone-borne devices

4.1 IMF screws

120

4.2 Plates

121

4.3 Spino-mental fixation

122

5

122

Dentures or Gunning-type splints

6 Important aspects of prolonged or long-term MMF

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7

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Summary

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Author Gerson Mast

1.5.10 T echniques of mandibulomaxillary fixation (MMF) Correct and precise intraoperative mandibulomaxillary fixation (MMF), often also called intermaxillary fixation (IMF), is a key for the successful establishment or preservation of the occlusal relationship of the upper and lower jaws in facial trauma, reconstructive and orthognathic surgery. Historically, mandibulomaxillary immobilization has been documented for more than 2,000 years and a variety of different techniques and devices have been developed over time in close relation to the evolution of trauma care and material research. Especially during the last century, a multitude of new methods and refinements were established.

MMF is also used for maintenance of the occlusion in mandibular reconstruction and for control of the interalveolar distance while reconstructing alveolar crests or the maxilla. In orthognathic surgery MMF is needed intraoperatively to secure the new jaw relationship before and during internal fixation. Postoperatively, the fixation device can be used to fix guiding elastics for functional training or in complications, eg, bad splits, as a support for an uneventful bone healing.

2

Mandibulomaxillary fixation options

The discussion about the need for MMF in combination with open reduction and internal fixation in simple fracture patterns is controversial, but there is no doubt about its necessity in complex fractures.

A multitude of immobilization devices have been described. The majority is tooth-borne, such as wire ligatures, arch bars, cap splints, adhesive cast splints, brackets, and selffixing plastic circumdental lugs/loops.

In this context it must be noted that internal fixation techniques without or in combination with inadequate devices to fix the occlusion can lead to preventable failures, especially in the hands of inexperienced surgeons.

Others are fixed to the bone, such as dentures and splints, plates, pins, and screws.

1

According to the medical schools of different countries there are preferences for one or the other technique, mostly depending on tradition and not on science.

Basic considerations

The suitability of MMF devices depends on several criteria, such as stability, applicability in dentate and edentulous patients, children, and adults, short- and long-term immobilization, additional harm to the patient (pain, teeth, gingiva), risk for the surgeon (such as injuries), time of installation, costs, and others. Main indications in trauma are: • Temporary fragment stabilization in emergency cases before definitive treatment • Intraoperative fixation in combination with internal fixation • Use as tension band • Long-term fixation in nonsurgical management • Fixation of avulsed teeth and alveolar crest fragments.

3

Tooth-borne devices

3.1 Wire fixation

Many different techniques for wire fixation exist. Ivy loops, Ernst ligatures, Stout intermaxillary loop wiring, and Obwegeser multiple loop wiring are only a few of the most popular. Wire fixation techniques for MMF have a somewhat reduced stability. Favorable features are the fast and simple procedures and the almost unrestricted, cost-effective availability. Unfavorable characteristics are the lack of stability, no adequate tension banding in combination with internal fixation, trauma to the gingiva, and the risk for extrusion of teeth. Therefore, wire fixation is mainly indicated in emergency

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cases for short-term immobilization in a full or partial dentition prior to surgery, and in selected cases with simple fracture patterns for intraoperative fixation. Several important aspects must be mentioned before starting: • In the case of severe malocclusion it may be impossible to use wire ligatures. • Loose teeth should not be included into the ligatures. • The ligatures of the upper and lower jaw must be in an opposite, symmetric position for correct immobilization. • Medical professionals are confronted with the risk of contamination from prick accidents. Two of the most popular and technically similar techniques, the use of Ivy loops and Ernst ligatures, are briefly described here.

a

b

Ivy loops

Positioning and insertion of the ligatures: Bending a wire to halves, a small loop is created in the middle part by twisting it around the shaft of a clamp. The two free wire ends are interdentally placed from the buccal side between two stable teeth. The wire ends are wrapped around each neighboring tooth and fed back through the next dental interspace. The posterior wire is passed through the original loop and then tightened by twisting the anterior and posterior wire ends together. The same procedure is performed for the other dental arch, directly opposite the first Ivy loop. The loops may each be tightened further over the wire to decrease the loop size and length. MMF is finally achieved by passing and tightening a second wire through two opposing Ivy loops or by placing elastic bands over the loops if preferred (Fig 1.5.10-1a–e).

c

d

Fig 1.5.10-1a–e Ivy loops. a A small loop is created with a 0.4 mm wire. b After passing both free ends through the space between the premolars, the wire ends are then passed around those premolars and fed back through the next dental interspace. c The distal wire is passed through the original loop. d The wire ends are then twisted together and the excess is cut off. The same procedure is performed in the opposite dental arch. e Finally, mandibulomaxillary fixation is achieved by passing a wire through the two opposing Ivy loops, which is then tightened.

e

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Author Gerson Mast

Ernst ligatures

3.2 Arch bars

Positioning and insertion of the ligatures: An Ernst ligature is applied to two neighboring teeth, preferably the premolars.

Arch bars are tooth-borne devices for MMF of dentate patients. They can be used:

One wire end is passed from the buccal side through the interdental space between the canine and premolar. The other end is passed between the second premolar and molar. Both ends are then fed back from the palatal/lingual to the buccal side via the interdental space between the premolars 4 and 5. One wire end must pass below, the other on top of the horizontal portion of the wire on the buccal side. By twisting with the twister, the wire is then tightened.

• For temporary fragment stabilization in emergency cases before definitive treatment • As tension band in combination with rigid internal fixation • As long-term fixation for nonsurgical fracture management • For fixation of avulsed teeth and alveolar crest fractures

Ligatures are placed in all four sections of the dental arches in a symmetric position. MMF is achieved by twisting the wire ends of two opposite ligatures together, after assuring proper occlusion (Fig 1.5.10-2a–b). Care must be taken not to break the wires at this point as restarting the procedure would be necessary. The wire ends are then cut and bent towards the dental surface to protect the oral mucosa.

Because of this extensive applicability, arch bars are still considered the gold standard for MMF. Advantages are the stability, the simplicity of the procedure, and the possibility to fix loose teeth. Disadvantages are the painful and time-consuming application, the damage to the gingiva associated with several types of arch bars, and the high potential for prick accidents with risk of inoculation of infected material. Different types of arch bars are in use. They come as custommade or commercially manufactured medical tools. Custommade arch bars allow precise placement of the bar to prevent damage to the surrounding soft tissues, if applied properly. Time for insertion is short. The disadvantage is the need for an experienced dental technician who is not always available, especially in emergency cases.

a

b

Fig 1.5.10-2a–b Ernst ligature. a A 0.3 or 0.4 mm wire is placed between and around the premolars. The two ends are twisted together. b After placement of two opposite ligatures in the premolar area of both jaws, these ligatures are twisted together.

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Commercially manufactured arch bars, for example, are Schuchardt, Erich, and Dautreys arch bars. Arch bars are available in aluminum, stainless steel, and nowadays also titanium, as well as various alloys. Before arch bars are applied the occlusion must be checked. The goal is to achieve full interdigitation of the teeth with regular contacts. In case of severe malocclusion, such as a deep bite deformity, it may be impossible to use bars. To have calculable tension vectors between the placed mandibulomaxillary wire loops or elastics, there should be a symmetrical positioning of the hooks in the upper and lower jaw. This is essential for functional training with elastics. If arch bars are used for long-term immobilization, the teeth should be fluoridated before insertion to prevent demineralization in the contact zone between tooth surface and bar. Two of the most common prefabricated types of arch bars, Schuchardt and Erich, are briefly described. Schuchardt arch bars

The prefabricated arch bars must be adjusted in shape and length to the individual situation. The arch bars should not damage the gingiva. Therefore, Schuchardt arch bars are available with occlusal stops to prevent migration of the bar to the gingiva. In a full dentition the amount of occlusal stops can be reduced to one on each side and one in the front.

a

Before fixation, the bars are adapted closely to the teeth. If maximum stability is needed, eg, for long-term fixation in multiple fractures, the bar is cut behind the second molar. If reduced stabilty is adequate, eg, for temporary fixation in condylar neck fractures, the bar can be trimmed behind the second premolar. For maximum stability, the bar is fixed to each healthy tooth (Fig 1.5.10-3a–c). Isolated avulsed teeth in combination with jaw fractures can be stabilized. For long-term immobilization, tension banding, or fixation of avulsed teeth, Schuchardt did recommend the use of methamethacrylate. Methamethacrylate is placed in a thin layer on the vestibular surface of bar and wires (Fig 1.5.10-3d–e). The objectives are to protect the wires and bars against loosening under function, to keep the wires and bars in the desired position preventing migration onto the gingiva, and to cover all sharp wire ends for protection of the surrounding soft tissues. For short-term MMF, the arch bars are typically used without methamethacrylate. After removal of the occlusal stops, the occlusion is established and rubber or 0.5 mm wire loops are inserted in a symmetrical fashion. Stable immobilization of the jaws in maximum intercuspidation is achieved (Fig 1.5.10-3f ).

b

Fig 1.5.10-3a–f Schuchardt arch bars. a The prefabricated Schuchardt arch bar is adjusted and cut in length to the individual situation. The occlusal stops prevent migration onto the gingiva. A first loop with a 0.3 mm wire is placed around the left second premolar, one end above and the other below the arch bar. b After passing the wires around each tooth, they are twisted and cut to length.

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c

d

e

f

Fig 1.5.10-3a–f (cont) Schuchardt arch bars. c All wire ends are placed onto the arch bar. d Methamethacrylate is placed in a thin layer onto the bar and covers the wires. e After removal of the occlusal stops, the ends are smoothed with a grindstone. f Intermaxillary fixation is achieved either with a 0.5 mm wire or elastics.

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Erich arch bars

Erich arch bars belong to the most popular devices for MMF. Usually made of a relatively soft alloy, they do not have occlusal stops. Fixation to the teeth is similar to the fixation of Schuchardt arch bars (Fig 1.5.10-4). 3.3 Brackets

These tooth-borne devices are directly bonded to the tooth surface. Usually used for orthodontic treatment, they can also be applied for MMF. They are commonly used in orthognathic surgery and in selected trauma cases with full permanent dentition and healthy teeth. Advantages are the noninvasive application and the simplicity of the procedure. Disadvantages are the need for access to the technology in emergencies, the problem of keeping the tooth surfaces dry for bonding, the costs, and the risk for extrusion of single teeth when used for long-term fixation.

4

Bone-borne devices

Recently bone-borne devices have gained increasing popularity for mandibulomaxillary immobilization. Besides screw anchored hooks, screw anchored 2 or 3-hole plates (“hanger plates”), and transmucosally fixed conventional osteosynthesis screws as retentions for MMF, today specific kits with specialized IMF screws are commercially available. Most of these screws are self-drilling and self-tapping with screw heads that offer a special geometry to serve as retention for wires or elastics. The increasing popularity is due to fast insertion, low risk for prick accidents for surgeons, missing traction on teeth, eg, in orthognathic surgery, and ease of removal. The strong commercial promotion focuses on these advantages but it must also be realized that there are considerable optional disadvantages reported like tooth root injuries, damage to the soft tissues (mucosa and nerves), undesired displacement of fragments by outward rotation, screw fractures, and loosening. Postoperative functional training with elastics becomes more difficult because of missing adequate retention points for directional guidance. Typical indications are short-term intraoperative immobilizations especially for treatment of simple fracture patterns in orthognathic and reconstructive surgery. The use of plates, pins, and screws is limited in severely comminuted and displaced fractures, in unstable segmented fractures, in fractures of the alveolar process, and in children, if tooth buds are still in place.

Fig 1.5.10-4 MMF with Erich arch bars. Like Schuchardt arch bars, Erich arch bars are fixed to each healthy tooth with 0.3 mm wire loops. Intermaxillary fixation is achieved with elastics that are placed onto the hooks of the bars.

Important aspects before applying bone-borne devices are: • Checking the position of the tooth roots, the infraorbital and mandibular nerve • Positioning the screws or pins in a symmetrical fashion from jaw to jaw if possible • Avoiding interference with the surgical approach and internal fixation devices 4.1 IMF screws

Intermaxillary fixation (IMF) screws are made from stainless steal. They are self-drilling and self-tapping. The screw head is elongated and contains two holes in a cruciform orientation for wire placement. Screw insertion can be performed directly through the mucosa. Care has to be taken that the screw head does not compress the gingiva when fully seated. Various IMF screw

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placement patterns exist and are dictated by the fracture location. The areas for screw application are limited by the tooth roots and the position of the infraorbital and inferior alveolar nerve. The recommended placement of IMF screws is superior to the maxillary and inferior to the mandibular tooth roots, and either lateral or medial to the long axis of the canine roots. For MMF 0.4 mm wires are inserted through the IMF screw holes. Wire ligatures can also be wrapped around the screw head grooves. Before tightening the wires, the correct occlusion has to be established. For additional stability, wiring in an X-pattern can be applied. Alternatively, elastics can be inserted (Fig 1.5.10-5). Looking at the results according to the originally recommended technique some problems have been reported. A lack of stability can occur due to the long distance between the IMF screws which is bridged with nonrigid wires.

Fig 1.5.10-5 MMF with special IMF screws placed opposite of each other in both jaws. 0.4 mm wires are inserted through the IMF screws holes.

In addition, tightening of the anterior wires may create a posterior open bite. To overcome this problem additional IMF screws or Ernst ligatures on the posterior dentition may be used. Overtightening of the wires may lead to an outward rotation of a fragment because of the position of the screws and the long lever arm. Further problems are the burying of screw heads in the soft tissues, especially in the anterior mandibular vestibulum, and interference of the wire loops with the upper incisor edges or canine facets. With research and experience in the field of screw placement close to and between teeth mainly coming from miniscrew application in orthognathics, new screw types have been developed which can also be used for MMF techniques.

Fig 1.5.10-6 MMF with 2-hole 2.0 adaptation plates.

4.2 Plates

In dentate patients so-called “hanger plates” can be used for short-term MMF. For this, 2 or 3-hole pieces are cut from a 2.0 adaptation plate. These pieces are bent in a slightly angular shape or as little hooks. After using a 1.5 mm drill the 2-hole plates are monocortically fixed with 2.0 mm screws of 6 mm length in the planned position. After establishing the occlusion, MMF is performed with wires or elastics running through the plate holes or around the hooks (Fig 1.5.10-6). Compared to IMF screws there is less risk of damage to the tooth roots and nerves, especially in the lateral aspect of the mandible. In edentulous patients plates can be used as “interarch plates” to fix and save the vertical dimension between the jaws (Fig 1.5.10-7).

Fig 1.5.10-7 MMF in an edentulous patient, with an adaptation plate fixing the vertical dimension between the jaws.

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4.3 Spino-mental fixation

This bone-borne technique is a simple method of MMF in dentate or denture wearing patients especially with subcondylar fractures. Under local anesthesia S-shaped steel wire hooks are placed below the nasal spine and slightly above the mental protuberance in the symphyseal region and fixed with miniscrews. MMF is achieved using wire ligatures or elastics. Similar to the problems related to IMF screws the burying of the hooks in the anterior mandibular vestibulum and the interference of the wire loops with the upper incisor edges can occur (Fig 1.5.10-8).

5

Dentures or Gunning-type splints

MMF in edentulous or partially edentulous patients can be achieved with the help of dentures. If those are not available acrylic splints may be fabricated. General aspects such as age and condition of the patient must be considered. Especially in elderly patients the immobilization period, which is often painful, should be restricted to a minimum and long-term use should be avoided whenever possible. For MMF retention elements can be applied to the dentures or splints. This can be achieved by fixing arch bars, metal hooks, or screws on the dentures or splints. Alternatively, bone-borne IMF screws can also be used for MMF in cases with sufficient bone stock. Nutrition must be assured by reducing the retromolar acrylic part of the dental prosthesis or by creating a “feeding hole” in the incisor region of the prosthesis or splint. The correct mandibulomaxillary relationship must be established either by an appropriate occlusal intercuspidation of the dentures or by positioning stops on the occlusal surfaces of the Gunning-type splints. The dentures or splints can be fixed with suspension wires to the bone, such as transalveolar, zygomaticomaxillary, or circumferential mandibular wiring, or, more easily, with screws. The maxillary prosthesis or splint should be fixed in the compact anterior part of the hard palate. The lower denture can easily be fixed in the symphyseal area because of the dense bone in this region. One or two screws are usually sufficient (Fig 1.5.10-9).

Fig 1.5.10-8 MMF with S-shaped steel wire hooks. A partial acrylic splinting is used to separate the elastics from the front teeth.

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Fig 1.5.10-9 MMF with Gunning splints. The patient’s dentures are fixed with screws to the jaws, the incisors are removed to create a feeding hole.


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6 Important aspects of prolonged or long-term MMF

If long-term MMF is planned, several important aspects should be respected. The patient must be provided with a wire cutter or scissors to cut elastics or wires in cases of emergency, to prevent airway problems following emesis, fainting, or epileptic attack, and he/she or escort should be instructed in its use to allow for urgent removal if necessary. Good oral hygiene is mandatory during immobilization periods. For this goal a water pick device is helpful. The use of fluoride gels prevents demineralization and reduces the risk for caries. During the immobilization period body weight should be controlled. Nutrition counselling and the use of soft diets should be part of the treatment. At least weekly follow-up appointments are recommended to check the stability of the occlusal relationship. Fatigue of wires, bruxism, or the removal of the wires or elastics by the patient may reduce stability and can lead to preventable complications, eg, malocclusion, nonunion, and infection.

7

Summary

Mandibulomaxillary fixation (MMF) can be achieved with many different devices depending on the local and general conditions of the patient, the medical needs in trauma, orthognathic and ablative or reconstructive surgery, the availability of technologies and technical support. All methods show advantages and drawbacks. In dentate or partially dentate patients, arch bars are still the gold standard to establish the occlusion. They have proven their usefulness in short- and long-term immobilization. Any surgeon dealing with craniofacial surgery should be able to use them properly. Devices with reduced long-term stability should not be used for long-term immobilization. In emergency and selected cases wire ligatures, plates, screws, and pins can be an alternative to arch bars. The growing interest in bone-borne fixation devices actually leads to increased activities to create better devices. In edentulous patients dentures or splints are helpful tools for MMF, though long-term use should be avoided. In selected cases interarch plating can be an alternative.

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1 General aspects 1.6 References and suggested reading

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(1993) Immune response to nickel and some clinical observations after stainless steel miniplate osteosynthesis. Int J Oral Maxillofac Surg; 22(4):246–250. Troulis MJ, Kaban LB (2001) Endoscopic approach to the ramus/condyle unit: clinical applications. J Oral Maxillofac Surg; 59(5):503–509. Williams DF (1981) Biocompatibility of Clinical Implant Material. Boca Raton: CRC Press, 30–35, 78–89,112–115. Yaremchuk MJ, Gruss JS, Manson PN (1992) Rigid Fixation of the Craniomaxillofacial Skeleton. Boston: Butterworth-Heineman, 15, 28–56, 79, 116, 124–125, 134–135. Waalkes MP, Rehm S, Kasprzak KS, et al

(1987) Inflammatory, proliferative, and neoplastic lesions at the site of metallic identification ear tags in Wistar [Crl(WI) BR] Rats. Cancer Res; 47(9):2445–2450.

Chapter 1.5.2

Bilkay U, Gürler T, Bilkay U, et al (1997)

Comparison of fixation methods in treating mandibular fractures: scintigraphic evaluation. J Craniofac Surg; 8(4):270–273. Champy MA, Wilk JH, Schnebelen (1975) [The treatment of mandibular fractures by means of osteosynthesis without intermaxillary immobilization according to F.X. Michelet.] Zahn, Mund, Kieferheilk; 63:339. German. Frost HM (1990a) Skeletal structural adaptations to mechanical usage (SATMU): 1, Redefining Wolff’s law: the bone modeling problem. Anat Rec; 226:403–414. Frost HM (1990b) Skeletal structural adaptations to mechanical usage (SATMU): 1, Redefining Wolff’s law: the bone modeling problem. Anat Rec; 226:414–421. Ghazal G, Jaquiéry C, Hammer B (2004) Non-surgical treatment of mandibular fractures: survey of 28 patients. Int.J.Oral Maxillofac. Surg; 33(2):141–145. Guerrissi JO (2001) Fractures of mandible: is spontaneous healing possible? Why? When? J Craniofac Surg; 12(2):157–166.

Chapter 1.5.6

Champy M, Lodde JP (1976) [Mandibular

synthesis. Placement of the synthesis as a function of mandibular stress]. Rev Stomatol; 77(8):971–976. French. Champy M, Lodde JP, Kahn JL, Kielwasser P

(1986) Attempt at systematization in the treatment of isolated fractures of the zygomatic bone: techniques and results. J Otolaryngol; 15(1):39–43. Champy M, Lodde JP, Schmitt R et al (1978) Mandibular osteosynthesis by miniature screwed plates via a buccal approach. J Oral Maxillofac Surg; 6(1):14–21. Härle F, Champy M, Terry BC (1999) Atlas of Craniomaxillofacial Osteosynthesis. Stuttgart New York: Georg Thieme Verlag. LaTrenta G, McCarthy J et al (1990) The role of rigid skeletal fixation in bone graft augmentation of the craniofacial skeleton. Plast Reconstr Surg; 84(4):578–587. Luhr HG (1985) Basic research, surgical technique and results of fracture treatment with the Luhr-Mandibular-CompressionScrew System (MCS System). HjortingHansen E (ed), Oral and maxillofacial surgery. Berlin: Quintessence,124. Luhr HG (1968) [On the stable osteosynthesis in mandibular fractures.] Dtsch Zahnärztl Z; 23(7):754. German. Perren SM, Cordey J (1980) The concept of interfragmentary strain. Uhthoff HK, Stahl E (eds), Current concepts of internal fixationof fractures. Berlin Heidelberg New York: Springer Verlag, 63–70. Phillips J, Rahn BA (1988) Fixation effects on membranous and endochondral bone graft resorption. Plast Reconstr Surg; 82(5):872–877.


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Rahn BA, Cordey J, Prein J, et al (1975) [Biomechanics of osteosynthesis in the mandible.] Fortschr Kiefer Gesichtschir; 19:37–42. German. Spiessl B (1989) Internal Fixation of the mandible. A manual of AO/ASIF Principles. Heidelberg New York: Springer-Verlag.

Cordey J, Perren SM, Steinemann SG (2000) Stress protection due to plates: myth or reality? A parametric analysis made using the composite beam theory. Injury; 31 Suppl 3:C1–13.

Chapter 1.5.7

Dujardin F, Fevrier V, Lecorvaisier C, et al

Andreasen JO, Andreasen FM (1999)

Essentials of traumatic injuries to the teeth. Copenhagen: Munksgaard. Blomlöf L (1981) Milk and saliva as possible storage media for traumatically exarticulated teeth prior to replantation. Swed Dent J Suppl; 8:1–26. Dewhurst SN, Mason C, Roberts GJ (1998) Emergency treatment of orodental injuries: a review. Br J Oral Maxillofac Surg; 36(3):165–175.

Chapter 1.5.8

Ellis E III (2002) Outcomes of patients with

teeth in the line of mandibular angle fractures treated with stable internal fixation. J Oral Maxillofac Surg; 60(8):863– 865. Iizuka T, Lindqvist C, Hallikainen D, et al

(1991) Infection after rigid internal fixation of mandibular fractures: a clinical and radiologic study. J Oral Maxillofac Surg; 49(6):585–593. Kahnberg KE, Ridell A (1979) Prognosis of teeth involved in the line of mandibular fractures. Int J Oral Surg; 8(3):163–172.

Chapter 1.5.9

Alexander R, Theodos L (1993) Fracture of

the bone-grafted mandible secondary to stress shielding: report of a case and review of the literature. J Oral Maxillofac Surg; 51(6):695–697. Altobelli DE (1992) Implant materials in rigid fixation: Physical, mechanical, corrosion, and biocompatibility considerations. Yaremchuk MJ, Gruss JS, Manson PN (eds), Rigid fixation of the craniomaxillofacial skeleton. Boston: Butterworth-Heinemann, 28–56. Bartlett SP, DeLozier JB III (1992) Controversies in the management of pediatric facial fractures. Clin Plast Surg; 19(1):245– 258. Brown SA, Simpson JP (1981) Crevice and fretting corrosion of stainless-steel plates and screws. J Biomed Mater Res; 15(6):867– 878. Chandler CL, Uttley D, Archer DJ, et al

(1994) Imaging after titanium cranioplasty. Br J Neurosurg; 8(4):409–414. Cook SD, Thomas KA, Harding AF, et al

(1987) The in vivo performance of 250 internal fixation devices: a follow-up study. Biomaterials; 8(3):177– 184.

Dechow PC, Ellis E III, Throckmorton GS

(1995) Structural properties of mandibular bone following application of a bone plate. J Oral Maxillofac Surg; 53(9):1044–1105. (1995) Allergic dermatitis caused by metallic implants in orthopedic surgery. Rev Chir Orthop Reparatrice Appar Mot; 81(6):473–484. Ellerbe DM, Frodel JL (1995) Comparison of implant materials used in maxillofacial rigid internal fixation. Otolaryngol Clin North Am; 28(2):365–372. Exner GU, Malinin TI, Weber D, et al (1996) Titanium implant for the osteosynthesis of massive allograft reconstruction to improve follow-up by magnetic resonance imaging. Bull Hosp Jt Dis; 54(3):140–145. Harris LJ, Tarr RR (1979) Implant failures in orthopaedic surgery. Biomater Med Devices Artif Organs; 7(2):243–255. Haug RH (1996) Retention of asymptomatic bone plates used for orthognathic surgery and facial fractures. J Oral Maxillofac Surg; 54(5):611–617. Haug RH, Cunningham LL, Brandt MT

(2003) Plates, screws, and children: their relationship in craniomaxillofacial trauma. J Long Term Eff Med Implants;13(4):271–287. Kennady MC, Tucker MR, Lester GE, et al

(1989) Histomorphometric evaluation of stress shielding in mandibular continuity defects treated with rigid fixation plates and bone grafts. Int J Oral Maxillofac Surg; 18(3):170–174. Kennady MC, Tucker MR, Lester GE, et al

(1989) Stress shielding effect of rigid internal fixation plates on mandibular bone grafts. A photon absorption densitometry and quantitative computerized tomographic evaluation. Int J Oral Maxillofac Surg; 18(5):307–310. Klaue K, Fengels I, Perren SM (2000) Long-term effects of plate osteosynthesis: comparison of four different plates. Injury; 31(2):52–62. Krischak GD, Gebhard F, et al (2004) Difference in metallic wear distribution released from commercially pure titanium compared with stainless steel plates. Arch Orthop Trauma Surg; 124(2):104–113. de Mello-Filho FV, Auader M, Cano E, et al

(2003) Effect of mandibular titanium reconstructive plates on radiation dose. Am J Otolaryngol; 24(4):231–235. Orringer JS, Barcelona V, Buchman SR

(1998) Reasons for removal of rigid internal fixation devices in craniofacial surgery. J Craniofac Surg; 9(1):40–44. Postlethwaite KR, Philips JG, Booth S, et al

(1989) The effects of small plate osteosynthesis on postoperative radiotherapy. Br J Oral Maxillofac Surg; 27(5):375–378.

Schiel H, Hammer B, Ehrenfeld M, et al

(1996) [Therapy of infected mandibular fractures.] Fortschr Kiefer Gesichtschir; 41:170– 173. German. Steinemann SG (1996) Metal implants and surface reactions. Injury; 27 Suppl 3:C16–22. Stoll P, Wächter R, Hodapp N, et al (1990) Radiation and osteosynthesis. Dosimetry on an irradiation phantom. Craniomaxillofac Surg; 18(8):361–366. Review. Stoll P, Wächter R, Hodapp A (1989) [Tumor irradiation after plate osteosynthesis. Dose determination on radiological phantom]. Dtsch Z Mund Kiefer Gesichtschir; 13(3):165–171. German. Sullivan PK, Smith JF, Rozzelle AA (1994) Cranio-orbital reconstruction: safety and image quality of metallic implants on CT and MRI scanning. Plast Reconstr Surg; 94(5):589–596. Thewes M, Kretschmer R, Gfesser M, et al

(2001) Immunohistochemical characterization of the perivascular infiltrate cells in tissues adjacent to stainless steel implants compared with titanium implants. Arch Orthop Trauma Surg; 121(4):223–226. Woo SL, Lothringer KS, Akeson WH, et al

(1984) Less rigid internal fixation plates: historical perspectives and new concepts. J Orthop Res; 1(4):431–449.

Chapter 1.5.10

Arthur G, Berardo N (1989) A simplified

method of maxillo-mandibular fixation. J Oral Maxillofac Surg; 47(11):1234. Bell RB, Wilson DM (2008) Is the use of arch bars or interdental wire fixation necessary for successful outcomes in the open reduction and internal fixation of mandibular angle fractures? J Oral Maxillofac Surg; 66(10):2116–2222. Cornelius CP, Ehrenfeld M (2010) The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature. Cranial Maxillofac Trauma Reconstruction; 3(2):55–80. Dal Pont G (1965) [On the employment of juxtaosseous metalic hooks in intermaxillary fixation in jaw fractures]. Riv Ital Stomat; 20:791–797. Italian. Dimitroulis G (2002) Management of fractured mandibles without the use of intermaxillary wire fixation. J Oral Maxillofac Surg; 60(12):1435–1438. Ernst F (1927) [The treatment of mandibular fractures by the dentist.] Kirschner M, Nordmann O (eds): Die Chirurgie, Band 4/1. Berlin Wien: Urban & Schwarzenberg, 842. German. Fordyce AM, Lalani Z, Songra AK, et al

(1999) Intermaxillary fixation is not usually necessary to reduce mandibular fractures. Br J Oral Maxillofac Surg; 37(1):422–423.

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Gear AJ, Apasova E, Schmitz JP, et al (2005)

Schneider AM, David LR, DeFranzo AJ, et al

Treatment modalities for mandibular angle fractures. J Oral Maxillofac Surg; 63(5):655– 663. Hippocrates H, Adams F (1849) The Genuine Works of Hippocrates. London: Sydenham Society. Ho KS, Tan WK, Loh HS (2000) Case reports: The use of intermaxillary screws to achieve intermaxillary fixation in the treatment of mandibular fractures. Ann Acad Med Singapore; 29(4):534–537. Hoffmann A, Mast G, Ehrenfeld M (2003) [Usage of IMF screws for mandibulomaxillary fixation.] AO OP Journal; 19:70–75. German. Iizuka T, Hallermann W, Seto I, et al (2006). A titanium arch bar for maxillomandibular fixation in oral and maxillofacial surgery. J Oral Maxillofac Surg; 64(6):989–992. Ivy RH (1922) Observations on fractures of the mandible. JAMA; 79(4):295–297.

(2000) Use of specialized bone screws for intermaxillary fixation. Ann Plast Surg; 44(2):154–157. Schuchardt K (1956) [A proposal for improvement of wire splint ligature]. Dtsch Zahn-Mund-Kieferheilk; 24:39–44. German. Sindet-Pedersen S, Jensen J (1990) Intermaxillary fixation of mandibular fractures with the bracket-bar. J Craniomaxillofac Surg; 18(7):297–298. Stout R (1943) Intermaxillary wiring and intermaxillary elastic traction and fixation. Manual of standard practice of plastic and maxillo-facial surgery. Military Surgical Manuals. London Philadelphia: W.B. Saunders. 272–276. Thor A, Andersson L (2001) Interdental wiring in jaw fractures: effects on teeth and surrounding tissues after a one-year follow-up. Br J Oral Maxillofac Surg; 39(5):398–401. Trinkle KL (2009) [Lesions of the dental roots through intermaxillary fixation screws. A radiologic and clinical follow-up examination.] Dissertation: LMU München: Department of Medicine. German. Vartanian AJ, Alvi A (2000) Bone-screw mandible fixation: an intraoperative alternative to arch bars. Otolaryngol Head Neck Surg; 123(6):718–721. Wolfe SA, Lovaas M, McCafferty LR (1989) Use of miniplate to provide intermaxillary fixation in the edentulous patient. J Craniomaxillofac Surg; 17(1):31–33. Yamada T, Sumi Y, Okazaki Y, et al (1998) A new intermaxillary fixation method using adhesive cast splints for avoiding skin puncture. Aust Dent J; 43(3):167–169.

López-Arcas JM, Acero J, Mommaerts MY

(2010) Intermaxillary Fixation Techniques. An EACMFS workbook on keying occlusion and restoring bony anatomy by intermaxillary fixation techniques. Bruges: EACMFS. McGinn JD, Fedok FG (2008) Techniques of maxillary-mandibular fixation. Operative Techniques in Otolaryngology- Head and Neck Surgery; 19(2):117–122. Obwegeser H (1952) [A simple method of off-hand wiring of jaw fractures]. Österr Z Stomatol; 49(12):652–670. German. Otten JE (1981) [Modified methods for intermaxillary immobilization]. Dtsch Zahnärztl Z; 36(2):91–92. German. Poggio PM, Incorvati C, Velo S, et al (2006) “Safe zones”: a guide for miniscrew positioning in the maxillary and mandibular arch. Angle Orthod; 76(2):191– 197. Roccia F, Tavolaccini A, Dell´Acqua, A et al

(2005) An audit of mandibular fractures treated by intermaxillary fixation using intraoral cortical bone screws. J Craniomaxillofac Surg; 33(4):251–254.

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2.1 Symphyseal and parasymphyseal fractures

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2.2 Body and angle fractures of the mandible

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2.3 Condyle, ascending ramus, and coronoid process fractures

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2.4 Fractures in bone of reduced quality

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2 Mandibular fractures 2.1 Symphyseal and parasymphyseal fractures

1

Anatomy and definition

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2

Imaging

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3

Surgical approaches

138

4

Osteosynthesis techniques

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4.1 Plate osteosynthesis

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4.2 Compression plate osteosynthesis

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4.3 Lag screw osteosynthesis

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5

Perioperative and postoperative treatment

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6

Complications and pitfalls

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2.1 Symphyseal and parasymphyseal fractures

1


The symphysis of the mandible is defined as the region between the roots of the central incisors, and the parasymphysis as the region between the lateral roots of the canines and the central incisors. Together they can be referred to as the chin or mental region (Fig 2.1-1).

2

Imaging

X-rays in two planes, such as an orthopantomogram (OPT) and a Clementschitsch view, are sufficient (Fig 2.1-2 a–b). A panorex view tends to blur the center (symphysis section), whereas a CT is the only image giving a clear picture of both

This region is characterized by very vascular bone whose blood supply comes from the lingual side of the chin via the attached lingual and sublingual muscles. In addition terminal branches of the lingual artery may enter the bone directly. Under masticatory load rotational forces may occasionally be observed in this particular region; this must be considered when internal fixation is performed. Linear and oblique fractures are the characteristic injury in this region. Comminution or bone loss is relatively rare. Occasionally, there is an inferior butterfly fragment which, if large, may involve the insertion of the suprahyoid musculature, and usually is associated with high-energy trauma seen in high-speed injuries such as motor-vehicle accidents and gun shots.

a

b Fig 2.1-2a–b a Orthopantomogram (OPT) of a midline fracture. b X-ray according to Clementschitsch with subcondylar fracture on the left.

Fig 2.1-1 Anatomy of the symphysis (red) and parasymphysis (green).

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cortices (Fig 2.1-3). In cases where a CT scan of the head has to be taken because of additional injuries, axial scans are usually sufficient and can be used instead of plain films.

Fig 2.1-3 CT of a midline fracture.

3

Surgical approaches

Typically, a transoral approach is used, however, under special circumstances a transcutaneous approach should be considered. The standard approach to the chin area is via a transoral vestibular approach. In dentate patients the incision line usually lies in the mobile gingiva at a distance of 8–10 mm to the junction between attached and mobile mucosa (Fig 2.1-4). In edentulous patients a crestal incision is preferred. Initially, a smaller incision from canine to canine is made. Some surgeons prefer to cut through the mucosa, underlying facial muscles and periosteum right to the bone, others prefer to mobilize the mucosa first and to incise muscles and periosteum on a different level (Fig 2.1-5a–b). From the central smaller incision the more lateral soft tissues can be elevated subperiostally to identify the mental nerves and mental foramina. Then the cut can be extended laterally without major risk of permanently damaging the mental nerve. The complete labial surface of the chin including the inferior mandibular border may be exposed via this approach. However, this approach does not permit visual control of the lingual cortex. Consequently, under some circumstances an external approach should be considered.

Fig 2.1-4 Incision line for a transoral vestibular approach (incision with an electric needle).

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Transcutaneous approaches may also be considered in cases of preexisting lacerations in the chin area. From time to time they are indicated when significant comminution or bone loss is present. In rare cases they are performed secondary to a transoral approach, when the repositioning is difficult and the lingual aspect has to be visualized. A planned transcutaneous incision is performed in the submental area taking the relaxed skin tension lines into account. An isolated submental incision can also be made in a curved line directly posterior to the border of the mandible. Care must be taken

a

not to extend it too laterally in order to avoid damage to the marginal branch of the facial nerve. In cases when a more extended submandibular approach is required an incision in the submandibular fold is recommended (Fig 2.1-6). Transoral and transcutaneous approaches are always closed in layers with resorbable or nonresorbable suture material (skin and mucosa only) depending on the surgeon’s preference. It is important to repair the transected mentalis muscle with meticulous suturing to avoid a drooping chin.

b

Fig 2.1-5a–b a Stepwise incision through the mucosa first, followed by the incision through the muscles and the periosteum. b Two-layer wound closure for muscle and mucosa.

Fig 2.1-6 Incision lines for transcutaneous approaches following skin creases.

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4


In healthy bone, fractures in the symphyseal and parasymphyseal region can be successfully treated with a variety of options. These include miniplate, compression plate, or lag screw osteosynthesis. Multifragmentary, defect, and infected fractures as well as fractures of an atrophic mandible should be treated with reconstruction plates according to the techniques described in chapter 2.4 (Fractures in bone of reduced quality). In nondisplaced and nonmobile fractures, nonsurgical therapy may occasionally be considered. Before internal fixation with plates and screws is performed, mandibulomaxillary fixation (MMF) should be applied with arch bars or splints. IMF screws can also be used. Fragment reduction in the chin area can be performed manually, with the help of reduction forceps, or with a positioning wire.

4.1 Plate osteosynthesis

Miniplate osteosynthesis is probably the technique most frequently applied for these fractures worldwide. The standard technique involves the placement of two miniplates 2.0 or corresponding plates from the Matrix system with 4 or 5 holes. One plate is placed directly above the inferior border, the second plate is placed considerably higher in the central portion of the mandible underneath the tooth roots (Fig 2.1-7a). Both locking and nonlocking plates can be used. One plate is bent and contoured to the bone surface first. This plate may be placed either at the upper or lower border. In bilateral subcondylar fractures in combination with a midline fracture, pressing on the angles and upper ramus bilaterally creates a gap in the labial cortex. The lingual cortex of the mandibular fracture is approximated and the width of the mandible is corrected. The screw fixation for the superior plate is always monocortical to avoid damage to tooth roots (Fig 2.1-7b). For the inferior plate fixation both monocortical and bicortical screw placement is possible. Miniscrews are inserted monocortically (without pretapping) in the self-tapping mode. If screws are inserted bicortically, pretapping reduces the torque. Without pretapping, there is a risk of fracture or sheering of screw heads when using miniscrews.

a

b

Fig 2.1-7a–b a Standard technique in plate osteosynthesis of the chin involves two 4- or 5-hole miniplates 2.0. b The screw fixation for the superior plate is always monocortical to avoid damage to tooth roots.

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4.2 Compression plate osteosynthesis

Compression plates in the chin area can be placed in the center of the symphysis at a safe distance from the tooth roots. Biomechanically, one compression plate in the center (neutral zone) of the mandible is sufficient to neutralize all forces within a normal range. In this area a 4-hole compression plate is usually used, either a limited contact dynamic compression plate (LC-DCP) 2.4, a universal fracture plate 2.4, or a compression plate from the Matrix Mandible system. The use of a tension band splint or at least a bridal wire is strongly recommended to neutralize distraction forces at the superior border of the mandible (Fig 2.1-8).

Alternatively, if placement of a tension band splint is not possible or not acceptable, a compression plate osteosynthesis can be performed in a 2-plate technique. In a 2-plate compression osteosynthesis one miniplate is used as a tension band plate directly underneath the apices of the front teeth. The second plate is a compression plate which is placed close to the lower border of the mandible (Fig 2.1-9). After reduction the tension band plate is applied first, usually with monocortical screw placement. Then the compression plate is inserted.

Fig 2.1-8 Compression plate osteosynthesis with an LC-DCP and a tension band splint.

Fig 2.1-9 Compression plate osteosynthesis with an LC-DCP and a 4-hole miniplate as tension band.

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A compression plate is primarily contoured to the bone surface, but must then be slightly overbent to avoid lingual gap formation during tightening of the screws. Only one screw on each side of the fracture line is placed in an eccentric manner to exert compression at the fracture surface. The compression screws are inserted eccentrically toward the

outside of the plate holes with the help of a drill guide (Fig 2.1-10a–b). After screw placement, the compression screws are alternately tightened applying compression at the fragment interface. The remaining screws are inserted in a neutral fashion toward the inside of the plate holes, again with the help of a drill guide (Fig 2.1-11a–b).

a

b

b

Fig 2.1-10a–b Eccentric screw placement into the oval-shaped plate hole of a DCP on either side of the fracture. The arrow on the drill guide is pointing towards the fracture line. The eccentric drill guide has a golden marker band. Alternative tightening of the screws leads to compression of the fracture.

142


a

Fig 2.1-11a–b Neutral screw placement in the outer holes after tightening of the inner screws. The neutral drill guide has a green marker band.


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4.3 Lag screw osteosynthesis

Lag screw osteosynthesis is another type of compression osteosynthesis. Typically two 2.4 mm lag screws are used to avoid torsion and for better stability, but one 2.4 mm lag screw in combination with a tension band splint can be sufficiently rigid. If two lag screws are used, one screw is placed at the inferior border while the second screw is placed a few millimeters superior to the first screw at a safe distance from the tooth roots (Fig 2.1-12a–b).

First the fragments are reduced. The gliding hole for the first screw is drilled using a 2.4 mm drill bit and a 2.4 mm drill guide for soft-tissue protection (Fig 2.1-13a–b). The gliding hole only penetrates the proximal fragment. It ends at the fracture surface, creating a canal in which the screw glides. After completion of the gliding canal, a second canal in the opposite fragment is drilled using a 1.8 mm drill bit and a 1.8 mm drill guide.

a a

b Fig 2.1-12a–b a Position of two horizontal lag screws. b With this technique the screw thread engages only the opposite fracture fragment in the far cortex.

b Fig 2.1-13a–b The gliding hole is drilled to the same diameter as the outer thread diameter of the screw (2.4 mm) using a 2.4 mm drill guide.

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A 1.8 mm drill guide is inserted into the gliding hole to determine the correct direction for drilling (Fig 2.1-14a–b). The depth is measured with a depth gauge, then the 1.8 mm canal is tapped (Fig 2.1-15a–b). The cortical bone on which the screw head is going to engage is countersunk to allow the screw head to snuggly fit onto the bone, thus avoiding microfractures within the cortical layer during tightening

and reducing palpability (Fig 2.1-16a–b). Finally, the first screw is inserted and fully tightened. The second screw is inserted using the same technique. It can be placed in the same direction or from the opposite side. It does not matter which screw is inserted first but the second hole must be drilled only after the first screw is tightened.

a

a

b

b

Fig 2.1-14a–b The traction hole is drilled to the same diameter as the core of the screw (1.8 mm) using a 1.8 mm drill guide.

Fig 2.1-15a–b The traction hole is tapped.

a

b Fig 2.1-16a–b Countersinking for the screw head.

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5


Miniplate osteosynthesis in the mandible is commonly addressed as being semirigid. The patients are allowed to fully function passively (unrestricted mouth-opening). They are not put into MMF, unless other injuries or special circumstances should require it. A soft diet for approximately 4 weeks postoperatively is recommended. In this period full masticatory function without any restrictions must be avoided. Compression plate osteosynthesis and lag screw osteosynthesis are functionally stable, and a soft diet is not necessary. Perioperative antibiotics can be considered, but are not needed unless the fracture area shows primary signs of infection or contamination, eg, with foreign bodies. It is strongly recommended to tape the soft tissues of the chin area for 2–3 days to avoid significant swelling that may lead to dehiscence and secondary soft-tissue healing (Fig 2.1-17). MMF for a few days can also be used to immobilize the soft tissues.

6


Care must be taken to place the transoral incisions as described. A misplaced incision may lead to secondary softtissue healing and damage to the mental nerve. Damaging the tooth roots must be avoided through proper screw placement. Especially in larger massive mandibles the outer contour of the alveolar sockets does not always indicate the anatomical location of the apices of the teeth. A preoperative OPT always shows the exact length of the teeth. Symphyseal or parasymphyseal mandibular fractures in conjunction with bilateral displaced condylar fractures, particularly in combination with comminuted midface fractures, risk losing the transverse dimensions of the mandible with the result of posterior widening (flaring). In such cases it is essential to check the lingual side of the mandible after reduction and after osteosynthesis, if necessary through a transcutaneous incision. These injuries are better fixed using longer heavy plates instead of miniplates, such as 10 to 12-hole reconstruction plates to control the width of the mandible through the angles, and lag screws may also be used. Miniplates may not be strong enough for challenging biomechanical scenarios.

Fig 2.1-17 Tape dressing of the chin area is recommended for 2–3 days postoperatively.

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2 Mandibular fractures 2.2 Body and angle fractures of the mandible

1


147

2

Blood supply

148

3

Imaging

149

4

Biomechanics

149

5

Fracture patterns

149

6

Treatment planning

149

7

Surgical approaches

150

8


152

9

Perioperative treatment

157

10

Postoperative treatment

157

11


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Authors Leon Assael, Brett Ueeck

2.2 Body and angle fractures of the mandible

1


The lateral body of the mandible is defined as the portion distal to the canine (parasymphysis) but proximal to the third molar. The angle of the mandible includes the third molar region and the junction of body and ramus (Fig 2.2-1). The anatomy of the mandible body and angle includes the well-defined buccal and lingual cortices, alveolar bone in the dental portion, a centrally or inferiorly located inferior alveolar canal, internally the mylohyoid ridge, and the external oblique ridge. The angle of the mandible is thinner inferiorly, with a concretion of the buccal and lingual cortex. An antegonial notch is noted anterior to the true angle of the mandible. Muscles of the mandibular angle and body often define a fracture pattern and access incisions designed to dissect be-

tween them and elevate aponeuroses. Important muscle attachments are: • Masseter muscle: lateral inferior border/angle attachment • Medial pterygoid muscle: medial inferior border/ angle attachment • Temporalis muscle: coronoid process anterior border attachment • Buccinator muscle: attachment on lateral border/ external oblique ridge • Superior pharyngeal constrictor: attachment at medial aspect of angle • Mylohyoid muscle: attachment along the well-defined mylohyoid ridge The lateral body of the mandible is characterized by the presence of two premolars and three molar teeth. The third molar, if still present, is often impacted, partially or fully submerged in soft tissue and bone.

Fig 2.2-1 The lateral body of the mandible (red): distal to the canine but proximal to the third molar. Angle of the mandible (green): from the area between the third molar and the junction of the ascending ramus.

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Somatosensory afferent peripheral nerves of the body and angle region are also factors to be considered in trauma and internal fixation of this region (Fig 2.2-2): • Inferior alveolar nerve: contained in the inferior alveolar canal, exiting in the premolar region from the mental foramen after sending off incisive nerves to the symphysis. The mental nerve curves downward just before its exit to provide innervation of the lip, chin, and mandibular teeth. • Lingual nerve: approximately 1–2 mm medial to the internal oblique ridge of the mandible at the angle, moving more medially into floor of the mouth and tongue. It relays sensation and taste (with the chorda tympani) to the anterior two thirds of the tongue. It is at risk during reduction and screw fixation of the superior border of the angle region. • Long buccal nerve: sensation to the check and buccal vestibule. It crosses the anterior ramus above the angle, and is at risk during transoral incision at the angle. Motor innervation to the region includes the motor division of the trigeminal nerve supplying the muscles of mastication, mylohyoid, and anterior belly of the digastric muscle. The facial nerve supplies the muscles of facial expression

with the marginal and cervical branches in the submandibular triangle. Depressors of the lip and chin may suffer paresis if attention is not given to the marginal mandibular branch as it courses 0 –10 mm beneath the antegonial notch of the angle.

2

Blood supply

While the blood supply and oxygenation to this region is generally excellent, it may be compromised due to trauma, access incisions, age, and disease. The arterial supply to the angle and body includes the periosteal plexus of vessels as well as the inferior alveolar artery. Edentulous and older patients rarely have a patent inferior alveolar artery due to arteriosclerosis and atrophy. In fracture situations this artery may often be damaged. When the periosteum is stripped, especially in multisegmented body fractures, fragments may become totally disconnected, and under this condition they can be compared with a free bone graft. It is often challenging to close the mucosa in this region. All these factors predispose comminuted fractures to infection.

Buccal nerve Lingual nerve

Mandibular nerve

Fig 2.2-2 Somatosensory afferent peripheral nerves of the body and angle region.

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3

Imaging

Two views are required, preferably at right angles, to effectively image fractures of the mandibular angle and body. The following are of value in imaging of fractures of the body and angle region: • Orthopantomogram (OPT): the standard universal imaging method for evaluation of the mandible rarely fails to identify fractures of the angle and body. New computed OPT can offer streaming contrast and magnification potential. • Posteroanterior view of the mandible: can identify fracture obliquity in the body and angle region. • Lateral oblique view of the mandible: an alternative to OPT when one is not available. • Occlusal view of the mandible: an intraoral film view where the buccal and lingual aspects of the cortex in the body and angle region may be delineated. • Computed tomography (CT) of the mandible: axial, coronal, and sagittal views as well as 3-D reconstruction can be used to identify most fractures as well as completely delineate fracture anatomy. Rarely, CT may miss fractures due to volume averaging that are noted on OPT. Rarely, a fracture may be missed by any x-ray technique. Fractures that are missed are nondisplaced. In this situation, the clinical signs are the only clues to identification.

5

Fracture patterns

Fracture patterns in the mandibular body depend on the energy of the impact and vector. They may be direct or indirect fractures. They are mostly linear, sometimes with a basal wedge or oblique surface. Comminution is seen in high-energy trauma. Most fractures of the angle of the mandible occur in the location of the third molar and extend to the antegonial notch anterior to the true angle. They are often oblique, extending more anteriorly in the external oblique ridge than in the internal oblique ridge. A triangular comminution at the inferior aspect of the mandible is common.

6

Treatment planning

Access incisions and proposed methods of osteosynthesis are selected before surgery. Managing impacted third molar

The third molar may be extracted or retained when associated with the fracture. Infected, fractured, or completely mobilized third molars should be removed either before or after reduction and stabilization, depending on the situation. Managing inferior alveolar nerve

4

Biomechanics

As noted in chapter 1.3.1 (Biomechanics of the craniomaxillofacial skeleton), after axial loading, the body and angle area constitute a tension zone at the superior border (dental arch), and a compression zone at the inferior border. The neutral zone lies in the center of the mandible and often corresponds to the region of the neurovascular canal. Biomechanically, the mandibular angle is a challenging region because anatomical changes from the body to ramus lead to a change of vectors during loading.

Preoperative neurosensory evaluation is indicated to determine whether neurotmesis might be a factor in treatment selection. Simultaneous microsurgical repair of this nerve is not commonly performed but may be considered as a treatment option.

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7

Surgical approaches

Mandibulomaxillary fixation (MMF) is normally applied before surgical approach. Both transoral and transcervical approaches to the angle and body region have their utility. For angle fractures, the standard transoral approach is a buccal vestibular incision medial to the buccal fat pad and lateral to the temporalis muscle separating buccinator fibers. If the third molar is not to be removed the incision may remain in the buccal vestibule. The incision is released into the buccal mucosa anteriorly, taking care to remain behind or above the mental nerve exit (Fig 2.2-3).

For fractures of the mandibular body, the transoral approach is via a vestibular incision beveled into mid root of the premolars to protect the exit of the mental nerve. Circumferential subperiosteal dissection around the mental nerve can be carried out to reveal the fracture and provide room for fixation. Marginal gingival incisions are also possible. Transcervical access is via the submandibular standard approaches. Attention to Langer’s lines of skin relaxation will permit an esthetic scar. Sharp dissection through subcutaneous tissue, platysma, superficial investing fascia, and periosteum is performed. The use of a nerve stimulator to assess and protect the marginal mandibular branch of the facial nerve may be useful. Ligation of the facial vein and/or artery is often indicated and may be helpful for protection of the facial nerve (Fig 2.2-4a–b).

Fig 2.2-3 Transoral approach for angle fractures. The incision is released into the buccal mucosa.

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a

b Fig 2.2-4a–b Transcervical access of the submandibular standard approach. a Sharp dissection stepwise through skin (red line cranial), platysma, and superficial cervical fascia (dotted line caudal). b Ligation of the facial vein and/or artery is often indicated. The bone surface is reached in a layer underneath the superior cervical fascia.

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8


MMF is applied and reduction of fractures is obtained either manually or with the assistance of reduction forceps. If an arch bar is applied across a fracture in the dental segment, the diastema in the fracture site should be eliminated. This allows the arch bar to act as a tension band.

Miniplate osteosynthesis in the lateral body is typically performed transorally with a single miniplate in the center of the mandible (neutral zone), and with screws engaging only the cortex next to the plate, ie, monocortical screw insertion (Fig 2.2-5). In the angle, a miniplate is typically placed in the region of the superior border (tension zone), either on the oblique ridge from a transoral approach (Fig 2.2-6a–b) or on

Depending on bone quality, quantity, and on special circumstances, such as comminution or bone loss, either a load-sharing or a load-bearing osteosynthesis is indicated. Load sharing can be achieved with miniplates 2.0, or corresponding plates from the Matrix Mandible system, compression plates, or lag screws.

a Fig 2.2-5 Transoral single miniplate fixation in the center of the mandible (neutral zone) with screws engaging only the cortex next to the plate.

b

Fig 2.2-6a–b Miniplate fixation in the angle of the mandible on the oblique ridge.

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the superior lateral surface of the mandible with the help of transbuccal instrumentation or an angulated screwdriver (Fig 2.2-7a–b). Care must be taken to avoid the roots of the teeth. Monocortical fixation permits safe placement. If a single miniplate is used it should be a 6-hole miniplate with three screws on either side of the fracture.

a

b

Fig 2.2-7a–b Miniplate fixation on the superior lateral surface of the mandible with the help of transbuccal instrumentation.

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In case of reduced bone buttress, for instance after wisdom tooth removal, some surgeons prefer using two miniplates, one at the superior and one at the inferior border of the mandible, with a minimum of two screws on either side of the fracture (Fig 2.2-8 , Fig 2.2-9). Miniplate fixation alone is generally adequate for well-buttressed fractures of the angle and body. A well-buttressed fracture has no comminution and there is adequate contact of good bone at the fracture site. Chewing may cause a reversal of forces resulting in an

opening of the inferior border if only the superior border is stabilized with a tension band. Using a plate of sufficient stiffness will mitigate this effect.

Fig 2.2-8 Double-plate fixation with miniplates for slightly dislocated mandibular lateral body fracture. Monocortical fixation of the superior plate avoids damage of tooth roots.

Fig 2.2-9 Miniplate fixation with two plates for a mandibular angle fracture.

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If greater stability is required, a load-sharing compression plate osteosynthesis can be performed with either an LCDCP 2.4, a universal fracture plate 2.4, or corresponding plate from the Matrix Mandible system. Compression plate osteosynthesis is performed at the inferior border of the


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mandible; screw fixation is bicortical. This type of osteosynthesis typically creates distracting forces at the superior border of the mandible and the lingual surface. To avoid superior gap formation, tension banding must be performed with either a tension band splint or a tension band plate before compression plating. A tension band splint can be applied using an arch bar, which can be reinforced with acrylic (Fig 2.2-10). A mandibulomaxillary wire fixation is not strong enough for tension banding. Alternatively, a ten-

sion band plate may be applied close to the superior border of the mandible (Fig 2.2-11). Placement of dynamic compression plates at the body and angle is usually possible with protection of the inferior alveolar nerve, but preoperative evaluation of the location of this nerve is useful.

Fig 2.2-10 Tension banding performed with an arch bar reinforced with acrylic. In addition a universal fracture plate 2.4 is placed at the inferior border.

Fig 2.2-11 Double-plate fixation with a miniplate as a tension band above the mandibular nerve, and a universal fracture plate 2.4 at the lower border of the mandible. Protection of the inferior alveolar nerve has to be considered.

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Lag screw fixation is another technique to perform loadsharing fixation. Typically lag screw fixation is indicated for fractures with oblique surfaces. To stabilize these, multiple lag screws (at least two) may be used in place of a stabilization plate. The principle for placement of these lag screws is to create compression across the sagittal portion of the fracture. At least two screws perpendicular to the fracture surface are required for 3-D stability and to neutralize rotational forces (Fig 2.2-12a–b).

Load-bearing osteosynthesis with either nonlocking or locking reconstruction technique is indicated for fractures with reduced bony buttress, such as comminuted, defect, or infected fractures; fractures of atrophic mandibles or treatment delayed fractures with nonunion (chapter 2.4, Fractures in bone with reduced quality). Combinations, for instance lag screw fixation with plate fixation, are possible (Fig 2.2-13a–b).

a

a

b

b

Fig 2.2-12a–b Oblique fracture stabilized with lag screw fixation. At least two screws perpendicular to the fracture surface are required for 3-D stability.

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Fig 2.2-13a–b Load-bearing osteosynthesis in an oblique fracture of the lateral body. Regular plate fixation combined with lag screw technique for the oblique area.


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9


The use of perioperative antibiotics for open reduction of the body and angle fracture remains controversial. Antibiotics should be given to all patients with fractures when treatment is delayed. If antibiotics are to be used prophylactically, preoperative high-dose parenteral application is recommended with good anaerobic gram-positive coverage. Clindamycin, penicillins, or first-generation cephalosporins are most widely used. The emergence of methicillin-resistant staphylococcus aureus infection in the patient with maxillofacial trauma has altered the prophylactic regimen in some centers. They prefer broad-spectrum penicillin in combination with clavulanic acid. Use of drains in buccal and transcutaneous incisions is at the surgeon’s discretion.

10

11


During internal fixation, complete visualization of the fracture can be problematic in angle and body fractures. Failure to fully identify the fracture anatomy may result in inappropriate fixation. Opening of the inferior border during superior border plating must be anticipated and controlled, typically with a second plate. Flaring of the ramus due to poor adaptation on the lingual aspect of the mandible is also a severe risk. Screw placement into the mandibular canal can be avoided through careful planning.


All methods of stable internal fixation of fractures of the body and angle region should have the goal of early restoration of full function including diet, airway, and speech. However, fixation techniques present with varying degrees of stability. No MMF is indicated unless necessitated by additional fractures that have undergone nonsurgical treatment (eg, associated condylar fractures). Single superior border plates for angle fractures provide sufficient stability where there is good buttressing of the fracture at the angle of the mandible. Factors that might compromise buttressing include removal of impacted third molar, oblique fracture lines, or comminution at the inferior border. If superior border plating is performed in these circumstances without an additional plate at the inferior border, a brief period of MMF may be necessary. A brief period of soft-tissue rest in occlusion using MMF may support soft-tissue healing.

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2 Mandibular fractures 2.3 Condyle, ascending ramus, and coronoid process fractures

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Imaging

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Nonsurgical treatment

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Surgical treatment

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Surgical approaches

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Surgical techniques

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01.06.12 15:17

Authors Nils-Claudius Gellrich, Ralf Schoen

2.3 Condyle, ascending ramus, and coronoid process fractures 1


Fractures of the mandibular condyle area are common and account for 9–45% of all mandibular fractures in adults and approximately for 50% of all mandibular fractures in children. Many classification systems describe condylar and subcondylar fractures; none is generally accepted and universally used. This presents a problem particularly when condyle fracture studies are compared. Today, simple classification systems are widely used. They address anatomical location of the fracture and distinguish between condylar head, subcondylar fractures (Fig 2.3-1), and pathological conditions such as dislocation of the condylar head. They also address angulation of the bones comprising the fracture segments and describe contact among the fragments. In condylar head fractures the fracture line may run inside the capsule of the temporomandibular joint (TMJ), but frequently condylar head fractures have an extracapsular component. Some condylar head fractures divide the head

sagitally, where a portion remains intact with the rest of the ramus. Subcondylar fractures are located below the condyle and can be classified into high (condylar neck) and low subcondylar fractures. Subcondylar fractures are located at the base of the condylar process at or below the level of the sigmoid notch. Fractures below the sigmoid notch are fractures of the ascending mandibular ramus. Various patterns of displacement and dislocation of the proximal fragment are possible. Condylar and subcondylar fractures are usually closed fractures. Coronoid process fractures are rare and may occur without involvement of the condylar process. Isolated fractures occur in combination with zygoma or zygomatic arch fractures, and marginal, submarginal, submuscular types have been described. Coronoid fractures may be a portion of a comminuted angle and ramus fracture.

Coronoid process Condylar head a b

Subcondylar: high = condylar neck (a), low = subcondylar (b) Ascending ramus

Fig 2.3-1 Fracture location can be anatomically distinguished.

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2

Imaging

For treatment planning, the anatomical location, comminution of the fracture, degree of displacement, and dislocation are evaluated preoperatively. The minimum standard required is plain x-rays in two appropriate planes, for instance AP projections such as Towne’s view, lateral oblique, and

a

panoramic x-rays (OPTs). Fractures of the condylar head are often not seen on standard x-rays. Computed tomography (CT) or cone beam tomography in axial, sagittal, and coronal planes allow for a more detailed evaluation of the fracture components and are considered the gold standard of preoperative diagnostics (Fig 2.3-2a–b, Fig 2.3-3).

b

Fig 2.3-2a–b Computed tomography allows for a detailed evaluation of the fracture components. a Coronal view. b Axial view.

Fig 2.3-3 Plain x-rays, such as panoramic x-rays, are the minimum standard for preoperative evaluation.

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In many centers condylar head fractures and fractures of the coronoid process are treated nonsurgically, although promising results have been reported for surgical treatment of condylar head fractures. Condylar neck, subcondylar fractures, and fractures of the ascending ramus may be treated nonsurgically or surgically by open reduction and fixation. The decision for or against open reduction depends on the following factors: • Condition of the patient (ie, cervical spine injury) • Compliance of the patient • Functional impairment (malocclusion, limited mouth opening) • Concomitant fractures of the mandible (body and symphysis/parasymphysis, bilateral condyle) or midface (especially panfacial fractures) • Dislocation of the condylar head • Degree of displacement and bone contact at the fracture interface • Status of dentition

3

Nonsurgical treatment

Nonsurgical management (also called conservative treatment or closed reduction) is still widely practiced. For the majority of pediatric fracture patterns, for undisplaced fractures, fractures without or with only minor functional disturbances, and condylar head fractures excellent long-term results can be obtained with nonsurgical treatment. Nonsurgical management may mean no treatment, observation, and mostly a period of soft diet. It may be indicated for patients with undisplaced or mildly displaced fractures of the condylar region with no significant functional impairment. Nonsurgical management can also include mandibulomaxillary fixation (MMF) for a short period of of time. This can be achieved with dental devices such as arch bars, wire loops, brackets, or bone-anchored devices (hooks, intermaxillary fixation (IMF) screws). For MMF elastics are widely used, typically for a short period of up to two weeks. This type of nonsurgical treatment is indicated for patients with functional problems, pain, disturbance of the occlusion, and displaced fractures. MMF is most widely performed with arch bars but can also be performed with two stainless steel transmucosal minihooks fixed with one bone screw each or two IMF screws anchored in the anterior median aspect of the mandible and maxilla (Fig 2.3-4). Arch bars allow for MMF in a multicontact interdentation. MMF established with limited points of contact (eg, IMF screws) may create a fractional open bite. IMF screws and single-point fixation devices have no flexibility.

Fig 2.3-4 Mandibulomaxillary fixation (MMF) performed by two stainless steel transmucosal minihooks fixed with one bone screw each, anchored in the anterior median aspect of the mandible and maxilla.

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Care has to be taken not to harm tooth roots. The fixation of bone-anchored devices is less time-consuming for the patient compared with applying arch bars, as mouth opening is not necessary. MMF may be difficult to perform if patients are partially or totally edentulous, present with preexisting bite deformities, or when they are noncompliant. In contrast to bone-anchored devices, MMF with arch bars allows for more flexibility with postoperative functional therapy with guiding elastics, especially if eccentric placement is indicated (Fig 2.3-5). After nonsurgical treatment, temporomandibular joint (TMJ) function depends on regeneration of the condylar area and adaptation of the tissues. In children younger than 6–8 years, nonsurgical treatment is regarded to be the treatment of choice for most condylar head and subcondylar fractures due to the high regeneration potential of the growing condylar process. However, in severely dislocated subcondylar fractures restitutional remodeling is not always achieved and growth anomalies with facial asymmetry may occur.

4

Surgical treatment

The surgical treatment of displaced condylar fractures aims for anatomical reduction and restoration of the vertical height of the ascending mandibular ramus to reestablish preinjury occlusion and adequate TMJ function. Injuries in the TMJ area typically include soft-tissue involvement with rupture of the capsule and ligaments and displacement or rupture of the disc. These soft-tissue injuries are generally not surgically addressed, although exposure and anatomical reduction of the bones may allow for reposition of lacerated soft tissues in the TMJ area. Superior functional results are reported following surgical treatment compared with nonsurgical treatment for fractures with dislocation of the condylar head and displaced fractures with functional impairment, such as malocclusion and open-bite deformity due to shortening of mandibular ramus height.

Fig 2.3-5 MMF with arch bars and guiding elastics allows for more flexibility during postoperative functional therapy, especially if eccentric placement is indicated to correct a mandible deviation.

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5

Surgical approaches

Open reduction can be performed by transcutaneous (Fig 2.3-6a–b) and transoral approaches. Endoscopically assisted approaches are also possible. Coronal approaches have also been used.

1 5 2

3

4

a

b

Fig 2.3-6a–b Different external approaches are possible: 1 Preauricular approach 2 Transparotid approach 3 Retromandibular approach 4 Submandibular approach 5 Retroauricular approach

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6

Surgical techniques

Biomechanical conditions in the condylar area are demanding and due to the reduced dimensions, the bone can only buttress on a limited basis. Osteosynthesis today is typically performed with plates and screws. Recommended are two miniplates. One stronger plate, such as a universal fracture plate, can also be used. In cases where the anatomy only allows for placement of one miniplate, stronger mandible miniplates should be used. A minimum of two screws need to be anchored in the proximal condylar fragment to allow for rotational stability. Lag screw fixation of condylar area fractures is not yet accepted as a routine method of treatment. For open reduction and internal fixation (ORIF) of condylar head fractures, it is mostly the only surgical option because typically there is not enough space for plate placement.

a

Intraoperative distraction of the TMJ area by downward pressure onto the posterior molars facilitates localization of the proximal fragment and anatomical reduction. A patient should therefore not be in MMF at the beginning of surgery, but after approach and fragment reduction. A wire can be inserted temporarily into the angle to pull the mandible inferiorly to distract the fracture. Miniplates 2.0 or corresponding plates from the Matrix Mandible system should be securely anchored with two screws on each side of the fracture for osteosynthesis. For fixation of the miniplate in the strong cortical bone along the posterior border of the ascending mandibular ramus, bicortical screw fixation is recommended. As the subcondylar area is a mechanically demanding site, two miniplates allow for increased stability and safety (Fig 2.3-7a–c). Alternatively, anatomically shaped condylar plates can be used. When two plates can be used for osteosynthesis precise

b

c

Fig 2.3-7a–c a Two miniplates (2.0 and 1.5) should be securely anchored with two screws on each side of the fracture. As the high subcondylar area is a mechanically demanding site, two miniplates allow for increased stability and safety. b–c Fixation with specific implants for the subcondylar region.

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anatomical reduction is facilitated by a first plate inserted close to the sigmoid notch. The initial fixation with only two screws positions the fracture segments. This facilitates the precise placement of a second (ideally more rigid) plate along the posterior border, especially in severely displaced fractures. If the size of the mandible allows placement of a stronger plate, such as a universal fracture plate, this may be used for increased stability (Fig 2.3-8a–b). Preferably a 4-hole noncompression miniplate 2.0 with space (tension band plate) is placed along the posterior border. Miniplates of the 2.0 or 1.5 system or corresponding plates from the Matrix system may be used in the sigmoid notch area (see

Fig 2.3-7a–c). More rigid plates such as mandible plates 2.0, universal fracture plates, or corresponding plates from the Matrix Mandible system may be more difficult to apply in an endoscopically assisted approach. Precise bending of stronger plates under such conditions is not always possible and displacement or malalignment of the fracture may be caused when tightening the screws. For transoral osteosynthesis angulated drills and screwdrivers with a screw-holding device facilitate the insertion of the first screw together with the plate. Transbuccal insertion of the screws can be performed without an angulated screwdriver. Endoscopically assisted transoral approaches with angulated scopes allow precise control of anatomical reduction in areas of limited visibility.

a

b Fig 2.3-8a–b If the size of the mandible allows, a stronger plate (universal fracture plate) may be used for increased stability.

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Fractures of the ascending ramus are treated according to the biomechanical requirements associated with the fracture type (Fig 2.3-9). Multifragmentary fractures are typically treated with a load-bearing osteosynthesis, if needed after simplification with miniplates. Immediate postoperative function without MMF is achieved following anatomical reduction and adequate osteosynthesis of subcondylar fractures. Some surgeons favor a short period of MMF with elastics to allow the soft tissue and joint to rest (up to 7 days). After that, guiding elastics, typically night-time elastics, are used. This treatment is purposely more conservative but results in far fewer problems, especially when midface fractures are present.

7


Malocclusion and impaired TMJ function may occur in condylar area fractures even after treatment. To evaluate the treatment outcome and to correct any undesired results a close follow-up of the patients is mandatory, until return to almost full function. Temporary functional problems or disturbances of the occlusion are typically treated with guiding elastics, both after open or nonsurgical management. To achieve adequate functional results with mouth opening of more than 40 mm, a prolonged functional therapy may be necessary. This will avoid deviation and bilateral protrusion, especially after nonsurgical management. Besides guiding elastics, functional therapy may involve physiotherapy or the use of orthodontic appliances. When functional treatment is offered, excellent results can also be achieved in nonsurgically treated severely displaced fractures. However, functional treatment with orthodontic appliances (ie, an activator) for rehabilitation is time-consuming and expensive, and may take up to 1 year. Therefore, it can only be performed in compliant patients and those who can afford such a treatment. If complications after surgical treatment lead to unsatisfying postoperative results, functional treatment can be performed to a certain extent.

Fig 2.3-9 Fracture of the ascending ramus stabilized with a miniplate 2.0 posteriorly and a miniplate 1.5 placed anteriorly.

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8


Surgical complications, such as injury to the facial nerve (especially the temporal branch in preauricular incisions and the marginal branch in submandibular incisions) or visible scars, may occur when open reduction by transcutaneous approaches is performed. To minimize the risk of these complications, endoscopically assisted techniques using limited transoral incisions have been developed. Surgical treatment of condylar fractures remains technically demanding. The fracture type influences the difficulty of reduction. In severely displaced and medially dislocated or overriding fractures, open reduction can be challenging and anatomical positioning of the condylar fragment may not always be possible. It is important to detect the condylar head position and zones of comminution in preoperative imaging to allow for adequate reduction with a specific approach or plate fixation, thus minimizing intraoperative surprises.

Due to intensive mechanical forces on the condylar process area failure of osteosynthesis due to fatigue fractures of the plates or loosening of screws occur in subcondylar fractures in 5–10% of cases (Fig 2.3-10a–b), especially when limited fixation with unstable plates has been used. To avoid micromovement at the fracture site, precise reduction and osteosynthesis with two plates are recommended. Avascular necrosis of the condylar head, perhaps because of excessive soft-tissue stripping after surgical treatment, is rarely seen. To avoid this, it is recommended to always leave the lateral pterygoid muscle attached. Following nonsurgical or surgical treatment impaired TMJ long-term function due to abnormally shaped condylar heads, shortened mandibular ramus height, or growth anomalies with facial asymmetry may occur. Limited TMJ mobility of the deranged condylar process may lead to functional dislocation of the contralateral condyle on jaw opening with chronic TMJ pain. Soft-tissue complications, such as scar formation, internal derangement, pain, or functional disorders, may be seen after surgical and nonsurgical management.

a

b

Fig 2.3-10a–b a X-ray showing a bilateral condylar fracture. b Failure of miniplate osteosynthesis with weaker midface plates in both subcondylar areas.

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2 Mandibular fractures 2.4 Fractures in bone of reduced quality

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Introduction

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Imaging

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Surgical approaches

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Treatment

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5.1 Atrophic mandibular fractures

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5.2 Multifragmentary mandibular fractures

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5.3 Defect mandibular fractures

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5.4 Infected mandibular fractures

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01.06.12 15:17

Authors Brian Alpert, George M Kushner

2.4 Fractures in bone of reduced quality

1

Introduction

Bone of reduced quality (and quantity) may result from atrophy, infection, comminution, and defects. The common denominator in these fractures is the inability to effectively use any form of load sharing, since the bone is inadequate in quality and quantity. Atrophic mandibular fractures

In these fractures the alveolar process and often much of the basilar bone has been lost. This is usually the result of long-term edentulism, although atrophy and edentulism are different conditions because edentulous does not necessarily mean atrophic. The remaining bone is markedly diminished in height and often width, and is frequently entirely cortical (and brittle) in nature. The highest degree of atrophy is seen typically in the lateral body of the mandible, an area without major muscle attachment. There is no effective endosteal blood supply. The nutrient vessel (inferior alveolar artery) is often outside of the bone.

ment is delayed, infection of the fracture site and/or surrounding soft tissues is inevitable. Initially, the infection process is characterized by purulent drainage; diffuse bone involvement with sequestration occurs later. All these fractures in bone with reduced quality are often additionally complicated by being both open and displaced. They are some of the more difficult fractures to manage and historically were subject to a high complication rate.

2

Imaging

Multifragmentary mandibular fractures

Imaging in two planes is mandatory to assess the fractures. Panoramic x-rays are usually necessary to define these fractures. Although they are often inadequate for diagnosis when used alone, they are still necessary to give the “big picture.” Axial and coronal CT scans properly define the individual fractures with respect to comminution, splaying, condylar inclination, and so on. They are also useful to judge symmetry.

This type of fracture typically arises from high-speed or intense blunt trauma or missile wounds and results in fragmentation of the bone into multiple pieces. The fragments are often located in open wounds.

3

Defect mandibular fractures

These fractures are characterized by loss of bone substance at the fracture site creating a gap of variable size with loss of bone buttressing. This loss of substance may be secondary to loss of a tooth, avulsion of a comminuted fragment, sequestration, or following an osteotomy for tooth removal. A pathologic entity such as a cyst or metastases, may also result in a defect. Infected mandibular fractures

When open mandibular fractures are untreated and if treat-

Surgical approaches

Fractures in bone of reduced quality are generally approached transfacially and require wide exposure to visualize and complete a stable fixation. Although transoral approaches may sometimes be used, exposure may be suboptimal and compromise the ultimate open reduction and internal fixation (ORIF). Transoral approaches may sever the inferior alveolar nerve and artery as they may be in soft tissue on the surface of the mandible. In addition, long reconstruction plates required for load-bearing fixation are difficult to place transorally. In such cases, the surgeon must be prepared to supplement the exposure with a transcutaneous approach.

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4


Rigid internal fixation (RIF) has been more effective in these complex injuries than in all other types of mandibular fractures in both improving outcomes and shortening the course of treatment. In the past, closed techniques with cumbersome mandibulomaxillary fixation (MMF) and/or external fixators often requiring prolonged periods of immobilization of the jaws were the rule for these fractures. Nonunion, malunion, sequestration, and trismus often resulted. Contemporary RIF in the form of load-bearing osteosynthesis is the treatment indicated as is free autogenous particulate marrow bone grafting in areas of bone defect or diminished healing capacity. Modern locking reconstruction plates anchored by at least three screws on either side of the fracture or defect allow for undisturbed healing. If wound complications occur, the internal fixator stabilizes the segments during further debridement, grafting, etc, with the patient continuing to function.

5

Treatment

5.1 Atrophic mandibular fractures

External fixators have been used with varying degrees of success. Both transoral and transcutaneous ORIF with wires, both with and without MMF, were used with limited success, as was ORIF with titanium or stainless steel mesh and screws. K-wires, both intramedullary and at the inferior border, had their advocates. ORIF stabilized with wire and split ribs for support and for osteogenesis has also been recommended. With the advent of plates and screws, many surgeons attempted fixation with miniplates both from transoral and transcutaneous approaches. Experience has shown two things: first, elderly infirm patients do not tolerate MMF well. They suffer a great deal and may even die. Second, in the management of these fractures, one should do what one knows will work, not what one hopes will work. In this sense the most effective treatment is a definitive initial surgical procedure. Today, this means a well-anchored reconstruction plate with autogenous particulate marrow bone grafting if necessary. Since the atrophic mandible has diminished vascularity, no load-sharing capacity, and is often brittle, the internal fixation device in the form of a reconstruction plate or locking reconstruction plate with bicortical screw placement must carry the functional load (Fig 2.4-1). The angle and symphysis typically provide the screw sites because this is where

Over the years, a variety of treatments have been used in the management of atrophic mandibular fractures. “Skillful neglect” means taking away the dentures from the patient and imposing a soft diet for nondisplaced fractures. Closed reduction with dentures or splints stabilized with suspension and circummandibular wires have been used for both monomaxillary and mandibulomaxillary fixation. These appliances are cumbersome, painful, and subject to infection. Outcomes are not predictable.

Fig 2.4-1 A reconstruction plate (locking or nonlocking) with bicortical screw placement (mostly only possible in chin and angle region) must bear the functional load in an atrophic mandible.

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the bone is of better quality and often of higher quantity. Unnecessary periosteal stripping should be avoided. Bone grafts can be placed primarily or secondarily. Bone can be cancellous, harvested from the iliac crest, or the tibia. No form of MMF is used. The functional forces on the atrophic mandible should not be underestimated. Wishboning, deformation of the bone during function, will rapidly cause fatigue failure of miniplates (Fig 2.4-2a–b). Reconstruction plates or locking reconstruction plates with bicortically anchored screws are indicated.

Fractured atrophic mandibles may be approached transorally with difficulty by an experienced team, but the most predictable approach is through a submandibular transcutaneous incision. Anesthesia techniques should use muscle relaxants to improve reduction after the facial nerve branches have been isolated and protected. Miniplates may be useful to provide temporary stabilization. Then, a loadbearing reconstruction plate is applied. This fixation may be larger in height and circumference than the bone at the fracture site. Particular bone graft is packed around the defect.

a

b Fig 2.4-2a–b a Miniplate fixation of bilateral fractures in an atrophic mandible. b Failure of miniplate fixation (plate fractures on both sides).

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5.2 Multifragmentary mandibular fractures

Multifragmentary fractures of the mandible are generally the result of a significant impact on a localized area causing a shattering of the bone. Most are open fractures that are difficult to treat and have a higher complication rate. Traditional treatment consisted of closed techniques that were designed to avoid devitalizing bone fragments, which often led to infection and sequestration. This was accomplished with MMF, splints, and external fixators. ORIF was believed to be contraindicated. Contemporary management involves rigidly fixing the teeth in proper occlusion with arch bars, wires, and acrylic. After reduction, the fragments are prelocalized with miniplates, typically with monocortically placed screws, and/or lag screws to position the fracture segments. Lingual perios-

a

c

172


teal attachments are preserved. The entire area of comminution is then spanned with a reconstruction plate, fixed with bicortically anchored screws which completes a load-bearing osteosynthesis. At least three screws are placed on either side of the area of comminution (Figs 2.4-3a–c , 2.4-4a–b, 2.4-5a–b). Additional screws may be used to lag or fix the smaller fragments to the plate. Small tooth-bearing fragments should always be aligned with an arch bar. Care must be taken to avoid too much periosteal stripping, which may result in devascularization and necrosis. Bone defects may be primarily grafted as necessary, as long as appropriate softtissue closure around the bone graft is feasible. Obviously, the preferred approach is transcutaneous with exposure wide enough to thoroughly appreciate alignment and adequately stabilize the fragments. After load-bearing fixation, MMF is released and the patient allowed limited function.

b

Fig 2.4-3a–c a Comminuted fracture of mandibular angle and ramus area. b Primary adaptation of the fragments with miniplates and monocortically placed screws. c Subsequent stabilization of the comminuted area with a reconstruction plate 2.4 and bicortical screw placement.


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This form of treatment has dramatically shortened the course of healing and improved outcomes in these complex fractures. Rigidly fixed fragments, though devitalized by periosteal stripping, usually do not sequester. Maintaining function minimizes the trismus from scarring and the disuse atrophy

a

seen after prolonged periods of MMF. These fractures are not suitable for splints, wires, or miniplates. Open reduction and internal fixation without load-bearing osteosynthesis, such as miniplate fixation, is unpredictable and often leads to infection and sequestration.

b

Fig 2.4-4a–b a Multifragmentary fracture of the left side of the mandibular body. The nerve remained intact. b Fracture stabilization with two miniplates as tension band (monocortical screw placement) and one reconstruction plate to bridge and stabilize the comminuted area. Tooth-bearing fragments should be aligned with an arch bar.

a

b

Fig 2.4-5a–b a Comminuted fracture in the chin area with considerable dislocation of the various fragments, including a subcondylar fracture on the left. b Adaptation and stabilization of the tooth-bearing fragments with an arch bar. Bridging and stabilization of the comminuted area with a reconstruction plate and at least three screws in the nonfractured body area. Superior small fragments are aligned through the arch bar. Sufficiently large fragments are fixed to the plate as well. Subcondylar fracture fixation with two miniplates.

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5.3 Defect mandibular fractures

Defect fractures result from loss of bony substance due to disease, injury, debridement, or infection. In such cases bone contact at the fracture site is often inadequate for union to take place. As with other complex mandibular fractures, load-bearing osteosynthesis is placed following MMF in the correct occlusal relationship. Transfacial access is traditional, yet transoral approaches for defect fractures anterior to the first molar may be effectively used for both the RIF and grafting. A reconstruction plate or locking reconstruction plate is anchored bicortically with three screws on either side, well away from the fracture and defect (Fig 2.4-6a–c).

a

Smaller defects with an intact and viable soft-tissue envelope are typically grafted with free nonvascularized bone, as long as the condition of the soft tissue allows tension-free and complete wound closure. Should the soft-tissue quality not allow primary bone grafting, secondary bone grafts are an option. Temporary exposure of a reconstruction plate is not a problem. In larger bone defects and in defects associated with poor soft-tissue status as well as in combined bone and soft-tissue defects, such as in gunshot injuries, microvascular bone and soft-tissue transplantation is preferred.

b

Fig 2.4-6a–c a Multifragmentary defect fracture in the chin area. Capitulum fracture on the left. b Primary adaptation of multifragmented fracture zone via MMF with arch bars. c Stabilization of fracture zone with a reconstruction plate fixed with three screws on either of the comminuted area. One fragment (tooth bearing) is fixed with a miniplate. The defect area is filled with a bone graft. The condylar head fracture is treated nonsurgically.

c

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5.4 Infected mandibular fractures

Historically, all open mandibular fractures were considered potentially infected if not treated within 24 hours. Indeed, open fractures were managed with closed techniques in the form of MMF appliances, splints, and external fixators. All teeth were removed from fracture sites and internal fixation was believed to be contraindicated. If the fracture became infected, drainage and sequestrectomy were performed while the occlusion was controlled with MMF. As treatment evolved, antibiotics were added to the treatment protocol but with little benefit. Debridement was initiated only after radiographic evidence of sequestrum formation and time to union was calculated from the time drainage ceased. If a bone graft was needed, this was done 3–6 months following cessation of the drainage. Modern therapy is based on the AO principle that the infected fracture is best managed by rigidly immobilizing the fragments. This allows the body’s defenses to eliminate the infection and permit healing.

a

Protocol calls for incision and drainage of the acute infection, antibiotics, and removal of involved nonpreservable teeth. If the process becomes chronic, MMF is performed, the fracture is adequately exposed and debrided, and loadbearing osteosynthesis is placed (Fig 2.4-7a–b). Either transoral access for fractures in the chin area or transcutaneous access may be used. Load-bearing fixation is performed with a reconstruction plate or locking reconstruction plate anchored bicortically with three or four screws placed on either side, well away from the infected fracture site. Aluminum bending templates greatly facilitate plate bending which must be precise for reconstruction plates to prevent the bone from being adapted to an improperly contoured plate. Bending of the locking reconstruction plate need not be as precise since it is a true internal fixator that does not depend on the plate-to-bone interface for stability. One must be cognizant of the anatomy of the area when placing screws. Avoid tooth roots and the inferior alveolar neurovascular bundle. The complications of treatment should not add to

b

Fig 2.4-7a–b a An acutely infected fracture of the mandibular angle. b Bridging of the infected area with a reconstruction plate. At least three screws are placed on either side and well away from the infected zone. If the soft tissue allows, a cancellous bone graft is placed into the defect zone.

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the complications of the injury. If soft tissue allows, primary autogenous particulate marrow bone graft may be placed in the resulting bone defect. MMF is released and the patient is allowed to function. This contemporary infected fracture protocol has dramatically shortened the course of treatment for these patients. If successful, which it is most of the time, healing and union rapidly occur. When it is not, with continued drainage, loss of the graft and further sequestration, the internal fixator allows mandibular function and provides a platform for further debridement and secondary grafting. This concept has been used with success and only minor complication rates have been experienced.

6


Culture-specific antibiotic regimen is indicated preoperatively and extending postoperatively. Used long term, it will only delay rather than prevent the emergence of a postoperative infection. If the wound is wet or potentially infected, it should be drained. This is seldom necessary but is preferred by some surgeons (by vacuum or simply a dependent drain).

7


These complex fractures are subject to complications such as nonunion, malunion, infection, sequestration, loss of teeth, and neurosensory deficits. Modern treatment with load-bearing osteosynthesis has minimized many of these. Complications from load-bearing osteosynthesis are generally related to inadequate reduction and/or fixation which are operator errors in judgement or technique. Proper reduction is facilitated by adequate imaging and exposure. Application of adequate fixation is often governed by the understanding that it is rare to have too much fixation but all too common to have too little.

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2.5 References and suggested reading Alpert B, Englestad M, Kushner G (1999)

Cillo JE Jr, Ellis E 3rd (2007) Treatment of

Ellis E III, Walker LR (1996) Treatment of

Small versus large plate fixation of mandibular fractures. J Craniomaxillofac Trauma; 5(3):33–39. Alpert B, Tiwana PS, Kushner GM (2009) Management of comminuted fractures of the mandible. Oral Maxillofac Surg Clin North Am; 21(2):185–192, v. Review. Anderson T, Alpert B (1992) Experience with rigid fixation of mandibular fractures and immediate function. J Oral Maxillofac Surg; 50:555–560. Assael LA (1994) Treatment of mandibular angle fractures: plate and screw fixation. J Oral Maxillofac Surg; 52:757–761. Review. Basdra EK, Stellzig A, Komposch G (1998) Functional treatment of condylar fractures in adult patients. Am J Orthod Dentofacial Orthop; 113(6):641–646.

patients with double unilateral fractures of the mandible. J Oral Maxillofac Surg; 65:1461–1469.

mandibular angle fractures using only one noncompression miniplate. J Oral Maxillofac Surg; 54:864–871. Ellis E III, Walker LR (1994) Treatment of mandibular angle fractures using two noncompression miniplates. J Oral Maxillofac Surg; 52:1032–1036.

Benson PD, Marshall M, Engelstad M, et al

(2006) The use of immediate bone grafting in reconstruction of clinically infected mandibular fractures: bone grafts in the presence of pus. J Oral Maxillofac Surg; 64:122–126. Braidy HF, Ziccardi VB (2009) External fixation for mandible fractures: Atlas Oral Maxillofac Surg Clin North Am; 17(1):45–53. Brumback RJ, Ellison PS Jr, Poka A, et al

(1989) Intramedullary nailing of open fractures of the femoral shaft. J Bone Joint Surg [Am]; 71: 1324–1331. Buchbinder D (1993) Treatment of fractures of the edentulous mandible, 1943 to 1993: a review of the literature. J Oral Maxillofac Surg; 51:1174–1180. Buitrago-Téllez CH, Audigé L, Strong B, et al (2008) A comprehensive classification of

mandibular fractures: a preliminary agreement validation study. Int J Oral Maxillofac Surg; 37(12):1080–1088. Cabrini Gabrielli MA, Real Gabrielli MF, Marcantonio E, et al (2003) Fixation of

mandibular fractures with 2.0-mm miniplates: review of 191 cases. J Oral Maxillofac Surg; 61(4):430–436. Champy M, Lodde JP (1976) Synthèses mandibulaires. Location de synthèses en function de contraintes mandibulaires. Rev Stomatol; 77(8):971–976. Champy M, Lodde JP, Schmitt R et al (1978) Mandibular osteosynthesis by miniature screwed plates via a buccal approach. J Oral Maxillofac Surg; 6(1):14–21. Chen CT, Lai JP, Tung TC, et al (1999) Endoscopically assisted mandibular subcondylar fracture repair. Plast Reconstr Surg; 103(1):160–165. Chotkowski GC (1997) Symphysis and parasymphysis fractures. Atlas Oral Maxillofac Surg Clin North Am; 5(1):27–59.

Collins CP, Pirinjian-Leonard G, Tolas A, et al (2004) A prospective randomized

clinical trial comparing 2.0-mm locking plates to 2.0-mm standard plates in treatment of mandible fractures. J Oral Maxillofac Surg; 62(11):1392–1395. Cordaro L, Rossini C, Mijiritsky (2004) Fracture and displacement of lingual cortical plate of mandibular symphysis following bone harvesting: case report. Implant Dent; 13:202–206. Dahlström L, Kahnberg KE, Lindahl L (1989) 15 years follow-up on condylar fractures. Int J Oral Maxillofac Surg; 18(1):18–23. Delaire J, Le Roux JC, Tulasne JF (1975) Le traitment fonctionnel des fractures du condyle mandibulaire et de son col. Revue Stomatol; 76:331–350. Ehrenfeld M, Roser M, Hagenmaier C, et al

(1996) [Treatment of mandibular fractures with different fixation techniques: results of a prospective fracture study]. Fortschr Kiefer Gesichtschir; 41:67–71. German. Ellis E III (2011) Is lag screw fixation superior to plate fixation to treat fractures of the mandibular symphysis? J Oral Maxillofac Surg; Dec 29 [Epub ahead of print]. Ellis E III (2010) A prospective study of 3 treatment methods for isolated fractures of the mandibular angle. J Oral Maxillofac Surg; 68(11):2743–2754. Ellis E III (2002) Outcomes of patients with teeth in the line of mandibular angle fractures treated with stable internal fixation. J Oral Maxillofac Surg; 60(8):863– 865. Ellis E III (1999) Treatment methods for fractures of the mandibular angle. Int J Oral Maxillofac Surg; 28:243–252 Ellis E III (1997) Lag screw fixation of mandibular fractures. J Craniomaxillofac Trauma; Spring;3(1):16–26. Ellis E III (1993) Treatment of mandibular angle fractures using the AO reconstruction plate. J Oral Maxillofac Surg; 51:250–254. Ellis E III, Dean J (1993) Rigid fixation of mandibular condyle fractures. Oral Surg Oral Me Oral Pathol; 76(1):6–15. Review. Ellis E III, Muniz O, Anand K (2003) Treatment considerations for comminuted mandibular fractures. J Oral Maxillofac Surg; 61(8):861–870. Ellis E III, Simon P, Throckmorton GS

(2000) Occlusal results after open or closed treatment of fractures of the mandibular condylar process. Int J Oral Maxillofac Surg; 58(3):260–268.

Feller KU, Schneider M, Hlawitschka M, et al (2003) J Craniomaxillofac Surg; 31(5):290–

295. Fox AJ, Kellman RM (2003) Mandibular angle fractures: two-miniplate fixation and complications. Arch Facial Plast Surg; 5(6):464–469. Hall MB (1994) Condylar fractures: surgical management. J Oral Maxillofac Surg; 52(11):1189–1192. Review. Hammer B, Prein J (1991) [Structural and biomechanical based differences of osteosynthesis in mandibular or mid-face fractures. Why does the AO still use stiff plates?]. Swiss Dent; 12(12):7–13. German. Hammer B, Schier P, Prein J (1997) Osteosynthesis of condylar neck fractures: a review of 30 patients. Br J Oral Maxillofac Surg; 35(4):288–291. Haug RH, Fattahi TT, Goltz M (2001) A biomechanical evaluation of mandibular angle fracture plating techniques. J Oral Maxillofac Surg; 59:1199–1210. Iizuka T, Lindqvist C, Hallikainen D, et al

(1991) Infection after rigid internal fixation of mandibular fractures: a clinical and radiologic study. J Oral Maxillofac Surg; 49:585–593. Jacobovicz J, Lee C, Trabulsky PP (1998) Endoscopic repair of mandibular subcondylar fractures. Plast Reconstr Surg; 101(2):437–441. Jaques B, Richter M, Arza A (1997) Treatment of mandibular fractures with rigid osteosynthesis: using the AO system. J Oral Maxillofac Surg; 55(12):1402–1406; discussion 1406–7. Kahnberg KE, Ridell A (1979) Prognosis of teeth involved in the line of mandibular fractures. Int J Oral Surg; 8(3):163–172. Kokemueller H, Konstantinovic VS, Barth EL, et al (2011) Endoscope-Assisted

Transoral Reduction and Internal Fixation Versus Closed Treatment of Mandibular Condylar Process Fractures-A Prospective Double-Center Study. J Oral Maxillofac Surg; [Epub ahead of print] Kearns GJ, Perrott DH, Kaban LB (1994) Rigid fixation of mandibular fractures: does operator experience reduce complications? J Oral Maxillofac Surg; 52:226–231.

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Klein MP, Rahn BA, Frigg R, et al (1990)

Newman L (1995) The role of autogenous

Schierle HP, Schmelzeisen R, Rahn B, et al

Reaming versus non-reaming in medullary nailing: interference with cortical circulation of the canine tibia. Arch Orthop Trauma Surg; 109(suppl 1):314–316. Kunz C, Hammer B, Prein J (2001) [Fractures of the edentulous atrophic mandible. Fracture management and complications] Mund Kiefer Gesichtschir; 5(4):227–232. German.

primary rib grafts in treating fractures of the atrophic edentulous mandible. Br J Oral Maxillofac Surg; 33(6):381–387. Obwegeser HL, Sailer HF (1973) Another way of treating fractures of the atrophic edentulous mandible. J Maxillofac Surg; 1(4):213–221. Prein J, Beyer M (1990) Management of infection and non-union in mandibular fractures. Oral Maxillofac Clin North Am; 2(1):187–194. Prein J, Eschmann A, Spiessl B (1976) [Results of follow-up examinations in 81 patients with functionally stable mandibular osteosynthesis]. Fortrschr Kiefer Gesichtschir; 21:304–307. Prein J, Hammer B (1991) Stable fixation of mandibular fractures in accordance with the AO Principles. Oral & Maxillofacial Trauma. Fonseca RJ, Walker RV (eds) Oral and maxillofacial trauma. WB Saunders Co, 1172–1232. Prein J, Kellman RM (1987) Rigid internal fixation of mandibular fractures – basics of AO Technique. Otolaryngol Clin North Am; 20(3):441–456. Prein J, Schiel H, Hammer B (1994) Modern treatment of infected mandibular fractures. J Cranio Maxillofac Surg; 22, Suppl.1:36. Prein J, Schmoker R (1976) Treatment of infected fractures and pseudarthrosis of the mandible. Spiessl, B (ed), New Concepts in Maxillofacial Bone Surgery. BerlinHeidelberg-New York: Springer Verlag.

(1997) One- or two-plate fixation of mandibular angle fractures? J Craniomaxillofac Surg; 25:162–168.

Kuriakose MA, Fardy M, Sirikumara M, et al

(1996) A comparative review of 266 mandibular fractures with internal fixation using rigid (AO/ASIF) plates or mini-plates. Br J Oral Maxillofac Surg; 34(4):315–321. Le Fort R (1901) [Experimental study of fractures of the upper jaw. Part I, Part II, Part III.] Rev Chir (Paris) 23, 208–227, 360–379, 479–507. French. Lovald S, Baack B, Gaball C, Olson G, et al

(2010) Biomechanical optimization of bone plates used in rigid fixation of mandibular symphysis fractures. J Oral Maxillofac Surg; 68(8):1833–1841. Luhr HG (2000) [The development of modern osteosynthesis]. Mund Kiefer Gesichtschir; 4 Suppl 1:84–90. German. Luhr HG (1985) Basic research, surgical technique and results of fracture treatment with the Luhr-Mandibular-CompressionScrew System (MCS System). HjortingHansen E (ed), Oral and maxillofacial surgery. Berlin: Quintessence,124. Luhr HG (1968) [On the stable osteosynthesis in mandibular fractures.] Dtsch Zahnärztl Z; 23(7):754. German. Luhr HG, Reidick T, Merten HA (1996) Results of treatment of fractures of the atrophic edentulous mandible by compression plating: a retrospective evaluation of 84 consecutive cases. J Oral Maxillofac Surg; 54(3):250–255. Madsen MJ, McDaniel CA, Haug RH (2008) A biomechanical evaluation of plating techniques used for reconstructing mandibular symphysis/parasymphysis fractures. J Oral Maxillofac Surg; 66(10):2012–2019. Marciani RD (2001) Invasive management of the fractured atrophic edentulous mandible. J Oral Maxillofac Surg; 59(7):792– 795. Mast J, Jakob R, Ganz R (1989) Planning and Reduction Technique in Fracture Surgery. 1st ed. Berlin Heidelberg New York: Springer-Verlag. Miles BA, Potter JK, Ellis E III (2006) The efficacy of postoperative antibiotic regimens in the open treatment of mandibular fractures: a prospective randomized trial. J Oral Maxillofac Surg; 64(4):576–582. Myall RWT (1994) Condylar injuries in children: what is different about them? Worthington P, Evans JR (eds), Controversies in Oral & Maxillofacial Surgery. Philadelphia: WB Saunders.

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(1996) Schussverletzungen des Unterkiefers [Gunshut injuries of the mandible]. Fortschr Kiefer Gesichtschir; 41:160–165. German. Prein J, Spiessl B (1976) Rigid internal fixation of compound mandibular fractures. Spiessl B (ed), New Concepts in Maxillofacial Bone Surgery. BerlinHeidelberg-New York: Springer-Verlag. Prein J, Spiessl B, Rahn B, et al (1975) [Mandibular fracture healing after surgical treatment]. Fortschr Kiefer Gesichtschir; 19:17–21. German. Rahn B, Cordey J, Prein J, et al (1975) [Biomechanics of osteosynthesis in the mandible]. Fortschr Kiefer Gesichtschir; 19:37–42. German. Roser M, Ehrenfeld M, Ettlin D, et al (1996) [Lag screw osteosynthesis in median mandibular fractures – technique and outcome.] Fortschr Kiefer Gesichtschir; 41:100–102. German. Sauerbier S, Schön R, Otten JE, et al (2008) The development of plate osteosynthesis for the treatment of fractures of the mandibular body – a literature review. J Craniomaxillofac Surg; 36(5):251–259. Schiel H, Hammer B, Ehrenfeld M, et al

(1996) [Therapy of infected mandibular fractures]. Fortschr Kiefer Gesichtschir; 41:170–173. German.

Schierle HP, Schmelzeisen R, Rahn B (1996)

[Experimental studies of the biomechanical stability of different miniplate configurations for the mandibular angle]. Fortschr Kiefer Gesichtschir; 41:166–170. German. Schmelzeisen R, Cienfuegos-Monrey R, Schön R, et al (2009) Patient benefit from

endoscopically assisted fixation of condylar neck fractures – a randomized controlled trial. J Oral Maxillofac Surg; 67(1):147–158. Schmidt BL, Kearns G, Gordon N, et al

(2000) A financial analysis of maxillomandibular fixation versus rigid internal fixation for treatment of mandibular fractures. J Oral Maxillofac Surg; 58(11):1206–10; discussion 1210–1211. Schön R, Fakler O, Gellrich NC, et al (2005) Five-year experience with the transoral endoscopically assisted treatment of displaced condylar mandible fractures. Plast Reconstr Surg; 116(1):44–50. Schön R, Gutwald R, Schramm A, et al

(2002) Endoscopy-assisted open treatment of condylar fractures of the mandible: extraoral vs intraoral approach. Int J Oral Maxillofac Surg; 31(3):237–243. Schön R, Roveda SI, Carter B (2001) Mandibular fractures in Townsville, Australia: incidence, aetiology and treatment using the 2.0 AO/ASIF miniplate system. Br J Oral Maxillofacial Surg; 39(2):145–148. Schön R, Schramm A, Gellrich NC, et al

(2003) Follow-up of condylar fractures of the mandible in 8 patients at 18 months after transoral endoscopic-assisted open treatment. J Oral Maxillofac Surg; 61(1): 49–54. Scolozzi P, Richter M (2003) Treatment of severe mandibular fractures using AO reconstruction plates. J Oral Maxillofac Surg; 61(4):458–461. Seemann R, Perisanidis C, Schicho K, et al

(2010) Complication rates of operatively treated mandibular fractures – the mandibular neck. Oral Surg Oral Med Oral Pathol Oral Radiol Endod; 109(6):815–819. Spiessl B (1989) Internal Fixation of the mandible. A manual of AO/ASIF Principles. Heidelberg New York: Springer-Verlag. Spiessl B, Schroll K (1972) Gelenkfortsatzund Kieferköpfchenfrakturen. Nigst H (ed),Spezielle Frakturen- und Luxationslehre, Band I/1: Gesichtsschädel. Stuttgart New York: Georg Thieme Verlag, 136–152. Tiwana PS, Kushner GM, Alpert B (2007) Lag screw fixation of anterior mandibular fractures: a retrospective analysis of intraoperative and postoperative complications. J Oral Maxillofac Surg; 65(6):1180–1185.


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Waiss W, Gosau M, Koyama K, et al (2011)

[Maxillary and mandibular fractures. Treatment concepts in maxillofacial surgery]. HNO; 59(11):1079–1087. German. Walker RV (1994) Condylar fractures: nonsurgical management. J Oral Maxillofac Surg; 52(11):1185–1188. Wassmund M (1927) Frakturen und Luxationen des Gesichtsschädels. Berlin: Meusser Verlag. Weinberg MJ, Merx P, Antonyshyn O, et al

(1995) Facial nerve palsy after mandibular fracture. Ann Plast Surg; 34(5):546–549. Widmark G, Bagenholm T, Kahnberg KE, et al (1996) Open reduction of subcondylar

fractures: a study of functional rehabilitation. Int J Oral Maxillofac Surg; 25(2):107–111. Woods WR, Hiatt WR, Brooks RL (1979) A technique for simultaneous fracture repair and augmentation of the atrophic edentulous mandible. J Oral Surg; 37(2):131–135. Zide MF, Kent JN (1983) Indications for open reduction of mandibular condyle fractures. J Oral Maxillofac Surg; 41(2):89– 98.

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3.1 Lower midface (Le Fort I and palatal fractures)

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3.3 Zygomaticomaxillary complex (ZMC) fractures, zygomatic arch fractures

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3.6 Fractures of the nasal skeleton

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3 Midfacial fractures


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3 Midfacial fractures 3.1 Lower midface (Le Fort I and palatal fractures)

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Definition

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Author Ricardo Cienfuegos

3.1 Lower midface (Le Fort I and palatal fractures) 1

Definition

Le Fort I or Guérin fractures are central midface fractures, located transversally above the dental apices, disjoining the maxilla just above the alveolar process together with the hard palate and the pterygoid processes typically in a single block. The fracture runs horizontally, crossing through the base of the maxillary sinus and the lower border of the piriform aperture (Fig 3.1-1a–b).

a

Central midface fractures were classified in three types by René Le Fort in 1901, referring to low-energy impacts. Today, however, those classic patterns are seldom found, since many Le Fort fractures are caused by high-energy mechanisms, often with comminution and combinations of fracture type. Commonly, with high-energy injuries and oblique force vectors, the fracture is higher on one side than on the other.

b

Fig 3.1-1a–b Le Fort I fracture, located transversally above the dental apices and disjoining the alveolar process, the hard palate, and the pterygoid processes.

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Intrapalatal fractures are present in 8–15% of Le Fort fractures, or they may be part of more complex injuries. They usually follow a sagittal or parasagittal direction, splitting the maxilla longitudinally close to the midline (Fig 3.1-2a–b). They are associated with rotational instability of dentoalveolar segments.

a

Palatal fractures mostly exit anteriorly between the central incisors, or between the lateral incisor and the canine tooth. They may also surround the tuberosity of the maxilla, separating a dentoalveolar segment containing the molar teeth with superior, lateral, and posterior displacement.

b

Fig 3.1-2a–b Le Fort I fracture combined with a sagittal palatal fracture. The maxilla is split longitudinally close to the midline.

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2

Imaging

Diagnosis should initially be clinical, aided by imaging studies. Maxillary fractures are confirmed by axial, coronal, and sagittal CT scans. Plain x-rays are of minor value. CT scans provide detailed images of fracture patterns, degree of comminution, or bone loss (Fig 3.1-3a–b). 3-D reconstruction gives information on the degree of displacement of the midface in relation to the mandible and the orbits.

If an adequate clinical and imaging diagnosis is not made, Le Fort I fractures with extension to the infraorbital rim may be incorrectly diagnosed as Le Fort II, especially on the basis of plain x-rays. Differential diagnosis depends on the presence or absence of fractures in the frontonasal region. Coexisting mandibular fractures, especially subcondylar fractures, should also be excluded.

Special care should be taken when diagnosing fractures in edentulous patients, or in those wearing dentures. A complete superior denture may act as a splint, directing the fracture forces toward different areas in the midfacial skeleton.

a

b

Fig 3.1-3a–b Preoperative evaluation a X-ray (Waters’ view) showing Le Fort I fracture. b CT scan (coronal view) documenting a Le Fort I fracture in more detail.

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3

Approaches

The standard approach to Le Fort I fractures is through a transoral vestibular incision. This approach is quick and simple, with few complications, and offers the additional benefit of leaving no visible scar. For irregular fracture types with higher fracture lines a facial degloving approach may also be appropriate. The incision is typically in the mobile mucosa 5–10 mm above the attached gingiva around the maxillary arch, leaving a “flange” for easier suturing. A central intact bridge of mucosa may be preserved for alignment. An alternative is the crestal incision in edentulous patients. Before the incision it is advisable to infiltrate local anesthesia with diluted adrenaline, which reduces bleeding considerably (Fig 3.1-4). Rarely, fractures are intraorally or extraorally open and may be treated through the lacerations. Lacerations should never be extended in preference to transoral incisions.

A subperiosteal dissection makes it possible to identify the four anterior, surgically accessible, vertical buttresses of the midface. Avoid injury to the infraorbital nerve by first performing careful dissection medial and lateral to it, then approaching the nerve between the now completed dissection pathways. If segmental alveolar fractures are also present, special care should be taken to maintain blood supply to the injured segments. Closure of the vestibular approach can be done with resorbable or nonresorbable sutures. Identify and reposition the alar base with a suture (Fig 3.1-5a–b) to avoid lateral position of the alae bases (the “alar-cinch technique”).

a

b Fig 3.1-4 Upper vestibular incision for exposure of a Le Fort fracture. Incision is commonly longer and higher laterally.

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Fig 3.1-5a–b Alar-cinch technique.


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4


The goal of treatment in Le Fort I fractures is correct repositioning of the fractured bones to restore their relation to the mandible, the cranial base, and the remaining midfacial structures. A successful maxillary reconstruction should involve recovering continuity, alveolar height, width and arch form of the maxilla, preserving the bone, and restoring the facial contour. Osteosynthesis with plates and screws offers the advantage of a precise reconstruction through 3-D stable fixation and improved chances of survival of bone grafts. Furthermore, the use of plates and screws for treating maxillary fractures has rendered postoperative mandibulomaxillary fixation (MMF) unnecessary, reducing costs of care and shortening recovery time. Reduction must be performed before fixation, either with the help of reduction forceps such as Rowe’s forceps, a stable wire loop placed through a drill hole near the thick bone of

the anterior nasal spine, or simply by applying arch bars and repositioning the fractured elements through traction with elastics (Fig 3.1-6). Incomplete or greenstick fractures may require an osteotomy, if reduction is not otherwise possible. If treatment is delayed, osteotomies may be necessary. Impacted fractures may appear relatively stable and show minimal deformity. However, once disimpacted or reduced, they may be very unstable and require extensive osteosynthesis and bone grafting. Before rigid internal fixation, dental occlusion should be reestablished and maintained through MMF. Inappropriate occlusion during surgery will lead to postoperative malocclusion, most commonly an anterior open bite. Unilateral fragmentation and loss of length may lead to a unilateral open bite. In edentulous patients and patients with a reduced dentition, in which an occlusal relation cannot be reestablished, the patient’s denture or a Gunning splint may be used for correct repositioning of the lower maxilla.

Fig 3.1-6 Repositioning of a Le Fort I fracture with the help of reduction forceps, shown here with Rowe’s forceps.

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In case of buttress fragmentation, undamaged buttresses should be used as a stable anatomical landmark for vertical height maintenance and fixation. Internal fixation is achieved by applying miniplates 1.5 or 2.0, or corresponding plates from the Matrix Midface system, and screws to the medial and lateral (the paranasal and zygomaticomaxillary) buttresses. These buttresses have the highest bone density and thus provide adequate bone stock for stable screw anchorage. If the screws are anchored in low-density areas, there is a risk of screw loosening, plate fractures, and subsequent midface collapse. Osteosynthesis is mostly performed with L- or Y-shaped plates, always placing two screws on either side of the fracture line to avoid rotational instability of the fracture seg-

ments (Fig 3.1-7). Plates should be carefully adapted to the bone surface in order to maintain the proper shape and dimensions of the maxilla, and to avoid forces such as traction on the underlying bone. Precise adaptation prevents secondary dislocation and avoids excess mechanical stress on the site of the screws, which may lead to microfractures in the bone. Particularly if the fracture lines are low, care should be taken to place the screws in the space between tooth roots. Fixation of palatal fractures intends to restore the width and projection of the maxillary arch. Conventional fixation of palatal fractures involves the placement of long plates and screws anteriorly under the piriform aperture and the anterior nasal spine and submucosally in the palatal vault. The latter stabilizes posterior palatal width and prevents rotation

Fig 3.1-7 Stabilization with L-shaped miniplates (1.5 or 2.0). Fixation with at least two screws on either side of the fracture line in order to avoid rotational instability. MMF is maintained only during surgery.

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of dentoalveolar segments. Placement of a plate across the posterior hard palate after reduction controls the posterior palatal width. This plate can be placed transmucosally if a locking miniplate is used to avoid compressing the mucosa. Additional fixation of the anterior and lateral buttresses is performed (Fig 3.1-8a–b).

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b

Fig 3.1-8a–b a Stabilization of Le Fort fracture as described in Fig 3.1-7. The additional sagittal fracture is stabilized subnasally with a miniplate 1.5 or 2.0. b Fixation of the palatal fracture with a miniplate.

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In the presence of comminution, longer plates should be used to bridge the fragmented zones with a minimum of two screws on either side of the comminuted zone. Bone fragments should be preserved and repositioned if possible. If the fragments are too small to be fixed with plates and screws, comminuted areas should be bone grafted (Fig 3.1-9a–c). The same applies for buttress defects. Bone grafts should be fixed with lag screws or separate plates and screws. Unstable “floating” bone grafts must be avoided. If plates are used to bridge bone defect zones without reconstruction of bony pillars, masticatory forces may lead to fatigue, rupture of the plates, and displacement.

a

Loose bone fragments are removed from the maxillary sinus, since they may act as sequestra. Loss of the anterior wall of the maxillary sinus may cause depression of overlying soft tissues, and later scar contractions may affect the infraorbital nerve. Larger anterior sinus wall defects should be treated with bone grafts or titanium meshes. Split calvarial bone grafts may be used for the maxillary sinus wall, as well as for reconstruction of the buttresses.

b Fig 3.1-9a–c a Le Fort I fracture with comminution on both sides. b Stabilization with longer miniplates bridging the areas of comminution. Reconstruction and stabilization of the right anterior maxillary sinus wall with a titanium mesh. c In situations with bone loss in buttress areas, bone grafts, often in combination with miniplate fixation, should be used to bridge the defect.

c

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5

Airway management

7


Midfacial trauma may cause displacement of bony or cartilaginous structures, edema, and hematoma formation which may make nasal intubation more difficult. Orotracheal intubation sometimes interferes with establishing an adequate MMF, especially in patients with complete dentition. The surgeon must decide which technique of airway management is suitable for an individual patient.

Fractures of the midface in general may be associated with severe, even life-threatening bleeding from the greater palatine arteries, internal maxillary arteries, or retromaxillary venous plexus. However, in isolated Le Fort I fractures this is rarely the case. If such bleeding occurs, anterior and posterior nasal packing and/or immediate reduction and internal fixation may be necessary as an emergency treatment.

At the end of surgery dislocated hard tissues which may compromise the airway, such as a luxated nasal septum or a dislocated medial wall of the maxillary sinuses, should be repositioned. If the fracture fixation has been done in nasal intubation, this may require a tube switch from nasal to oral intubation.

Inadequate reduction of maxillary fractures may cause shortening of the midface, as well as an anterior open bite. Pseudoprognathism may also appear, as well as asymmetry between the maxillary and mandibular midline, malocclusion, and superior rotation of the nasal tip. If any of these findings are diagnosed postoperatively, the patient should be returned to surgery immediately for correction.

6


Dental and oral hygiene with tooth brush and mouth rinse must be encouraged. The fact that MMF is not used in the postoperative period makes oral hygiene easier and oral feeding possible; although a soft diet is recommended for 4 weeks. Perioperative and postoperative antibiotics are indicated. Maxillary sinus drainage is supported by the use of nasal vasoconstrictors.

Infection is usually due to instability, mostly caused by loosening of one or more screws, or instability of a graft. The problem is solved by exchanging or removing the screw or graft, depending on whether the fracture has healed or not. Inadequate or failed treatment of palatal fractures may lead to complications, such as increase in the transversal diameter of the maxilla, rotation of dentoalveolar segments, and fragment instability. Intraorally exposed osteosynthesis material should be eventually removed.

After repair of palatal fractures postoperative MMF for up to 3 weeks should sometimes be considered, especially in cases with comminuted fractures.

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3 Midfacial fractures 3.2 Upper midface (Le Fort II and III)

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Diagnosis

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Osteosynthesis technique

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Airway management

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Authors Marcelo Figari, Thiam-Chye Lim

3.2 Upper midface (Le Fort II and III)

1


The upper midface (Le Fort II and III) comprises the facial bones situated above the projection of the Le Fort level I fracture including the zygomas, the upper part of the maxilla with its frontal process, the bones that form the lateral, inferior, and medial orbital walls, and the nasal bones. It is

located between the upper face (frontal and anterior temporal bones) above and the occlusal unit below; it includes the outer facial frame, the orbital, and nasoorbitoethmoidal (NOE) regions (Fig 3.2-1). In 1901, René Le Fort described the facial fracture patterns observed in cadaver midfaces after blunt

Fig 3.2-1 Upper midface, located between the occlusal unit and the frontal facial unit. It consists of the zygomas laterally, the NOE area centrally, and the internal portion of the orbits bilaterally.

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impacts. Today, Le Fort II (Fig 3.2-2a–b) and III (Fig 3.2-3a–b) classic fracture patterns (pyramidal fracture and craniofacial disjunction, respectively) are rarely seen in pure form due to the increased amount of energy involved in trauma

mechanisms. Most midfacial fractures today combine a variety of different midfacial fracture patterns and in addition are frequently associated with cranial vault, skull base, palatal, and mandibular fractures.

b

a Fig 3.2-2a–b Le Fort II fracture shows dislocation and occlusal disturbance–high and low variations as it crosses the nasal bridge; high at the frontal bone, low variations just under the nasal bone.

a

b

Fig 3.2-3a–b Le Fort III fracture shows typical dislocation and occlusal disturbance.

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2

Diagnosis

Clinical evaluation provides some information in terms of occlusal disturbances, face shortening, nose flattening, or external facial frame dislocation, depending on the given fracture pattern. Nevertheless, soft-tissue swelling frequently masks underlying bone deformity. Classic evaluation using plain facial x-rays is usually not helpful. Computed tomography (CT) with axial and coronal sections, bone and soft-tissue windows, and special (sagittal)

reconstructions is the standard. These images provide clear understanding of fracture line location, bone displacement, and bone and soft-tissue relation. In recent years, volume CT scans have become more widely available in trauma centers and general hospitals. Besides the faster acquisition of data, enabling patients to have facial scans while other organ scans (spine, liver, spleen) are performed, the improved quality provides more accurate information of the comminution and displacement with less motion artifact than traditional CT scans. Additionally, 3-D reconstruction allows rapid orientation of the complex fracture pattern (Fig 3.2-4a–d).

a

b

c

d

Fig 3.2-4a–d a CT scan, axial view of a Le Fort II fracture, shows the fracture line through anterior and posterior maxillary sinus walls. b CT scan, axial view of a Le Fort II fracture, shows the fracture line through both infraorbital rims and zygomatic arch on the right. c C T scan, coronal view, shows the fracture at Le Fort III level on the right and Le Fort II level bilaterally. d CT scan; 3-D reconstruction of a panfacial fracture.

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3

Approaches

Le Fort II and III fractures require a wide surgical exposure for proper reduction and stabilization. The upper midface and the craniofacial junction may be exposed by coronal or transcutaneous incisions, and the combination of the two. The choice of approach depends on the fracture pattern, the amount of displacement, other accompanying fractures, and surgeon’s preference. Today the coronal incision is the most important surgical approach, allowing exposure in the subperiosteal plane of the glabella, the supraorbital rims, both zygomatic arches, and the superior, medial, and lateral orbital walls. Routinely, the cutaneous incision is made from

a

c

the helix root on one side to the vertex of the skull and then to the contralateral helical root. Depending on the need to completely expose the zygomatic arch or the temporomandibular joint capsule, further extension of the incision posteriorly or anteriorly to the tragus level may be necessary. Besides the classic linear incision, several modifications have been described, such as the sinusoidal or saw-tooth stealth incision, or the extension of the incision behind the pinna in the postauricular area instead of the preauricular region. In individuals with male-pattern baldness, the incision may be made further back over the vertex. These alternatives improve esthetical aspects, preserve hair vitality, and facilitate skin closure (Fig 3.2-5a–e).

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d

e

Fig 3.2-5a–e Incision lines for the coronal approach and the various modifications.

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Care must be taken to preserve the frontal branch of the facial nerve by transection of the superficial layer of the deep temporal fascia about two finger widths above the zygomatic arch, thus protecting the nerve by dissecting only beneath the deep fascia. The surgical dissection and release of the supraorbital nerve is required for complete exposure of the orbital roof and medial and lateral orbital walls (Fig 3.2-6).

In some cases of craniofacial disjunction the zygomaticofrontal suture areas are exposed through the lateral portion of an upper blepharoplasty incision (Fig 3.2-7a–b), therefore avoiding a coronal incision. Nevertheless, this approach has the disadvantage of limited exposure, making a symmetrical control of reduction impossible, particularly in the zygomatic arch region. For the same reason, hemicoronal approaches should be avoided.

a

b Fig 3.2-6 Surgical dissection and freeing of the supraorbital nerve for unhindered approach of the supraorbital rim and orbital roof. The nerves are freed from the foramina with small osteotomes. Additional periosteal incision in the nasal bridge area is helpful to improve access.

Fig 3.2-7a–b a Upper blepharoplasty and lateral eyebrow incisions, and transconjunctival incision with lateral canthotomy. b Exposure of the lateral orbital rim trough upper blepharoplasty incision.

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Access to the orbital floor requires subciliary, midpalpebral, or transconjunctival approaches (Fig 3.2-8a–d). The decision is based on patient age, lid anatomy, orbicular muscle tone, and the presence of traumatic lacerations but mostly on the pattern and extent of the fracture. The older the patient and the more lax the eyelids, a lower placement of the cutaneous palpebral incision is recommended to avoid ectropion.

In case of Le Fort II fractures or combination with Le Fort I or palatal fractures, a transoral upper vestibular incision is necessary for reduction and stabilization of the nasomaxillary and zygomaticomaxillary buttresses.

Subciliary incision Mid-eyelid incision

Transconjunctival incision

a

c

b

d

Fig 3.2-8a–d a Subciliary and mid-eyelid incision (lateral view). b Transconjunctival incision (lateral view). c Mid-eyelid incision (frontal view). d Exposure of the infraorbital rim through mid-eyelid incision.

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4

Osteosynthesis technique

Once all fractures have been exposed, adequate reduction is critical before any osteosynthesis is performed. Heavily impacted or partially fractured midfacial trauma frequently necessitates osteotomies or, less preferably, the use of reduction clamps to reposition the fragments. Although restoration of pretrauma occlusion by means of arch bars, screws, or wire dental ligatures is mandatory, it is insufficient to reestablish facial contour, especially in the upper midface. In the past, it was stressed that reestablishing occlusion was the initial and most important step of facial reconstruction. The combination of mandibulomaxillary fixation (MMF), wire osteosynthesis, and craniofacial suspensions frequently led to midfacial bone-segment telescoping and did not reliably stabilize fragments in a threedimensionally accurate position, causing long-term facial deformation, despite the occlusion being correct. Today, open reduction and internal fixation using plates and screws is the most reliable way to achieve and preserve proper and stable three-dimensional bone-segment alignment. In some cases, such as severely comminuted fractures, temporary wire ligatures may help achieve preliminary bone approximation before definitive osteosynthesis with plates and screws is performed.

Adequate selection of osteosynthesis material depends on several factors. A variety of implants should be available at all times for the surgical team. The surgeon must know and select the most suitable plate and screw combinations for each location. The reconstruction of nasomaxillary and zygomaticomaxillary pillars at the Le Fort I level and the zygomatic arches allows for the use of miniplates of the 2.0, 1.5, or Matrix Midface systems, thus taking advantage of their rigidity in a region where the soft tissues are thick enough to provide sufficient coverage and to avoid postoperative palpability. The periorbital regions, such as the frontozygomatic suture and infraorbital rim, and other smooth facial areas with thin soft-tissue coverage such as the glabella, are better fixed with miniplates 1.5, 1.3, or corresponding Matrix Midface plates. Small fragments and bone in nonloaded areas, such as the frontal sinus walls, may be stabilized with microplates 1.0, 1.3, or corresponding Matrix plates. In other words, loaded areas are fixed with stronger plates and nonloaded areas with weaker plates. The quality and quantity of the overlying soft tissues as well as plate thickness have to be considered to avoid palpability and, sometimes, visibility of plates. The sequencing of osteosynthesis in Le Fort II and III fractures depends on associated facial injuries, the degree of displacement, and the surgeon. Comminuted areas providing insufficient stable bone for adequate screw fixation may need to be bridged with longer plates, and defect areas may need to be bone grafted.

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In an isolated pyramidal Le Fort II fracture, the contour of the upper facial unit and the zygoma area provides excellent reference for proper reduction. In addition, MMF avoids postoperative malocclusion. After satisfactory reduction, the frontomaxillary area and infraorbital rims are fixed with miniplates 1.3, and the strong zygomaticoalveolar crest is typically fixed with L-shaped miniplates 1.5 or 2.0 or corresponding implants from the Matrix Midface system (Fig 3.2-9).

Le Fort III fractures, in the rare case of isolated craniofacial disjunction or in association with additional NOE patterns, first require the reconstruction of the outer facial frame (Fig 3.2-10). Today it is generally accepted, as originally described by Gruss et al, that precise reduction of the zygoma and zygomatic arches and subsequent stable fixation with fixation in the root of the zygomatic arch and in the frontozygomatic suture represent a crucial step in reestablishing facial dimension in this type of facial injuries. The best place

Fig 3.2-10 Reconstruction and fixation of outer facial frame as the first step during repair of a Le Fort III fracture.

Fig 3.2-9 Le Fort II fracture miniplate osteosynthesis. The infraorbital and NOE area are stabilized with miniplates 1.3. Zygomaticomaxillary buttresses are stabilized with miniplates 2.0. MMF is maintained during surgery only.

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to control the position of the zygoma is the junction between the greater wing of the sphenoid and the zygoma in the lateral orbital wall. Multiple point position control is preferred. After reconstruction of the so-called outer facial frame the remaining surgical treatment will depend on the existence of associated NOE, Le Fort II, or Le Fort I fracture lines (Figs 3.2-11a–b, 3.2-12).

a

Approximately 10% of Le Fort fractures are not accompanied by maxillary mobility due to incomplete fractures. The only physical finding may be a subtle malocclusion. This is frequently not detected in polytrauma patients with oral intubation. Early detection and timely treatment of these fractures depends on the clinical experience of the attending craniomaxillofacial surgeon. The possibility of such a fracture is suggested by the presence of bilateral maxillary sinus fluid levels.

b

Fig 3.2-11a–b a Le Fort III fracture in combination with zygomatico-orbital fracture on the left and typical occlusal disturbance. b Fixation of Le Fort III and zygomatico-orbital fracture with miniplates 2.0 and 1.3. The patient is in MMF during surgery only.

Fig 3.2-12 Fixation of Le Fort I, II, and III fractures with miniplates 2.0 and 1.3. On the left, a bone graft is covering a bony defect at the zygomaticomaxillary buttress area. MMF during surgery only.

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5

Airway management

During the early postinjury period, Le Fort fractures may produce various degrees of airway compromise which are rarely critical. Nasopharyngeal bleeding may obstruct the nasal airway while the posteroinferiorly displaced hard palate and swollen soft palate/uvula may cause oropharyngeal obstruction. However, these are infrequent reasons for urgent intubation, routinely managed through careful clearing of oral secretions, and if necessary by the placement of an oropharyngeal cannula. On initial assessment the emergency room physician must be aware of potential cranial base involvement when introducing a nasogastric tube. For the same reason, orotracheal intubation is preferred for airway control. 75% of patients, who sustained a severe facial trauma and require airway control, are best managed through orotracheal intubation. Only a minority of these patients (< 12%) will need a surgical tracheotomy. With respect to intraoperative airway control, the selected method must not interfere with the application of MMF. This is necessary to reproduce the preinjury occlusal status. Nasotracheal intubation is common, and in cases of skullbase injuries performed with the help of an endoscope. Oral intubation is feasible, passing the spiraled tube behind the last teeth or through an edentulous area.

6


Preoperative and postoperative ophthalmologic consultation is important. A number of midfacial trauma cases will have associated ocular impairment related to the trauma mechanism, either direct injury to the globe and adnexae, or indirect functional disability related to orbital wall compromise or muscular entrapment. These examinations are not only important for medico-legal reasons but the preoperative examination may also modify the timing of the surgery. Patients with fractures of the upper midface should be treated surgically under antimicrobial prophylaxis with broadspectrum antibiotics. As a guideline, antibiotic administration can be stopped immediately after surgery or after a number of postoperative doses, depending on the hospital protocol. Drains are rarely used after Le Fort fracture therapy. Postoperative MMF is considered individually. It is recommended that patients stay on a soft diet for approximately 4 weeks. In comminuted and panfacial fractures, a brief period of MMF may be indicated.

Submental intubation, a method described by Hernandez Altemir in 1986, has progressively gained acceptance over the last decade. It is essentially an oral intubation where the tube is afterward passed through the submental area, internal to the mandibular arch and anterior to the facial artery and lingual nerve. The procedure must be converted again to an oral or nasal intubation after surgery. It has few complications and provides excellent access to the nasal and oral cavities during surgery. Finally, transcutaneous or endoscopically assisted tracheostomy can be preformed if none of the above-mentioned procedures are feasible. At the end of the surgical procedure the nasal cavity must be inspected, and septal luxations as well as loose bony fragments must be treated (chapter 3.1 Lower midface: Le Fort I and palatal fractures).

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7


Postoperative complications are generally related to inadequate surgical planning and/or therapy. Inadequate surgical access and poor reduction of the fracture may lead to misalignment of the fragments. In patients with associated palatal fractures, special emphasis must be given to establishing and controlling palatal width. Incomplete assessment or incorrectly treated orbital wall or NOE fractures may be associated with postoperative enophthalmos or telecanthus, respectively. Inaccurate repositioning of the outer facial frame is the main cause of undesired changes in facial proportions, typically presenting increased facial width and orbital dystopia. Furthermore, insufficient midface disimpaction may result in a lack of anteroposterior facial projection. Postoperative plate palpation is sometimes caused by inadequate implant selection for the location, or thin soft-tissue cover. Sensory disturbances during extreme temperature exposure may require implant removal.

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3 Midfacial fractures 3.3 Zygomaticomaxillary complex (ZMC) fractures, zygomatic arch fractures

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Author Carl-Peter Cornelius

3.3 Zygomaticomaxillary complex (ZMC) fractures, zygomatic arch fractures 1


The zygoma or cheek bone is the most prominent element in the upper lateral midface, connecting to the adjacent craniofacial skeleton with five articulations (Fig 3.3-1). In an upward, downward, medial, backward, and dorsomedial direction, these are the following: • Frontal process • Maxillary margin building the zygomaticomaxillary buttress • Infraorbital margin going into the infraorbital rim • Temporal process conveying into the zygomatic arch, three quarters of which belong to the temporal bone • Lateral orbital process (orbital surface or facies orbitalis) or zygomaticosphenoid flange constituting the anterior part of the lateral wall of the internal orbit

The zygomatic bone is solid, acts as a vertical and horizontal buttress, and does not relate directly to the maxillary antrum. Only the anterolateral 40% of the orbital floor (inferior orbital process) consists of the zygoma, while the medial 60% is formed by the maxilla.

1 5 3 4

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1 5 3 2

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Fig 3.3.-1 Zygomatic bone separated from the craniofacial skeleton. Five articulations are identified: 1 Frontal process 2 Zygomaticomaxillary buttress 3 Infraorbital rim 4 Zygomatic arch 5 Lateral orbital wall

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Since fractures involving the zygoma are not usually confined to its strict anatomical boundaries but most often extend into adjacent maxillary or orbital structures (antrum, orbital walls including the infraorbital canal, rim, and orbital floor, respectively) it is appropriate terminology to refer to them as zygomaticomaxillary complex (ZMC) or orbitozygomaticomaxillary fractures. Fractures of the zygomatic arch are often associated with ZMC fractures, but also occur as an isolated fracture (Fig 3.3-2a–b).

Prior to imaging, the diagnosis of a ZMC fracture is clinically confirmed by the presence of characteristic acute sequelae and signs of potential long-term consequences (Table 3.3-1) . Depending on the type and extent of the zygomatic injury (degree and vector of displacement, involvement of the globe and orbit, comminution, etc) clinical signs and symptoms will vary.

Skeletal deformities

Ocular/ophthalmic symptoms

Sensory impairment

Oral symptoms

Nasal symptoms

• A symmetry of the midface

• P eriorbital edema or hematoma (“monocle hematoma”)

Sensory deficit (hypoesthesia, anesthesia) in the distribution of the following nerves:

• E cchymosis of the gingivobuccal maxillary sulcus

• Ipsilateral epistaxis

• P seudoptosis

• Infraorbital nerve: - lower eyelid - upper lip - a la and lateral sidewall of the nose

• D epression/flattening of the malar prominence • F lattening, hollowing (bony indentation) or broadening over the zygomatic arch • P alpable step offs or gap deformities of orbital margins (infraorbital/lateral)

• Increased scleral show • D ownward slant of palpebral fissure or horizontal lid axis respectively • M alposition of the lateral canthus • V ertical shortening of the lower eyelid (ectropion) • S ubconjunctival ecchymosis (temporal/medial) • C hemosis

• Zygomatiofacial nerve: - malar eminence - cheek • Zygomaticotemporal nerve: - lower lateral orbital rim - a nterior temporal/lateral/ frontal region

• P upillary or globe level disparity (hypoglobus)

• Ipsilateral hematosinus

• S ubjective occlusal disorder due to altered sensation of the maxillary premolars/ molars and gingiva, no objective malocclusion • P alpable contour disturbance of zygomaticomaxillary buttress • R estriction of mandibular opening (trismus) or closing—blockage of temporal muscle or coronoid process either by impacted zygomatic arch or retrodisplaced zygoma

• P roptosis bulbi • E nophthalmos (outward displacement of zygoma) • E xophthalmos (inward displacement of zygoma) • S ubcutaneous periorbital air emphysema (skin crepitation) • P neumoexophthalmos • D iplopia (neurogenic ocular motility disorder – III, IV, VI; enophthalmos; entrapment, revealed by forced duction test) • A maurosis • S uperior orbital fissure syndrome Table 3.3-1 Possible clinical signs and symptoms accompanying ZMC fractures.

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A detailed functional and structural ophthalmic examination is of priority during initial clinical assessment, listed in Table 3.3-2 .

Functional examination

Structural examination

Visual field loss

Corneal abrasion

Anisocoria or mydriasis

Hyphema

Amaurosis

Iridodialysis

Diplopia

Lens subluxation or dislocation Vitreous hemorrhage Retinal detachment Globe rupture

Table 3.3-2 Functional and structural opthalmic examination for ZMC fractures.

2

Imaging

Among imaging modalities, high-resolution CT scans in axial, coronal, and sagittal reconstructions provide complete radiological visualization of the fracture sections with bone and soft-tissue windows: • Comprehensive and precise information on the number, localization, and extent of fracture lines • Displacement, angulation, and rotation of the individual fragments, and the condition of soft tissues within the orbital cavity (eg, retrobulbar hematoma) • Integrity of its osseous orbital walls and any adjacent fractures Systematic analysis of CT sections of the face in axial planes starts at the maxillary alveolar process and extends cephalad until the anterior cranial fossa is passed. Conventional plain x-rays in combination with a detailed clinical examination are an option if CT scans are not available; however, only limited radiological information is provided. The axial sections (Figs 3.3-2a , 3.3-3a–b, 3.3-4a–b) have to be checked successively for discontinuities, defect size, and malposition: • Zygomaticomaxillary buttress, anterior and posterior antral walls, pterygomaxillary fissure, retromaxillary space • Temporal root of the zygomatic arch, articular tubercle, course of zygomatic arch • Infraorbital canal, infraorbital rim, inferior orbital fissure • Postequatorial convexity at the transitional zone between orbital floor and medial wall (“posteromedial bulge”) • Outer orbital frame: frontal process and lateral orbital flange of zygoma, and junction with the greater sphenoid wing

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Fig 3.3-2a–b CT scans of isolated zygomatic arch fracture. The apex of the V-shaped fracture is indented toward the coronoid mandibular process.

a

b

Fig 3.3-3a–b CT scans of lowenergy ZMC fracture. a Axial scan through maxilla: undisplaced zygomatic arch–small antral impaction of the zygomaticomaxillary buttress. b Axial scan through orbit: undisplaced zygomaticosphenoid suture.

a

a

208


b

b

Fig 3.3-4a–b CT scans of mid-energy ZMC fracture. a Axial scan through the maxilla: lateral displace ment of the triple fractured zygomatic arch, comminution of the zygomaticomaxillary buttress. b Axial scan at midglobe level: dorsolateral displacement of the lateral orbital rim, outward bending of greater wing of sphenoid, medial wall blow-out fracture with tissue herniation into the ethmoid sinus.


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Evaluation in the perpendicular coronal plane sections will begin with anterior slices at the level of the nasal skeleton and pass posteriorly to the level of the mastoid and temporal bone. In the coronal sections (Figs 3.3-5a–b, 3.3-6a–b) it is essential to check systematically for anatomical irregularities: • Circumference of the zygomaticomaxillary buttress, lower antral walls • Infraorbital rim, cross-sections of zygoma body and arch

• Inferior orbital fissure, infraorbital canal, lateral orbital wall • Orbital floor (teardrop herniation), medial orbital wall, posteromedial bulge • Posterior recess of maxillary antrum (sinus roof), infraorbital groove, transformation of orbital cross-section from rhomboid into a triangle shape indicating entrance to the orbital apex

Fig 3.3-5a–b Low-energy ZMC fracture. a Coronal scan at the level of anterior orbit: rotation of the ZMC into the maxillary sinus, zygomaticomaxillary buttress disrupted, linear fracture of orbital floor, hemorrhage of left maxillary sinus and ethmoid. b Coronal scan posterior to the globe: medial impaction of the lateral antral wall.

a

a

b

b

Fig 3.3-6a–b High-energy ZMC fracture. a Coronal scan at midorbit level: dorsolateral dislocation of the zygoma, comminution of orbital floor, defect in lamina papyracea, medial orbital roof fracture. b Coronal scan at the rear end of inferior orbital fissure confirming the 4-wall orbital fracture: depression of posterior third of orbital floor, fragmentation of lateral antral wall, fragmentation of lamina papyracea extending into orbital roof, loss of posterior medial “bulge” of the orbit, fragmentation of the zygomatic process of the frontal bone, and disruption of the lateral orbit.

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Additional reformatted sagittal views can depict the presence of stable bony ledges on the sides of defects in the posteromedial orbit and help determine the required extent of surgical exploration of the orbit (periorbital dissection) and the selection of adequate material for reconstruction. 3-D reformatted views assist in spatial visualization of the fracture pattern and displacement, but provide little additional diagnostic value over 2-D scans. Valuable information on soft tissues or orbital walls is not obtained in 3-D reformatted images, and therefore cannot replace 2-D multiplanar CT scans. Based on the imaging features, the severity of fractures of the ZMC can be clearly delineated to ascertain indication and invasiveness of surgery, particularly the necessity for concomitant reconstruction of the internal orbit. Several classification systems of lateral midface fractures were proposed in the past, mostly using plain film x-rays in different projections with the intention of identifying cases for closed reduction and predicting postoperative stability or the risk of secondary dislocation. Currently, three basic fracture categories are differentiated according to treatment relevance based on CT findings. These categories are characteristic for low-, medium-, and high-energy trauma mechanisms and range from nondisplaced or minimally displaced en bloc fractures (Figs 3.3-3a , 3.3-5a)

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at the lower end, over displaced fractures with or without fragmentation at the infraorbital rim and the zygomaticomaxillary buttress, to extreme variants with massive displacement, comminution of the zygomatic body and arch (Figs 3.3-4a–b, 3.3-6a–b), as well as fragmentation at or beyond the articulations. Such extended fractures require more invasive treatment with craniofacial techniques of wide exposure, primary bone repair, and multiple reduction and fixation points. Isolated fractures of the zygomatic arch frequently display three fracture lines, creating two fragments. These may be medially displaced in a V-shaped fashion (Fig 3.3-2a–b). In response to the vector of the traumatic impact M- or W-shape displacement occurs with multiple fragmentation. In complex fracture patterns and following difficult surgical procedures, postoperative imaging is best done with CT scans, which provide an accurate assessment of the reassembly of fragments, an estimate of the precision of fracture reduction, and the position of bone grafts or radiopaque alloplasts for defect repair inside the orbit and for volume restoration. Plain x-rays in two plains are seldom helpful and are not suited for precise quality control. Malposition and malalignments require revisional surgery in a separate operative session. Intraoperative navigation, cone beam CT, or CT scanning allows immediate assessment and facilitates immediate correction within the same intervention.


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3

Approaches

A stepladder concept for ZMC and isolated arch fracture repair encompasses a variety of surgical routes from limited exposure to extended access according to the degree of fracture severity. The ZMC can be exposed through anterior and posterior approaches. Anterior

• Inferior maxillary approach - Upper gingivobuccal sulcus incision (Fig 3.3-7) • Inferior orbital approaches - Transconjunctival exposure (pre- and postseptal) (Fig 3.2-8b, page 198) - Transconjunctival incision combined with lateral split canthus (“swinging lower eyelid”) (Fig 3.2-7a , page 197) - Medial transconjunctival / transcaruncular (semilunar fold) exposure - Transcutaneous lower eyelid incisions - Subciliary/extended subciliary incision (Fig 3.2-8a , page 198) - Midtarsal or mid lower eyelid incision (Fig 3.2-8c , page 198) - Infraorbital rim or lower eyelid incision • Superolateral approaches - Supraorbital lateral eyebrow incision - Upper blepharoplasty-type incision (Fig 3.2-7a–b, page 197) - Transconjunctival combined with complete lateral incision - Canthotomy/cantholysis (“swinging upper eyelid”) - Lateral transconjunctival retrocanthal incision

Posterior

• Superioposterior approach - Coronal incision (Fig 3.2-5a–e , page 196) • Lateroposterior approach -P reauricular (pretragal or transtragal)/ temporal = hemicoronal The location and displacement of the fracture sites define the type and number of approaches needed to adequately treat a given ZMC fracture. The osteosynthesis concept is also of influence. Noncomminuted medially displaced ZMC fractures are typically approached anteriorly, aiming at a 1- to 3-point fixation concept, depending on the degree of displacement and the involvement of the zygomaticofrontal suture, whereas comminuted laterally displaced fractures often require extended craniofacial approaches. The indication for surgical orbital floor exploration and treatment is based on preoperative CT imaging. Severe sensory disturbances of the infraorbital nerve may be an indication for a nerve release and neurolysis. Simple one-piece fractures of the zygoma and isolated V-shaped zygomatic arch fractures are often stable after closed reduction and do not require internal fixation. The zygomatic arch can be visualized and repaired under endoscopic visualization. Through a maxillary antrostomy window, the orbital floor is also accessible for transantral control and reconstruction under endoscopic assistance.

Fig 3.3-7 Upper gingivobuccal sulcus incision in a hockeystick s hape to expose the anterior antral wall up to the infraorbital rim.

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4


An optimal fracture repair of the ZMC will proceed in the order of precise skeletal reduction, subsequent internal fixation with plates and screws, and, if necessary, contour and volume restoration of the internal orbit. Facial dimensions must be reestablished in transverse width, sagittal projection, and vertical height by relocating the zygoma into its original position. The length of the zygomatic arch is a key parameter for determining the sagittal projection of the zygoma. Outward or inward bowing of the arch will shorten the arch length resulting in retrodisplacement of the zygoma, whereas unbending, flattening, or elongation of the arch will cause advancement and increased projection (Fig 3.3-8a–b). A rotational motion of the zygoma about a vertical hinge axis and transverse shifting ensue simultaneously. Outward rotation and lateralization create a diastasis along the zygo-

a

maticosphenoid suture line and increase facial width and orbital volume. The typical impaction dorsomedially of the zygoma into the maxillary antrum produces a step-off dislocation of the anterior lateral orbit. The severity of the injury increases with the amount and direction of displacement and the location and number of zygomatic articulation sites that are comminuted. The solid zygomaticofrontal process almost always separates along the suture line, but the zygomaticomaxillary buttress, the infraorbital rim, and the zygomatic arch are commonly comminuted in medium- and high-energy trauma. Comminution of the infraorbital rim often extends far medially into the ascending process of the maxilla. The sphenozygomatic suture line is important because it provides an excellent anatomical reference to the skull base in the reassembly of zygomatic fractures with multifragmented articulations. Incomplete, nondisplaced, or minimally displaced fractures usually do not justify any surgical treatment.

b

Fig 3.3-8a–b a Inward bending due to multifragmentary fracture of zygomatic arch with medial displacement. b Outward bending due to multifragmentary fracture of zygomatic arch with lateral displacement.

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4.1 Reduction

Very simple one-piece fractures not requiring orbital floor repair have predictable postreduction stability and can frequently be managed by transcutaneous reduction only. A direct percutaneous elevation of the depressed zygoma and/or the zygomatic arch can be accomplished using the Strohmeyer hook (Fig 3.3-9a). The J-curved bone hook is inserted through a short incision posterior to the zygomaticomaxillary buttress and rotated medially and upward to engage behind the temporal surface of the zygoma or the inner aspect of the arch fragments. Care is taken not to enter the inferior orbital fissure. Anterior and lateral traction

a

under palpation and external inspection brings the bone back into its proper position often accompanied by an audible crepitation sound. Alternate reduction procedures use small transoral (buccal sulcus) or external incisions (temporal) for the passage of elevators underneath the zygomatic body or zygomatic arch. Carrol-Girard or Byrd bone screws with a T-bar handle (Fig 3.3-9b) are typically inserted percutaneously or transorally or by using extended transeyelid approaches during open reduction to manipulate the disrupted zygoma in a joystick fashion.

b

Fig 3.3-9a–b Instrumentation and reduction techniques for ZMC fractures: a Strohmeyer bone hook for percutaneous elevation. b Carrol-Girard bone screw inserted into the zygomatic body.

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In an individualized stepladder concept, zygomatic fractures of moderate severity are managed by 1-point up to 5-point visualization for reduction control and fixation (Table 3.3-3). The stepladder sequence begins at the zygomaticomaxillary buttress site for the following arguments. A wide transoral degloving approach allows exposure up to the anterior aspect of the infraorbital rim without external scarring. Transoral reduction and position control of the ZMC is achievable. It is a first-rate fixation site because of the solid bone at the buttress area. Additional osteoplastic fenestration in the canine fossa allows transantral reposition of the tuber region or endoscopic control and endoscopically assisted repair of the orbital floor. No further surgical steps (and external incisions) subsequent to this open 1-point approach are required if the zygomaticofrontal suture is undisplaced, or if palpation reveals a stable reposition of the zygoma and if the postreduction status of the lateral and medial orbital walls is unimpaired. However, with the exception of linear fractures and minimal presurgical involvement (or postreduction transantral endoscopic control, intraoperative cone beam CT, or CT control) confirmation of the integrity of the internal orbit remains questionable. The common need for an orbital exploration, especially in fractures with more displacement, is the rationale for choosing the infraorbital rim as the second exposure and reduction site. Together with the horizontal and vertical reorientation

of the zygoma along the infraorbital rim, the periorbital dissection into the orbital cavity offers visualization of the zygomaticosphenoid junction at the lateral wall. The zygomaticosphenoid suture line, ie, the junction between the lateral orbital process and the greater wing of the sphenoid, is ranked as a reliable positioning guide in the reduction of isolated fractures of the ZMC or in the rebuilding of the outer facial frame in major midface or panfacial trauma. Even if the zygomaticomaxillary buttress and the infraorbital rim are highly fragmented, comminuted, or present with bony defects, it is still possible to reduce the zygoma exactly by gap and pivot control at the zygomaticosphenoid junction. Access from inside the orbit to the zygomaticosphenoid junction as the third reduction point in the graduated realignment of the zygoma is greatly facilitated by an appropriate single lower eyelid incision or an additional upper blepharoplasty approach. The extended subciliary approach or the swinging lower eyelid option with complete cantholysis gives a full view over the caudolateral surface of the orbital cavity and makes additional exposure of the zygomaticofrontal suture line unnecessary. The zygomaticofrontal suture is the fourth reduction point. In concert with control of points 1 to 3 (particularly 3) it enhances the precise readjustment of the zygoma in the overall reduction process. The zygomaticofrontal suture line is unreliable for 1-point reduction because its short course in one plane does not exclude unnoticeable rotation, mainly around the transverse and sagittal axis.

Assessing accuracy of reduction in descending order

Stability of fixation

1. Zygomaticosphenoid suture

1. Zygomaticomaxillary buttress

2. Zygomatic arch

2. Zygomaticofrontal suture line

3. Zygomaticomaxillary buttress

3. Zygomaticosphenoid suture

4. Infraorbital rim

4. Zygomatic arch

5. Zygomaticofrontal suture line

5. Infraorbital rim

Table 3.3-3 Zygomatic articulation points in descending order and stability of fixation in descending order.

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The classic tripod concept for the treatment of malar fractures breaks down the zygoma into a simple 3-limb structure consisting of the frontal process, the infraobital rim, and the zygomaticomaxillary buttress. These articulations are handled via open reduction accompanied by a closed arch reduction with an accuracy left somewhat at random. The tripod concept works in most moderate trauma cases, but obviously meets its limits if there is comminution at the medial and lower limb ends. In these more severe fractures the tripod concept may lead to malalignment and malrotation, since it omits multipoint reduction in a tetrapod or pentapod fashion under visualization of the zygomaticosphenoid junction or exposure of the zygomatic arch. In fact, more serious high-energy fracture variants and their rare extremes require aggressive treatment by way of a coronal flap approach for reduction and stabilization right from the beginning of the procedure. The following criteria mandate extended exposure (anterior and posterior approaches) and multipoint realignment supported by the zygomatic arch: • Multifragmentation of the arch with lateral displacement of the middle section • Fracture of the temporal arch root and glenoid fossa with tendency to shear and telescope posteriorly • Fragmentation of the zygomatic body • Fragmentation of the lateral orbital margin and orbital process with need for fixation • Fractures through the upper base of the zygomatic process of the frontal bone • Extensive fractures of the medial orbital wall or associated nasoorbitoethmoidal (NOE) fractures • Skull-base fractures involving the orbital apex, the greater wing of the sphenoid, and its transition into the middle cranial fossa

The reassembly of the seriously injured, multifragmented ZMC starts with an initial arbitrary reduction of the zygoma and the simultaneous reversal of the laterally displaced arch to its former position and length by finger pressure. After this approximation, a provisional link at the zygomaticofrontal suture with a loose temporary wire fixation holds the major fragments in place. The interfragmentary positioning wire limits the degree of freedom eliminating translational movements but allowing for some rotation of the fragments. With transverse or diagonal fragmentation of the zygomatic body in particular, the lateral orbital wall is realigned at the zygomaticosphenoid junction from inside the orbit as the next step. This provides a basis for the realignment of the zygoma under guidance of the zygomatic arch. With a one-piece zygoma body fragment it is beneficial to refine the initial bone approximation reviewing the zygomaticosphenoid suture line and the zygomatic arch configuration and visualizing both alternately. Fragmentation of the zygomaticosphenoid junction is not uncommon but usually easy to overcome. The separated and encroached rectangular bone pieces along the suture line can be conveniently reintegrated into the reestablished straight plane course of the lateral orbit. Severe displacement of the greater sphenoid wing and loss of this rather constant reference to the skull base is exceedingly rare. In that instance, restoration of the posterior lateral orbit and apex is performed via a temporal/infratemporal fossa approach. With the most serious injury types including craniofacial structures, no single predetermined sequence for reduction and repair can be mandated. The loss of all points for reduction due to comminution or defects will necessitate free positioning and reshaping of the zygomatic bone remnants.

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4.2 Stabilization

The zygoma as a subunit of the midfacial buttress system is subject to dynamic forces during mastication and contraction of the facial muscles. Biomechanical data detailing the intricate real-life conditions are not available. In a rudimentary model, stress distribution varies in loading cycles of downward tension and upward compression produced by masseter and temporal muscle action and the transfer of occlusal bite forces at alternating sites along the dental arch. Plate and screw fixation must resist these muscle vector forces and stabilize the ZMC against translational movements and rotation. For optimal support and long-term bone healing the plates and screws must be congruent with pretraumatic anatomical load paths that match with the major buttresses. A number of issues has to be considered for selection of the appropriate hardware. At the zygomaticomaxillary buttress the use of stronger miniplates 1.5, 2.0, or corresponding plates from the Matrix Midface system is necessary regardless of the overall fracture constellation. Comminution and missing bone at any one of the remaining zygomatic articulations may turn a load-sharing into a load-bearing situation requiring larger plates for adequate interfragmentary support. Weakness and mobility due to comminution at one articulation site can be compensated by stronger or longer plates at that or other locations. An otherwise intact midfacial skeleton contributes to the stability of ZMC fractures through a rigid fixation point at the zygomaticomaxillary buttress. It allows the application of miniplates 1.3, 1.5, or corresponding Matrix Midface plates at the zygomaticofrontal suture. In coexisting midface fractures, however, a stronger fixation at the frontal process is required. The thinness of soft tissues above the zygomaticofrontal process and the infraorbital rim can present a relative contraindication for large profile plates. The infraorbital rim, for instance, in view of its delicate cross-section and horizontal orientation, does not add much to the total stability, so a low-profile plate 1.3 or similar Matrix Midface plate will suffice for realignment.

216


In theory, 28 combinations of a 1-point up to a 5-point plating pattern exist. The essence of any mechanically efficient stabilization pattern is to build up 3-D stability through a framework of self-retaining articulations (buttressing) and/ or osteosyntheses. Note that the stability of fixation differs at the points of articulation due to bone properties and spatial orientation. In practice, a few schemes using plate combinations from the whole assortment will cover standard fracture situations. In the clinical setting, stabilization of the reduced ZMC with titanium plates is obtained in incremental steps. No fixation is added if the position of the zygoma is stable after the initial reduction maneuver. A 1-point fixation with an L-, T-, or Y-shaped miniplate 1.5, 2.0, or corresponding Matrix Midface plates at the zygomaticomaxillary buttress provides sufficient stability in less severe injuries (Fig 3.3-10). The same is true for a 1-point fixation at the zygomaticofrontal suture with the use of the above-mentioned plates, although this site alone is associated with the drawbacks of an external incision, potential palpability, and lack of confirmation of reduction of the remainder of the zygoma (Fig 3.3-11). After each fixation step, stability is rechecked by rocking the zygoma moderately. For more stability, a 2-point fixation may be accomplished using miniplates 1.5, 2.0, or corresponding Matrix plates placed at the zygomaticomaxillary buttress combined with plating of the infraorbital rim (especially if exploration of the orbital floor is indicated) or the zygomaticofrontal suture (Figs 3.3-12 , 3.3-13). A 3-point fixation at the zygomaticomaxillary buttress, the zygomaticofrontal suture, and the infraorbital rim has been classically advised to deal with comminution zones at the lower vertical and the inner horizontal buttress in the medium injury category (Fig 3.3-14). While this 3-point fixation pattern can still be achieved with anterior approaches, every 3-point plate osteosynthesis in other locations will demand an additional posterior approach, commonly a coronal flap.


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a

b

Fig 3.3-10 1-point fixation using an inverted L-plate at the zygomaticomaxillary buttress. The inset shows a Y-plate as an alternative.

Fig 3.3-11 1-point fixation using an adapta tion plate 2.0 at the zygomaticofrontal suture.

Fig 3.3-12 2-point fixation using an L-plate at the zygomaticomaxillary buttress and a nonstabilizing, curved orbital plate 1.0 for realignment of the comminuted infraorbital rim.

Fig 3.3-14 3-point miniplate fixation: Comminution at the zygomaticomaxillary buttress and the infraorbital rim demands miniplate application at the three anterior fracture sites. Option for use of miniplates 1.3, 1.5, 2.0, or corresponding Matrix Midface plates.

Fig 3.3-13 2-point fixation for increased stabilization using an L-plate 2.0 at the zygomaticomaxillary buttress (Y- or T-plates are also possible) and an adaptation plate 2.0 at the zygomaticofrontal suture.

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Severely dislocated, comminuted, and defect ZMC fractures typically require wider exposure, mostly by a combination of anterior and posterior approaches, for adequate reduction and fixation. This can be a 4-point or a 5-point fixation (Figs 3.3-15a–e , 3.3-16a–c). Plating the lateral orbital wall after elevation of the temporal muscle is reserved for those extreme injuries that displace the adjacent skull base (rarely indicated).

The typical V-shaped isolated zygomatic arch fracture can be reduced and does not require any fixation. In contrast, isolated zygomatic arch fractures may be multifragmented, grossly displaced, and free floating, resulting from the downward pull of the masseter muscle. In such rare instances instability exists and predetermines open reduction via an extended preauricular incision or a coronal or hemi-coronal approach.

b

c

d

e

a Fig 3.3-15a–e 4-point fixation pattern: comminution of the zygomaticomaxillary buttress, the zygomatic arch, and the infraorbital rim. a Miniplates 1.3–2.0 may be applied. b Adaptation plate 1.3. c Adaptation plate 2.0. d T-plate 2.0. e Y-plate 2.0.

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The craniofacial locking plates 2.0 and similar Matrix Midface plates offer the advantages of larger plate profiles and enhanced security against secondary displacement, since tightening the screws will not pull the fragments onto the plate surface causing torsion. The locking plates can be applied at the zygomaticomaxillary buttress, the zygomatic arch, and in thick-skinned individuals at the zygomaticofrontal process.

The size and the biomechanical properties of bioresorbable plates and screws have raised questions about their routine use in ZMC fractures. In selected cases (low- to mediumenergy category) these plates may be indicated and are best applied in a 2-point or 3-point pattern. Bioresorbable plates can also be used in a hybrid fashion together with titanium miniplates.

b

c

a Fig 3.3-16a–c 5-point fixation using all accessible articulation sites of the ZMC. The insets show different types of miniplates.

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5

Treatment of the internal orbit

The lateral orbital wall will usually be restored together with the realignment and fixation of the zygomatic part of the external orbital rim. Defects of the lateral wall, if present, are uniplanar and simple to bone graft or to cover with titanium meshes. Defects and fragment dislocations within the internal orbit are commonly treated after the external orbital frame and the facial buttresses have been reestablished. For details of repair and volumetric restoration of orbital wall defects refer to chapter 3.4 Orbital fractures.

6


A complete ophthalmologic examination is necessary prior to any surgery to determine the structural and functional status of the globe itself and the orbital contents. Acute or gradually occurring blindness is of major concern before or after the repair of ZMC fractures and orbital surgery. Since any intervention must be immediate, eye examination and monitoring of the visual function at short intervals is the standard of care. Any dressings on the eye are an obstacle to regular observation and should be minimized. Only transparent eye ointments, lubricants, or eye drops should be instilled before, during, and after surgery in order not to interfere with visional testing. Nose blowing is not allowed pre- and postoperatively in order to prevent orbital and subcutaneous emphysema which predisposes to infection. Perioperative antibiotic cover with single-dose intravenous administration immediately before surgical intervention, or repeated doses in long surgical interventions, is routinely used. Serious injuries and polytrauma may require different regimens. The risk of infection may increase with a history or signs of chronic sinusitis. Short-term use of nasal decongestants and mucolytic agents may be indicated in such cases to help resolve antral hematomas and nasal congestion.

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High-dose preoperative and intraoperative steroids reduce tissue swelling and periorbital edema. Postoperative ice packs contribute to the resolution of chemosis and diminish the intensity of pain. For the same reason regional nerve blocks with long-acting local anesthetics may be performed at the end of surgery. Regular pain medication is administered over several days to provide sufficient analgesia. The risk of a dehiscence along the upper buccal sulcus incision is minimized with a soft diet. Chlorhexidine mouth rinses and a good oral hygiene keep the incision line clean. Following the reduction of an isolated zygomatic arch fracture, protection (taping or splints) may be used to prevent recurrent displacement.

7


The acute and late sequelae of ZMC fractures may persist as a result of no intervention or inadequacy of treatment. Errors in the management of ZMC fractures relate to poor imaging techniques, underestimation of fracture severity, and the effects of localized comminution, inappropriate exposure for multipoint reduction, malreduction of bone, inadequate or loose fixation, fixation without proper reduction, instability, persistence of orbital volume changes, and failure of the resuspension of soft tissues. A thorough understanding, a systematic approach, and precise reduction and fixation help prevent unwanted sequelae and surgical complications after treatment. Critical issues are impairment or loss of vision, neurogenic ocular motility disturbances, and neurosensory deficits of involved maxillary tri geminal branches. All of the above symptoms may be encountered posttrauma or postsurgery. Suitable investigative and precautionary measures as part of a coordinated interdisciplinary strategy of treatment are mandatory, in particular to deal with potential optic nerve lesions and their disastrous consequences (details in chapter 3.4 Orbital fractures).


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3 Midfacial fractures 3.4 Orbital fractures

1

Definition

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2

Anatomy

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2.1 Anterior orbital section

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2.2 Middle orbital section

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2.3 Posterior orbital section

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3

226

Diagnosis

3.1 Clinical assessment

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3.2 Imaging

226

4

Treatment

227

4.1 Indications

227

4.2 Exposure

227

4.3 Materials for reconstruction

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4.4 Principles of orbital fracture repair

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4.5 Superior orbital rim and roof fractures

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5


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6


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Author Christoph Kunz

3.4 Orbital fractures

1

Definition

Fractures involving the orbit are observed frequently. In more than 40% of all facial fractures, parts of the orbital rim and/or the internal orbit are injured showing various fracture patterns. Commonly, multiple portions of the orbit are involved. Zygomaticomaxillary complex, nasoorbitoethmoidal (NOE) injuries and combinations thereof reveal fractures of the orbital rim and (several) internal orbital walls ranging from simple to complex comminuted fractures, the latter being responsible for most unfavorable results. In simple fracture patterns, such as the common single-wall “blow-out” fracture, only one portion of the internal orbit is involved. However, even these should not be underestimated, as the orbit is a complex 3-D structure which needs precise repair after traumatic derangement.

2

Anatomy

The shape of the bony orbit is similar to a pyramid, quadrilateral at its base, the orbital rim, and triangular at its apex. The configuration changes by the transition of the posterior part of the orbital floor into the medial wall. This area, the posteromedial wall, is of major impact for orbital reconstruction and is therefore known as the “key area.” The posteromedial wall together with the posterolateral wall support the globe and are responsible for its anterior projection. Being a very thin bony structure, it is often damaged in orbital fractures and its rigid reconstruction may be required for complex internal orbital fracture treatment. From a functional point of view, it is helpful to divide the bony orbit into three sections (Fig 3.4-1). The anterior section is a thick bony structure, the orbital rim. The middle section consists of four subunits: orbital floor, medial orbital wall, lateral orbital wall, and orbital roof. The bone of this section is thin with the exception of the lateral wall and often primarily affected by fractures before the orbital frame breaks. The bone in the posterior section is thick protecting cranial nerves which enter the orbit in the apex. It contains the optic foramen and the inferior and superior orbital fissures.

Fig 3.4-1 The three sections of the orbit: • Anterior orbital section: thick bony structure forming the orbital rim • Middle orbital section: including orbital floor, medial orbital wall, lateral orbital wall, orbital roof, and inferior orbital fissure • Posterior orbital section: thick bone protecting the cranial nerves which enter through the apex region, containing the optic foramen, and the inferior and superior orbital fissures

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2.1 Anterior orbital section

The orbital rim itself is subdivided into three segments: the NOE (medial), the zygomatic (lateral and inferior), and the supraorbital (superior) segment. The NOE segment, ie, the lower two-thirds of the medial orbital rim, is characterized by the attachment of the medial canthal ligament and the medial insertion of Lockwood’s ligament, a part of the inferior support sling of the globe. It blends to the inferior orbital rim, formed by the zygomatic bone, which extends as the lateral orbital rim to the frontozygomatic suture. The lateral canthal complex inserts onto the orbital surface of the zygomatic bone. It consists of the anterior (superficial) and posterior (deep) limbs of the lateral canthal ligament, the latter attaching to Whitnall’s tubercle located 3–4 mm posterior to the lateral rim, 8–10 mm below the frontozygomatic suture. The lateral portion of Lockwood’s ligament and the levator aponeurosis is also attached here. The supraorbital segment includes the frontal bone laterally and lateral aspects of the frontal sinus medially, and extends from the frontomaxillary to the frontozygomatical suture. The orbital rim is perforated by the supraorbital foramen (or notch), the zygomaticofacial foramen at the lateral aspect of the malar eminence, and the infraorbital foramen. The latter is often involved in fractures which may result in symptoms of anesthesia or hypesthesia of the infraorbital nerve. Surgical impact: The thick bone of the rim allows stable fixation of the orbital frame as a basis for internal orbital reconstruction. Reattachment of the canthal ligaments to the orbital rim must be performed to reestablish bone–soft-tissue relations after detachment. Adequate decompression of the infraorbital nerve should be insured after each reduction. 2.2 Middle orbital section

The middle orbital section has four thin bony walls: the lateral wall, roof, medial wall, and floor. The lateral orbital wall consists of the greater wing of the sphenoid and the orbital process of the zygoma. Anteriorly, the small zygomatico-orbital artery perforates the bone. Because of its firm structure, higher energy is necessary for it to fracture compared with the other orbital walls. However, the thickness of the bone allows stable fixation of plates, and alignment of the entire lateral wall is of major impact for correct orbital volume restoration. The inferior orbital fissure separates the lateral orbital wall from the floor. It communicates with the retromaxillary space and is crossed by several smaller arteries and nerves. Posteriorly, the maxillary portion of the trigeminal nerve, the infraorbital artery, and the zygomaticofacial nerve pass through. Fractures of the orbital floor

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with extension to the posterior third of the orbit and displacement of the posterior wall of the maxillary sinus may result in critical enlargement of the inferior orbital fissure. Repair of these fractures should provide complete obliteration of the fissure to prevent enophthalmos. Surgical impact: As the lateral wall usually is not comminuted, it is a reliable starting point for orbital dissection. Alignment and rigid fixation of the lateral wall may be a key step in restoration of orbital volume in complex orbital fractures. Dissection of the inferior orbital fissure requires meticulous hemostasis for assessment of a possible enlargement of the inferior orbital fissure. It should be performed in case of a posteriorly extended floor fracture to expose the complete fracture pattern. The orbital roof separates the orbit from the anterior cranial fossa as a thin, curved structure. In a sagittal plane from anterior to posterior the roof first inclines upward just behind the supraorbital rim. The midportion extends posteriorly followed by a final inclination inferiorly to the apex region. The medial orbital wall is a paper-thin delicate structure formed by the orbital plate of the ethmoid bone, reinforced by the septae of the ethmoid sinuses. Looking at the orbit from anteriorly, the wall is directly in line with the optic foramen. The two ethmoid arteries perforate the bone at the same vertical level as the optic nerve enters into the orbit. Thus, they allow reliable orientation with regard to the optic canal. The foramina can be used as a landmark, being located about 25 mm and 35 mm posterior to the anterior lacrimal crest. The optic nerve lies 5–8 mm posteriorly to the posterior ethmoid artery (40–45 mm from the anterior lacrimal crest). Surgical impact: Dissection of the medial wall must be delicate with regard to the thin bony plate and possible natural bony gaps. The anterior ethmoid artery usually requires transsection for adequate exposure of extended medial wall fractures, whereas the posterior ethmoid artery should be preserved as a sentinel. The posterior medial wall and its transition into the posterior orbital floor is one of the most critical components of orbital reconstruction and therefore called the key area. The restoration of injuries with an intact key area is much less difficult than the repair of fractures involving this area. Thus, it is recommended to restore the key area by means of rigid fixation as a first step.


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The orbital floor is often involved in orbital wall injuries. It separates the orbit from the maxillary sinus and contains the infraorbital nerve, which lies in a canal or in a groove in the middle orbit. Lateral to the nerve, the floor is more resistant to fractures. Therefore, floor fractures tend to extend to the inferior medial wall. Anteriorly (in a sagittal plane) the floor follows a concave curve behind the rim, inclines upward behind the globe and also upward towards the medial wall (key area), forming a postbulbar constriction. For correct projection of the globe this retroocular bulge has to be restored (Fig 3.4-2a–c).

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2.3 Posterior orbital section

The posterior third contains the apex of the orbital pyramid, where the cranial nerves III, IV, V, and VI enter the orbit from the middle cranial fossa through the superior orbital fissure, and the optic nerve through the optic canal. The superior orbital fissure is formed by the greater and lesser wings of the sphenoid bone. The bone of this section is thicker and rarely involved in fractures, thus protecting the delicate structures contained in the fissure. The inferior orbital fissure originates in the posterior orbit, separating the lateral wall from the floor in the middle section of the orbit.

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c Fig 3.4-2a–c a Lateral view of the orbit showing concavity of the orbital floor behind the rim and more posteriorly the convexity right behind the globe. The vertical lines b and c mark the CT cuts as shown in 3.4-2b and c. b Reconstruction of orbital floor and lower third of medial orbital wall; relatively straight curved line. c Retrobulbar area reconstruction of floor and medial orbital wall with typical convexity.

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3

Diagnosis

3.1 Clinical assessment

The diagnosis of orbital fractures requires clinical and radiological examination. As orbital fractures often present a rather uniform clinical appearance, radiological assessment is of major impact for precise diagnosis. However, clinical examination may provide important hints about the severity of the trauma and indications for further diagnostic procedures and treatment. Fractures of the bony orbit are frequently associated with trauma to adjacent structures. Thus, clinical examination has to identify simultaneous injuries of the globe and adnexae. Every patient with an orbital fracture should have a preoperative ophthalmologic assessment to prevent visual impairment or additional trauma to the globe by means of reconstruction of the bony orbit. Rupture of the globe and intraocular hemorrhage or posttraumatic glaucoma may be reasons for visual impairment with a need for immediate ophthalmologic intervention. An ophthalmologic assessment should include eye inspection, visual acuity in the cooperative patient, pupillary function testing, ie, testing of relative or incomplete afferent pupillary defect RAPD (also adequate for the unconscious patient), as well as an assessment of eye motility (double vision testing).

The most precise information about orbital fractures is provided by computed tomography (CT) in several planes (coronal and axial, hard- and soft-tissue windows, and perhaps sagittal images) and should be a routine part of orbital trauma diagnosis. CT allows precise assessment of the extent of fractures of the bony orbit and adjacent structures. For an accurate diagnosis bone windows as well as soft-tissue windows should be assessed, the latter being helpful in detection of retrobulbar hematoma, adhesions between the musculoseptal apparatus and the bony orbital walls, or optic nerve sheath edema and muscle incarceration or injury. A systematic approach enhances interpretation of the fracture pattern. Fractures of the orbital frame are assessed with regard to the degree of fragmentation and displacement. Besides diagnosis of orbital wall defects, CT scans allow assessment of important features of orbital fracture patterns. A widened inferior orbital fissure, a possible reason for enlargement of the orbital volume, can be detected in the coronal plane. Axial scans allow the assessment of the posterior orbital cone with regard to the presence or absence of a bony shelf, providing support to bone grafts or orbital plates. If this posterior ledge is lacking, rigid reconstruction is highly recommended.

Compression of the structures traversing the superior orbital fissure by fracture of the greater sphenoid wing or hematoma in the posterior orbit may result in the superior orbital fissure syndrome. Dysfunction of the cranial nerves III, IV, V1, and VI with internal ophthalmoplegia, ptosis of the upper eyelid, sensory disturbance (V1), and retrobulbar pain may indicate compression of the orbital apex. In case of additional involvement of the optic nerve, the orbital apex syndrome is apparent. Other frequently associated injuries in orbital trauma are fractures of the frontal sinus or the skull base, which are often difficult to assess by clinical examination alone.

However, under certain circumstances, evaluation of CT scans may be misleading and may result in underestimation of the fracture pattern. Linear fractures creating orbital wall instability and enlargement are sometimes difficult to detect and the size of orbital wall defects is difficult to assess correctly. Defects are often larger than they actually appear on CT scans.

3.2 Imaging

Magnetic resonance imaging (MRI) is no alternative to CT examination; the assessment of the thin bony structures and the orbital walls is insufficient. However, there are advantages in the diagnosis of adhesions and in herniation of orbital soft tissues or optic nerve injury. Additional information may be gained by oculodynamic MRI examination, a technique which is currently being evaluated.

Plain x-rays may be adequate for fracture diagnosis of the outer orbital frame and in some instances for fracture assessment of the inner orbital frame. However, fractures of the orbital walls usually cannot be detected directly. Adequate projections for the diagnosis of orbital wall fractures are the Waters’ view or the submental vertex view.

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Certain symptoms demand immediate CT examination, such as visual impairment, retrobulbar pain, severe exophthalmos, or obvious displacement of the globe and severe disturbances of the motility of the globe.


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4

Treatment

4.1 Indications

Treatment of orbital fractures is planned according to the severity of the fracture. Note that possible secondary problems, such as enophthalmos and diplopia, often develop as a late functional impairment due to scar formation or asymmetric shrinkage of the intraorbital tissues, are difficult to correct, and often result in an insufficient final appearance. Displacement of the orbital rim, fractures involving several orbital walls or including the posterior orbital floor and medial wall (key area) are indications for a surgical treatment. Vertical globe dystopia and/or enophthalmos immediately after trauma may be signs of a distinct enlargement of the bony orbit. Injuries revealing severe restriction of eye motility (confirmed by forced duction testing) indicate herniation of orbital soft tissues with the need for release. Especially in cases of direct entrapment of muscles immediate surgery has to be performed to minimize damage to the traumatized soft tissues. Herniation itself requires less acute exploration.

Fig 3.4-3 Area of possible orbital exposure (pink) through local incisions.

4.2 Exposure

Extent and type of exposure depend on the fracture pattern of the orbital frame, the orbital walls, and the patterns of associated midfacial fractures. Basically, exposure should provide a view of the complete extent of the injury. Simple fracture patterns (including nonfragmented lateral midface fractures) and single orbital wall defects are usually treated by local incisions. The lower and lateral aspects of the orbit can be adequately exposed by mid-eyelid, subciliary, or transconjunctival approaches, which can include a lateral canthotomy, detaching the lateral canthal ligament (Fig 3 .4-3). The transcannular approach offers additional access to the medial wall. However, isolated displacement or defects of the posterior orbital floor and medial wall (key area) must not be underestimated. They can be indications for a wider exposure via combined local and coronal approaches, the latter exposing the entire upper midface skeleton including the zygomatic arches, crucial for correct facial projection, and providing 3-D assessment of the medial and lateral orbital wall as well as the roof including the deep (posterior) third of the orbital cone (Fig 3.4-4). In addition, the access to the posterior cone can be enhanced by supraorbital marginotomies providing an excellent visualization of the ethmoid arteries, which are landmark structures for dissection. Complex fracture patterns requiring wide exposure are: • Complex orbitozygomaticomaxillary fractures • NOE fractures • Combined lateral and central midface fractures • Large defects in the posterior third of the orbit

Fig 3.4-4 Area of possible exposure (pink) through coronal approach.

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In case of orbital wall defects, it is of utmost importance to expose intact bony ledges on all sides of the defect during dissection and to identify widening of the inferior orbital fissure. Performed before and after dissection, the forced duction test provides assessment of the mobility of the muscular ligament system which may be influenced by edema or impingement of the musculofibrous system. It is important to repeat the duction testing after reduction and reconstruction of the orbit to recognize impingement of the musculofibrous ligament system (MFLS) by implants and prevent secondary herniation and motility disorders of the adnexae of the eye.

4.3 Materials for reconstruction

Isolated internal orbital defects can be reconstructed using either bone grafts or alloplastic implants, such as titanium mesh and orbital plates, porous polyethylene implants, bioactive glass or resorbable materials, and others. Due to the complex 3-D orbital shape, autogenous bone grafts are often difficult to contour. In complex orbital fractures with large wall defects the need for a rigid, but highly malleable implant is obvious. In these fractures prefabricated orbital plates or titanium mesh plates are considered the gold standard today. There is no evidence of a higher short-term infection rate using alloplastic implants compared with autogenous tissues. It is important to cut alloplastic materials to the minimum required size, to meticulously contour internal orbital plates and titanium meshes, and to trim anchoring tabs and edges to prevent malposition and interference with the adjacent intraorbital soft tissues. To prevent displacement of a bone graft or alloplastic implant, they should be anchored to the orbital rim or the lateral orbital wall which provides bone stock adequate for screw fixation. For bone grafts the “cantilever” technique is useful (Fig 3.4-5a–d); if alloplastic materials are used direct fixation with screws or sutures is possible. For complex wall defects, insertion and rigid fixation of orbital floor or wall plates provide the support for additional grafts or sheets to cover remaining defects (Fig 3.4-6a–b).

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Fig 3.4-5a–d a Fixation of bone graft for orbital floor reconstruction with cantilever technique. b Orbital roof reconstruction with intracranial plating for bone graft fixation.

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Fig 3.4-5a–d (cont) c Orbital roof reconstruction with extracranial plating for bone graft fixation. d Reconstruction of medial orbital wall (ethmoid defects) with a bone graft stabilized with cantilever technique.

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Fig 3.4-6a–d a Extensive defect of orbital floor and medial wall reconstructed with an orbital floor plate. b Reconstruction of same defect with orbital floor plate and bone grafts. c Extensive defect of the orbital roof, middle orbital wall and orbital floor on the right side. d Reconstruction of right and left orbits. Right orbit reconstruction with a combination of orbital floor plate and bone grafts.

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4.4 Principles of orbital fracture repair

Trauma to the bony orbit may occur as isolated internal orbital fractures or injuries, simultaneously involving the internal orbital walls and the orbital frame. With higher energy impact during trauma, increased severity fracture patterns are observed. Defects involving two or more orbital walls extending to the posterior third of the orbital pyramid indicate high-energy impact. As a principle, anatomical reassembly of the orbital frame should precede orbital wall reconstruction because reduction of associated orbital frame fractures will alter the size of orbital defects. Among the defect fractures of the orbital walls simple fracture patterns have to be distinguished from complex orbital wall defects, as inadequate treatment in the latter often results in severe functional and esthetic problems. In simple (one wall) defects of less than 2 cm in diameter located in the anterior and middle third of the orbital floor, commonly referred to as blow-out fractures, exposure is achieved by eyelid local incisions such as the mid-eyelid, subciliary, or transconjunctival approach (Fig 3.2-8 , page 198). After identification of the stable bony ledges around the defect, herniated soft tissues are retrieved atraumatically and the defect is bridged with bone grafts or alloplastic materials. If the graft overlaps the defect 3–4 mm, fixation is not usually necessary. Defects extending to the posterior section of the orbit and/ or involving more than one orbital wall significantly add to the complexity of the injury. These defects usually cannot be assessed by one single approach and fat protrusion after periorbital laceration impairs visibility. The posterior bony ledge may be difficult to identify and may be insufficient for adequate graft support. Moreover, a widening of the inferior orbital fissure is easily missed and results in a critical enlargement of orbital volume. To find the posterior ledge (which is often covered by prolapsed fat), it is recommended to place a freer elevator against the posterior wall of the antrum and move it superiorly. The ledge will be felt as a distinct shelf which the elevator encounters under the fat. The fat may then be gently lifted from the ledge, remembering that the inferior rectus muscle is just within the most inferior fat. In secondary or late reconstruction cases, it is prudent to do an oste-

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otomy at a nonfractured area and extend the exposure to the area of entrapment. The contents can then be “teased” from their adherence to mucosa with minimal injury. For adequate treatment of complex intraorbital fractures complete exposure of all defect cases is crucial, and in most cases a combination of a lower eyelid incision and a coronal approach is required. Dissection is started at an uninjured part of the internal orbit and visibility enhanced by temporary insertion of a flexible sheet, such as a polydioxan sheet (PDS) 0.25 mm, preventing protrusion of orbital fat. Additional orbital rim marginotomies (osteotomies in nonfractured rim bone) may be useful to improve access to the posterior orbital walls. Fractures where the posteromedial orbital wall is left intact are less difficult with regard to reconstruction. Therefore, in complex orbital defect repair, reconstruction of this key area should be the first step. As this area, when fractured, offers little or no support for grafts, rigid reconstruction using cantilevered bone grafts or titanium preformed orbital plates is performed providing a stable shelf for further grafting (Fig 3.4-6a–d). Small residual defects are covered with either thin bone grafts or thin alloplastic sheets. Anatomical positioning of the walls frequently results in slight overcorrection of about 2–3 mm in the anteroposterior dimension, as the globe tends to sink back postoperatively due to resolution of intraorbital edema, bone graft resorption, and possible fat atrophy or scarring. The vertical dimension, however, remains nearly unchanged and should not be overcorrected. Before soft-tissue suspension and wound closure is accomplished, a final forced duction test is performed to ensure free motility of the eye and MFLS. Soft-tissue resuspension after extended exposure of complex orbital fractures minimizes eyelid and cheek ptosis and is crucial for achieving the best possible cosmetic result. Due to the extent of subperiosteal undermining, the anterior and lateral cheek is resuspended at the infraorbital rim and at the temporal fascia. After detachment of the lateral canthal ligament, transosseous reinsertion in a slightly overcorrected position is important to avoid asymmetry. After coronal flap exposure additional reattachment of the upper eyebrow at the supraorbital rim is recommended. This is accomplished by closing the incision in the periosteum over the frontal process of the zygoma.


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4.5 Superior orbital rim and roof fractures

Isolated orbital roof fractures, more frequently seen in children, are uncommon in adult patients and in most cases result from simultaneous injuries of the supraorbital rim with involvement of the frontal sinus. As the orbital roof is a part of the anterior skull base, interdisciplinary treatment is required. Exploration of the complete fracture may in some cases require removal of the supraorbital rim and the segments of the frontal bone. The segments should be marked in sequence in order to simplify the reassembling. Additional intracranial neurosurgical exposure by frontal craniotomy may be recommended for an optimal assessment of the complete fracture pattern and for treatment of additional dural injury at the skull base. As the frontal bone commonly consists of external and internal tables, harvesting of the internal table provides an ideal source for bone grafts for frontal bone reconstruction or orbital wall repair.

After dural repair and reconstruction of the frontal bar, the orbital roof has to be aligned anatomically to achieve a proper globe position. The graft should not be placed within the orbit in order to prevent reduction of the orbital volume. Rigid fixation either by intracranial or extracranial fixation (Fig 3.4-5a–d) is important, the latter offering an easier approach in case of postoperative removal. As an alternative for large orbital roof and combined wall defects, anatomical reconstruction using a titanium mesh plate fixed at the orbital rim can be recommended (Fig 3 .4-7). Additional layering of bone grafts at the skull base provides bony repair of the skull-base floor, of the frontal sinuses, and supraorbital ethmoid areas. Following orbital roof reconstruction and management of the frontal sinus, realignment and fixation of the frontal bone segments is performed, beginning with the frontal bar (supraorbital rim segments).

Fig 3.4-7 Reconstruction of extensive roof and medial orbital wall defects with titanium mesh plates.

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5


Orbital surgery should not be performed without preoperative visual assessment with the goal to detect conditions where immediate treatment by the ophthalmologist is required and reconstructive surgery should be postponed. Moreover, as orbital surgery may affect visual acuity and result in motility disorders, reliable preoperative documentation is important for medical record reasons. Preoperative, intraoperative, and postoperative administration of steroids to prevent severe intraorbital edema is considered, especially when extensive surgery is planned. To protect the cornea from iatrogenic damage it is recommended to close the eyelids with a 6-0 intermarginal suture or insertion of a protective eye shield. This is particularly important when a coronal flap interferes with a direct evaluation of the periorbital region. As it is the most sensitive evaluation of optic nerve dysfunction, pupillary reaction to light is checked regularly. Pupillary dilatation may occur during deep orbital reconstruction, and is not related to visual loss, but to pressure on the ciliary ganglion. A final check by the surgeon either before leaving the operating theatre or postoperatively in the recovery room should be performed in every case. During orbital dissection and reconstruction, close communication with the anesthesiologist is helpful to minimize dangerous bradycardia by vagal stimulation. Postoperatively, close follow-up of visual acuity and pupillary functions during the first 24 hours is advisable, as delayed development of increased intraconal pressure or loss of visual acuity can occur. Regular monitoring should be continued for several days. Close continuous ophthalmologic assessment should also be provided for the unconscious patient, although monitoring is more challenging. For documentation of double vision, long-term follow-up by Hess screen evaluation and evaluation of the binocular field of vision are the most efficient methods. As swelling and intraorbital edema resolve over time, Hertel exophthalmometry may document enophthalmos. Early evaluation of postoperative CT scans allows precise confirmation of proper graft position and therefore restoration of orbital volume. Alternatively, the scan may indicate a need for corrective surgery in case of malaligned grafts or malreduction of the orbital walls.

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6


Besides local hematoma and infection, specific problems related to the orbit may occur as early postoperative complications. Severe retrobulbar hematoma is characterized by intraorbital pain, exophthalmos, visual impairment and/ or diplopia, often combined with mydriasis. These symptoms indicate the need for immediate CT examination and immediate orbital decompression. A lateral canthotomy and release of lid sutures may be performed at the bedside before the CT is performed. Visual impairment may also result from malpositioned bone grafts or orbital plates, detectable by CT evaluation. Immediate surgical intervention is indicated. Postoperative ocular motility disorders due to edema causing diplopia frequently occur and disappear after resolution of swelling. More frequent, however, is muscle damage due to dissection. This is minimized by exceedingly careful dissection. However, as the reason for restricted mobility of the eyeball may also result from malaligned bone fragments, bone grafts, or intraorbital plates, diplopia not resolving or improving within 3–4 days requires CT evaluation. Late complications include deformities caused by malpositioning of the orbital frame and inadequate reconstruction of the orbital volume. Enophthalmos is the most common postoperative deformity following orbital reconstruction. Mild enophthalmos of less than 3 mm (the difference between the unaffected eye measured by Hertel exophthalmometry) is hardly noticed by the patient and usually needs no correction if functional sequelae are absent. Severe enophthalmos (more than 3 mm difference between the unaffected eye measured by Hertel exophthalmometry) is esthetically disturbing and may be correlated with functional problems as it is usually related to untreated volume defects in the posterior orbit. The muscle may be prolapsed, resulting in an altered muscle pathway and diplopia. Other reasons for facial deformities may be telecanthus by malreduction of the inner orbital frame, and/or inadequate reattachment of the medial canthal ligament, malpositioning of the zygoma, or malposition of the lateral canthus. Among functional problems, visual impairment and diplopia are the most severe sequelae after blindness which follows orbital surgery. Early diagnosis is crucial for the best outcome. While the prognosis for improvement of


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visual loss on admission is poor, early optic nerve decompression for relief of nerve compression and retrobulbar hematoma or removal of malpositioned intraorbital grafts may be successful. Significant diplopia may be based on motility disorders (neurogenic or mechanical), incongruent visual axes by malposition of one or both eyeballs, or fusion problems. When mechanical reasons such as residual herniation, entrapment of orbital soft tissues, or impinging graft material have been excluded or treated, further management is symptomatic as spontaneous improvement of edema and neurogenic disorders can be expected over 6–12 months. Usually, extraocular muscle surgery is postponed for 10–12 months. Frontal nerve palsy after coronal incision can be avoided by dissecting beneath the deep temporal fascia when approaching the zygomatic arch. The frontal branch runs with the superficial temporal fat pad. The deep fascia is located underneath the nerve. Cranial nerve dysfunction (superior orbital fissure syndrome or optic nerve injury) may occur after compression of the superior orbital fissure or optic canal during trauma or deep orbital dissection. Clinical symptoms are upper lid ptosis, internal ophthalmoplegia (III, IV, and VI), disturbance of V1 sensation, or visual loss. Frequent complications related to approaches are lid shortening, scleral show, or permanent ectropion more common after high (subciliary) eyelid incisions. Unfavorable scars may result from incisions at any location, but are most frequent after lateral eyebrow incisions, lower orbital rim, and medial nasal transcutaneous incisions. Visible and palpable plates may be observed in the region of the lateral and inferior orbital rim where the skin is thin. If possible, plates placed anterior to the lacrimal crest or the medial nose and orbital frame should be avoided. Fractures of the NOE region may result in epiphora due to lacrimal duct obstruction. Initially this may be observed, but chronic dacryocystitis may follow. If this is persistent secondary dacryocystorhinostomy is recommended. Pitfalls

Severe orbital fracture repair is a challenging and difficult procedure with potential for severe iatrogenic complications. Underestimation of the fracture pattern (due to insufficient

diagnosis) may result in inadequate exposure and fracture treatment and will lead to unfavorable results. Thus, meticulous diagnosis including proper CT evaluation is crucial for treatment planning. The indication for a wide exposure including a coronal incision and possibly additional access osteotomies should be fully evaluated. The assessment of CT scans should detect linear fractures causing dents and gaps or widening of the inferior orbital fissure, both resulting in enlargement of the orbital volume. Orbital floor defects are often combined with a displaced medial wall but may be underdiagnosed as isolated floor fractures. Therefore, exposure of the entire fracture pattern has to be the first step with no graft or plate inserted until evaluation has been used as a determinant of treatment. As a rule, correct 3-D reconstruction of the orbital frame should precede internal orbital wall repair. Errors made during reduction of the frame are transmitted to the internal orbit. The shearing of the root of the zygomatic arch is one reason for abnormal facial dimensions and is often underestimated. If this problem is not adequately addressed, a lateral midfacial malposition will result, creating volume expansion in the lateral orbital wall. Therefore, the lateral orbital wall, where the alignment of the zygomatic body and the greater sphenoid wing can be assessed, is a landmark for reduction of lateral orbital fractures and should be routinely exposed to prevent errors in positioning. The inferior orbital rim is often fragmented and cannot serve as a reliable landmark due to its small cross-section. Generally, the inferior orbital rim is straight and not curved inferiorly. Bridging large orbital wall defects with unstable “too flexible” sheets is a common error and results in orbital enlargement. Large defects need rigid fixation of the walls and usually cannot be grafted with one single graft. Identification of the position of posterior bony ledge is of utmost importance and no graft should be inserted unless posterior support is provided. If the posterior ledge cannot be identified, rigid fixation of a properly angulated graft is mandatory. If the graft is laid over the edges of the defect, care has to be taken to prevent penetration into the soft tissues. It is therefore recommended to assure that the transition of the graft to the defect is smooth (with or without rigid fixation), in order to provide a smooth surface over the circumference of the defect.

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3 Midfacial fractures 3.5 Nasoorbitoethmoidal (NOE) fractures

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Anatomy, definition, and classification

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Imaging

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Approaches

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4.1 Reduction sequence

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4.2 Rigid skeletal fixation

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4.3 Primary bone grafting

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Management of the central segment

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Medial canthoplasty

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Nasal reconstruction

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7.1

Nasal bone fixation

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7.2 Nasal cantilever bone graft

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NOE fracture-related problems

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Lacrimal duct injuries

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Frontal sinus injuries

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Skull-base injuries

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Airway management

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14 Complications and pitfalls

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Author Oleh Antonyshyn

3.5 Nasoorbitoethmoidal (NOE) fractures

1

Anatomy, definition, and classification

by the cribriform plate. These bones are thin and closely associated with the olfactory nerves and dura.

The nasoorbitoethmoidal (NOE) complex is a distinct anatomical region in the central upper midface defined by the interorbital space. It is circumscribed by the anterior cranial fossa superiorly and the medial orbital walls laterally. NOE fractures therefore potentially involve the cranial, orbital, and nasal cavities, as well as the lacrimal pathways.

Within the interorbital space (Fig 3.5-2) lie the paired upper nasal fossae separated by the septum and the perpendicular plate of the ethmoid in the midline. The intervals between the nasal fossae and the medial orbital walls are occupied by the ethmoid labyrinths.

The interorbital space is supported anteriorly by structural buttresses consisting of the frontal processes of the maxilla, nasal processes of the frontal bone, and the paired nasal bones (Fig 3.5-1). The roof of the NOE complex is made up of the floor of the anterior cranial fossa. Specifically, this consists of the fovea ethmoidalis, strengthened in the midline

The medial walls of the orbit are composed of the lacrimal bone anteriorly and the lamina papyracea of the ethmoid bone posteriorly. These extremely thin and fragile bones form the lateral boundaries of the NOE complex. The lacrimal drainage system is intimately related to the bone in this area.

IOD

3 1

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Fig 3.5-1 NOE region: 1 Nasal bones 2 Septum 3 Frontal bone 4 Nasal process of maxilla 5 Lamina papyracea (orbital plate of ethmoid bone) Green dotted lines: supraorbital and infraorbital transverse buttresses

Fig 3.5-2 Coronal section (interorbital space). Interorbital distance (IOD). Green arrows indicate potential sites of cerebrospinal fluid (CSF) leaks.

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The medial canthal tendon anchors the tarsal plate and the orbicularis oculi musculature to the medial wall of the orbit. At its point of insertion, the tendon splits into anterior, posterior, and superior limbs, attaching to anterior and posterior lacrimal crests. Morphologically, the medial canthal tendon maintains the configuration of the palpebral fissure and the intercanthal distance. In formulating a treatment plan, the surgeon must be able to recognize the pattern of NOE injury, the status of the medial canthal tendon and central bone fragment, and the degree of disruption or loss of stability in the NOE complex. Markowitz et al first described and classified NOE fractures according to the involvement of the so-called central fragment, defined as the fragment of bone on which the medial

a

canthal tendon inserts. Three fracture patterns are recognized: Type I, single segment central fragment (Fig 3.5-3a). Type II, comminuted central segment with fractures remaining external to the medial canthal insertion, but with the medial canthal ligament attached to a fragment large enough to be stabilized with a plate (Fig 3.5-3b). Type III, comminuted central fragment with fractures extending into the bone which bears the canthal insertion. In this case the canthal ligament is either attached to a bone fragment too small for plate fixation, or totally detached (Fig 3.5-3c). Classification of the fracture pattern with respect to the central bone segment is clinically useful in that it provides guidelines for graded exposure and fixation appropriate to the degree of injury.

b

c

Fig 3.5-3a–c Three fracture patterns are recognized: a Type I: Single central fragment bearing the canthal ligament. b Type II: Comminuted central segment with medial canthal ligament still attached to a bone fragment. c Type III: Comminuted central segment with totally detached medial canthal ligament.

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2

Imaging

Optimal visualization of the NOE region is provided by coronal CT images (Fig 3.5-4). Coronal images clearly demonstrate fractures through the anterior cranial base, medial orbital rim and medial orbital walls. Coronal images are particularly useful in comparative analysis of orbital dimensions.

3-D images can also be constructed from standard volume CT scans (Fig 3.5-5). These images are particularly useful to demonstrate the orientation and displacement of the central fracture fragment and to plan how to approach the NOE injury.

Unfortunately, coronal images can be difficult to obtain in a patient with potential cervical spine or head injury. With most acute trauma patients, image data is acquired using high-resolution axial CT scans which are subsequently reformatted into coronal images.

Fig 3.5-4 Coronal CT scan showing fractures through the anterior cranial base. Comparative analysis of medial orbital rims and walls is particularly useful in understanding orbital dimensions.

Fig 3.5-5 3-D reconstruction showing the displacement of the central fracture fragment.

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3

Approaches

Reconstruction of the fractured NOE complex begins with an adequate exposure. Local lacerations generally do not suffice. Although they can provide useful adjunctive visualization of immediately underlying fractures, formal craniofacial approaches are favored in accessing the NOE complex.

4


Once sufficient exposure of the craniofacial skeleton is obtained, displaced fracture segments are anatomically reduced. This is accomplished most effectively if a strategy for fracture reduction is consistently followed in all cases. 4.1 Reduction sequence

The coronal flap provides access to the superior aspect of the NOE complex, the entire upper and lateral craniofacial skeleton, and the roof, lateral, and medial walls of the orbital cavity. Significant fracture segments are dissected subperiosteally. The margins of the central fragment in particular, and the anterior and posterior lacrimal crests are specifically identified. The insertion of the medial canthal tendon into the central fragment is preserved. The central fragment is then dislocated anteriorly and laterally to facilitate direct access to the medial orbit. Access to the inferior aspect of the NOE complex is obtained through lower eyelid incisions. Periosteum is widely elevated to expose the inferior orbital rims, inferomedial aspect of the orbital cavity, and anterior surface of the maxilla. When fracture lines extend into the lower midface, further access is provided by a transoral upper buccal sulcus approach. Isolated NOE fractures in which the nasofrontal junction is undisplaced or minimally disrupted (type I injuries) can be accessed through limited local incisions. Generally, combined upper eyelid (blepharoplasty) and lower eyelid incisions, or alternatively a retrocaruncular transconjunctival incision, are employed for this purpose. It is extremely important, however, to be aware of the limitations of these local incisions in providing adequate visualization when the nasofrontal junction is disrupted.

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The craniofrontal and zygomaticomaxillary regions have a higher impact tolerance than the NOE region, and tend to fracture into larger segments. Accurate 3-D reconstruction of the upper (craniofrontal) and outer zygomaticomaxillary facial skeletal frame is technically simpler and anatomically more reliable, and is therefore always completed first. There is, of course, no single acceptable method. The arguments for doing the NOE segment first are also valid (see chapter 5 Panfacial fractures). The presence of stable and reliable skeletal references peripherally is very helpful in restoring an anatomically accurate NOE complex. Within the NOE complex itself, reconstruction proceeds from the deepest and most inaccessible areas toward the surface. In the presence of lacerations, fractured nasal bones and nasomaxillary segments are displaced laterally to allow unrestricted access to the medial orbits. Following completion of medial wall reconstruction, the central segments are reduced and rigidly fixed. The nasal bones and restoration of dorsal nasal projection are addressed last. 4.2 Rigid skeletal fixation

Rigid skeletal fixation of NOE fractures requires specific identification and control of regional functional forces. In the upper NOE region, the functional forces acting on fracture segments are those exerted by the orbicularis oculi muscle through the medial canthal tendon, and the forces generated by overlying soft tissue, particularly during the phase of postinjury edema and subsequent soft-tissue contracture. Titanium miniplates 1.3 or corresponding Matrix Midface plates are therefore generally sufficient. Lower NOE fractures, ie, fractures of the medial buttresses of the maxilla, must resist transmitted forces of mastication and, therefore, larger plate systems (1.5, 2.0, or corresponding Matrix Midface plates) are most commonly used for this purpose.


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4.3 Primary bone grafting

Primary bone grafting in the acute management of NOE fractures is indicated in comminuted unstable NOE injuries when actual loss of bone or the degree of bony comminution preclude a stable 3-D reconstruction. Under these circumstances, bone grafts obliterate defects and restore bony continuity, thereby increasing stability of the reconstruction. Primary bone grafts are employed for three specific purposes in NOE reconstruction: • Restoration of bony continuity along the nasomaxillary buttresses or orbital rims. The bone graft is carved meticulously and precisely to fit into the skeletal defect as an inlay graft. Any contour irregularity will be clearly visible externally and must be avoided. The inlay graft is fixed using miniplates. The use of bone grafts under these circumstances ensures normal external contour, maintains stability at the fracture site, and potentially speeds consolidation. • Reconstruction of the medial orbital wall to prevent orbital soft-tissue prolapse and to provide a skeletal base for medial canthal tendon attachment. Bone grafts are shaped to the appropriate size for the medial orbital wall and are rigidly fixed in place by miniplates both at the superior and at the inferior orbital rims. Calipers measure the distance between the two medial orbital walls to ensure that the interorbital distance does not exceed 25 mm. • Reestablishment of dorsal nasal projection in central maxillary fractures which destroy the perpendicular plate of the ethmoid, the septum, and the nasomaxillary buttresses. This is an absolute indication for primary dorsal nasal bone grafting. Split skull bone graft is best employed for this purpose. The bone is fixed as a cantilever graft.

5

Management of the central segment

The specific approach to rigid fixation of NOE fractures is based on the pattern of NOE injury. Type I fractures are most effectively treated by anatomical reduction and rigid fixation of the central segment (Fig 3.5-6). Three plates are generally required at the frontomaxillary, zygomaticomaxillary, and medial maxillary buttress fracture lines, respectively. When there is virtually no disruption of one of these fracture sites, fixation at two sites may be sufficient. The type I fracture is frequently “greensticked” superiorly and can be managed without fixation superiorly.

Fig 3.5-6 Fracture fixation of a type I fracture with three miniplates (1.3, 1.5, or corresponding Matrix Midface plates).

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Type II injuries are comminuted NOE fractures which circumscribe and spare a central canthal tendon-bearing bone segment. Such injuries are more difficult to treat due to the number of comminuted segments, the small size of these segments, and the inherent instability of the medial canthal tendon-bearing bone. Reconstruction requires sequential reduction of each bone segment to restore the nasomaxillary buttresses bilaterally, and, frequently, supplemental inlay bone grafts where skeletal gaps exist (Fig 3.5-7a). Miniplates are used to span defects in the nasomaxillary buttress. The critical part of the procedure is to ensure anatomical 3-D placement of the central canthal ligament-bearing bone segment. The tendency to outward rotation or displacement of the central segment often requires placement of supplementary transnasal canthopexy wires posterior to the medial

canthal tendon insertion (Fig 3.5-7b). At all times the insertion of the medial canthal tendon is preserved and no attempt is made to dissect it. Type III injuries are comminuted NOE fractures which transect or avulse the medial canthal tendon. As such, there is no sizeable bone fragment to use in reconstruction. Under these circumstances, a formal medial canthoplasty must be performed (Fig 3.5-8). Fracture reduction is performed by sequential alignment of comminuted segments as described above. However, a formal transnasal medial canthopexy is absolutely necessary. Frequently such injuries are associated with marked comminution of the medial orbital walls and rims, and bone graft reconstruction of the medial orbits is required to provide an adequate skeletal fixation point for medial canthal tendon insertion.

a

b Fig 3.5-7a–b Reconstruction of a type II fracture. Plate fixation as in type I fracture. a Special attention must be given to the correct anatomical 3-D placement of the bone segment to which the medial canthal ligament is attached. b Placement of a transnasal canthopexy wire avoids outward rotation or displacement of the bone fragment to which the medial canthal ligament is attached. The insertion point of the transnasal canthopexy wire must be posterior and superior to the lacrimal fossa.

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Fig 3.5-8 Fracture reduction in type III injuries is performed by sequential alignment of comminuted segments as described in Fig 3.5-7a . A formal transnasal medial canthopexy is absolutely necessary.


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6

Medial canthoplasty

Restoration of the premorbid medial canthal position is the single most important step in restoring preinjury NOE and orbital surface morphology. In types I and II injuries, anatomical reduction of the tendon-bearing fracture segment generally ensures adequate placement of the medial canthus. However, in type III injuries and in total avulsions or lacerations of the medial canthal tendon, specific restoration of the medial canthal bony insertion is indicated. The reconstructed medial orbital walls will provide the skeletal base for tendon reinsertion. Medial wall bone graft must be perfectly stable so that there is no tendency for lateral displacement, and the distance between the medial walls must not exceed 25 mm. Once an adequate skeletal foundation is provided, the 3-D location of the medial canthal tendon insertion is precisely identified. Ideally, the tendon is inserted at the superior aspect of the posterior lacrimal crest. This ensures appropriate depth and vertical placement of the medial canthus. However, in grossly comminuted fractures when all adjacent anatomical landmarks are destroyed, placement is chosen arbitrarily at a point 5 mm posterior to the medial orbital rim, midway between the orbital roof and floor, just superior to the upper edge of the lacrimal fossa.

a

Various techniques for canthal tendon fixation have been published. Classically, a 3.0 stainless steel wire, used to secure the medial canthal tendon insertion, is passed transnasally through a drill hole in the medial orbital wall or bone graft to the contralateral medial orbit. The wire is secured distally over bone or bone graft in the contralateral orbit, or over a central screw in the glabella (Figs 3.5-7a–b, 3.5-8). The transnasal wiring techniques offer the advantage of providing additional stability to the fractured medial orbital wall or medial wall bone graft by providing a posterior point of fixation. However, disadvantages include the need for dissection in the contralateral orbit and the mechanical disadvantage associated with a substantial length of wire. The wire can stretch, potentially leading to medial canthal drift. An alternative means of medial canthoplasty uses a boneanchoring device (Fig 3.5-9a–b) to allow ipsilateral fixation of the medial canthal tendon to the medial orbital wall. These ipsilateral techniques isolate the dissection and fixation to the affected side only, and are therefore particularly effective in cases of unilateral medial canthal dystopia. Use of this technique is restricted to those cases where the medial orbital wall is intact or previously reconstructed with a perfectly stable bone graft.

b

Fig 3.5-9a–b A bone-anchoring device allows ipsilateral fixation of the medial canthal tendon to the medial orbital wall. Use of this technique is restricted to those cases where the medial orbital wall is intact or reconstructed with a perfectly stable bone graft.

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7

Nasal reconstruction

The degree of nasal disruption dictates the requirements for optimal restoration and maintenance of nasal projection. This is determined clinically by the resistance of the nasal dorsum to direct digital pressure, ie, the Brown-Gruss vault compression test (Fig 3.5-10), and radiologically by the degree of comminution of the nasal bones and septum.

7.1 Nasal bone fixation

Open reduction and fixation of the fractured nasal bones can effectively restore dorsal nasal projection provided two conditions are met. First, the nasal fracture segments must be of an adequate size to permit mini- or microplate fixation. Second, the residual structural integrity in the septum and upper lateral cartilages must be sufficient to support the middle third of the nose. The proximal nasal bones are reduced and fixed to the glabella with an H- or T-shaped miniplate, taking care to restore the nasofrontal angle (Fig 3.5-11). Fractures of the septum are then repaired. The entire reconstructed osseocartilaginous framework is further stabilized by suspending the septal cartilage and/or upper lateral cartilages with suture fixation to drill holes in the distal margin of the fixed nasal bones.

Fig 3.5-10 A positive Brown-Gruss vault compression test suggests that a cantilever primary bone graft will be required.

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Fig 3.5-11 The proximal nasal bones are reduced and fixed to the glabella with an X-shaped miniplate, taking care to restore the nasofrontal angle.


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7.2 Nasal cantilever bone graft

Telescoping collapse of the nasal dorsum with direct digital pressure indicates complete loss of support and the need for cantilever bone graft reconstruction (Fig 3.5-12a–b). A split skull bone graft is best used for this purpose. The bone is fixed as a cantilever graft. Particular attention must be paid to the following details:

a

• The bone graft must be of adequate length to support the nasal dorsum. • If nasal tip support is adequate, the bone graft extends only as far as the alar domes. If, however, nasal tip support is inadequate, the graft must span the distance from the root to the tip of the nose. • Stabilization must be adequate and is achieved by a single miniplate from the glabella to the dorsal nasal graft. • Finally, it is imperative that the nasofrontal angle be maintained and not obliterated by the bone graft.

b

Fig 3.5-12a–b Split skull bone fixed as a cantilever graft to reconstruct the nasal dorsum. Fixation with a single plate from the glabella to the dorsal nasal graft.

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8

NOE fracture-related problems

Control of soft-tissue redraping is the single most problematic issue in NOE fracture reconstruction. When widely undermined, tissues must be redraped and the ridges and depressions comprising the surface contours of the NOE region are easily obscured. Postoperative edema and formation of subperiosteal seroma or hematoma result in a permanent thickening of the soft tissue, loss of definition in the nasofrontal angle and nasoorbital valley, and development of epicanthal fullness. The redraping of soft tissues can be controlled by surgically ensuring direct and accurate apposition of soft tissues to bone in key areas. This is done most effectively by using external bolsters which are adapted to the surface of the lateral nose (Fig 3.5-13). Metal splints padded with foam or felt are secured by transnasal wires to compress the soft tissues. These bolsters adapt the soft tissues only, and play no role in fracture stabilization.

9

Lacrimal duct injuries

During NOE fracture repair, the nasolacrimal sac should be identified but not probed or intubated unless obviously lacerated. The upper lacrimal pathway is protected by the medial canthal ligament. Obstruction usually occurs in the bony nasolacrimal canal, and can arise as a consequence of bone displacement, impingement, or swelling and duct stenosis. Postoperative epiphora is generally due to eyelid malposition or edema, and will resolve spontaneously in more than 80% of patients. Formal assessment with probing and dacryocystography is undertaken only in those patients with persistent epiphora more than 2 months following primary fracture repair. When dacryocystorhinostomy is necessary, it should be performed at least 3 months after the primary repair.

10

Frontal sinus injuries

The floor of the frontal sinus and nasofrontal duct are generally involved in NOE fractures. Despite this, specific frontal sinus repair is not undertaken in the absence of anterior or posterior wall fractures. Under those circumstances when a concomitant fracture of the anterior or posterior wall of the frontal sinus exists, formal repair of the anterior and sometimes the posterior wall, obliteration, and/or exclusion from the nasal cavity are performed.

Fig 3.5-13 Metal or lead splints padded with foam, used as xternal bolsters contoured to the nasal surface for the adaptation e of the soft tissues of the nose. Application of these should be done with great caution to avoid skin necrosis.

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11

Skull-base injuries

13


The anterior cranial fossa defines the superior boundary of the interorbital space. NOE fractures therefore frequently extend superiorly to involve the skull base. Specific clinical and radiological assessment of the forehead and cranial base is required in all patients with NOE fractures to rule out associated cerebral spinal fluid (CSF) rhinorrhea, intracranial injury, or skeletal disruption.

Preoperative and postoperative ophthalmologic examinations to detect additional intraorbital injuries, especially injuries to the globe and vision impairment, are strongly recommended. Perioperative antibiotics and eye-lubricating ointments are routinely used. Patient neurological status and vision are closely monitored in the first 48 hours following surgery.

Under certain circumstances, a neurosurgeon may be required to elevate a frontal bone flap to provide intracranial access to the NOE fracture. Generally this is done specifically for neurosurgical indications, ie, a suspected major dural tear with a CSF leak, in the presence of compound or grossly displaced frontal bone fractures, or in the presence of intracranial injury requiring direct intervention. Concomitant intracranial exposure provides optimal access to the NOE complex and allows anatomical reduction of fractured segments of the supraorbital rims, glabella, and nasomaxillary processes.

The skin adjacent to the NOE bolsters is repeatedly assessed and transnasal wires are untwisted and loosened if edema is excessive. The bolsters are removed 10 days after surgery.

12

Airway management

Intraoperative management of the airway in NOE fractures is dictated by the presence or absence of associated facial fractures. Isolated NOE injuries are preferably treated with the patient orally intubated. This allows unparalleled access to the NOE region and permits accurate reduction of associated nasal injuries. Even when associated with maxillary fractures, the endotracheal tube is placed orally in the retromolar area, thereby allowing restoration of premorbid occlusion. However, when these injuries are associated with grossly disrupted maxillary or panfacial fractures, nasal intubation may be indicated. Nasal intubation will compromise reconstruction of nasal anatomy. Sometimes this can be overcome by an intraoperative switch from nasal to oral intubation or with a submandibular tube placement. In rare cases of combined maxillary and mandibular fractures with gross comminution, use of a tracheostomy may be necessary to facilitate surgical repair.

14 Complications and pitfalls

NOE contour irregularities, nasal deformities, disproportions, and asymmetries in periorbital morphology are the most commonly observed complications. Primary repair generally relies on the reapproximation and consolidation of multiple comminuted fracture segments and bone grafts. Bone resorption and surface contour irregularities commonly occur, particularly over the glabella and nasal root, but are rarely sufficiently deforming to necessitate subsequent hardware removal or recontouring procedures. Posttraumatic nasal deformities are characterized primarily by deviations or inadequate projection of the nasal dorsum, particularly in the middle vault, and septal deviations associated with nasal airway obstruction. The hardware used in primary reconstruction precludes the use of nasal osteotomies. Secondary rhinoplasties therefore rely on the effective use of cartilage grafts to restore the midline and dorsal nasal projection. Soft-tissue deformities are particularly obvious in the periorbital region, where minor discrepancies result in canthal dystopias and asymmetries in palpebral fissure height, width, or inclination. Previous critical reviews of periorbital morphology following fracture repair show that posttraumatic telecanthus is effectively corrected in the horizontal dimension by primary surgery. However, corrections of vertical canthal displacements are far less satisfactory. Mild degrees of asymmetry (> 2 mm) in medial canthal position in the vertical plane produce obvious deformities. In particular, vertical canthal displacements produce asymmetries in palpebral inclination which are readily apparent.

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3 Midfacial fractures 3.6 Fractures of the nasal skeleton

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2

Imaging

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3

Approaches

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3.1 Coronal approach

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3.2 The gull-wing approach

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3.3 Lacerations

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3.4 Sublabial approach

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Classification of nasal skeletal fractures

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Management of nasal skeletal fractures

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5.1 Medially and laterally displaced fractures

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5.2 Centrally depressed fractures

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5.3 Avulsed upper lateral cartilages

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5.4 Comminuted nasal fractures

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5.5 Septal fractures

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Perioperative and postoperative management

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Authors Kevin A Shumrick, Jon B Chadwell

3.6 Fractures of the nasal skeleton

1


The nasal skeleton is responsible for maintaining the nasal airway as well as providing one of the most prominent esthetic features of the face. Slight distortions of nasal architecture (from trauma) can adversely affect both nasal function and appearance.

The nasal skeleton is the only composite structure of the midfacial skeleton consisting of both bony and cartilaginous components (Fig 3.6-1a–b). The nasal skeleton consists of the paired nasal bones, the midline, septal cartilage and bone (vomer), the paired upper lateral cartilages which attach to the nasal bones, and the paired lower lateral cartilages. Finally, although not technically part of the nose, the ascending processes of both maxillae are frequently involved in nasal trauma and should be considered as basal support for the nasal skeleton.

NB

MC

LC

BCJ APM ULC LLC

CNS

LCAC

a Fig 3.6-1a Anatomy of the nasal skeleton, 45º angle view. NB Nasal bone BCJ Bone cartilaginous junction APM Ascending process of the maxilla ULC Upper lateral cartilage LLC Lower lateral cartilages LCAC Lateral crus alar cartilage

b

ANS

Fig 3.6-1b Anatomy of the nasal skeleton, inferior view. MC Medial crus LC Lateral crus CNS Cartilage nasal septum ANS Anterior nasal spine

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2

Imaging

3

The nasal skeleton is perhaps the only midface structure that is superficial enough to be largely assessed by physical and visual exam. While plain films of the nose are often performed during an emergency room visit for facial trauma, they are rarely helpful. Often, a fracture will be noted on the plain film, but the nasal appearance and function have not changed. Or, conversely, no fracture is seen on the film, but the nose is crooked. Definitive imaging of the nasal skeleton is performed by high-definition coronal and axial CT scans.

Approaches

Fortunately, the majority of nasal fractures can be managed with closed approaches. However, for more severe trauma an open approach may be required. Unfortunately, there is no single approach which will expose the entire nasal skeleton. Additionally, the fact that the nose is centrally positioned in the face presents few opportunities for camouflage of incisions and therefore, esthetic approaches to the nasal skeleton are challenging. Exposure of the nasal skeleton may be achieved by several different approaches. In extensive trauma, a combination of approaches may be required. 3.1 Coronal approach

This approach provides excellent exposure of the nasal bones and their junction with the frontal bone down to the upper lateral cartilages, with sufficient exposure for plate and screw application (Fig 3.2-5 , page 196). The coronal approach is rarely indicated for isolated fractures limited to the nasal skeleton. The most common use of the coronal approach is for fractures extending into the nasoorbitoethmoidal (NOE), nasofrontal, or frontal sinus regions. 3.2 The gull-wing approach

This approach should never be used. It is an incision across the nasion, extending laterally under or above the eyebrows. This approach provides excellent exposure of the upper two thirds of the nasal skeleton, but has the disadvantage of a very visible scar, and possible transection of the supratrochlear and supraorbital nerves. There are two acceptable approaches (Fig 3.6-2a–b): • The horizontal limb of the converse open-sky incision • The vertical midline nasal incision over the nasal radix These incisions can be used for isolated nasal or limited NOE fractures.

a

b Fig 3.6-2a–b

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Horizontal and vertical incisions for transfacial access.


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3.3 Lacerations

Occasionally, significant lacerations over the nose or central midface may provide sufficient exposure for reduction and repair of nasal injuries. Care should be taken when considering extending a laceration in order to avoid iatrogenic scarring or injury to the perinasal sensory nerves. It is rarely justified to extend a laceration in contrast to using standard incisions. 3.4 Sublabial approach

The sublabial approach through a gingival buccal incision (Fig 3.1-4 , page 186) provides excellent exposure of the medial maxilla as it forms the piriform aperture and ascending portion of the maxilla. Although the maxilla is not technically part of the nasal skeleton, the nasal bones articulate with the ascending process of the maxilla. Fractures involving the medial maxilla frequently involve the nasal skeleton and may require an open approach with reduction and plating.

4

Classification of nasal skeletal fractures

There is no universally accepted classification system for nasal skeletal fractures. The following simple scheme deals with the most common clinical scenarios. Laterally displaced fractures usually occur from a blow coming diagonally across the face. Typically, both nasal bones fracture at their nasomaxillary sutures or below, with the bone ipsilateral to the trauma being pushed medially and the contralateral bone being pushed laterally (Fig 3.6-3a). Additionally, there will usually be a fracture of the superior portion of the nasal septum (Fig 3.6-3b). This type of fracture may involve one or both nasal bones (depending on the amount of force involved) and sometimes the nasal process of the maxilla (Fig 3.6-4).

a

b Fig 3.6-3a–b Lateral displacement of the nasal bones: a Septum not displaced. b With involvement of the superior portion of the nasal septum.

Fig 3.6-4 CT scan of a nasal fracture with involvement of both nasal bones.

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Posteriorly depressed fractures occur from a “straight-on blow” over the nasal bones (Fig 3.6-5). Typically, the nasal bones are pushed posteriorly inside the ascending processes of the maxilla. There will also be a septal component for this type of fracture, which may be significant. Considerable force is required to cause a fracture of this type and it is common for these fractures to extend into the piriform aperture or NOE region. Avulsion of upper lateral cartilage: With significant, localized, central third nasal trauma (such as striking the central nose on a steering wheel) the upper lateral cartilages may be avulsed from the nasal bones (Fig 3.6-6a–b). The avulsion may be either unilateral (from a side blow) or bilateral. This is an important diagnosis to be made because management of a cartilaginous injury is quite different from that of a bony injury. Additionally, the diagnosis of carti-

laginous avulsion is made primarily by physical exam because a cartilaginous injury will typically not be appreciated on a CT scan. Nasal septal fractures: In almost all nasal fractures the nasal septum will be involved to some degree (the exception being an isolated, unilateral distal nasal bone fracture). In most cases septal involvement requires intervention. With lateral trauma the septal fracture rarely realigns itself with external nasal bone repositioning and must be reduced separately. However, with direct anterior–posterior trauma there may be significant comminution of the nasal septum with loss of height. This comminution may result in nasal airway obstruction as well as an external dorsal nasal depression. This type of dislocation cannot be repaired or stabilized. It is managed by dorsal grafting (chapter 3.5 Nasoorbitoethmoidal (NOE) fractures).

a

b Fig 3.6-5 Centrally depressed nasal fracture. The nasal bones are pushed posteriorly inside the processes of the maxilla.

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Fig 3.6-6a–b Upper lateral cartilage avulsion after significant localized central third nasal trauma.


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Nasal septal hematoma: In case of inferior third nasal trauma when the cartilaginous septum is involved, disruption of the cartilaginous septum and its investing perichondrium may occur and may result in a septal hematoma (Fig 3.6-7). The natural history of a septal hematoma is for the hematoma to lift the perichondroma off the cartilage (depriving the cartilage of blood) and put significant pressure on the cartilage. This combination of pressure and loss of vascular supply may lead to infection, cartilage necrosis, and subsequent loss. The end result of an untreated septal hematoma is frequently the loss of a large portion of the septal cartilage with an inferior third nasal depression and the so-called “saddle nose deformity” of the external nose. Because of the severe sequelae of an untreated septal hematoma, it is recommended that all patients with significant nasal trauma undergo an endonasal examination in the early posttrauma period in order to rule out a developing hematoma.

5

Management of nasal skeletal fractures

5.1 Medially and laterally displaced fractures

Laterally displaced fractures make up the bulk of nasal fractures and most can be managed by closed reduction. Obviously, with a closed reduction the fracture segments are not visualized and, therefore, an accurate diagnosis and proper technique is essential in order to assure a suitable outcome. Some surgeons recommend waiting 5–10 days prior to a closed reduction in order to allow some initial swelling to resolve. The type of anesthesia to be used is an important consideration. Local anesthesia with topical, intranasal cocaine and nasal sidewall infiltration with Xylocaine® may be sufficient anesthesia in selected patients, but it has several drawbacks. First, administration of the topical and injected anesthesia can be quite painful. Second, most patients will only allow one attempt at reduction of the fracture and, if this is unsuccessful or incomplete, patient discomfort will prevent a chance for further manipulation. Third, if there is any bleeding from fracture manipulation patients often become very uncomfortable and quite apprehensive. As an alternative to topical and injected anesthesia we prefer a brief general anesthesia with an endotracheal tube in order to minimize the chance of aspiration.

Fig 3.6-7 Septal hematoma after isolated septal fracture.

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With the patient asleep, the nose is decongested with cottonoids impregnated with a topical decongestant (cocaine or oxymetazoline). Reduction is performed using a blunt elevator placed on the side of the depressed nasal bone (Fig 3.6-8a–b). A rough estimate of the distance from the nostril to the fracture site is measured with the elevator externally on the nose. The elevator is then introduced into the nostril on the side of the depressed nasal bone (side of traumatic impact). It is imperative that the elevator is as far anterior in the nasal cavity as possible, and under the nasal bone. Positioning the elevator under the nasal bone may be difficult because the depressed nasal bone may be lodged against the septum. Failure to make sure that the elevator is under the nasal bone will result in a failed reduction and considerable bleeding. The opposite hand wraps the fingers around the frontal temporal region (to provide countertraction) and the index finger is placed over the laterally displaced nasal bone. Reduction takes place by the simultaneous elevation of the nasal bone with the elevator, medial displacement of the laterally displaced nasal bone with the index finger, and countertraction applied by the fingers. Often a distinct click is heard as the fracture snaps into place.

a

5.2 Centrally depressed fractures

As noted, isolated centrally depressed fractures are relatively uncommon and the possibility of a NOE component should be ruled out by examination and CT scan because a closed reduction will not correct these more severe injuries. Centrally depressed nasal fractures require posterior to anterior elevation. Often the ascending processes of the maxilla are splayed laterally with the nasal bones inside them. Reduction requires elevation of the nasal bones anteriorly and then squeezing the ascending processes medially. 5.3 Avulsed upper lateral cartilages

Avulsed upper lateral cartilages require an accurate diagnosis to assure a satisfactory outcome. It is important to recognize that reduction of bony segments will not reposition the avulsed cartilages and a central depression will persist. In our experience, attempts at reattachment of the cartilages have been disappointing, even with direct visualization through a laceration. Attempts at suturing the cartilages back to the nasal bones have typically resulted in the sutures pulling through. We have found that accurate reduction of the bony fragments with crushed cartilage onlay grafting (either acutely or delayed) to fill the depression left by the avulsed cartilage provides the best result.

b

Fig 3.6-8a–b Reduction and position control of the laterally displaced left nasal bone fracture with an elevator inside the nose and index finger outside the nose.

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5.4 Comminuted nasal fractures

Comminuted nasal fractures are often associated with significant lacerations. These lacerations can be quite helpful for reduction and stabilization. The fractures are visualized using a combination of approaches (such as open rhinoplasty and coronal), the fractures are aligned, and then plated with a low profile plating system. The microplate 1.0 system is preferred, but 1.3 is also acceptable. 5.5 Septal fractures

Management of septal fractures depends largely on symptoms and physical findings. As noted, there will almost always be a septal fracture with any displaced nasal fracture, but reduction is always indicated using forceps. Indications for open surgery are 1) septal hematoma, 2) septal deviation with nasal airway obstruction, 3) protrusion of bone or cartilage through septal mucosa (which will preclude healing and give rise to recurrent epistaxis). Septal hematoma is managed by incision, drainage, and transseptal mattress sutures. Displaced septal fractures can be treated with a closed approach or with an open septoplasty approach. In our experience, in severe fractures an open septoplasty approach with preservation of septal cartilage and removal of comminuted bone gives the most predictable results. Optimal timing for septal repair seems to be within 5 days. With significant delay in repair of a septal fracture, scarring and fibrosis will develop and make a straightforward septoplasty a major ordeal.

6

Perioperative and postoperative management

For simple, uncomplicated nasal fractures, which have been reduced in a closed fashion, an external splint is applied for 5–7 days simply to protect the nose from inadvertent trauma in the early postoperative period. When applying a nasal splint following a closed reduction, it is important to remember that the fracture is not fixated and if the splint is crimped too tightly, it can displace the fracture (Fig 3.6-9). If the septum has been repaired, then the septal mucosal flaps will be coapted with either transseptal mattress sutures or the nose is packed overnight with rolled, nonabsorbent gauze. There is no significant advantage to leaving the packing in longer than one night and it is a source of considerable discomfort for the patient. There have been reports of using nasal packing to hold an unstable nasal bone in place, but it is questionable whether intranasal packing is reliable for maintaining a nasal bone in reduction. Internal splint septum stabilization, such as Doyle splints, can also be used.

Fig 3.6-9 An external splint can be used for stabilization in simple and uncomplicated nasal fractures.

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7


The two major complications of nasal skeletal fractures are nasal airway obstruction and external deformity. The major cause of nasal obstruction is either a deviated nasal septum or a medially displaced lateral nasal sidewall. They actually look different: in one the septum is dislocated laterally, in the other the turbinate and sidewall are dislocated medially. A CT scan may be helpful in differentiating between a septal deflection versus a sidewall fracture. Correction of a deviated nasal septum secondary to a septal fracture can be quite difficult when performed on a delayed basis. It should be noted that the chances of a postoperative septal perforation increase when repairing a delayed septal fracture because mucosa is often trapped in fracture lines and dissection will result in mucosal disruption. Correction of residual external nasal deformities requires an accurate diagnosis as to which nasal components are responsible for the deformity. Lower third dorsal depressions are commonly caused by avulsed upper lateral cartilages (unilateral or bilateral). These residual depressions are best managed by crushed septal cartilage onlay grafting utilizing either an endonasal or open rhinoplasty approach. Upper third deviations are usually the result of unreduced nasal bone fractures. Additionally, these deformities are often accompanied by dorsal irregularities. Once 4–6 weeks have passed, attempts at closed reduction are rarely successful. The most reliable method of managing bony nasal deflections (with or without dorsal irregularities) is with a rhinoplasty technique resecting the dorsal hump, if indicated, and performing lateral osteotomies. Attempts at recreating the original fracture by performing simple lateral osteotomies, without resecting the dorsal hump, often fails to completely straighten the nose or relieve the hump.

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3.7 References and suggested reading Alpert B, Gutwald R, Schmelzeisen R

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(2003) New innovations in craniomaxillofacial fixation: the 2.0 lock system. Keio J Med; 52(2):120–127. Alvi A, Carrau RL (1996) The bicoronal flap approach in craniofacial trauma. J Craniomaxillofac Trauma; 2(2):40–55.

grafting in facial fracture management: indications and clinical considerations. Clin Plast Surg; 19(1):207–217. Ellis E III, Reddy L (2004) Status of the internal orbit after reduction of zygomaticomaxillary complex fractures. J Oral Maxillofac Surg; 62(3):275–283. Ellis E III, Zide MF (1995) Maxillary vestibular approach. Ellis E III, Zide MF (eds), Surgical Approaches to the Facial Skeleton. 1st ed. North Providence: Lippincott Williams & Wilkins, 114–120. Ellis E III, Zide MF (1995) Surgical Approaches to the Facial Skeleton. Baltimore: Williams & Wilkins. Eppley B (2000) Zygomaticomaxillary fracture repair with resorbable plates and screws. J Craniofac Surg; 11(4):377–385. Forrest CR, Philips JH, Prein J (1998) Le Fort I-III fractures. Prein J (ed), Manual of Internal Fixation in the Cranio-Facial Skeleton. Berlin: Springer-Verlag, 108–126. Fox AJ, Tatum SA (2003) The coronal incision: sinusoidal, sawtooth, and postauricular techniques. Arch Facial Plast Surg; 5(3):259–262. Girotto JA, MacKenzie E, Fowler C (2001) Long-term physical impairment and functional outcomes after complex facial fractures. Plast Reconstr Surg; 108(2):312–327.

The importance of the zygomatic arch in complex midfacial fracture repair and correction of posttraumatic orbitozygomatic deformities. Plast Reconstr Surg; 85(6):878–890. Hackl W, Fink C, Hausberger K, et al (2001) The incidence of combined facial and cervical spine injuries. J Trauma; 50(1):41–45.

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(1989) Complex orbital fractures: a critical analysis of immediate bone graft reconstruction. Ann Plast Surg; 22:220–233. Antonyshyn O, Weinberg M, Dagum A

(1996) Use of a new anchoring device for tendon reinsertion in medial canthopexy. Plast Reconstr Surg; 98:520–523. Buitrago-Téllez CH, Schilli W, Bohnert M, et al (2002) A comprehensive classification of

craniofacial fractures: postmortem and clinical studies with two- and threedimensional computed tomography. Injury; 33(8):651–668. Carlin CB, Ruff G, Mansfeld CP, et al (1998) Facial fractures and related injuries: a ten-year retrospective analysis. J Craniomaxillofac Trauma; 4(2):44–48. Caron G, Paquin R, Lessard MR, et al

(2000) Submental endotracheal intubation: an alternative to tracheotomy in patients with midfacial and panfacial fractures. J Trauma; 48(2):235–240. Champy M, Lodde JP, Kahn JL, et al (1986) Attempt at systematization in the treatment of isolated fractures of the zygomatic bone: techniques and results. J Otolaryngol; 15(1):39–43. Chen CH, Wang TY, Tsay PK, et al (2008) A 162-case review of palatal fracture: management strategy from a 10-year experience. Plast Reconstr Surg; 121:2065–2073. Coleman JR Jr (2001) State of the art in facial trauma repair. Curr Opin Otolaryngol Head Neck Surg; 9:220–224. Converse JM, Smith B, Obear MF, et al

(1967) Orbital blowout fractures: a ten-year survey. Plast Reconstr Surg; 39(1):20–33. Review. Cooter RD, Dunaway DJ, David DJ (1996) The influence of maxillary dentures on mid-facial fracture patterns. Br J Plast Surg; 49(6):379–382. Dawar M, Antonyshyn O (1993) Long-term results following immediate reconstruction of orbital fractures: a critical morphometric analysis. Can J Plast Surg; 1:24–29. Dolan R, Smith DK (2000) Superior cantholysis for zygomatic fracture repair. Arch Facial Plast Surg; 2(3):181–186.

Glassman RD, Manson PN, Vanderkolk CA, et al (1990) Rigid fixation of internal

orbital fractures. Plast Reconstr Surg; 86(6):1103–1111. Gruss JS (1986) Complex nasoethmoidorbital and midfacial fractures: role of craniofacial surgical techniques and immediate bone grafting. Ann Plast Surg; 17(5):377–390. Gruss JS (1985) Naso-ethmoid-orbital fractures: classification and role of primary bone grafting. Plast Reconst Surg; 75:303–317. Gruss JS, Bubak PJ, Egbert MA (1992) Craniofacial fractures: an algorithm to optimize results. Clin Plast Surg; 19(1):195–206. Gruss JS, Mackinnon SE (1986) Complex maxillary fractures: role of buttress reconstruction and immediate bone grafts. Plast Reconstr Surg; 78(1):9–22. Gruss JS, Phillips JH (1992) Rigid fixation of Le Fort maxillary fractures. Yaremchuk MJ, Gruss JS, Manson PN (eds), Rigid Fixation of the Craniomaxillofacial Skeleton. Stoneham, Mass: Butterworth-Heinemann, 245–262.

Hallikainen D, Lindqvist C, Söderholm AL

(2002) Radiographic evaluation of the craniomaxillofacial region. Greenberg AM, Prein J (eds), Craniomaxillofacial Reconstructive and Corrective Bone Surgery: Principles of Internal Fixation Using the AO/ ASIF Technique. New York: Springer-Verlag, 210–219. Hammer B (1995) Orbital Fractures: Diagnosis, Operative Treatment, Secondary Corrections. Göttingen: Hogrefe & Huber. Hammer B, Prein J (1995) Correction of post-traumatic orbital deformities: operative techniques and review of 26 patients. J Craniomaxillofac Surg; 23(2):81–90. Haug RH, Bradrick JP, Morgan JP (1997) Complications in the treatment of midface fractures. Kaban LB, Pogrel MA, Perrot DH (eds), Complications in Oral and Maxillofacial Surgery. Philadelphia: WB Saunders, 147–163. Hendrickson M, Clark N, Manson PN, et al

(1998) Palatal fractures: classification, patterns, and treatment with rigid internal fixation. Plast Reconstr Surg; 101(2):319–332. Hernandez Altemir F (1986) The submental route for endotracheal intubation. J Maxillofac Surg; 14(1):64–65. Hollier LH, Thornton J, Pazmino P, et al

(2003) The management of orbitozygomatic fractures. Plast Reconstr Surg; 111(7):2386–2393. Jackson IT (1989) Classification and treatment of orbitozygomatic and orbitoethmoid fractures. The place of bone grafting and plate fixation. Clin Plast Surg; 16(1):77–91. Jaquiéry C, Aeppli P, Cornelius CP, et al

(2007) Reconstruction of orbital wall defects: critical review of 72 patients. Int J Oral Maxillofac Surg; 36(3):193–199. Klotch DW, Gilliland R (1987) Internal fixation vs. conventional therapy in midface fractures. J Trauma; 27(10):1136–1145. Knize DM (1995) A study of the supraorbital nerve. Plast Reconstr Surg; 96(3):564–569.

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Kunz CN, Sigron GR, Jaquiéry C (2012)

Markowitz BL, Manson PN, Sargent L, et al

Putterman AM, Stevens T, Urist MJ (1974)

Functional outcome after non-surgical management of orbital fractures – the bias of decision-making due to defect size: critical review of 48 patients. Br J Oral Maxillofac Surg. (submitted) Lee CH, Lee C, Trabulsy PP, et al (1998) A cadaveric and clinical evaluation of endoscopically assisted zygomatic fracture repair. Plast Reconstr Surg; 101(2):333–345. Le Fort R (1901) Etude expèrimentale sur le fractures de la machoire supèrieure. Rev Chir; 23:201, 360, 479.

(1991) Management of the medial canthal tendon in nasoethmoidal fractures: the importance of the central fragment in classification and treatment. Plast Reconstr Surg; 87(5):843–853. Marx RE (1994) Clinical application of bone biology to mandibular and maxillary reconstruction. Clin Plast Surg; 21(3):377–392. Mast G, Ehrenfeld M, Cornelius CP (2012) [Maxillofacial fractures: midface and internal orbit; Part 2: therapeutic options]. Unfallchirurg; 115(2):145–164. German. Mathog RH, Hillstrom RP, Nesi FA (1989) Surgical correction of enophthalmos and diplopia: a report of 38 cases. Arch Otolaryngol Head Neck Surg; 115(2):169–178. Michelet FX, Deymes J, Dessus B (1973) Osteosynthesis with miniaturized screwed plates in maxillo-facial surgery. J Maxillofac Surg; 1(2):79–84. Moss CJ, Mendelson BC, Taylor GI (2000) Surgical anatomy of the ligamentous attachments in the temple and periorbital regions. Plast Reconstr Surg; 105(4):1475–1490. Ng M, Saadat D, Sinha UK (1998) Managing the emergency airway in Le Fort fractures. J Craniomaxillofac Trauma; 4(4):38–43. Noffze MJ, Tubbs RS (2011) René Le Fort 1869-1951. Clin Anat; 24(3):278–281. Patel PC, Sobota BT, Patel NM, et al (1998) Comparison of transconjunctival versus subciliary approaches for orbital fractures: a review of 60 cases. J Craniomaxillofac Trauma; 4(1):17–21. Pearl RM (1987) Surgical management of volumetric changes in the bony orbit. Ann Plast Surg; 19(4):349–358. Perrot DH (1997) Complications associated with the use of rigid internal fixation in maxillofacial surgery. Kaban LB, Pogrel MA, Perrot DH (eds), Complications in Oral and Maxillofacial Surgery. Philadelphia: WB Saunders, 223–235. Peter H, Freihofer M (1980) Experience with transnasal canthopexy. J Maxillofac Surg; 8(2):119–124. Philipps JH, Gruss JS, Wells MD, et al (1991) Periosteal suspension of the lower eyelid and cheek following subciliary exposure of facial fractures. Plast Reconstr Surg; 88(1):145–148. Pollock RA (1992) Nasal trauma: pathomechanics and surgical management of acute injuries. Clin Plast Surg; 19(1):133–147. Posnick JC, Goldstein JA, Clokie C (1992) Advantages of the postauricular coronal incision. Ann Plast Surg; 29(2):114–116. Prein J, Hammer B (1988) Stable internal fixation of midfacial fractures. Facial Plast Surg; 5(3):221–230.

Nonsurgical management of blow-out fractures of the orbital floor. Am J Ophthalmol; 77(2):232–239.

Linnau KF, Stanley RB Jr, Hallam DK, et al

(2003) Imaging of high-energy midfacial trauma: what the surgeon needs to know. Eur J Radiol; 48(1):17–32. Luce EA (1992) Developing concepts and treatment of complex maxillary fractures. Clin Plast Surg; 19(1):125–131. Luhr HG (2000) [The development of modern osteosynthesis]. Mund Kiefer Gesichtschir; 4 Suppl 1:84–90. German. Luhr HG (1988) A micro-system for cranio-maxillofacial skeletal fixation. Preliminary report. J Craniomaxillofac Surg; 16(7):312–314. Luhr HG (1987) Vitallium Luhr systems for reconstructive surgery of the facial skeleton.Otolaryngol Clin North Am; 20(3):573–606. Review. Manson P (1999) Computed tomography use and repair of orbitozygomatic fractures. Arch Facial Plast Surg; 1(1):25–26. Manson PN, Clark N, Robertson B, et al

(1999) Subunit principles in midface fractures: the importance of sagittal buttresses, soft-tissue reductions, and sequencing treatment of segmental fractures. Plast Reconstr Surg; 103(4):1287–1306; quiz 1307. Manson PN, Clifford CM, Su CT, et al (1986) Mechanism of global support and posttraumatic enophthalmos, I: the anatomy of the ligament sling and its relation to intramuscular cone orbital fat. Plast Reconstr Surg; 77(2):193–202. Manson PN, Crawley WA, Yaremchuk MJ, et al (1985) Midface fractures: advantages

of immediate extended open reduction and bone grafting. Plast Reconstr Surg; 76(1):1–10. Manson PN, Glassman D, Van der Kolk C, et al (1990) Rigid stabilization of sagittal

fractures of the maxilla and palate. Plast Reconstr Surg; 85(5):711–717. Manson PN, Markowitz B, Mirvis S, et al (1990) Toward CT-based facial

fracture treatment. Plast Reconstr Surg; 85(2):202–214. Manson PN, Shack RB, Leonard LG, et al

(1983) Sagittal fractures of the maxilla and palate. Plast Reconstr Surg; 72(4):484–489.

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(2001) Experimental trauma to the malar eminence: fracture biomechanics and injury patterns. Otolaryngol Head Neck Surg; 125(4):351–355. de Roche VR, Kuhn A, de Roche-Weber P, et al (1996) [Development of a resorbable

implant: experimental reconstruction of the orbits with polylactate membranes. Animal model and preliminary results]. Handchir Mikrochir Plast Chir; 28(1):28–33. German. Rohner D, Tay A, Meng CS, et al (2002) The sphenozygomatic suture as a key site for osteosynthesis of the orbitozygomatic complex in panfacial fratures: a biomechanical study in human cadavers based on clinical practice. Plast Reconstr Surg; 110(6):1463–1471. Romano JJ, Iliff NT, Manson PN (1993) Use of Medpor porous polyethylene implants in 140 patients with facial fractures. J Craniofac Surg; 4(3):142–147. Romano JJ, Manson PN, Mirvis SE, et al

(1990) Le Fort fractures without mobility. Plast Reconstr Surg; 85(3):355–362. Rudderman RH, Mullen RL (1992) Biomechanics of the facial skeleton. Clin Plast Surg; 19(1):11–29. Sargent LA (2007) Nasoethmoid orbital fractures: diagnosis and treatment. Plast Reconstr Surg; 120(7 Suppl 2):16S–31S. Schilli W, Ewers R, Niederdellmann H

(1981) Bone fixation with screws and plates in the maxillo-facial region. Int J Oral Surg; 10(suppl 1):329–332. Stanley RB (1999) Use of intraoperative computed tomography during repair of orbitozygomatic fractures. Arch Facial Plast Surg; 1(1):19–24. Stanley RB, Sires BS, Funk GF, et al (1998) Management of displaced lateral orbital wall fractures associated with visual and ocular motility disturbances. Plast Reconstr Surg; 102(4):972–979. Stoll P, Schilli W, Joos U (1983) The stabilization of midface-fractures in the vertical dimension. J Maxillofac Surg; 11(6):248–251. Sullivan WG (1991) Displaced orbital roof fractures: presentation and treatment. Plast Reconstr Surg; 87(4):657–661. Tessier P (1972) The classic reprint: experimental study of fractures of the upper jaw. I and II. Rene Le Fort, M.D., Lille, France. Plast Reconstr Surg ; 50(5):497–506. Tessier P (1972) The classic reprint: experimental study of fractures of the upper jaw. III. René Le Fort, M.D., Lille, France. Plast Reconstr Surg; 50(5):600–605.


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(2001) C-shape extended transconjunctival approach for the exposure and osteotomy of traumatic orbitozygomaticomaxillary deformities. J Craniofac Surg; 12(6):603–607. Wolfe SA (1982) Application of craniofacial surgical precepts in orbital reconstruction following trauma and tumor removal. J Maxillofac Surg; 10(4):212–223. Wright DL, Kellman RM (2002) Craniomaxillofacial bone infections: etiologies, distributions, and associated defects. Greenberg AM, Prein J (eds), Craniomaxillofacial Reconstructive and Corrective Bone Surgery: Principles of Internal Fixation Using the AO/ASIF Technique. New York: Springer-Verlag, 76–89. Yamamoto K, Matsusue Y, Murakami K, et al (2011) Maxillofacial fractures in older

patients. J Oral Maxillofac Surg; 69(8):2204–2210. Zingg M, Laedrach K, Chen J, et al (1992) Classification and treatment of zygomatic fractures: a review of 1025 cases. J Oral Maxillofac Surg; 50:778–790.

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4.1 Frontal sinus, frontal bone, and anterior skull base

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4 Skull and skull base fractures 4.1 Frontal sinus, frontal bone, and anterior skull base

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Definition

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Imaging

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Approaches

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4 Special conditions influencing open reduction and internal fixation

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Sinus function and operative technique

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Authors Robert B Stanley, Robert M Kellman

4.1 Frontal sinus, frontal bone, and anterior skull base 1

Definition

The frontal bone provides the convex contours of the forehead, the frontal bar, and the orbital roofs (Fig 4.1-1a). The frontal bar is the thickened bone that bridges the zygomaticofrontal sutures to form the superior horizontal (transversal) buttress of the facial skeleton. It gives structure and strength to the supraciliary and glabellar areas, and serves as a platform for the thin orbital plates projecting superiorly and posteriorly to separate the anterior cranial fossa from the orbits and ethmoid sinuses (Fig 4.1-1b). Medially, the orbital plates surround the crista galli and cribriform plate of the ethmoid bone. Posteriorly, the orbital plates, in combination with the cribriform plate, abut the lesser wings and planum of the sphenoid bone to complete the anterior skull base.

The frontal sinus is an epithelial-lined cavity within the frontal bone. The anterior table of the sinus typically defines the contours of the medial brow, glabella, and lower forehead. The posterior table forms part of the anterior cranial vault, and the floor corresponds to the medial orbital roof. The sinus as a whole is variable in size and is usually divided by a thin septum into two asymmetric sinuses, each of which is drained by a separate orifice located in the posteromedial aspect of the floor (Fig 4.1-1b). The drainage orifice lies protected behind the glabellar bone and the thick maxillary process of the frontal bone, and is most often a relatively large opening directly into the frontal recess of the nose or anterior ethmoid sinus, rather than a true duct (Fig 4.1-2).

A

P S

a

b

Fig 4.1-1a–b a Anterior view of the frontal bone. The overlying frontal bar is the sturdy cornerstone of the forehead and anterior skull base. b Anterior skull base from above. The relatively thin bone of the central third separates the cranial cavity from the nose and paranasal sinuses, extending from the frontal sinus anteriorly to the optic chiasm posteriorly. Arrows indicate the outflow tracts of the frontal sinus. A = anterior ethmoid, P = posterior ethmoid, S = sphenoid sinus.

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The ethmoid sinuses are paired labyrinths of thin-walled respiratory epithelial-lined air cells, collectively referred to as sinuses, separating the nasal cavity from the orbits. These air cells open through many small orifices into the middle and superior meatus of the nose. The roof (fovea ethmoidalis) of an ethmoid sinus corresponds to the floor of the anterior cranial fossa adjacent to the cribriform plate. The olfactory bulbs and tracts are in close contact to the cribriform plate, and the dura is tightly adherent to bone in the olfactory groove. Underlying the cribriform plate is the olfactory mucosa of the upper nasal cavity. Any fracture of the frontal bone may involve one or more walls of the frontal sinus, thus creating frontal sinus (wall) fractures. Extension of the fracture into or beyond the ethmoid sinuses and cribriform plate creates a frontobasilar fracture, a distinctly different and more complex injury.

2

Imaging

Plain skull x-rays may be of value in screening for fracture lines in the frontal bone or for air–fluid levels in the frontal sinus, but they provide insufficient information for definitive diagnosis and treatment planning. Thin-section axial and coronal (direct or reformatted) computed tomographic (CT) scans are required for accurate documentation of frontal, frontal sinus, and frontobasilar fractures following forehead trauma. Unfortunately, due to the ethmoid air cells surrounding the drainage orifices of the frontal sinus, the sensitivity and specificity of even high-resolution scans is insufficient to allow precise identification of each orifice and evaluation of the extent of injury. CT scans may suggest but do not provide direct evidence of potential outflow obstruction that could lead to infectious complications.

Superior concha

Medial concha

Inferior concha

Fig 4.1-2 Sagittal section of the skull through the nose and nasal base. Arrow indicates pathway of the drainage of the frontal sinus into the frontal recess.

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3

Approaches

In the absence of a large forehead laceration immediately over the bony injury, the coronal incision is standard for access to the entire spectrum of fractures, ranging from fractures isolated to the anterior table of the frontal sinus to extensive skull base disruptions. In contrast to the limited exposure provided by smaller local incisions, the coronal approach exposes the entire frontal area. This facilitates manipulation of fracture fragments, management of the internal components of a frontal sinus injury, and entrance into the cranial cavity if repair of dural injuries is required (see Fig 3.2-5a–e , page 196). The panoramic view afforded by the coronal approach includes adjacent intact structures that can be used as starting points for a more accurate reconstruction of the gentle frontal convex contours. In theory, the coronal incision leaves a more esthetic scar as it lies behind the hairline. In men with receding hairlines, a facial scar from an incision placed in a forehead crease or above or below the brows may be preferable; however, these incisions generally result in loss of forehead and anterior scalp sensation. Occasionally, a c oronal incision can leave a very visible scalp scar in patients with shorter hair, particularly in the temporal areas, even when correctly performed. It is also more time-consuming than facial incisions. For those reasons, endoscopic brow-lifting instrumentation and techniques have been adapted to repair injuries for which a coronal incision might seem excessive. The operative field is viewed endoscopically through small incisions placed behind the hairline, and reduction

and fixation is accomplished percutaneously through small stab incisions over the fractures, or the fracture depression is camouflaged using an onlay implant (solid or moldable). This type of approach appears suitable for treatment of fractures limited to the anterior table of the frontal sinus. Management of the internal components of a frontal sinus fracture requires removal of the anterior table, either through elevation of depressed fragments or osteotomies of intact segments (Fig 4.1-3). Ideally, periosteal attachments are maintained, but this is usually neither possible nor even necessary for the survival of larger pieces of bone that are later repositioned. Smaller fragments can be replaced with bone grafts. Entrance into the cranial cavity for repair of dural injuries adjacent to the posterior table of the sinus can be accomplished by removing the relatively thin posterior table of the sinus. Additional osteotomies through the superior orbital rims, orbital roofs, and nasal bones, and removal of these segments, provide direct access to the floor of the anterior cranial fossa for repair of deeper injuries without the need for brain retraction. This subcranial approach provides access equivalent to a limited frontal craniotomy and allows evaluation and treatment of adjacent dural and parenchymal injuries. The approach can be easily converted to a formal frontal craniotomy if the injuries are found to extend over the convexities of the frontal lobes. Repair of frequently associated nasoorbitoethmoid (NOE) fractures is also facilitated by direct access to the internal aspects of the medial canthal attachments.

Fig 4.1-3 The anterior table of the sinus has been removed to expose the posterior table. The central third of the anterior skull base can then be exposed by gradual removal of the posterior table and block removal of the outlined segment of frontal bar, nasal bones, and medial orbits.

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4 Special conditions influencing open reduction and internal fixation

Factors to be considered when evaluating the need for repair of frontal injuries fall into the following categories: Loss of convex bony contours: External appearance soon after trauma may be inconsistent with the actual severity of fractures of the frontal bone, frontal sinus, and anterior skull base. Edema of the forehead and brow-area soft tissues may mask depressed fractures of the supraorbital ridges and anterior wall of the frontal sinus in particular. The surgeon must relate the amount of bony displacement seen on the CT scan to the flattening that will occur in these areas if the fractures are not realigned. In general, early open reduction and fixation is preferable to more complex delayed reconstructions that invariably involve osteotomies and bone grafting. A possible exception to this is an isolated, mildly depressed anterior table fracture that may or may not lead to noticeable forehead flattening. This type of defect should be amenable to delayed recontouring with an onlay graft, placed through either an open or endoscopic approach, if required. Internal derangement of the frontal sinus: The typical frontal sinus orifice is, unless severely injured, large enough to maintain adequate drainage function during the acute phase of the injury, and subsequent cicatricial narrowing should not cause delayed dysfunction. This natural safety factor may explain the low incidence of reported infectious complications following both untreated and treated frontal sinus injuries. Unfortunately, the response of each orifice to trauma cannot be predicted, and the immediate proximity of the sinus to the orbit and cranial cavity means infection within the injured sinus wich may quickly lead to disastrous neurological complications. Fracture patterns most likely to involve the floor of the sinus, and thus one or both orifices, include anterior table fractures with accompanying impacted supraorbital rim or NOE fracture, and comminuted frac-

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tures of both the anterior and posterior tables. A fracture line in the posterior table is not an absolute indication for surgery unless it is displaced, or there are associated intracranial findings. Endoscopic evaluation of the orifices and posterior table by way of a small frontal sinus trephination may be helpful in cases with borderline indications for open repair. Intracranial injuries: Pneumocephalus is often seen adjacent to fractures of the posterior table and anterior skull base. Although it does raise suspicion of a dural injury, pneumocephalus adjacent to a nondisplaced posterior table fracture does not demand surgery unless, in the unlikely event, serial CT scans fail to document resolution. In the absence of other indicators for surgery, a cerebrospinal fluid (CSF) leak through the frontal sinus is very unusual. Progressive pneumocephalus and CSF leaks are more likely to accompany fractures of the fovea ethmoidalis and cribriform plate, where the tight adherence of the dura to bone can lead to large tears with relatively small fracture displacements. These skull base injuries usually connect with posteriorfractures. Concurrent repair can be performed by way of an open approach through the frontal sinus, or via a subcranial approach if access back to the planum sphenoidale and optic canals is required. In very select cases where observation of the frontal sinus is appropriate, small to medium-sized defects in the skull base can be repaired using transnasal endoscopic techniques. Subdural and epidural bleeding in themselves should not effect the need for or type of repair of an injured frontal sinus. Indeed, an urgent frontal craniotomy may violate a sinus by adding the equivalent of a displaced posterior table fracture to traumatic injuries that may have otherwise been observed or treated less aggressively. Associated maxillofacial injuries: A properly aligned frontal bar is required before reduction and fixation of fractures of the zygomas, orbits, NOE complex, and maxilla can be undertaken.


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5

Sinus function and operative technique

It is generally agreed that depressed fractures limited to the anterior table of the sinus can be managed without concern for future obstruction of the drainage system, assuming that the sinus has been irrigated clear of debris (Fig 4.1-4a–b). Debate begins when anterior wall fractures are accompanied by a supraorbital rim or NOE fracture, and visual inspection at the time of repair of these fractures confirms injury of one or both orifices (Fig 4.1-4c–d). Most surgeons feel compelled at this point to treat the drainage system injury in order to prevent future episodes of sinusitis that would necessitate a second open surgery. Stenting has been favored by some, in the belief that sinus function can be preserved. However, lack of long-term success of stenting in cases of outflow obstruction due to chronic inflammatory disease has led many surgeons to avoid the use of stents to treat an acute injury. Instead, the trend has been to eliminate the sinus with an obliteration procedure. All vestiges of mucosa

are removed from the sinus with a high-speed drill and progressively smaller burrs, and the orifices are occluded with muscle, fascia, or contoured bone grafts. The sinus is then filled with fat, cancellous bone chips, or a pedicled flap of pericranial tissue. Success with hydroxyapatite cement has also been reported, but its use in a potentially contaminated field remains controversial. Some have advocated leaving the sinus to obliterate itself through osteoneogenesis. An appealing but so far unproven alternative for compliant patients with no evidence of a posterior table fracture has emerged with the advances in transnasal endoscopic sinus surgery, which has proven to be very effective in the treatment of chronic frontal sinus disease. The surgeon can now perform the necessary reduction and fixation of the fractures and manage the injury to the drainage system expectantly with follow-up CT scans, knowing that the few cases of outflow obstruction that will develop can be treated endoscopically rather than with an open procedure.

a

b

c

d

Fig 4.1-4a–j Injury patterns and recommended treatment. a A displaced fracture limited to the anterior table should not affect sinus outflow. b Reconstruction and fixation of the anterior sinus wall with non-load-bearing material. c An accompanying NOE fracture predisposes to outflow obstruction. d In case of outflow obstruction, sinus obliteration is the preferred option.

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Characteristic of most fractures involving the anterior and posterior table of the frontal sinus are comminution with displacement of the bone fragments of both tables, and extension across the floor of the sinus damaging the drainage orifices (Fig 4.1-4e–f ). Despite the increased risk of intracranial spread should infection occur in the sinus, some surgeons have again advocated reconstruction of the sinus walls and stenting of the orifices in order to preserve sinus function. Most surgeons, however, now choose to eliminate the sinus with either an obliteration procedure or cranialization of the sinus. The sinus is obliterated as previously described if the posterior table fragments are sufficiently intact to be easily realigned, and there are no underlying dural lacera-

f

e

CSF PF

g

h

tions that require repair. The sinus is cranialized if the posterior wall is severely fragmented, or the presence of CSF in the sinus signals a need to inspect and repair the dura (Fig 4.1-4g–h). Cranialization differs from obliteration in that the posterior table is removed so that the once epitheliallined sinus cavity becomes part of the intracranial cavity. The new intracranial space is left to be filled by fibrous tissue and expansion of the frontal lobes —a process that may take several months. Therefore, a pedicled flap of pericranium should be rotated intracranially to reinforce the occlusion of the drainage orifices and the dural repairs. Cranialization of the sinus is also a key component of the subcranial approach to more extensive skull base injuries (Fig 4.1-4i–j).

Fig 4.1-4a–j (cont) Injury patterns and recommended treatment. e Combined anterior and posterior table fractures also predispose to outflow obstruction. f Obliteration is the preferred option if the posterior table is relatively intact and there is no evidence of a dural injury. g When the posterior table is comminuted, as often seen with an accompanying NOE fracture, the dura will usually be lacerated and a cerebrospinal fluid (CSF) fistula may develop. h The posterior table fragments should be removed to allow repair of the lacerations and cranialization of the sinus. A pericranial flap (PF) enhances the seal of the floor of the sinus. i The subcranial approach should be considered for more extensive injuries with disruption of the central third of the anterior skull base. j A pericranial flap (PF) is essential for reinforcement of fascial grafts used to repair the dura and bone grafts covering the skull base defect.

PF

i

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6


Once the fracture fragments have been realigned, edge-toedge contact and the convex contours of the forehead and supraorbital ridges can be maintained with plates and screws from the 1.0, 1.3, or corresponding Matrix systems (Fig 4.1-5). Restoration of the convexities will produce a self-reinforcing reconstruction adequate to resist the physiological loads that are transmitted to the frontal bar. Thicker miniplates are more likely to be outlined under the forehead skin and are unnecessary from a biomechanical point of view, even when the frontal bone reconstruction is part of the overall repair of a panfacial injury. It is also unnecessary to use long screws that penetrate beyond the diploic space of the frontal bone. Small bone fragments are difficult to stabilize, even with very small plates, and may be quickly lost to resorption. Small bone fragments therefore should be replaced by cranial bone grafts to facilitate placement of the plates and screws, and provide a more substantial scaffolding to maintain soft-tissue position during remodeling and new bone formation. Alternatively, comminuted fractures of the anterior wall of the frontal sinus can be reconstructed using titanium mesh, possibly reducing the need for bone grafts. Fixation of posterior table fractures is usually not performed. If the posterior table injury allows for an obliteration pro-

cedure, exact edge-to-edge realignment of large bone fragments is not mandatory. Displacement that allows for insertion of a malleable retractor just under the thin bone actually lessens the chances of an iatrogenic injury of the dura during removal of the mucosa adjacent to the fracture lines with high-speed burrs. The material then used to obliterate the sinus will stabilize the fragments until fibrosis or new bone formation closes the gap. Fibrosis can be enhanced in a sinus obliterated by fat if a fascial graft is applied over the posterior wall injuries. Fixation is also not usually required when bone grafts are used to bridge defects of the cribriform plate and fovea ethmoidalis. The subcranial approach should provide exposure adequate to create opposing ledges of the orbital plates of the frontal bone and planum sphenoidale that will support the grafts. The bone grafts support a fascial graft or, preferably, a pedicled pericranial flap that actually seals the skull base under pressure from the frontal lobes. Fibrin glue may also be used to hold the flap in place in the early postoperative period. Fixation is required to maintain the shape of the orbit if the orbital plate is fragmented and unstable. Large in-situ fragments or grafts can be cantilevered from the frontal bar with the 1.3 system, or plates 1.5 and screws if the bridging segment extends all the way to the posterior orbit. The uppermost level of the convexity of the orbital roof must be restored to prevent downward displacement of the globe (Fig 4.1-6a-b).

a

Fig 4.1-5 Reconstruction of the lower forehead and NOE complex. Small miniplates are particularly useful in the glabellar and frontonasal areas where surface to apply the plates might be limited.

b

Fig 4.1-6a–b a The orbital roof is convex superiorly behind the frontal bar. Bone grafts used to reconstruct the roof must remain tangential to the convexity to prevent downward displacement of the globe. b Bone grafts are cantilevered in an arched configuration to maintain the convexity.

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7


Because of the proximity to the nasal cavity, fractures that extend into the frontal sinus or central area of the anterior skull base are considered by most surgeons to be contaminated. Therefore, a therapeutic course of an intravenous broad spectrum antibiotic is empirically started upon admission and continued for 3–7 days postoperatively. Surgery must be performed in a timely fashion so that infection with resistant organisms does not result from an excessively prolonged course of the antibiotic. Lumbar drains are not used routinely, in an attempt to limit the duration of postoperative CSF leaks. However, a drain should be considered when extensive loss of skull base bone in a specific area indicates a tenuous reconstruction in the presence of profuse CSF rhinorrhea. An example of this would be the posterior orbit/planum sphenoidale where even with fibrin glue a seal might not be obtainable without excessive pressure from the bone grafts and pericranial flap on the optic nerves and chiasm.

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Early postoperative wound infections are uncommon in correctly managed cases, even when multiple nonvascularized grafts are placed. A CSF leak is the most likely early complication to be seen, occurring in up to 10% of patients with frontobasilar fractures. Management should be with a lumbar drain for 7–10 days before re-exploration is considered. Most leaks are through the skull base rather than the frontal sinus, and may be amenable to transnasal endoscopic repair if the site of the leak is small and definitely identified to be through the cribriform plate, fovea ethmoidalis, or planum sphenoidale. Postoperative meningitis occurs less frequently, and may or may not be related to a predisposing CSF leak. Delayed postoperative complications, though known to occur years later and therefore frequently unknown to the original surgeon, are relatively uncommon. Most are related to the obstruction of a drainage orifice in a frontal sinus that was preserved, or ingrowth of mucosa from the frontal recess through an inadequately occluded orifice into a sinus that was obliterated. A mucocele or mucopyocele with pressure symptoms or perhaps chronic infection may develop in the sinus and require reoperation. Only rarely do these delayed infections spread intracranially, but the potentially fatal consequences of such spread emphasize the need for appropriate initial management. Failure to permanently occlude an orifice during a cranialization procedure creates a direct opening from the frontal recess into the cranial cavity. All patients must understand that they are at lifelong risk of delayed complications following any procedure to treat frontal sinus and frontobasilar fractures.


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4 Skull and skull base fractures 4.2 Lateral skull base fractures

1

Introduction

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2

Definitions

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2.1 Anatomy of the lateral skull base

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2.2 Demographics of temporal bone injury

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2.3 Accompanying injuries

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2.4 Classification of temporal bone fractures

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3

Imaging

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Treatment strategies and approaches

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Preoperative and postoperative treatment

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6

Conclusion

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Authors Douglas J Colson, Robert M Kellman

4.2 Lateral skull base fractures

1

Introduction

Fractures of the lateral skull base have long challenged surgeons dealing with the management of facial nerve injuries. In addition to the facial nerve, the temporal bone contains the vestibular and cochlear nerves, the complex structures of the inner and middle ear, as well as critical vascular and nerve structures. Management of lateral skull base fractures requires a particularly careful approach.

2

Definitions

2.1 Anatomy of the lateral skull base

The lateral skull base includes the greater wing of the sphenoid and the temporal bone. The rich and complex neurovascular content of the lateral skull base and temporal bone are the reason for morbidity associated with trauma to this region. The lateral skull base foramina and their respective contents include: the foramen lacerum and carotid canal with the internal carotid artery and nerve plexus, the foramen ovale and the mandibular nerve (CN V3), the foramen spinosum and the middle meningeal vessels, the foramen rotundum and the maxillary nerve (CN V2), and the pterygoid canal through which passes the vidian nerve and artery (Fig 4.2-1). Also intimate with the lateral skull base are cranial nerves III through XII and vascular structures including the sigmoid sinus and jugular bulb. The muscular attachments to the lateral skull base include the temporalis, medial and lateral pterygoids, masseter, digastric, sternocleidomastoid, tensor and levator veli palatini, strap muscles of the neck, and the paraspinal muscles of the neck.

Optic canal Foramen rotundum Foramen ovale Foramen spinosum Foramen lacerum External acoustic meatus Jugular foramen

Fig 4.2-1 Skull base and most important foramina.

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The temporal bone is composed of the squamous, mastoid, tympanic, and petrous portions, and the styloid process. Contained within the temporal bone are the vestibulocochlear apparatus, the facial nerve, the ossicular chain, the endolymphatic sac, and the origin of the eustachian tube. Injury to the facial nerve can cause significant morbidity (Fig 4.2-2). The facial nerve passes from the brainstem into the temporal bone, entering through the internal auditory canal. The nerve courses through the meatal segment (8– 10 mm) and the labyrinthine segment (2–4 mm) to the geniculate ganglion. At this point it turns into the tympanic or horizontal segment (11 mm). It then courses to the second genu where it turns again, becoming the mastoid or vertical segment (12–14 mm) which exits at the stylomastoid foramen. The intermediate nerve, which travels with the facial nerve, provides branches which include the chorda tympani and greater and lesser superficial petrosal nerves. The geniculate ganglion is the most common site of traumatic injury to the facial nerve.

Facial nerve

Geniculate ganglion

2.2 Demographics of temporal bone injury

Causes of temporal bone injuries include motor vehicle accidents (MVA), all-terrain vehicle accidents, motorcycle accidents, bicycle accidents, falls, assault, gunshot wounds, equestrian accidents, sports injuries, and others. The peak age for temporal bone injury is 21–30 and there is a 3:1 male to female preponderance. Pediatric temporal bone fractures occur most commonly due to MVA, falls, bicycle accidents, and blows to the head, with bimodal age distribution peaks at age 3 and 12. 2.3 Accompanying injuries

Any of the contents of the lateral skull base and temporal bone can be injured by trauma to this region. Otological complications following lateral skull base fractures include deafness (24–42%), vertigo (20%), cerebrospinal fluid (CSF) otorrhea (18%), facial nerve palsy (4–7%), tinnitus (2%), and chorda tympani dysfunction (2%). The most common surgically correctable lateral skull base fracture complication is thought to be ossicular discontinuity, with the most com-

Trigeminal nerve

Trigeminal ganglion Ophtalmic nerve Maxillary nerve Mandibular nerve

Chorda tympani Lingual nerve

Stylohyoid muscle Digastric muscle Fig 4.2-2 Course of the facial nerve (VII) within the petrous portion of the temporal bone and its relation to the inner ear.

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mon site of injury being the incudostapedial joint. Fractures involving the otic capsule are more commonly associated with sensorineural hearing loss (100%), facial nerve injury (48%), and CSF fistula (31%) than otic sparing fractures. However, sensorineural hearing loss may be seen in extra labyrinthine fractures due to cochlear concussion, disruption of the membranous labyrinth not seen on imaging, or intralabyrinthine hemorrhage seen as hyperintensity on T-1 weighted MRI. In Brodie’s review of 820 temporal bone fractures, 24% sustained hearing loss (21% conductive hearing loss, 57% sensorineural, 22% mixed). Facial paralysis was seen in 7%, and was immediate (27%) or delayed (73%). Complete paralysis was seen more frequently in patients with immediate weakness (47%) than delayed weakness (22%). All patients with incomplete paralysis and 97% of the patients with delayed onset paralysis had complete recovery. CSF fistulas may manifest as otorrhea, rhinorrhea, or both. Most CSF fistulas close spontaneously within 9 days (78%). The incidence of meningitis increases with CSF leaks that persist longer than 7 days. Benign paroxysmal positional vertigo (BPPV) is a well-described entity known to occur following trauma. Therapeutic maneuvers such as the Epley maneuver have been shown to be successful in the management of most cases of BPPV. Epley and modified Epley maneuvers are sequential physiotherapeutic measures to reposition otolithic debris. Other causes of posttraumatic vertigo include traumatic perilymphatic fistula and posttraumatic Ménière’s disease.

Acute intracranial complications that may accompany temporal bone trauma include cerebral midline shift, subarachnoid hemorrhage, subdural hemorrhage, cerebral edema, ipsilateral and contralateral temporal lobe contusion, and often require emergent neurosurgical management. Internal carotid artery injuries as a result of blunt head trauma are unusual. They occur typically due to shearing forces anywhere along the length of the vessel, and include dissection, intimal tear, spasm, thrombosis, occlusion, transaction, dissecting aneurysm, pseudoaneurysm, arteriovenous fistula, and carotid-cavernous fistula. Massive bleeding may require packing and angiography with embolization or common carotid ligation with middle fossa craniotomy to control back bleeding. Pediatric injuries have a higher incidence of hearing loss and intracranial complications. Facial nerve injuries, however, are less common in pediatric trauma. Penetrating temporal bone injury, as seen in gunshot wounds, carries an increased risk of life-threatening vascular compromise. Vessels at risk from gun shot wounds involving the lateral skull base include the facial artery, lingual artery, internal maxillary artery, superficial temporal artery, vertebral artery, jugular vein, and internal carotid artery. Angiography should be included in the evaluation of penetrating injuries to this region, and embolization may be useful in the stabilization and management of these injuries.

Posttraumatic cholesteatoma is another well described complication of temporal bone fracture that may occur even later than 10 years after the incident. Periodic long-term follow-up may be useful in monitoring for this complication.

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2.4 Classification of temporal bone fractures

Traditional classifications of temporal bone fractures describe the relationship of the fracture to the petrous ridge and otic capsule: longitudinal (Fig 4.2-3a–d), transverse, and mixed (Fig 4.2-4). Early reviews described longitudinal fractures as the most common type (70–90%). These tend to occur secondary to a temporal or parietal blow and run along the length of the petrous pyramid anterior to the labyrinthine capsule and are often associated with tympanic membrane

a

b

perforation, external auditory canal skin rupture, and ossicular chain disruption. Facial nerve injury occurs in 10– 20%. Transverse fractures are less common (10–30%) and occur from a frontal or parietal blow and course perpendicular to the long axis of the petrous pyramid, passing through the labyrinthine capsule. They are associated with sensorineural hearing loss, vertigo, nystagmus, and facial nerve injury in up to 50% of cases.

c

d

Fig 4.2-3a–d Head CT of patient with a right longitudinal temporal bone fracture and delayed onset, incomplete right facial palsy. The fracture line involved (a) the glenoid fossa, (b) the external auditory canal, and (c) the middle ear space, and it approximated but did not violate the otic capsule (d).

Fig 4.2-4 Temporal bone CT of patient showing a complex temporal bone fracture with both longitudinal (short arrow) and transverse (long arrow) components.

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Recently, new efforts at classification of temporal bone injuries have looked to modify the classification of fractures into groups with greater clinical significance. Studies comparing high resolution computed tomography (HRCT) of the temporal bone and clinical course have found little correlation between the traditional classifications of fractures and patient complications. Kelly and Tami proposed a temporal bone fracture categorization system based upon the status of the otic capsule. Yanagihara et al describe a classification system based upon 97 fractures evaluated with surgical exploration: Yanagihara types 1–4. Type 1 (6%) fractures traverse the mastoid process. They do not involve the facial canal. Type 2 fractures (43%) cross the mastoid process into the external auditory canal; they involve the vertical portion of the facial nerve. Type 3 fractures (18%) include a type 2 that extends to the pyramidal or horizontal portion of the facial nerve. Type 4 (31%) fractures extend through the tegmen, the antrum, the facial nerve between labyrinthine segment and horizontal segment, and cross the geniculate ganglion. Type 4A fractures spare the inner ear and internal auditory canal while type 4B fractures, traditionally a transverse fracture, violate either structure. Yanagihara felt that this grading system, when compared to the traditional system, more accurately correlated fracture type with associated injuries, complications, and intraoperative findings. Dahiya et al reviewed 90 patients with temporal bone fractures and found that when compared to fractures that spare the otic capsule, fractures that violate the otic capsule are more frequently associated with facial paralysis (2x), CSF leaks (4x), profound hearing loss (7x), and intracranial complications such as epidural hematoma and subarachnoid hemorrhage. Subsequently, Ishman and Friedland reviewed CT scans of 148 temporal bone fractures and found that the traditional classification system showed poor prediction of facial nerve weakness, CSF fistulas, and hearing loss. However, facial nerve injuries and CSF leaks were significantly more prevalent in fractures that involved the petrous bone than in nonpetrous bone fractures, and conductive hearing loss was more common in the nonpetrous fractures involving the middle ear.

3

Imaging

Lateral skull base trauma is most frequently seen in patients with significant, often life-threatening, concurrent injuries. Work-up of the lateral skull base injury must often wait until primary assessment and resuscitation have been completed. Evaluation of these injuries begins with a history, often limited, and physical examination. Signs and symptoms of lateral skull base injuries may include neuropathy of cranial nerves III–XII, hematotympanum, bleeding from the external auditory canal, tympanic membrane perforation, otorrhea, rhinorrhea, hearing loss (sensorineural or conductive), horizontal nystagmus with the fast phase toward the uninjured ear, or postauricular ecchymosis (Battle’s sign). Battle’s sign is thought to be due to mastoid emissary vein rupture or extravasation of blood along the postauricular artery. In patients with suspected lateral skull base injury, additional evaluation may include imaging, electrodiagnostics, vestibular testing, and audiometrics. Audiometric evaluation at the initial evaluation, from tuning fork examinations to audiogram, can help determine the nature of hearing loss and extent of temporal bone injury. With conductive hearing loss, the most common injury is middle ear hemorrhage, and follow-up audiometry at 6–7 weeks after injury can help differentiate hemorrhage from ossicular chain injury. Auditory brainstem response studies in the initial evaluation may also provide complementary information on neurootologic integrity. The most commonly used electrodiagnostic test for evaluation of acute facial paralysis is electroneurography (ENOG). Maximum electrically evoked stimulus with amplitude measurement of facial muscle compound action potential allows for objective calculation of neural degeneration through comparison of the affected and unaffected sides of the face. Most authors agree that degeneration of greater than 90– 95% seen on ENOG is associated with a greater amount of neurotmesis and subsequent Wallerian degeneration and, therefore, a decreased possibility of favorable recovery. Electromyography (EMG), with evidence of voluntary action potentials versus fibrillation potentials, may provide additional information on the status of an injured nerve when performed three weeks after the onset of complete facial paralysis.

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The development of HRCT and enhanced MRI has allowed precise localization and description of lateral skull base and temporal bone injuries. The use of these studies in the evaluation of patients with these injuries remains somewhat controversial. Some authors report that temporal bone CT is important in diagnosis and treatment plan development while others question the clinical utility of routine temporal bone imaging. Kahn et al reviewed 105 patients with clinical suspicion for temporal bone injury and subsequent HRCT and found poor correlation between CT findings and clinical course or management decision. They recommended the selective use of HRCT to complement decision making when surgery is planned, clinical examination is unreliable, or the clinical course is unusual. HRCT has been shown to identify temporal bone injuries that may be obscured by more serious neurological injury and to identify occult vascular injuries such as carotid canal fracture. In a prospective review of 350 consecutive patients with head trauma evaluated with HRCT, Exadaktylos et al found that of the 38 fractures identified on imaging, 12 were missed on clinical examination. In light of the 12% complication rate seen in their patients, they recommend routine HRCT in all patients with a suspicion for temporal bone injury. In patients where surgical intervention is warranted, authors agree that imaging is useful in preoperative planning. HRCT and MRI have been shown to be useful in identifying ossicular injury in patients with conductive hearing loss, localization of the site of nerve injury in patients with facial paralysis, and in identifying concomitant intracranial injury helping the surgeon tailor the timing and nature of surgical intervention.

4

Treatment strategies and approaches

Indications for surgery

After reviewing literature on traumatic facial nerve injury, Chang and Cass proposed the following algorithm for management of facial nerve injury due to temporal bone trauma. Facial nerve injury that is delayed in onset should be observed because of the excellent prognosis for normal to nearnormal recovery seen in this group. Patients with acute onset of incomplete facial injury which, with observation, does not progress to complete paralysis should also be observed and complete recovery is expected. Patients with acute onset of complete paralysis or acute onset of incomplete injury which progresses to complete paralysis should receive serial ENOG until greater than 95% degeneration within 14 days from injury is seen, qualifying this group for surgical exploration. Otherwise, observation is recommended with a good outcome expected. Subsequent authors have made similar recommendations. After review of 115 patients with traumatic facial paralysis, 65 of which were treated surgically, Darrouzet et al recommended surgery for patients with total paralysis of immediate onset and evidence of denervation seen on EMG. Nosan et al prospectively followed 35 patients with temporal bone fracture associated facial paralysis and recommended surgery for patients with greater than 90% degeneration seen on ENOG, regardless of the time of onset from injury. As previously described, Brodie found that patients with delayed or incomplete paralysis rarely required surgery to obtain excellent recovery. Facial nerve decompression: approach and extent

The approach to decompress the facial nerve and the extent of facial nerve decompression required are topics of debate that have persisted over the past 30 years. The most common site of injury to the facial nerve is the perigeniculate area, with published frequencies ranging from 66–93%, though multiple sites of injury are not uncommon. Because of this, most authors agree that extensive decompression of the nerve is usually required, though the extent and approach described by each author has varied. May described a transmastoid supralabyrinthine approach to decompressing the region of the geniculate ganglion. Fisch described utilizing a translabyrinthine approach for transverse fractures with sensorineural hearing loss and a combination transmastoid middle cranial fossa approach for longitudinal fractures with intact hearing. Most recent recommendations have been modifications of the approaches described by May and Fisch. Yanagihara found that with a modification of the technique described

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by May, a transmastoid supralabyrinthine approach with disarticulation of the incus, the geniculate ganglion could be decompressed in 36 of 41 patients, with the remaining 5 requiring a middle cranial fossa approach. Some authors have described the use of topographic tests, such as the Schirmer test, to determine if the lesion is proximal or distal to the geniculate ganglion, and tailoring the extent of the dissection based upon the site of the lesion. Pulec argued that most cases require decompression only to the cochlea riform process and described another modification of the May transmastoid supralabyrinthine approach in which the incus is left intact. This approach is combined with a middle cranial fossa or retrolabyrinthine approach if more proximal decompression is required. Chang and Cass, in their review, made the following recommendations. Since most injuries are in the perigeniculate region and proximal degeneration occurs after nerve trauma, facial nerve decompression should include the meatal foramen through the stylomastoid foramen. In patients with no residual hearing the translabyrinthine approach provides adequate access for decompression and repair. In patients with residual hearing they felt that the supralabyrinthine approach is inadequate for exposure and recommended a combined transmastoid middle cranial fossa approach. They recommended bony decompression without nerve sheath slitting, as nerve sheath slitting puts the nerve at risk of iatrogenic injury and no study has shown a benefit to this step. They recommended nerve repair only if there is total or near-total transection, with delayed repair if spontaneous nerve recovery accounting to grade 3 or 4 of the HouseBrackmann facial nerve grading system is not attained. Darrouzet described the use of a geniculectomy in facial nerve decompression. He describes the cauterization of the distal ends of the ganglionic content and proximal petrous nerves to prevent crocodile tear syndrome with errant secretory fiber regrowth within the petrous nerves. Other surgical interventions

Management of hearing loss following temporal bone injury may require surgical intervention. Conductive hearing loss following temporal bone injury is most frequently due to middle ear hemorrhage. However, conductive hearing loss of greater than 30 dB that persists longer than 6–7 weeks after injury increases the likelihood of ossicular injury and warrants exploration and repair of the ossicular chain. In cases with profound sensorineural hearing loss secondary to temporal bone fracture, cochlear implantation has been described for patients with bilateral hearing loss or hearing loss in only one ear.

Surgical intervention may be useful for the management of vertigo seen in temporal bone trauma. Benecke described the use of transmastoid labyrinthectomy in patients with vertigo following temporal bone trauma and recommended it for patients with symptoms of long duration, diagnostic testing showing peripheral and not central disease, and failed medical management. Posttraumatic perilymphatic fistulas require surgical intervention with middle ear exploration and patching of the fistula. Posttraumatic vertigo is often multifactorial and surgical intervention may have suboptimal results. Posttraumatic CSF fistulas management may also benefit from surgical intervention. Though most posttraumatic CSF fistulas close spontaneously, in those that do not close within 7–10 days there is a decreased incidence of spontaneous closure and an increased incidence of meningitis. Surgical closure is therefore recommended.

5

Preoperative and postoperative treatment

Medical management of temporal bone injuries, like many of the issues addressed above, remains controversial. This includes the use of antibiotics in patients with CSF fistulas to prevent meningitis, and the use of steroids in facial nerve injury to increase the likelihood of good recovery. Two meta-analyses looked at the efficacy of prophylactic antibiotics in temporal bone and basilar skull trauma. Villalobos et al reviewed 12 studies with 1,241 patients with basilar skull base fractures and found no reduction in meningitis with antibiotic prophylaxis, including those patients with CSF fistulas. Brodie reviewed six studies with 324 patients with posttraumatic CSF fistulas and found that none of these studies demonstrated a reduction in the incidence of meningitis with antibiotic prophylaxis. However, analysis of pooled data from these studies revealed that prophylactic antibiotic treatment significantly reduced the incidence of meningitis. The use of steroids in the treatment of incomplete or delayed facial paralysis has been described, but no study has looked at the efficacy of steroids in the management of posttraumatic facial paralysis. Based on the pathophysiology of facial nerve injury and the anti-inflammatory properties of steroids, Chang and Cass argue that a short course of steroids, being inexpensive and of minimal risk to the patient, may lead to an improved outcome in these injuries.

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6

Conclusion

Lateral skull base and temporal bone trauma complications range from subtle changes in hearing, to debilitating vertigo, to life-threatening blood loss and intracranial injury. Care for these patients requires a physician knowledgeable in the diagnosis and skilled in the management of this common and potentially complex group of injuries. Unfortunately, literature on the management of these injuries is controversial and inconclusive. Current recommendations in the literature include the following: • HRCT scans of the temporal bone may not be necessary in the diagnosis of temporal bone fractures but may be useful in surgical planning. • Traditional classifications of temporal bone fractures (longitudinal versus transverse) may yield little clinical utility. Evaluation of the otic capsule, however, may help predict complications and guide the clinical course. • Conductive hearing loss of > 30dB 7–8 weeks postinjury requires surgical evaluation of the ossicular chain. • Facial nerve paralysis that is delayed or incomplete should be observed, with good expected outcome. • CSF leaks that persist for more than 7–10 days and posttraumatic vertigo consistent with perilymphatic fistula may benefit from surgical exploration and repair. • Immediate and complete facial nerve injury with an ENOG revealing 90–95% degeneration within 14 days from injury should be treated with total nerve decompression as soon as possible. • Decompression of the meatal foramen through the stylomastoid foramen will decompress the most common site of nerve injury (perigeniculate region) and any concurrent injury sites. This may be accomplished through a translabyrinthine approach in the non-hearing ear or through a combination transmastoid and middle cranial fossa approach in the hearing ear.

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4 Skull and skull base fractures 4.3 Cranial vault fractures

1

Anatomy, fracture patterns, and pathophysiology

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2

Imaging

283

3

Treatment strategies

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Symptoms requiring operation

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Approaches

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Surgical technique including reduction

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Types o f fixation

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Side effects of treatment and complications

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Conclusion

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Author Paul N Manson

4.3 Cranial vault fractures

1

Anatomy, fracture patterns, and pathophysiology

The cranium is at first unicortical and partially cartilaginous in its vault and base, becoming bicortical in the 5–10 year age period. The frontal sinus is rudimentary until after age 10, when it begins to enlarge into the frontal bone to assume its adult shape (Fig 4.1-1a–b, page 261). Generally, depression of the frontal region may create an unpleasant cosmetic deformity. Depressed fractures are usually broader in area at the inner table than they are at the external table. Therefore, a burr hole and widening of the external table area of fracture must frequently be accomplished to free the entrapped skull fragment. A cranioplasty must then be employed to achieve a smooth skull. However, the primary consideration in depressed, closed, or open skull fractures is the brain and the meninges. Depression of the inner table more than a few millimeters has the potential to lacerate the dura, creating a cerebrospinal fluid (CSF) leak. If the fracture and the leak are in communication with the sinuses, CSF may drain into the nose or pharynx (CSF rhinorrhea). If the leak is in communication with the structures of the ear and temporal bone, otorrhea may be produced. The leak may also occur in the orbit, producing a leak into a confined, potentially closed space unless the medial (ethmoid) portion of the orbit is fractured. In that situation, the leak ultimately drains into the nose. A CSF leak may be perceived by documenting clear fluid draining from the nose or ear. Initially, the fluid may be blood tinged. When absorbed onto a paper towel, such bloody fluid produces a double ring sign with the clear fluid extending outside the blood tinged central ring. Pneumocephalus may also occur. Rarely, a “ball valve” obstruction may produce tension that builds up inside the skull from air blown inside the cranial vault by a struggling patient and a tension pneumocephalus may be produced which requires decompression in order to prevent brain compression. If a skull fracture is not repaired and has lacerated the dura, the pressure and expansion of the pulsating brain over months may be sufficient to slowly

erode the bone creating pseudogrowth of the skull fracture. This is a phenomenon which occurs in children and can be detected by follow-up x-rays at 6 months and 1 year to determine any widening of the fracture. If widening occurs, an intracranial repair of the dura is necessary. If the cortex of the brain is damaged, surgery may be indicated for debridement of dead tissue. Intracerebral hematoma or extracerebral hematoma may require evacuation if pressure is produced. The pressure may increase as the hematoma begins to dissolve due to osmotic effects of the dissolving clot. An extradural collection of blood may occur from a ruptured middle meningeal artery producing acute brain compression from extradural hematoma. Such emergent conditions require immediate operative intervention. Generally, cranial vault fractures begin in one of the skull areas and are located initially between cranial sutures, “buttresses of the skull” (Fig 4.3-1). Fractures may extend to

Fig 4.3-1 Impression fracture of lateral cranial vault.

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penetrate an adjacent anatomical area (again delineated by sutures) and the initial linear fracture then spreads in a stellate fashion, giving rise to comminution with increasing force. One- and two-area cranial vault fractures are common, such as the lateral frontal temporal orbital fracture. Occasionally, three-area skull fractures occur involving both

a

b

lateral frontal temporal orbital areas and the central region. It must be noted however, that subtle fractures may begin in the cranial base even with blows to the vault, then extend into the vault with increasing force, and then comminute the calvarium (Fig 4.3-2a–c).

c

Fig 4.3-2a–c Frontobasal fractures, type I–III. a Frontobasal fracture type I. Longitudinal fracture of the cranial base, initially paralleling the cribriform plate and extending to separate the anterior and middle fossa from the posterior fossa. b Frontobasal fracture type II. Linear fracture of the frontal bone extending into the cranial base. c Frontobasal fracture type III. Comminution of the entire frontal bone segment on the right involving the lateral and central area, along with comminution of the orbital roof and extension into the cranial base.

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2

Imaging

A complete cranial and midface CT scan including the skull vault and base, the orbits, sinuses, and the temporal bones should be obtained with both bone and soft-tissue (brain) windows. Ideally, both axial and coronal scans are necessary to detect and analyze all the fractures in different planes, and to confirm the degree of displacement and the extent of the fracture. Since the base changes in level with each slice, neither the length nor the direction of skull base fractures can be fully reflected in a single “cut” of a CT scan. Soft-tissue conditions such as extradural hematoma and pneumocephalus are detected. Depending on the degree of displacement of supraorbital fractures, the eye may be dislocated downward and forward as the supraorbital area collapses, expanding into space normally occupied by the globe. Isolated fractures of the orbital roof can occur with or without supraorbital fractures, and parallel fracture patterns seen in orbital floor fractures in that single hinge, double hinge and “punched-out” fractures occur. The displacement of orbital roof fragments may either be superior or inferior, depending on the contour of the fracture and the deforming forces. Fractures of the skull may also be seen in plain skull films, but CT scan documentation is superior and preferred. Plain x-rays may reveal an area of chronically infected bone as a radiolucent region. Plain x-rays are no longer routinely used since the advent of CT scans, because they do not provide 3-D information including soft tissues. CT scans should be utilized to determine the area, extent, and displacement of the fractures and potential to compromise structures such as the orbit, the function of the ethmoidal and frontal sinuses, mastoid region, and adjacent soft tissues. A 3-D reconstructed CT scan may be obtained which shows larger fractures, asymmetry, and the position of the individual segments and is helpful for evaluating position and asymmetry problems, especially involving the orbits. MRI examination is standard for determining the specifics of soft-tissue injury including the brain.

3

Treatment strategies

Nondisplaced fractures of the cranial vault generally require no operative intervention. However, even nondisplaced fractures can have late sequelae such as frontal sinus nonfunction (obstruction). If the fracture extends into the frontal sinus area and compromises the function of the nasal frontal duct, or creates laceration of a mucous membrane which heals as a mucocele, lesions caused by pressure will be created (chapter 4.1 Frontal sinus, frontal base, and anterior skull base). A linear cranial vault fracture may also tear the dura, producing resorption of the bone and pseudogrowth of skull fractures. This occurs mostly in children. Fractures may be open or closed in terms of communication with the outside environment through the skin. Fractures that enter the sinuses are considered open because of communication with the oral and nasal environment. Fractures may also be open to the skin through a laceration. A subcutaneous hematoma may require drainage despite the simplicity of the fracture if there is sufficient accumulation. Again, the presence of an epidural hematoma requires consideration for evacuation.

4

Symptoms requiring operation

Depressed fractures must be evaluated for correction based on esthetic and functional considerations. Functional considerations requiring operative intervention are compression of the brain through fragments or hematoma formation, compromise of a sinus or interference of space normally occupied by the orbit, impaction into the structures in the superior orbit such as the levator, or extension into the superior orbital fissure with the superior orbital fissure syndrome (partial or complete interference with function of cranial nerves): • Olfactory nerve (central cranial base fractures), cranial nerve I • Optic nerve (medial orbit), cranial nerve II • The structures in the superior orbital fissure, cranial nerves III–VI, produce interference with levator and extraocular muscle function, and altered sensation in the frontal branches of the trigeminal nerve.

Postoperatively, the study of the cranial bone with bone scans or CT scans may help to detect areas of chronic inflammation. Perfusion studies may also detect areas of dead bone.

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5

Approaches

6

Surgical technique including reduction

Approaches to cranial vault fractures include lacerations and surgical incisions. Coronal incisions can generally be reflected with less retraction pressure the farther they are brought forward in the scalp. However, the anterior position of the incision is more visible with a forward location. Generally, a midcoronal incision which can be either straight or zigzagged (called the stealth incision) is preferable. The latter is camouflaged by its varying angulation within the hair (Fig 3.2-5a–e , page 196).

Cranial vault fractures may be elevated most safely by burr holes remote from the fracture and approaching the fracture area after dissecting the dura free. The fragments of bone produced by drilling the burr holes should be captured (drillhole shavings) with a small strainer with the curve of its lip designed to fit the curve of the skull so that the bone can be utilized in repair. They are reserved in saline on a back table until required. The shavings are placed into areas of bone defect, such as fracture sites, osteotomies, or burr holes.

The coronal incision provides panoramic exposure and is optimal for access to the entire anterior portion of the skull. Even in the presence of a cutaneous forehead laceration the vascular supply is usually preserved despite damage to some of the anterior blood supply. Local incisions should not generally be extended for frontal sinus exploration.

Calvarial skull fracture fragments are removed in sequence, marked for orientation and position, and a diagram drawn with brilliant green or marking pencil to identify by labeling where the fracture fragment came from and what its orientation was. This pattern assists reassembly.

Lacerations can be used for very limited fractures. Local approaches or lacerations usually permit only limited visualization and generally do not provide exposure for bilateral exploration, control of bleeding, or management of other dural or intracerebral injuries. Management of a torn sagittal sinus is usually difficult. It can either involve acute repair or ligation of the sinus (which is an injury rarely tolerated in an adult). Depressed skull fragments can be left, if there is no bleeding at operation, but this delays an onlay cranioplasty in situations where cosmetic considerations require cranial vault repair.

Any intracranial neurosurgery such as dural repair, removal of any dead or damaged brain, and control of hemorrhage is performed. Any weak area of the dura, especially along the cranial base, should be reinforced with a dural patch. Autogenous material (fascia lata) or alloplastic material (alloderm) or Duragen® may be utilized. Appropriate aerobic and anaerobic cultures are obtained. The fracture fragments are then reassembled by the reconstructive surgeon on a back table while intracranial surgery is in process, and then may easily be replaced into the defect. Gaps occur at osteotomies and fracture lines in fracture treatment, and may be filled with calvarial or iliac shavings as previously described. Occasionally, fragmentation is so extensive that a bone graft should replace the fractured cortical fragments. The bone graft may be taken by harvesting noninvolved full thickness skull and splitting it with a right angle saw or chisels. A calvarial bone graft may be split through the diploë with chisels. The bone graft can be used to plug the frontal sinus and nasofrontal duct, fill dead space, reconstruct portions of the cranial vault, or seal communication of the anterior cranial base with the nose. Larger cranial bone pieces should be stabilized with fixation. In some cases, a periosteal or galeal frontalis flap should be used in the anterior cranial base as an additional soft-tissue seal between the cranial base of the frontal sinus and the nose. These flaps thin the frontal skin, and caution must be used in their application. Sometimes, extensive brain edema and swelling do not allow immediate reconstruction of the cranial vault. In these cases the bones should nevertheless be reassembled to preserve orientation, after which the bone is deep-frozen and stored for secondary use.

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7

Types o f fixation

Fixation of calvarial fragments can involve long spanning plates, or fragments can be serially united to each other with smaller plates (Fig 4.3-3a). The latter type of fixation was called “chain link” fixation when interfragmentary wires were utilized. It would seem that a stronger fixation is provided by the long spanning plate, and the author prefers this technique, although no data are available to prove its superiority. Yet another option is the fixation of these fractures with a mesh (Fig 4.3-3b). Other areas of the cranial vault can be used for bone graft harvesting. Gaps between fragments can be filled with bone grafts or shavings (Fig 4.3-4). Cranial vault shapes are more easily reconstructed with plate and screw fixation, particularly when compared to wires. The use of wires shortens the distance between the bone fragments and creates asymmetry compared with the con-

Fig 4.3-3a Fixation of a lateral cranial vault fracture after reduction using short and long mini- and/or microplates and burr hole covers.

tour of the other side because of loss of bone at fracture gaps. With rigid fixation and bone grafts, the proper anatomy of the bone is reestablished. Bone grafts are also used to replace comminuted bone segments. Generally, plates 1.3 or corresponding Matrix plates provide sufficient stability for the (almost) nonloaded cranial vault and forehead. In general, thicker plates such as miniplates 1.5 and 2.0 are not necessary and often yield visible plate silhouette, especially in the forehead area if the skin has been thinned by injury or flap harvest. Bone flaps are often required to provide intracranial exposure for dural or cerebral injury management. Plate and screw fixation can be helpful to stabilize these bone flaps. Burr holes should be covered either by specially contoured plates or filled with bone graft material to avoid noticeable depressions. Alternatively, burr hole covers can be used.

Fig 4.3-3b Fixation of a lateral cranial vault fracture with a mesh.

Fig 4.3-4 When the anterior table is excessively comminuted, the esthetic result is improved by use of a bone graft to reconstruct the entire anterior sinus wall. It is stabilized with miniplates.

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8

Side effects of treatment and complications

A consequence of harvesting a galeal-frontalis forehead flap is thinning of the forehead skin. Sometimes the skin is so thin that late postoperative plate exposure occurs, or there is a visible permanent deformity. This kind of deformity can only be improved with thin free tissue transfers (fat transfer followed by secondary liposuction). “Plate silhouette” also occurs when replaced frontal bone partially resorbs, revealing a plate that stands on a ridge above the bone. This may require hardware removal and recontouring.

9

Conclusion

In the last 10 years, treatment options and outcomes of frontal sinus and cranial vault fractures were studied and short- and long-term complications noted. These data suggest that an aggressive complete initial management strategy produces the best esthetic and functional results minimizing complications such as dural fistula and sinus obstruction.

The “take” of replaced calvarial bone is generally in the region of 50%. This may cause contour deformities which are managed by late onlay cranioplasty. In each case, the smooth contour of the forehead should be reestablished with minimally profiled contoured plates, either applied to the bone surface or in a small inset created to avoid “plate silhouette.” Coronal incisions occasionally result in hypertrophic scars but are rarely keloidal. The keloid variant occurs mostly in patients with non-white skin and is very difficult to treat. Certainly, a minimally displaced frontal sinus fracture where duct function is intact would produce far less deformity than a keloid occurring in a coronal incision. Infections after raising cranial bone flaps for access to intracranial structures or infections in comminuted cranial vault areas are rare. They may present as acute soft-tissue infections such as abscess formation requiring incision and drainage. Late sequelae can be due to chronic bone infections such as osteomyelitis, which is treated either surgically, with hyperbaric oxygen, or with a combination of the two. Antibiotic prophylaxis is indicated in all cases with intracranial dural repair, drainage of hematomas, or major bone surgery. All patients with postoperative infections are treated with antibiotics as well.

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4.4 References and suggested reading Aguillar EA III, Hall JW III, Mackey-Hargadine J (1986) Neuro-otologic

evaluation of the patient with acute, severe head injuries: correlations among physical findings, auditory evoked responses, and computerized tomography. Otolaryngol Head Neck Surg; 94(2):211–219. Ahmed KA, Alison D, Whatley WS, et al

(2009) The role of angiography in managing patients with temporal bone fractures: a retrospective study of 64 cases. Ear Nose Throat J; 88(5):922–925. Alvi A (1998) Battle’s sign in temporal bone trauma. Otolaryngol Head Neck Surg; 118(6):908. Alvi A, Bereliani A (1998) Acute intracranial complications of temporal bone trauma. Otolaryngol Head Neck Surg; 119(6):609–613. Asano T, Ohno K, Takada Y, et al (1995) Fractures of the floor of the anterior cranial fossa. J Trauma; 39(4):702–706. Asha’ari ZA, Ahmad R, Rahman J, et al

(2012) Patterns of intracranial hemorrhage in petrous temporal bone fracture. Auris Nasus Larynx; 39(2):151–155. Bächli H, Leiggener C, Gawelin P, et al

(2009) Skull base and maxillofacial fractures: two centre study with correlation of clinical findings with a comprehensive craniofacial classification system. J Craniomaxillofac Surg; 37(6):305–311. Bell RB, Chen J (2010) Frontobasilar fractures: contemporary management. Atlas Oral Maxillofac Surg Clin North Am; 18(2):181–196. Review. Benecke JE (1994) Surgery for nonMenière’s vertigo. Acto Otolaryngol Suppl; 513:37–39. Brodie HA, Thompson TC (1997) Management of complications from 820 temporal bone fractures. Am J Otol; 18(2):188–197. Brodie HA (1997) Prophylactic antibiotics for posttraumatic cerebrospinal fluid fistulae: a meta-analysis. Arch Otolaryngol Head Neck Surg; 123(7):749–752. Brookes GB, Graham MD (1984) Posttraumatic cholesteatoma of the external auditory canal. Laryngoscope; 94:667–670. Burstein F, Cohen S, Hudgins R, et al (1997) Frontal basilar trauma: classification and treatment. Plast Reconstr Surg; 99(5):1314–1321. Camilleri AE, Toner JG, Howarth KL, et al

(1999) Cochlear implantation following temporal bone fracture. J Laryngol Otol; 113(5):454–457. Cannon CR, Jahrsdoerfer RA (1983) Temporal bone fractures: review of 90 cases. Arch Otolaryngol; 109(5):285–288.

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Gladwell M, Viozzi C (2008) Temporal bone

Frontal sinus fractures: a review of 132 cases. Eur Rev Med Pharmacol Sci; 13(1):57–61. Chang CYJ, Cass SP (1999) Management of facial nerve injury due to temporal bone trauma. Am J Otol; 20(1):96–114. Chen DJ, Chen CT, Chen YR, et al (2003) Endoscopically assisted repair of frontal sinus fracture. J Trauma; 55:378–382. Chen KT, Chen CT, Mardini S, et al (2006) Frontal sinus fractures: a treatment algorithm and assessment of outcomes based on 78 clinical cases. Plast Reconstr Surg; 118(2):457–468.

fractures: a review for the oral and maxillofacial surgeon. J Oral Maxillofac Surg; 66(3):513–522. Review. Glarner H, Meuli M, Hof E, Gallati V, et al

(1994) Management of petrous bone fractures in children: analysis of 127 cases. J Trauma; 36(2):198–201. Goldenberg RA, Leonetti JP (1994) Anatomy of the lateral skull base. Jackler RK, Brackmann DE (eds), Neurotology. Chicago: Mosby, 1003–1010. Gruss JS, Pollock RA, Phillips JH, et al

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(2000) [Cranialization of the frontal sinus. Indications, technique and results]. HNO; 48(5):361–366. German. Crawley WA, Manson P (1991) Problems and Complications in Cranioplasty in Craniomaxillofacial Trauma. Manson PN (ed), Perspectives in Plastic Surgery. Philadelphia, PA: Lippincott-Raven, 458–465.

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(1999) Temporal bone fractures: otic capsule sparing versus otic capsule violating clinical and radiographic considerations. J Trauma; 47(6):1079–1083. Darrouzet V, Duclos JY, Liguoro D, et al

(2001) Management of facial paralysis resulting from temporal bone fracture: our experience of 115 cases. Otolaryngol Head Neck Surg; 125(1):77–84. Esslen E (1973) Elecrodiagnosis of facial palsy. Niehlke A (ed), Surgery of the Facial Nerve. Philadelphia: WB Saunders, 45–51. Exadaktylos AK, Sclabas GM, Nuyens M, et al (2003) The clinical correlation of

temporal bone fractures and spiral computed tomographic scan: a prospective and consecutive study at a Level 1 trauma center. J Trauma; 55:704–706. Fisch U (1984) Prognostic value of electrical tests in acute facial paralysis. Am J Otol; 5(6):494–498. Fisch U (1981) Surgery for Bell’s palsy. Arch Otolaryngol; 107(1):1–11. Fisch U (1980) Management of intratemporal facial nerve injuries. J Laryngol Otol; 94(1):129–34. Fisch U (1974) Facial paralysis in fractures of the petrous bone. Laryngoscope; 84:2141–2154. Gantz BJ, Rubinstein JT, Gidley P, et al

(1999) Surgical management of Bell’s palsy. Laryngoscope; 109(8):1177–1188. Gabrielli MF, Gabrielli MA, Hochuli-Vieira E, et al (2004) Immediate reconstruction of

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with heterogeneous corticocancellous bone versus spontaneous osteoneogenesis in monkeys (Cebus apella): histologic analysis. J Oral Maxillofac Surg; 61(2):214–221. Holland BA, Brant-Zawadzki M (1984) High-resolution CT of temporal bone trauma. AJR Am J Roentgenol; 143(2):391–395. House JW, Brackmann DE (1985) Facial nerve grading system. Otolaryngol Head Neck Surg; 93(2):146–147. Ioannides C, Freihofer HP, Vrieus J, et al

(1993) Fractures of the frontal sinus: a rationale of treatment. Br J Plast Surg; 46(3):208–14. Erratum in: Br J Plast Surg 1993; 46(8):718. Ishman SL, Friedland DR (2004) Temporal bone fractures: traditional classification and clinical relevance. Laryngoscope; 114(10):1734–1741. Johnson F, Semaan MT, Megerian CA

(2008) Temporal bone fracture: evaluation and management in the modern era. Otolaryngol Clin North Am; 41(3):597–618. Review. Johnson DW, Hasso AN, Stewart CE, et al

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(2000) Acute temporal bone trauma: utility of high-resolution computed tomography. Am J Otol; 21:743–752. Kalavrezos ND, Grätz KW, Warnke T, et al

(1999) Frontal sinus fractures: computed tomography evaluation of sinus obliteration with lyophilized cartilage. J Craniomaxillofac Surg; 27(1):20–24. Kelly K, Manson PN, Vander Kolk C, et al

(1990) Sequencing Le Fort fracture treatment. J Craniofac Surg; 1(4):168–178. Kelly KE, Tami TA (1994) Temporal bone and skull base trauma. Jackler RK, Brackmann DE, (eds), Neurotology. Chicago: Mosby: 1127–1147. Klotch DW (2000) Frontal sinus fractures: anterior skull base. Facial Plast Surg; 16(2):127–134. Kuttenberger JJ, Hardt N (2001) Long-term results following reconstruction of craniofacial defects with titanium micro-mesh systems. J Craniomaxillofac Surg; 29(2):75–81. Lakhani RS, Shibuya TY, Mathog RH, et al

(2001) Titanium mesh repair of the severely comminuted frontal sinus fracture. Arch Otolaryngol Head Neck Surg; 127(6):665–669. Lambert PR, Brackmann DE (1984) Facial paralysis in longitudinal temporal bone fractures: a review of 26 cases. Laryngoscope; 94(8):1022–1026. Lancaster JL, Alderson DJ, Curley JWA

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pediatric skull base fractures. Int J Pediatr Otorhinolaryngol; 74(11):1245–1250. Petruzzelli GJ, Stankiewicz JA (2002) Frontal sinus obliteration with hydroxyapatite cement. Laryngoscope; 112:32–36. Pulec JL (1996) Total facial nerve decompression: technique to avoid complications. Ear Nose Throat J; 75: 410–5. Raveh J, Vuillemin T, Sutter F (1988) Subcranial management of 395 combined frontobasal-midface fractures. Arch Otolaryngol Head Neck Surg; 114:1114–1122. Rodriguez ED, Stanwix MG, Nam AJ, et al

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5 Panfacial fractures


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1

Introduction

293

2

Anatomy and definitions

293

3

Order of treatment

295

4

Graded (anterior and posterior) approaches

295

5

Facial subunits and energy of the fracture

295

6 The importance of first excluding other injuries in the head and neck

295

7

295

The occlusion

8 The maxilla, the hard palate, and alveolar fractures of the mandible and maxilla

296

9

Preinjury photographs

297

10 Upper face: the cranial unit

297

11 Upper face: the midfacial unit

298

12 Lower face

300

13 Linking the upper to the lower face

302

14 Edentulous patients with panfacial fractures

302

15 Soft-tissue considerations

304

16 References and suggested reading

305

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1

Introduction

In the presence of multiple simultaneous facial fractures, an order of treatment should be developed. In the past, so-called inside-out, top-to-bottom, or bottom-to-top philosophies have prevailed, each with its own vigorous proponents. Recently, an outside-to-inside management scheme for the midface has been proposed, emphasizing the zygomatic arch as a key midface structure.

2

Anatomy and definitions

The face is divided into an upper face and a lower face at the Le Fort I level. Each facial half is divided into two facial units. The buttresses of the midface, skull, and mandible are indicated in Fig 5-1a .

Fig 5-1a Transversal, vertical, and sagittal buttresses of the facial skeleton (arrows).

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Lower face

The occlusal and the mandibular units are situated in the lower face. The occlusal unit consists of the teeth, the palate, and the alveolar processes of the maxilla and mandible. The mandibular unit consists of horizontal and vertical sections. The vertical section of the mandible includes the condyle, the ramus, and the angle. The horizontal section includes the body, parasymphysis, and symphysis. Upper face

In the upper face are the frontal and upper midfacial units. The frontal unit consists of the supraorbital, frontal, and temporal bones, the supraorbital rims, the orbital roofs, and the frontal sinus. The upper midfacial unit is composed of the zygomas laterally, the nasoorbitoethmoidal (NOE) area centrally, and the internal portion of the orbits bilaterally. The upper and lower face meet at the Le Fort I level (Fig 5-1b–c).

Fig 5-1b View of the face with a division line for upper and lower face at the level of Le Fort I.

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Midface fracture treatment is based on an accurate physical examination and on evaluation with a thorough CT scan of the face. Considering the complexity of the face and its multiple parts, it is important that an order of facial fracture treatment be developed to address midface and accompanying fractures of the mandible and frontal bone. There are three areas of the facial skeleton, (mandible, midface, and frontal bone including skull base) and four facial units (Fig 5-1c). Extended midface fractures combining two or more anatomical facial areas are referred to as panfacial fractures.

Fig 5-1c View of the face identifying the facial units: frontal, upper midface, occlusal, and mandibular units. The occlusal unit consists of the teeth, the palate, the alveolar process of the maxilla, and the mandible. The mandibular unit consists of a vertical and a horizontal part. The vertical consists of the condyle, ramus, and angle; the horizontal consists of the body, symphysis, and parasymphysis. The frontal unit consists of the frontal bone area medially and two lateral frontotemporal-supraorbital segments. The upper midface unit consists of the zygoma laterally, the nasoorbitoethmoidal areas centrally, and the internal portion of the orbits bilaterally.


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3

Order of treatment

The exact order of treatment is not as important as the development of a plan which permits accuracy of anatomical positioning of the various facial segments. Exposure, identification, and fixation of the facial buttresses guarantee the best anatomical alignment. The application of fixation stabilizes the facial skeleton three-dimensionally.

4

Although it may seem obvious, patients must have other significant injuries evaluated prior to undertaking facial fracture treatment. The airway is ensured by intubation or tracheostomy. The endotracheal tube should be placed either through the nose, through a gap in the dentition, behind the molar teeth, or may be brought through the floor of the mouth via a submental skin incision, or a formal tracheostomy may be employed.

Graded (anterior and posterior) approaches

The approach described is the author’s uniform format for recreating facial dimensions for any fracture and proceeds from intact cranial vault or cranial base landmarks through the entire anterior portion of the face. The treatment of all Le Fort and any associated fractures may be integrated into this plan, which provides for both simple and panfacial injuries in all degrees of complexity. The treatment plan emphasizes reconstruction in anatomical areas, such as the horizontal part of the mandible, the vertical part of the mandible, the Le Fort I level and the palate, the zygomas, the NOE area, and the frontal bone with the frontal sinus.

5

6 The importance of first excluding other injuries in the head and neck

Facial subunits and energy of the fracture

Four anatomical units are identified. Treatment is organized by identifying the degree of injury (energy or comminution of the fracture) in each of the four anatomical units and applying the fracture severity classification in a scheme for determining the necessity for anterior or anterior and posterior exposures. The selection of these two separate exposure techniques depends on the anatomical area and the energy or fragmentation of the fracture.

It is obvious that when the anatomical unit of the head and neck carries extensive facial fractures, the presence of skull, brain, and neck injuries needs to be excluded or addressed before operative planning is completed. Similarly, all injuries need to be assessed and their effect on facial injury treatment determined prior to initiating operative facial intervention in order to determine preoperative facial fracture positioning and monitoring strategies.

7

The occlusion

Attention is directed first to the dentition. Arch bars, such as Erich or Schuchardt arch bars, are applied to the teeth of the maxilla and the mandible and should extend the entire length of the dental arch. For edentulous patients, the dentures or suitable splints can be used to position the alveolar ridges for fixation. IMF screws are only satisfactory for simple, undisplaced single-unit fractures but do not provide multiple points of forced occlusal contact or permit any possibility of adjustment required by panfacial or complex fracture treatment.

This algorithm allows for an individually adjusted treatment plan and brings order to the operative intervention by structuring efficient, sequential manipulation.

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8 The maxilla, the hard palate, and alveolar fractures of the mandible and maxilla

Alveolar fractures of the maxilla and mandible as well as fractures of the hard palate should be reduced and stabilized with stable fixation before mandibulomaxillary fixation (MMF) is completed (Fig 5-2). Two areas of stabilization are required. Small plates can be applied in the palate paracentrally in median fractures, or laterally along the alveolar ridge, or at the junction of the alveolus with the basal bone of the maxilla. The piriform aperture may additionally be stabilized with a plate or a lag screw. Two-dimensional palato-alveolar fracture fixation stabilizes the Le Fort I segment as a one-piece unit. It may be then managed as a traditional Le Fort I fracture segment. When mandibular alveolar fractures exist or when comminuted fractures involve tooth-bearing bone in mandibular fractures, the smaller pieces carrying the teeth can be reattached to larger pieces using small plates. The reassembled larger pieces may then be oriented for a final reduction (Fig 5-3).

Fig 5-2 Sagittal fractures of the maxilla should be stabilized by an approach through the roof of the mouth. The maxillary alveolus is stabilized at the piriform aperture. One or two plates 1.5 or corresponding Matrix plates are used.

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These steps set the template for the correct width of the lower face by providing an anatomically reduced maxillary arch as an absolute guide for mandibular width. Similarly, alveolar fractures of the mandible may be reduced and fixed with small plates, such as miniplates 1.5, or corresponding Matrix plates. Microsystems can be considered in some cases as well. When stabilizing the occlusion, special consideration is required with regard to the occlusal plane. The patient is placed in MMF, usually with the help of arch bars. In edentulous or partially edentulous patients it is sometimes necessary to use the original dentures or splints to establish MMF. Special attention must be paid to the presence of subcondylar fractures, especially the low subcondylar fracture which begins at the sigmoid notch and exits the ramus posteriorly. If these fractures are present and treated closed, the lack of an anatomically correct and stable reduction of ramus height may lead to an unstable vertical dimension. An unstable, non-level occlusal plane, a retruded Le Fort I mandibular unit, or a rotated facial unit will create a change in facial height or facial alignment producing an oblique occlusal plane or retrusion of the entire unit in MMF.

Fig 5-3 Alveolar fractures of the mandible should be reduced with small plates and screws of the midface system placed monocortically.


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9

Preinjury photographs

Preinjury photographs assist in the definition of the facial dimensions to be achieved. Prominence of the eyes, the prominence and shape of the nose, the amount of lip-tooth (incisor) show, and the architecture of facial features is clearly demonstrated by preinjury photographs. These facts are not apparent from CT scans alone or from an examination of the injured patient.

10 Upper face: the cranial unit

Exposure is provided by a coronal incision which should be carried retroauricularly if an inferior extension is required and can be of a stealth (zigzag) pattern across the calvaria (chapter 3.2 Upper midface (Le Fort II and III)). Frontal bone fracture fragments are marked in orientation and sequence as they are removed for exposure of any intracranial neurosurgery. Reassembly of the removed cranial bone fragments can be completed on a back table while neurosurgical exploration

is in progress. The surgeon should preoperatively prepare one or two bone graft donor sites (ribs, iliac) and a thigh in case a fascia lata graft is necessary to reinforce the closure of the dura. In frontal or ethmoid sinus obliteration, any remaining frontal sinus mucosa must be thoroughly removed from the fracture fragments and the walls of the sinus burred lightly to eliminate mucosa which follows the veins of Breschet into the internal layers of the skull. This mucosa may regrow if it remains. The frontal sinus is then either obliterated or cranialized depending on the presence or absence of a relatively intact posterior wall. Cranial base bone grafting must also be complete to provide a layer of bone between the nose and the intracranial cavity. The frontal bar (which includes the supraorbital rims and the internal and external angular processes of the frontal bone) must be reconstructed as a stable unit (Fig 5-4). The lower section of the supraorbital rims and lower anterior frontal sinus form the frontal bar, and this structure provides the inferior stable positioning in frontal bone reconstruction. Cranial base bone grafting (the orbital roof and anterior cranial fossa) is generally attached to the frontal bar or floor of the anterior cranial fossa for stability. The frontal bar is reconstructed and the anterior sinus wall reassembled. Temporal bone alignment must be correct in narrowness (facial width) and length (anterior projection).

Fig 5-4 The frontal bar should be used as the key lower landmark in frontal-bone reconstruction.

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11 Upper face: the midfacial unit

The author prefers to initially link all fragments of the orbital rims including superior, lateral, inferior, and medial segments in the upper midfacial unit with interfragmentary wires. A temporary stabilization with malleable small plates such as mini- or microplates is also possible. In the upper midfacial unit, the NOE area is reduced first. It is important to establish a narrow intercanthal distance by first tightening the transnasal wires, thereby narrowing the intercanthal distance. This step is the most important procedure in NOE fracture reduction, as the transnasal wire links one medial orbital rim with the other (Fig 5-5a–b). The NOE area, reduced with interfragmentary transnasal wires, is then linked superiorly to the frontal bar reconstruction and inferiorly to the maxillary Le Fort I level by plate and screw fixation. This technique, called junctional rigid fixation, implies that the central NOE area is linked to its peripheral attachments with rigid fixation. This step stabilizes projection of the entire reassembled NOE complex. Le Fort I level and orbital-rim fixation stabilize the lower NOE segment projection. Thick plates extending along the medial orbital rim above the canthal ligament produce an unnatural thickness and do

a

not fully stabilize the area against rotation, and should be avoided. Junctional rigid fixation is preferred. An alternative approach, especially for patients with severe comminution of the NOE complex, is to reconstruct the outer facial frame first. This implies reduction and fixation of the zygomatic arches and zygomas to the cranium (Fig 5-6a). Stable fixation of the zygoma begins by exposing all articulations of the zygoma with its adjacent bones (Fig 5-6b). These are the zygomaticofrontal suture, the infraorbital rim, and the zygomatic arch, intraorbital inferior and lateral orbital walls, and the maxillary buttresses. The zygomatic arch is explored if the fracture in the arch is laterally displaced or if there is a severe posterior dislocation of the malar eminence. These fractures benefit from arch exposure for stability and alignment of the width of the midface. Additionally, the inferior internal orbit is explored, as are the lower medial and lateral orbit. Interfragmentary wires may initially be placed in the zygomaticofrontal suture and in the inferior orbital rim or zygomatic arch to provide initial positioning of the zygoma. Conceptually, exposure of all of the articulations of the zygoma would require two to four different incisions, as only one or two of these fracture sites

b

Fig 5-5a–b a NOE fracture with dislocation as part of a panfacial injury. b Initially, all bone fragments in the NOE area can be linked with wires. Junctional stable fixation then stabilizes the assembled NOE unit to the frontal bone superiorly, the inferior orbital rim (midface plans recommended), and the piriform aperture inferiorly.

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can be viewed through one incision. Positioning wires protect the initial position achieved in one area, while the other areas are visually assessed. The zygomaticomaxillary buttress is visualized to confirm approximate position. Next, the zygomatic arch is reduced beginning with the intact segment posteriorly, holding the anterior arch segments in a flat reduction which emphasizes the anterior projection of the malar eminence. If the most posterior fracture in the zygomatic arch is oriented sagittally through the glenoid fossa, a lag screw technique should be used. Rarely, the superior aspect of the glenoid fossa should be plated. A midface plate 2.0 or a corresponding Matrix plate is placed over the remaining arch segments laterally. This plate should be of the stronger adaptation-plate variety which resists muscular loading. Before arch reduction is stabilized, the zygoma at the inferior orbital rim and in the lateral orbit must be checked for alignment so that proper reduction of the lateral orbital wall and reduction of the zygoma with the medial NOE orbital segments is achieved. The zygoma is then stabilized with miniplates 1.5 or 1.3 at the inferior orbital rim in panfacial fractures. The use of a smaller miniplate in this region is insufficient for cases in

a

which NOE support is lost. When multiple segments of the infraorbital rim are present, the segments are initially linked with interfragmentary wires or with smaller miniplates with one screw in each rim segment. Rim fragments can then be held superiorly and anteriorly as stable fixation is completed. The zygomaticofrontal suture is reduced using a miniplate 1.5 or a Matrix miniplate. The inferior orbital rim is to be corrected in terms of anterior projection and vertical positioning. Proper zygomatic reduction can be confirmed only by repeatedly visualizing multiple areas of alignment with adjacent bones through several incisions. A key area for position control is the lateral orbital wall, especially the junction between zygoma and greater wing of the sphenoid bone. After stabilization of the inferior orbital rim is complete, the inferior internal orbit must be reconstructed. Stable posterior bone ledges in the back of the orbit are identified medially, laterally, and inferiorly. Meshes, orbital plates, or bone grafts should then be strutted between the reconstructed rim and the stable posterior ledges, completing the reduction of the internal orbit and, in so doing, the upper midface. If desired, the bone grafts may be stabilized behind the orbital rim with plates or screws.

b

Fig 5-6a–b a Reconstruction and fixation of the outer facial frame consisting mainly of correct positioning of zygomatic bones to the cranial vault and posterior root of zygoma. This may be the first step in outside-to-inside management. b Initial alignment of the zygoma is achieved by positioning its five peripheral articulations. Subsequently, stable fixation of the zygoma is achieved at the zygomaticofrontal suture, the infraorbital rim, and the zygomaticomaxillary buttress.

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12 Lower face

The first step in the treatment of the lower face is to ligate arch bars to the maxillary and mandibular dentition and place the patient in MMF in occlusion. Sometimes, dental models or old dental records are helpful in more difficult cases of preexisting malocclusion. In the case of a split palate, the arch bar may be ligated to the major segment and a provisional reduction of the palate in the roof of the mouth performed. The arch bar may then be ligated to the minor segment. The patient should then be placed in occlusion and the piriform aperture plate applied. In the case of a mandibular fracture, the arch bar is ligated to the major segment and a provisional reduction of the fracture is performed with an interfragmentary or circumdental wire or one loose screw on each side of an upper border plate. The minor segment is then ligated to the arch bar and the patient placed in MMF. In general, fractures in the horizontal portion of the mandible are exposed through transoral incisions. Sometimes transcutaneous incisions are utilized; however, scarring may be disfiguring. If a skin laceration exists and is of suitable size, it can be used for fracture treatment.

a

Temporary reduction of a displaced mandibular fracture can also be performed using interfragmentary wires which permit some degree of mobility or adjustment of the fracture alignment prior to plate and screw fixation. The reduction of comminuted mandibular fractures can also be simplified by using miniplates to place the small pieces to the larger pieces, and then one can deal with the major fragments. Internal fixation is performed using at least three screws for each of the major mandibular fragments (if one screw becomes loose, the two others hold the reduction). After the initial wire reduction, adjustments in bone position are made and stable plate fixation is completed in the horizontal mandibular section. Simple angle fractures may be reduced through a transoral incision with superior border fixation. The occlusion must be checked after the final reduction. The patient is taken out of MMF after the final reduction of the mandible and the mandible is closed with the fingers on the lower border at the angle, seating the condyle in the fossa to see that the occlusion is ideal and reproducible with condylar motion. Make sure the condyle is not displaced from the fossa when bringing the patient into proper occlusion (Fig 5-7a–b).

b

Fig 5-7a–b a Fixation of the midface in the Le Fort I plane in displaced position due to subcondylar fractures which are not fixed and not reduced properly, with anterior rotation of the maxilla and shortening of the face. b Fixation of the midface in the Le Fort I plane in correct position after reduction and fixation of subcondylar fractures and proper positioning of the condyles. The defect of the maxillary wall on the right is bridged with a bone graft.

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Complex comminuted angle fractures are more easily reduced with transcutaneous exposures. The hyoid crease, Risdon, or retromandibular incisions are preferred. The correct width of the mandible is obtained by translating the anatomically reduced maxillary arch to the dental inclination of the lateral mandibular dentition. This serves as a guide to prevent lingual rotation of the lateral mandibular segments which results in excessive lateral width of the mandible at the angles. The lingual cortex of the mandible is not routinely visualized in transoral fracture reductions. The fracture line tends to open (gap) lingually if complete approximation of the entire thickness of the mandible’s fractured surfaces is not achieved. There is a tendency in parasymphysis fractures (especially in combination with bilateral subcondylar fractures) for the bicondylar width to be too wide, and for the mandibular angles to flare (Fig 5-8a–c). The lateral mandibular dentition rotates lingually, increasing the flare (width at the inferior angles). The lingual cusps of the lateral mandibular teeth come out of occlusion creating a crossbite or “fractional” open bite.

a

b

Open reduction of the vertical (ramus and condylar) segments of the mandible is required if significant malalignment or overlapping of ramus or subcondylar fractures exists. Condylar head dislocation produces a loss of ramus height which may change facial dimensions, complicating the treatment of the multiply fractured patient. Condylar dislocation in the presence of a loose Le Fort fracture is an indication for open reduction to place the condyle in the fossa and stabilize the height of the ramus and, therefore, the downward and forward projection of the mandible. Depending on the anatomical location of the fracture in the ramus, exposure is performed either by a preauricular, retromandibular, transparotid, or Risdon incision. In difficult exposures (comminution of the ramus), the facial nerve is best identified and protected. The temporomandibular joint can be examined at the time of condylar open reduction. This may be best done by visualization through a preauricular incision. Any meniscus injury is assessed and corrected. Reconstruction of the ramus (in the author’s opinion) should precede that of the horizontal mandible in order to achieve proper position of the entire mandible in relation to the cranial base. This maneuver corrects the projection of the mandible. Open reduction also assists the correction of the facial width at the mandibular angles and reestablishes the vertical height of the ramus.

c

Fig 5-8a–c Fractures in the anterior symphyseal/parasymphyseal area in combination with bilateral subcondylar fractures tend to create a gap on their lingual surface. a–b If insufficient correction of the mandibular width is obtained, the fracture may appear to be in good reduction on the buccal surface anteriorly, but actually there is an excessive width at the angles allowing the lateral mandibular segments to rotate lingually, tipping the dentition and creating a fractional open bite by bringing the lingual and palatal cusps out of alignment. c Situation as before, but with correct fixation of the chin fractures by means of a correctly bent reconstruction plate.

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13 Linking the upper to the lower face

14 Edentulous patients with panfacial fractures

The lower and the upper facial units are then united at the Le Fort I level by plating the four anterior vertical maxillary buttresses. Midface height and facial length are set by using an intact or an anatomically reconstructed buttress as a guide. If no complete buttress is available, one or more buttresses can almost always be reconstructed anatomically by piecing together existing fragments. One intact buttress gives a clue to the height of the rest of the buttresses. In the absence of a buttress which can be reconstructed, the lip-tooth position provides the best clue to the preinjury facial height. Further photographs may suggest the correct lip-tooth relationship and facial height to be achieved.

In edentulous patients with panfacial fractures the anterior maxilla often drifts superiorly and posteriorly compromising the internal volume of the nose and exacerbating the adverse retracted appearance of the edentulous patient (Fig 5-10a). Posterior displacement of the maxilla is common despite what appears to be satisfactory visual alignment of the anterior maxillary buttresses when the maxilla is not related in anteroposterior position to a properly positioned mandible. The four anterior maxillary buttresses should be visualized, but then the maxilla has to be related to the mandible with regard to anterior projection. If available, the original dentures of the patient provide the correct mandibulomaxillary relationship. If mandibles are broken, a simple fixation should be performed before midface treatment, thus allowing the mandible to act as a guide to midfacial position. If broken, the dentures may be repaired and/or splints made to provide maxillary and mandibular alignment. Plate and screw fixation in an edentulous maxilla may require the use of alveolar bone itself as a stable lower fixation point as the intervening bone may be too thin or splintered (Fig 5-10b). Bone grafts may have to be added at the Le Fort I level and the piriform aperture (Fig 5-10c). Often these bone grafts also improve the esthetic appearance. The buttress plates, if extended to the alveolus, sometimes must be removed before a denture can be tolerated postoperatively. Proper maxillary projection is confirmed only by relating the maxillary and mandibular alveolar ridges with splints and/or dentures (Fig 5-10b). Maxillary vertical buttress reconstruction is therefore a reliable guide for facial height, but not for projection.

The Le Fort I level fixation of the nasomaxillary buttress is the third area where NOE projection is stabilized. The other two areas are the frontal bar and the inferior orbital rim. Buttress bone gaps exceeding 5 mm should be bone grafted for both functional and esthetic reasons. It is the author’s current recommendation that defects in the anterior maxillary sinus wall should be bone grafted or repaired with a mesh graft as this prevents prolapse of soft tissue into the sinuses. Dorsal nasal bone grafting improves the height of the nose in profile or a thin graft can be used to smooth the dorsal nasal contour. This completes the facial reconstruction. Nasal bone grafting is performed most accurately after the nasomaxillary buttress reconstruction and the anterior nasal spine stabilization of the septum have been completed (Fig 5-9). If the medial canthal ligaments have been detached, they should be positioned only after bone grafting of the medial orbit and nose. A separate set of transnasal wires (placed before the NOE reduction is completed) are utilized for canthal reduction (chapter 3.5 Nasoorbitoethmoid (NOE) fractures).

Fig 5-9 Nasal bone grafting is performed.

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a

b

Fig 5-10a–c a Midfacial and mandibular fractures of an edentulous patient with dislocated midface in posterior-caudal direction. b After correct reduction with correct MMF using the patient’s dental prostheses and midface fixation with miniplates and reconstruction plate on the mandible. c Similar as in (b), with stabilization of midface fracture on the right side with bone grafts.

c

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15 Soft-tissue considerations

Current facial fracture reduction schemes emphasize complete degloving of all bones by subperiosteally detaching periosteal soft-tissue attachments and incising fascial layers. It is important when closing incisions to close the periosteum and reposition soft-tissue attachments to the reassembled craniofacial skeleton. Generally, closure is best begun by first closing the periosteum. The areas for periosteal closure include the zygomaticofrontal suture, the inferior orbital rim, and the periosteal layer over medial and lateral canthus areas. Muscular layers underneath the gingivo-buccal sulcus incisions require muscular closure. The incisions in the temporal fascia for zygomatic arch exposure require closure of the deep temporal fascia. Marking the edges of the periosteal incisions with sutures allows precise identification at the end of the case for periosteal closure. This is especially important in lower eyelid incisions. Soft-tissue injury

The fundamental challenge in facial fracture treatment is the restoration of the preinjury facial appearance and not simply linking together edges of bone at fracture sites. Deformity following facial fractures results from both softtissue changes and from bone malalignment. Deformity of both bone and soft tissue significantly increases in the presence of highly comminuted fractures, especially when they involve the upper midfacial and orbital areas. The contribution of blunt soft-tissue injury and soft-tissue contracture to residual facial deformity has not been emphasized in the literature on facial fractures. Contused soft tissue heals with a network of internal scarring, the configuration of which is dictated by the position of the underlying bone fragments. When soft tissue heals over malreduced fractures, shrinkage and contracture of the soft tissue may occur. Scarring and internal rigidity in soft tissue occur in the pattern of the unreduced bone segments as the soft tissue heals. The internal scarring thickens soft tissue, creating a dense internal scar and an internal stiff web which opposes restoration of the preinjury shape and appearance even if the underlying bone is finally replaced into its proper anatomical position. Examples of soft-tissue envelope rigidity accompanying malreduced fractures include the conditions of enophthalmos, medial canthal-ligament malposition, short palpebral

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fissure, rounded canthus, and an inferiorly displaced malar soft-tissue pad. Secondary management of any one of these conditions is more challenging and less effective than primary reconstruction of the soft tissue. A unique opportunity thus exists in immediate fracture management to maintain shape, expansion, and position of the soft-tissue envelope, and to determine the geometry of soft-tissue fibrosis by providing an anatomically aligned facial skeleton as support. Excellent restoration of appearance results from primary softtissue positioning. The double insult to soft tissue

Delayed reconstruction of facial fractures more than 7–10 days after injury results in a second soft-tissue injury through dissection and incisions in healing areas of contusions and hemorrhage. A second injury is thus created: first, the initial injury and, second, the surgical manipulation. Delayed treatment creates a double insult to the already contused and damaged soft tissue. This is especially harmful, creating dense subcutaneous fibrosis. The skin, following delayed facial fracture repair, is more thickened, rigid, lusterless, reddened, hyperpigmented, and fibrotic than skin from early injury repairs where the initial contusions, fractures, incisions, and dissection are all part of a single soft-tissue injury and recovery. Accurate skeletal reconstruction requires anatomical assembly and stabilization of the basic configuration of the bone buttresses. Missing or unstable bone fragments should be replaced with bone grafts to recreate the preinjury skeletal framework. If soft tissue and bone do not exist, plates alone maintain the volume of the expanded soft tissue. A thorough reconnection of all buttress fragments must proceed from intact bone to intact bone and must be complete and accurate in three dimensions throughout the entire area of injury. Conceptualizing each unit of the patient skeleton in three dimensions emphasizes supervision of width and therefore restoration of projection. Finally, correction of the facial height in each unit allows assembly of the whole skeleton based on a conceptually precise framework for bone reconstruction. Performing bone reconstruction early in complicated facial injuries allows the most natural restoration of preinjury appearance to be determined by the combined relationship of bone and soft tissue.


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treatment (Organization of treatment for a panfacial fracture). J Craniofac Surg; 1(4):168–178. Liau JY, Woodlief J, van Aalst JA (2011) Pediatric nasoorbitoethmoid fractures. J Craniofac Surg;22(5):1834–1838. Review. Manson PN (1986) Some thoughts on the classification and treatment of Le Fort fractures . Ann Plast Surg; 17:356–363.

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(1990) Toward CT-based facial fracture treatment. Plast Reconstr Surg; 85:202–212. Markowitz B, Manson P, Sargent L, et al

Romano JJ, Manson PN, Mirvis WE, et al

(1990) Le Fort fractures without mobility. Plast Reconstr Surg; 85:355–362. Ranganath K, Hemanth Kumar HR (2011) The correction of post-traumatic panfacial residual deformity. Oral Surg; 10(1):20–24. Rohner D, Tay A, Meng CS, et al (2002) The sphenozygomatic suture as a key site for osteosynthesis of the orbitozygomatic complex in panfacial fractures: a biomechanical study in human cadavers based on clinical practice. Plast Reconstr Surg; 110(6):1463–1471; discussion 1472–1475. Smoot EC III, Jernigan JR, Kinsley E, et al

(1997) A survey of operative airway management practices for midface fractures. J Craniofac Surg; 8(3):201–207. Stoll P, Galli C, Wächter R, et al (1994) Submandibular endotracheal intubation in panfacial fractures. J Clin Anesth; 6(1):83–86. Tang W, Feng F, Long J, et al (2009) Sequential surgical treatment for panfacial fractures and significance of biological osteosynthesis. Dent Traumatol; 25(2):171–175. Wenig BL (1991) Management of panfacial fractures. Otolaryngol Clin North Am; 24(1):93–101. Review.

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6 Fractures in the growing skeleton


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1

Introduction

309

2

Facial growth and trauma

310

3

Rigid fixation

310

4

Mandibulomaxillary fixation (MMF)

311

5

Surgical approaches

311

6

Surgical reconstruction

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6.1

Dentoalveolar fractures

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6.2

Fractures of the mandible

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6.2.1 Condylar fractures

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6.2.2 Body fractures

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6.2.3 Symphyseal and parasymphyseal fractures

312

6.3

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Midfacial fractures

6.3.1 Central midface fractures (Le Fort type)

312

6.3.2 Zygomaticomaxillary complex fractures and zygomatic arch fractures

312

6.4

313

Orbital fractures

6.4.1 Orbital apex

313

6.4.2 Orbital wall

313

6.5

Nasal fractures

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6.5.1 Newborn nose

313

6.5.2 Frontal sinus fractures

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6.5.3 Nasoorbitoethmoidal (NOE) fractures

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7

314

Conclusions

8 References and suggested reading

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315


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Authors Paul Krakovitz, Peter Koltai


1

Introduction

In treatment of pediatric facial fractures surgeons must not only understand how facial fractures can affect growth, but they must also be aware of the differences in treatment strategies between adults and children and among children of different age. At birth the craniofacial ratio is 8:1 and the face is located in a recessed position relative to the large skull. The cranium and forehead effectively shield the smaller lower and middle thirds of the face from injury. By 1.5 years old, the cranium has grown to 80% of its mature size (Fig 6-1).

Fig 6-1 Lateral view of a 1.5-year-old child’s skull. Craniofacial ratio is 6:1.

Facial growth is also rapid during this period, but it is only after the second year that facial growth outpaces cranial growth. Brain and ocular growth are near completion by the age of 6 (Fig 6-2). Facial growth continues into the second decade of life, with a final craniofacial ratio of 2:1 (Fig 6-3). As a result, the cranium absorbs most of the impacting force, especially the prominent forehead overhanging the face. This disparity in facial structure explains to some degree, why young children experience more skull fractures and fewer facial fractures (including serious midfacial fractures) than adults. In children, the force necessary to cause major craniofacial disruption often results in brain injury and death.

Fig 6-2 Lateral view of a 6-year-old child’s skull. Brain and ocular growth are nearly completed.

Fig 6-3 Lateral view of an adult skull. Craniofacial ratio is 2:1.

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2

Facial growth and trauma

Craniofacial bone growth is a complex process that is not understood completely. The nose, nasoorbitoethmoidal (NOE) complex, and maxilla are more prone to growth abnormalities caused by trauma. This is most likely because of the minor restorative functional movement that these bones are subject to, the physiologic derangements that result from the fractures, the importance of the septum as a regional growth site, and the vulnerability of the multiplesuture sites to scar formation. These factors suggest that some basic tenets should be followed when pediatric fractures are repaired:

3

Rigid fixation

Use of rigid fixation in the developing face is a controversial topic. Fixation should be performed with caution and reserved for fractures when the original features are difficult to restore by other means (Fig 6-4). Although excellent for fixation, there are several drawbacks to leaving a metallic foreign material in a growing child. Resorbable osteosynthesis material is comparable in efficiency to metallic fixation material in nonload-bearing bone. At present, resorbable plates are not recommended for all types of pediatric facial fractures. The use of resorbable plates in the mandible and load-bearing bone in children is still being studied and longterm results are limited.

• Careful restoration of injured soft tissue, particularly the periosteum • Close attention to septal injuries with an emphasis on realignment rather than resection • Reduction of fractures into their stable anatomical locations • Correct realignment of suture lines • Minimal periosteal elevation • 3-D stable fixation of complex fractures • Use of rigidly fixed bone grafts as a substrate for growth in areas of bone loss

Fig 6-4 Fixation of mandibular and midfacial fractures with titanium miniplates in a 5-year-old child.

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4


To obtain mandibulomaxillary fixation (MMF), one must consider the age and development of the teeth. Arch bars and interdental wiring are often impractical especially in young children, who lack teeth or have poor retentive shape of the deciduous teeth. In those cases, alternative methods need to be considered. Fortunately, 2–3 weeks of mandibular immobilization in children younger than 12 years is adequate for nonoperative management. One alternative approach for treating mandibular fractures involves using an overlay acrylic mandibular splint that is held in place by circummandibular wires. In children between 2 and 5 years the deciduous incisors have firm roots, and if the deciduous molars have formed, they can be used for cap splints or arch bars. After age 10, the presence of permanent teeth generally provides safe anchors. However, children develop at different rates and the strength of the teeth should be carefully examined before placing any type of tooth-anchored MMF. An alternative to arch bars is the use of orthodontic brackets that are glued to the teeth.

goma, anteriorly to the infraorbital nerve, and medially up to the lacrimal fossa. The exposure provides for the reestablishment of both the lateral zygomaticomaxillary buttress and the medial nasomaxillary buttress. The lower NOE area can be exposed by a midfacial degloving incision. The sequencing of severe midfacial fractures, especially when the mandible is fractured, is important. Reestablishing occlusion by MMF and repairing the mandible establishes a solid base for upper face reconstruction. The approach to pediatric injuries is based on the knowledge that the face is composed of component units connected by their associated buttresses and that the most prominent and most challenging esthetic unit is the NOE area. First, occlusion is established and, if necessary, the mandible is repaired. The central core is then reconstructed, followed by positioning of the orbits and the outer facial frame to the central core. In cases with severely comminuted mandibles, midface fixation can be done first, in order to use the midface as a reference for the mandible. In children, fractures in the area of the mandibular body are mostly exposed by transoral incisions in the same fashion as in adults (see chapters 2 and 5).

MMF today is generally performed with elastics rather than with steel wires. 6

Surgical reconstruction

6.1 Dentoalveolar fractures 5

Surgical approaches

The entire facial skeleton can be accessed and reconstructed using a combination of six incisions. The coronal approach exposes the upper third of the face including the zygomatic arches, the lateral, medial, and superior orbital rims, and the NOE region. Orbital roof and NOE exposure can be obtained by mobilizing the supraorbital neurovascular bundle. Detaching the temporalis fascia from the lateral orbital rim and zygomatic arch reveals the bones of the entire upper face, completely from the zygomatic root on one side around to the other side. The exposure provides a means to realign and rigidly fix the frontozygomatic suture, the entire zygomatic arch, and the nasal skeleton. The inferior orbital rims and floor can be exposed by either a subciliary, high crest lid or transconjunctival incision. The medial orbit and apex can be exposed by a transcaruncular approach. The gingivolabial sulcus approach provides access to the entire maxilla, laterally to the lower part of the zy-

When an alveolar fracture is associated with a tooth fracture or luxation, the treatment is more problematic. It can be very difficult to properly reposition the alveolar fragments, although reduction should be attempted. Prolonged periods of MMF are often required to maintain these fragments. It is sometimes helpful to stabilize the fracture with miniplates, if the bone is large enough to accept screw fixation and there is enough space to avoid injury to the healthy surrounding roots. 6.2 Fractures of the mandible 6.2.1 Condylar fractures

Most children with unilateral and some with bilateral condylar fractures will present with normal occlusion and almost normal mobility. Treatment in these patients usually consists of a soft diet and movement exercises. Children with condylar fractures who present with an open bite, mandibular retrusion, or limited movement are best treated with 2 to 3 weeks of MMF. Early and persistent movement with an elastic jaw exerciser generally prevents ankylosis and helps restore function.

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The indications for an open surgical approach of pediatric condylar fractures are limited and reserved for the displacement of the condyle into the middle cranial fossa or severely displaced fractures. These are best approached with either a preauricular or a retromandibular approach, depending on the location of the fracture. Endoscopically assisted fixation via a transoral incision is another option. 6.2.2 B ody fractures

MMF with elastic traction is usually adequate for nondisplaced or mildly displaced body fractures. However, if misalignment of fragments cannot be controlled in a nonsurgical manner, open reduction with internal fixation and the placement of miniplates fixed monocortically is necessary. 6.2.3 S ymphyseal and parasymphyseal fractures

Fractures with minimal to moderate displacement can often be realigned with careful manual manipulation under anesthesia and immobilized with the methods described for pediatric MMF. The decision to treat with soft diet, MMF, or open reduction and internal fixation (ORIF) should be based on the degree of disruption in the fracture, the extent of occlusion change, and associated pain. To better reduce serious displacement, ORIF of the fragments is required. Fixation is usually performed with titanium or biodegradable miniplates and screws. During screw insertion, exercise great care when placing the drill holes, to prevent injury to the developing tooth buds. Once preinjury occlusion is established, a minor degree of osseous gap at the fracture site is of less consequence in bony healing of pediatric mandibular fractures. 6.3 Midfacial fractures

Central midfacial fractures in children rarely follow the typical Le Fort patterns of injury. Significantly displaced fractures should be reduced within 10 days because of the high osteogenic potential of the periosteum. Rapid interfragmentary healing makes late reduction difficult. Acute reduction should be considered when fractures are accessible through open wounds. 6.3.1 Central midface fractures (Le Fort type)

Central midface fractures of the Le Fort type are rare, especially in small children, but they do exist (chapter 3.2 Upper midface (Le Fort II and III), Fig 3.2-2a–b). Similar to Le Forttype fractures in adults, they rarely follow the pure Le Fort classification.

312


Le Fort-type fractures with no occlusion derangement and no severe displacement can be managed nonsurgically with a soft diet, especially in small children. Central midface fractures with severe displacement and/or disturbances of the occlusion require active treatment with open reduction and internal fixation. In these cases, the occlusion is typically secured by mandibulomaxillary fixation, frequently with arch bars or other tooth-anchored devices, for instance ortho dontic brackets. Exposure to the lower midface is done from an upper sulcus transoral incision, and exposure to the orbits and the craniofacial junction is achieved either through a craniofacial coronal approach, transfacial approaches, or combinations. After fragment reduction, internal fixation can be performed with titanium miniplates or biodegradable osteosynthesis material, according to the size of the skull and the fragments. Hardware placement is, along the facial buttresses, similar to the techniques described for adult midfacial fractures. In cases of orbital wall involvement, the orbital walls are treated as described below. 6.3.2 Z ygomaticomaxillary complex fractures and zygomatic arch fractures

Zygomaticomaxillary complex fractures correspond to the maxillary sinus pneumatization and are uncommon before 5 years of age. The frontozygomatic suture tends to be weak in children and is easily displaced. Nondisplaced or minimally displaced fractures are not treated. An elevation from a Gillie’s approach, with a transcutaneous bone hook or a Carroll-Girard–type device (chapter 3.3 Zygomaticomaxillary complex fractures, zygomatic arch fractures) can reduce greenstick-type injuries, which frequently will not require internal fixation for stability. When simple reduction techniques result in unstable or nonanatomical reduction, ORIF is indicated. Surgical correction involves adequate control of the frontozygomatic suture, the infraorbital rim, and the lateral buttresses. In simple fractures, control of the infraorbital rim and frontozygomatic suture can be accomplished with external palpation. Open visualization is only necessary for the zygomaticomaxillary buttress via an transoral gingivolabial sulcus incision. For more complex fractures, for instance with segmentation, open visualization can be accomplished through a brow, subciliary, or transconjuctival with lateral canthotomy incision and an upper buccal sulcus incision. When reconstruc-


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tion of the zygomatic arch is required, a coronal or hemicoronal approach is necessary. Once exposure is achieved, most injuries can be reconstructed by 1-point fixation of the zygomaticomaxillary buttress or by 2-point fixation with miniplates at the frontozygomatic suture, infraorbital rim, or zygomaticomaxillary suture. Severe fractures will require at least 3-point fixation (see chapter 3.3 Zygomaticomaxillary complex fractures, zygomatic arch fractures, Fig 3.3-14 , page 217). Zygomatic arch deformities can usually be repositioned by elevating through a step, Gillie’s-type, or transoral incision. When indicated, orbital floor exploration and reconstruction should be performed (chapter 3.4 Orbital fractures). 6.4 Orbital fractures

Suspected orbital trauma warrants an ophthalmologic evaluation. The extraocular musculature is tested for voluntary range of motion and, if necessary, with forced duction under anesthesia.

doentrapment conditions, such as orbital soft-tissue swelling, extraocular muscle contusion, and cranial nerve injuries are distinguished from true muscular entrapment, because patients with the former condition can be observed. Patients with a tight restriction of extraocular muscles or a true muscle incarceration are more likely to recover their ocular motility with early intervention, which is preferably administered as early as possible, ideally not later than within 48 hours, but the sooner the better. Up to 86% of orbital roof fractures are associated with intracranial injury. The orbit and globe rarely sustain long-term damage, thus, surgery is rarely necessary. Fracture fragments that are displaced into the orbit require combined intracranial and extracranial exploration with cranial bone graft or titanium mesh reconstruction of the deficit to correct dystopia and exophthalmos, and to prevent encephaloceles. 6.5 Nasal fractures

Orbital wall fractures in children are treated similar to orbital fractures in adults. Orbital wall reconstruction is done with titanium meshes, mesh plate, porous polyethylene, or bone grafts. Orbital roof fractures rarely require repair. However, if ocular mobility has not improved within 7–10 days of injury, repair should be performed. Permanent exophthalmos, vertical dystopia, and encephaloceles can result from unattended fractures.

Immediate intranasal examination is essential to evaluate for septal injury, particularly septal hematoma. When present, these injuries should be treated immediately with evacuation. In most cases, this will require general anesthesia. The use of a Killian septal incision allows for both drainage of the hematoma as well as investigation and suture reduction of any displaced septal fragments. Following exploration, the mucoperichondrial leaflet is sewn back to the cartilage with a through-and-through suture. Septal splints and packing should be used for 2–3 days, to prevent the reformation of the hematoma.

6.4.1 Orbital apex

Orbital apex injuries in children are exceedingly rare, probably because the force required is often lethal. Fractures of the apex are usually due to posterior extensions of complex craniofacial injuries. Blindness is the greatest concern, which occurs as a result of optic nerve injury and vascular injury to the ophthalmic artery. Loss of visual acuity and afferent pupil defect are the hallmark findings for an optic neuropathy. Initial treatment consists of high-dose steroids. If visual acuity is absent or does not improve, optic nerve decompression may be considered using a transphenoidal, intracranial, or endoscopic approach. 6.4.2 Orbital wall

Indications for surgical intervention after an internal orbital fracture include significant (> 2 mm) enophthalmos, extraocular muscle restriction with positive forced ductions (> 30º), symptomatic diplopia, and/or computed tomographic findings of large orbital wall defect. It is crucial that pseu-

If a bony or septal fracture is present resulting in a cosmetic deformity or a fixed nasal obstruction, definitive surgical management is undertaken. Closed reduction of the bony fracture can be performed with intranasal instrumentation and bimanual external manipulation. Ideally, this is performed within a maximum of 10 days after the injury. Greenstick fractures may not always reduce into the desired position, and they sometimes require small osteotomies for proper alignment of the fragments. If significant dislocations are present or if the injury is more than 2 weeks old, then open reduction may be necessary. The timing of open reduction is of some debate, and often waiting is the best approach. 6.5.1 Newborn nose

Infants are occasionally born with a symmetric tip deformity. They typically have a flattened nasal tip off to one

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side, with the septum tilted in the same direction. The bony dorsum is invariably straight. Some surgeons advocate immediate surgical reduction of these deformities by straightening and relocating the septum. However, in the authors’ experience, these deformities generally straighten over time without intervention or late sequelae. It is possible that such a displacement can cause airway obstruction, and if this occurs, relocation of the septum is indicated. 6.5.2 Frontal sinus fractures

The frontal sinus is the last of the paranasal sinuses to develop in children and is, therefore, not prone to injury until adolescence. However, when such injury occurs, 70% involve the posterior table. The rate of cerebrospinal fluid (CSF) leaks is with 18% nearly twice as high as in the adult population. Management of frontal sinus fractures in children is similar to that of adults. When forehead deformity is present in an anterior table fracture, it must be reduced. The nasofrontal drainage should be investigated using both direct visualization of the sinus floor and endoscopy. Posterior table fractures require open reconstruction, and severe comminution warrants neurosurgical consultation. Most posterior fractures are associated with anterior fractures and can be repaired concurrently. The need for sinus obliteration is based on the same criteria as for adults. Long-term sequelae include cerebrospinal fluid leak, intracranial abscess, and mucopyocele formation. Fractures of the supraorbital rim can be approached either through the extension of overlying lacerations or by coronal incision. Occasionally, a brow incision may be used, especially if a patient does not agree to coronal incision. 6.5.3 Nasoorbitoethmoidal (NOE) fractures

NOE fractures are anatomically defined as fractures of the nasofrontal suture, nasal bones, medial orbital rim, infraorbital rim, medial orbital wall, and orbital floor. This makes up “the central fragment” core of the midface. Comminution of this core determines the severity of the fracture and complexity for providing optimal cosmetic and functional results. Evaluation of the medial canthal ligaments is mandatory and best performed by inserting a hemostat in the nose up toward the medial orbital rim with the patient under anesthesia. Traumatic hypertelorism is evaluated by the intercanthal distance. The average intercanthal distance is about 25 mm at age 3, 28 mm at age 12, and 30 mm by adulthood, with great variation among individuals and ethnicities. An additional 5 mm of soft-tissue widening above the age-adjusted average is indicative of displaced fractures of the NOE complex, with 10 mm being diagnostic.

314


Most NOE fractures are best treated with ORIF. Although technically difficult, overcorrection of the NOE fracture is esthetically superior to undercorrection. Exposure of the nasal dorsum is best obtained using preexisting lacerations or through coronal incisions. The major fragments and the medial canthal ligaments are identified. Care is taken to preserve the attachment of the ligament to the bony insertion. Resetting the intercanthal distance is the most important step for esthetically optimal results. Interorbital growth is nearly complete by the age of 8 years. It is crucial in children to set the intercanthal distance narrower than anticipated. In medial canthal reconstruction, a drill hole is made in the anterior lacrimal crest just above the insertion of the anterior limb of the tendon. A second drill hole is made in the posterior lacrimal crest just behind the insertion point of the posterior limbs. Contralateral drill holes are made, and a 28-gauge stainless steel wire is passed transnasally between the two fragments and tightened in an effort to overcorrect the deformity. An alternative technique is to use a small screw as the anchor for the transnasal wires (chapter 3.5 Nasoorbitoethmoidal (NOE) fractures). Interfragmentary wiring is completed and, if unstable, can be further supported by plate fixation of the medial orbital rim. The final step is reconstruction of the nasal dorsum, which often loses its support. A cantilever calvarial bone graft can be used to correct this deformity, which should be rigidly fixed to limit reabsorption. The tip of the graft should be deep to the upper border of the lower lateral cartilages. Direct injury to the lacrimal drainage system is uncommon in NOE fractures. Nevertheless, the lacrimal sac, duct, and canaliculi should be examined, and if injured, definitive repair with stents should be performed to prevent epiphora.

7

Conclusions

Children can sustain severe craniomaxillofacial injuries that require appropriate repair. The primary factors that distinguish the treatment of pediatric and adult fractures are facial growth, a faster healing process, and a higher potential for remodeling (eg, condyle). Inadequate treatment of upper and midfacial injuries may result in serious alterations of facial growth. CT scanning, craniofacial exposure, bone grafting, and the advent of rigid fixation facilitate our ability to reconstruct the most complex 3-D disfigurements. These techniques have solid theoretic and practical applications in severe facial trauma.


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Midfacial trauma and facial growth: a longitudinal case study of monozygotic twins. Am J Orthod Dentofacial Orthop; 138(5):641–648. A maratunga NAS (1987) The relation of age to the immobilization period required for healing of mandibular fractures. I Oromaxillofac Surg; 45:111–113. Banks P (1998) A pragmatic approach to the management of condylar fractures. Int J Oral Maxillofac Surg; 27(4):244–246. Bartlett SP, DeLozier JB III (1992) Controversies in the management of pediatric facial fractures. Clin Plast Surg; 19(1):245– 258. Blez P, Champy M, Klink M, et al (1992) [Fractures of the middle third of the face in children: anatomo-clinical, diagnostic and therapeutic characteristics]. Rev Stomatol Chir Maxillofac; 93(3):148–150. French. Bos RR (2005) Treatment of pediatric facial fractures: the case for metallic fixation. J Oral Maxillofac Surg; 63(3):382–384. Bowman MK, Mantle B, Accortt N, et al

(2011) Appropriate hearing screening in the pediatric patient with head trauma. Int J Pediatr Otorhinolaryngol; 75(4):468–471. Bansagi ZC, Meyer DR (2000) Internal orbital fractures in the pediatric age group: characterization and management. Ophthalmology; 107(5):829–836. Champy M, Lodde JP, Muster D, et al (1977) [Osteosynthesis using miniaturized screws on plates in facial and cranial surgery. Indications and results in 400 cases]. Ann Chir Plast; 22(4):261–264. French. Chao MT, Losee JE (2009) Complications in pediatric facial fractures. Craniomaxillofac Trauma Reconstr; 2(2):103–112. Crockett DM, Funk GF (1991) Management of complicated fractures involving the orbits and nasoethmoid complex in young children. Otolaryngol Clin North Am; 24(1):119. Demianczuk AN, Verchere C, Phillips JH

(1999) The effect on facial growth of pediatric mandibular fractures. The effect on facial growth of pediatric mandibular fractures. J Craniofac Surg; 10(4):323–328. Ellis E (1993) Sequencing treatment for naso-orbito-ethmoid fractures. J Oral Maxillofac Surg; 51:543–558. Enlow DH (1990). Facial Growth. 3rd ed. Philadelphia: WB Saunders Co; 1–24. Eppley BL (2005) Use of resorbable plates and screws in pediatric facial fractures. J Oral Maxillofac Surg, 63(3):385–391. Glarner H, Meuli M, Hof E, et al (1994) Management of petrous bone fractures in children: analysis of 127 cases. J Trauma; 36(2):198–201.

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demographics, injury patterns, and associated injuries in 772 consecutive patients. Plast Reconstr Surg; 128(6):1263–1271. Graham S, Thomas R, Carter K, et al (2002) The transcaruncular approach to the medorbital wall. Laryngoscope; 112:986–989. Gussack GS, Lutterman A, Rodgers K, et al

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(1993) Sequelae of unrecognized, untreated mandibular condylar fractures in the pediatric patient. Ann Dent; 52(1):5–8. Liau JY, Woodlief J, van Aalst JA (2011) Pediatric nasoorbitoethmoid fractures. J Craniofac Surg;22(5):1834–1838. Review. Lund K (1974) Mandibular growth and remodeling processes after condylar fracture: a longitudinal roentgen cephalometric study. Acta Odontol Scand; 32(suppl 64):3–117. Mast G, Ehrenfeld M, Cornelius CP (2012) [Maxillofacial fractures: midface and internal orbit; Part 2: therapeutic options]. Unfallchirurg; 115(2):145–164. German. Messinger A, Radkowski MA, Greenwald MJ, et al (1989) Orbital roof fractures in the

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(2010) Complex pediatric orbital fractures combined with traumatic brain injury: treatment and follow-up. J Craniofac Surg; 21(4):1054–1059. Parker MG, Lehman JA (1989) Management of facial fractures in children. Perspect Plast Sur;g 3:1. Paskert JP, Manson PN, Iliff NT (1988) Nasoethmoidal and orbital fractures. Clin Plast Surg; 15:209–223. Perheentupa U, Kinnunen I, Grénman R, et al (2010) Management and outcome of

pediatric skull base fractures. Int J Pediatr Otorhinolaryngol; 74(11):1245–1250. Polayes IM (1989). Facial fractures in the pediatric patient. Habal M, Aryan S (eds), Facial Fractures. Philadelphia: BC Decker, 257–288. Posnick JC, Wells M, Pron GE (1993) Pediatric facial fractures: evolving patterns of treatment. J Oral Maxillofac Surg; 51(8):836–844; discussion 844–845. Reedy BK, Bartlett SP (1997) Pediatric facial fractures. Bentz MI (ed), Pediatric Plastic Surgery. Stamford, Conn: AppletonLange, 463–486. Regev E, Zeltser R, Shteyer A (2002) [The overlooked chin trauma in children]. Refuat Hapeh Vehashinayim: 9(2):56–61, 79. Hebrew.

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(2011) Occurrence, types and severity of associated injuries of paediatric patients with fractures of the frontal skull base. J Craniomaxillofac Surg. Nov. 9. [Epub ahead of print]. Schweinfurth J, Koltai PJ (1998) Pediatric mandibular fractures. Facial Plast Surg; 14(1):31–44. Shumrick KA, Kersten RC, Kulwin DR, et al

(1992) Extended access/internal approaches for the management of facial trauma. Arch Otolaryngol Head Neck Surg; 118:1105–1112. Siy RW, Brown RH, Koshy JC, et al (2011) General management considerations in pediatric facial fractures. J Craniofac Surg; 22(4):1190–1195. Review. Stolsted P, Schonsted-Madsen V (1979) Traumatology of the newborn’s nose. Rhinolaryngology; 17:77. Thorén H, Schaller B, Suominen AL, et al

(2012) Occurrence and severity of concomitant injuries in other areas than the face in children with mandibular and midfacial fractures. J Oral Maxillofac Surg; 70(1):92–96. Thorén H, Seto I, Büttner M, et al (2011) Patterns of frontobasal and frontosinal fractures in children and teenagers relative to developmental stage of the facial skeleton. Arch Otolaryngol Head Neck Surg; 137(6):549–556. Wheeler J, Phillips J (2011) Pediatric facial fractures and potential long-term growth disturbances. Craniomaxillofac Trauma Reconstr; 4(1):43–52. Williams WT, Ghorayeb BY, Yeakley JW

(1992) Pediatric temporal bone fractures. Laryngoscope; 102(6):600–603. Wright DL, Hoffman HT, Hoyt DB (1992) Frontal sinus fractures in the pediatric population. Laryngoscope; 102:1216–1219. Wright RJ, Murakami CS, Ambro BT (2011) Pediatric nasal injuries and management. Facial Plast Surg; 27(5):483–490. Yaremchuk MJ, Fiala TG, Barker F, et al

(1994) The effects of rigid fixation on craniofacial growth of rhesus monkeys. Plast Reconstr Surg; 93:1–10. Zimmermann CE, Troulis MJ, Kaban LB

(2006) Pediatric facial fractures: recent advances in prevention, diagnosis and management. Int J Oral Maxillofac Surg; 35(1):2–13. Review.

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7.1 Definitions, diagnosis, and treatment planning

321

7.2 Standard osteotomies in the mandible

335

7.3 Standard osteotomies in the maxilla

353

7.3.1 Le Fort I

357

7.3.2 Surgically assisted rapid palatal expansion (SARPE)

363

7.3.3 Subapical (block) and segmental maxillary osteotomies

369

7.4 Special considerations and sequencing in 2-jaw osteotomies

377

7.5 Perioperative and postoperative management

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385


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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery)


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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.1 Definitions, diagnosis, and treatment planning

1

Introduction

321

2

Indications

322

3

Diagnosis and clinical examination

322

3.1 Frontal

322

3.2 Profile

324

3.3 Temporomandibular joints and function

324

3.4 X-ray examination

324

3.5 Models

326

4

326

Classification

4.1 Mandibular excess

326

4.2 Mandibular deficiency

326

4.3 Mandibular asymmetry

327

4.4 Vertical discrepancies of the mandible

327

4.5 Maxillary hyperplasia

327

4.6 Apertognathia (open bite)

327

4.7 Maxillary hypoplasia

327

5

Treatment planning

330

5.1 General considerations

330

5.2 Orthognathic surgery versus distraction osteogenesis

332

5.3 Stability

332

5.4 Treatment

333

5.5 Morbidity of surgical procedures

333

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Authors Joseph E Van Sickels, George Kushner

7.1 Definitions, diagnosis, and treatment planning 1

Introduction

Orthognathic surgery has both functional and esthetic goals. Functional goals include improved mastication, speech, temporomandibular joint function, and, in patients with sleep apnea, an increase of airway space. With careful planning both the occlusion and the patient’s appearance are improved. After the introduction of rigid fixation, the dental and skeletal results achieved are more stable and predictable compared to those seen after wire osteosynthesis. Several studies have shown an improvement in patient’s temporomandibular joint function as well. Orthognathic surgery today is usually conducted by an interdisciplinary team which includes surgeons, orthodontists, and, if needed, other disciplines. Therefore, before making the decision to start the treatment, patients should always meet at least both an orthodontist and a surgeon to receive as much information and as reliable a diagnosis and treatment option as possible. Preoperative orthodontic care takes on average 1.5 years and when the patients are ready for surgery, they meet the surgeon again to get further information. It must be kept in mind that the inclusion of patients in decision making increases their awareness and acceptance of the result. Postsurgical support is also mandatory. In addition to these functional improvements, orthognathic surgery can have a profound psychological effect on a patient. It has been shown that many dental and facial disfigurements have significant effects on patients and result in social disadvantage for them. Esthetic correction is often a motivation for surgery. Improvement of the occlusion is also important to patients. The majority of the patients seem to have more than one reason for undergoing surgery.

In the initial evaluation of the patient, the patient’s motivation for surgery should be assessed. While patient satisfaction following orthognathic surgery is high, with many patients reporting improved self-confidence and social skills after treatment, a few patients report dissatisfaction with their results. Patients with poor self-concept may be prone to postoperative dissatisfaction. Conceptually, patients presenting for care should be viewed as variations from the average. It is implied that the average individual is able to occlude, breathe, or has some other functional or esthetic difference from the patients presenting for orthognathic care. The goal of treatment should be to address those patient concerns that make this individual vary from the average, given their ethnic and gender differences. Diagnosis then becomes a matter of assessing the magnitude of those differences and how they can best be managed. Extra care must be taken with patients suspected of exhibiting dysmorphophobic tendencies. If there is any doubt, psychiatric referral should be undertaken. Preoperative consultation and sometimes also therapy can be very valuable in order to avoid unnecessary surgery or, on the other hand, to diminish the risk of postoperative problems. Regarding dysmorphic disorders, it is generally accepted that surgery rarely improves the situation. Questionnaires and interviews for assessing patients have been published but they are time-consuming and difficult to analyze without formal training in this field. When taking an ordinary patient history, it is important to remember that these patients are usually unmarried and unemployed, they avoid social contacts, they may be depressive, they spend a lot of time in front of the mirror, their concerns are very specific, they have visited many clinicians, and they see the surgery as the solution to all their problems.

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2

Indications

The general indications for surgical correction of a maxillofacial skeletal deformity are physical evidence of musculoskeletal, dento-osseous, and/or soft-tissue deformity. These abnormalities may result in difficulties with breathing, lip incompetence, speech pathology, masticatory and/or swallowing abnormalities, temporomandibular joint/associated muscular disorders, dental and/or periodontal pathology, and social or psychological impairment. Causes of these abnormalities may be congenital, developmental, or traumatic. Multiple studies have shown that patients who have vertical maxillary excess and mandibular retrognathia with a low hyoid bone can have narrow airways in the retropharyngeal region and at the base of the tongue. As a consequence, they are more predisposed to sleep apnea and can be helped by advancement and superior repositioning of the maxilla and advancement of mandible and chin. Examples of congenital deformities are patients with cleft lip and palate, hemifacial microsomia, and a variety of other deficiencies and excess states. Development deformities usually become more evident with growth of the patient. Traumatic injuries can result in a variety of hard and softtissue deformities as well. The timing of surgery is related to the age of the patient and severity of the symptoms. In general, waiting until adolescent patients reach the end of growth before doing surgery is the norm. This concept is generally accepted as the patient may otherwise grow after surgery with reoccurrence of the skeletal discrepancy. It also assumes that the patient does not have a significant functional problem that would necessitate earlier surgery. However, timing can vary with the skeletal discrepancy. With mandibular deficiency, surgery may be considered early, prior to the end of growth. If the jaw continues to grow after correction, it will usually be in a direction that counters any tendency for relapse. With mandibular excess, though, it is wise to wait until after growth is complete as future growth may result in reappearance of the malocclusion. Patients who have primary vertical disorders can have surgery after the cuspids and second molars have erupted as there is little vertical growth of the maxilla at this point. In patients with hemifacial microsomia, surgery to correct skeletal discrepancies and to improve soft-tissue discrepancies is often undertaken before the age of ten with one reason being early expansion of the soft-tissue envelope. Functional issues such as airway problems can prompt earlier surgery.

322


3

Diagnosis and clinical examination

3.1 Frontal

Patients may have discrepancies in multiple planes. The clinical examination is combined with the radiological and model assessments to establish a diagnosis and eventually a treatment plan. However, the accent should be on the clinical examination with x-rays confirming the clinical findings. The patient is examined noting hard- and softtissue relations. Discrepancies between the soft tissue and the underlying hard tissue structures can be managed either with primary surgery or in a delayed fashion. The clinical examination of the patient should be done in two steps. The first is a preliminary examination, where postural, occlusal, or habitual movements are noted. The second examination is more detailed and the patient is assessed from both frontal and lateral views. Soft-tissue, skeletal, and dental issues should be noted in detail and documented with photographs. While the patient must be viewed as a complete individual, it is convenient to think of them as having vertical, horizontal, and transverse discrepancies. Included in this assessment is any asymmetry that may exist in isolation or in combination with discrepancies in other planes. A systematic examination should be done and recorded. This can start from the top of the head downwards, looking at symmetry of the face and vertical balance. The patient should be positioned at a level compatible with the examiner, with their head orientated with both the Frankfurt horizontal and the interpupillary lines parallel to the floor. Measurements should be taken directly from the patient in addition to obtaining facial photographs to document the clinical findings. At a minimum, photographs should include a frontal view with the lips at rest and in smile, three-quarter views, right and left profiles at rest and smiling, a submental vertex view, and intraoral views of the occlusion. The face, extending from the hairline to the chin point, should roughly be divided into thirds. Facial height is subdivided into the region from the hairline to glabella, glabella to subnasale, and subnasale to chin. The normal balance is 30%, 35%, and 35% of the face respectively (Fig 7.1-1). To assess facial width, the face is divided into fifths (Fig 7.1-2).


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Tr

¹/³ Gb

¹/5

¹/5

¹/5

¹/5

¹/5

N´

P

¹/³

Or´

Sn

Pog´

¹/³

²/³

¹/³

Me´ KPF

Fig 7.1-1 Vertical facial proportions. The face is divided into thirds. Upper third: hairline to glabella. Middle third: glabella to subnasale. L ower third: subnasale to menton. The lower third is subdivided into an upper third from subnasale to stomion and lower two thirds from stomion to menton.

Tr Gb Or' Sn

Trichion Glabella Orbitale (soft tissue) Subnasale

Fig 7.1-2 Transfacial proportions. The face is divided into five equal parts, each of which with the approximate width of the eye.

Pog' Pogonion (soft tissue) Me' Menton (soft tissue) KPF Kieferprofilfeld P Porion

The upper third of the face is almost entirely comprised of the forehead. The forehead should be examined looking for symmetry, rhytides, and the position of the supraorbital rims. As part of an esthetic examination, the position of the eyebrows in relation to the supraorbital rims is noted. The position of the ears and the periorbital region is examined next as part of the middle third of the face. Presence or absence of antihelical folds is noted as well as the stiffness of the cartilage. The intercanthal and interocular distances should be documented as well as soft-tissue abnormalities in the upper and lower eyelids. The nose should be examined for both functional and esthetic concerns. This is critical as maxillary surgery can have a dramatic effect on both the

function and esthetics of the nose. For instance, numerous unfavorable changes can occur to the nose and nasolabial esthetics following a Le Fort I osteotomy. Many of these changes are preexistent conditions that are accentuated by the surgery. Minor modifications in the surgical procedure can alleviate some of these preexisting conditions. The width of the nose and any asymmetry is noted. Each subunit of the nose should be examined separately including the tip, alar base, and dorsum. An intranasal examination should be done looking for deviation of the septum and enlarged turbinates. Frequently when there is asymmetry in the base of the nose, the septum is deviated and the nostril sills will also be asymmetric. Examining the patient’s ability to breath through both nostrils is an important part of the presurgical examination.

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The prominence of the cheeks and whether they are symmetric should be noted. The point of malar prominence is usually 10 mm lateral and 15 mm inferior to the lateral canthus of the eye. It is not uncommon for patients with maxillary deficiency to have deficient malar prominences. The infraorbital rim should be within 2 mm of the projection of the globe when viewed from profile. In the paranasal areas, the nasolabial folds should not be excessively deep. In the lower third of the face, the maxillary and mandibular midlines should be noted and whether they are congruent with the facial midline. The lips should be symmetric. A cant in the soft tissue of the lips is often indicative of a cant in the occlusion. If such a cant is suspected, placing a tongue blade between the teeth and viewing the patient from a short distance to see if the tongue blade is parallel to the interpupillary line will confirm whether a cant is present. The length of the upper lip is determined at rest to differentiate vertical maxillary excess from deficient soft tissues. Normal exposure of the upper central incisor is between 2 and 5 mm during smile. Amount of tooth show at rest and at smile should be noted. Patients who habitually posture their jaws and have active perioral muscles may need help to learn to relax their lips so that an adequate assessment can be made. Excessive tooth show at rest may be due to vertical maxillary hyperplasia or a short lip. Excessive tooth show in animation may be due to either horizontal or vertical maxillary excess. While it is important to note whether the patient has an Angle’s Class I, II or III malocclusion, it should be remembered that the dental relationships do not necessarily parallel skeletal discrepancies. Thickness and symmetry of the vermillion should be noted. Maxillary and mandibular dental midlines are noted in relation to the facial midline, to one another, and to the midline of the chin. The chin should be symmetric and in harmony with the facial midline. The shape of the chin should be examined. The angles of the mandible should be symmetric. Asymmetric angles of the mandible may look worse with advancement of the mandible, especially if the patient’s mandibular midline is deviated to one side. Prominent angles and inferior border of the mandible define the breaking point between the face and the neck. Intraorally, the position and size of the tongue should be noted. Tongue position is classified based on the ability of the examiner to the see the pharynx of the patient. Occlusal classification of the teeth is noted as well as any obvious pathologic conditions involving the teeth.

324


3.2 Profile

In profile, the balance of the face is again examined. The upper facial third is examined for frontal bossing or depression. Supraorbital and infraorbital rim projection are noted. The supraorbital rim should project 5–10 mm beyond the most anterior projection of the cornea. In the middle facial third the nose is inspected for columellar show, supra tip break, and nasolabial angle. The radix of the nose is normally 5–8 mm anterior to the cornea. Whether the mandibular plane angle is flat or obtuse and what sort of cervicomental soft-tissue angle the patient has is documented. 3.3 Temporomandibular joints and function

Any examination should include an assessment of jaw and joint function. This includes maximum vertical opening, right and left lateral excursion and protrusive movements. Clicking of the joints and muscular tenderness should be noted. Functional shifts of the occlusion either forward or from one side to the other should be documented. 3.4 X-ray examination

Routine x-rays include a panoramic x-ray, periapical films (when necessary), and frontal and lateral cephalograms. The panoramic film is a general screening film to assess gross changes in the dentition and surrounding structures. Periapical films are used to detect divergence of tooth roots, periapical pathology, and space between teeth when interdental osteotomies are considered. A frontal cephalogram is used to assess asymmetry and transverse deficiencies in the maxilla. The lateral cephalogram is used to confirm the findings of the clinical examination and in the treatment planning phase it is used as a basis for planning the surgical phase of the therapy. There are a variety of cephalometric analysis systems that can be used to aid in the assessment of a patient. What most cephalometric analysis systems have in common is that the skeletal and dental positions in space are related to some reference line in the cranial base. This assumes that there is no discrepancy in the cranial base. While many of the analysis systems were designed prior to the advent of routine orthognathic surgery, some of the more recent ones were designed with orthognathic surgery in mind.


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An in-depth discussion of all cephalometric analysis systems available is beyond the scope of this chapter. A brief review of one frequently used system will be included. The cephalometrics for orthognathic surgery (COGS) system was developed at the University of Connecticut. Similar to a clinical examination, it describes the horizontal and vertical position of the facial bones. The size and relative position of bones are represented by linear measurements both horizontally and vertically (Fig 7.1-3). Use of this system can isolate vertical discrepancies in the anterior and posterior components of the face. Vertical dental dysplasia is divided into an anterior and posterior component. Angular measurements are used to further assess the positions of bones in space. The system also accounts

for differences in males and females. The standards are based on a population of northern Europeans, and this should be kept in mind when individuals of other ethnic groups are examined. In addition, as with all two dimensional cephalometric analyses, it does not account for the three-dimensional nature of patients. Traditionally, x-rays were traced and analyzed on acetate paper. More recently, there have been a number of commercially available programs where the x-ray can be digitalized and then a number of different systems may be used to analyze the patient. These programs can also be used to predict different surgical procedures for the patient. Today the tendency is to plan three-dimensionally on the basis of a CT scan with 3-D cephalometry.

Tr

Gb N N'

S Or

Ns Spa

ar

A

Spp

Ba

Sn Ls Sto Li

Go

Fig 7.1-3 Lateral cephalometric radiological examination. Bone and soft-tissue landmarks are marked. A A-point or subspinale ar Articulare B B-point or supramentale Ba Basion Gb Glabella Go Gonion Li Labrale inferior Ls Labrale superior Me Menton Me’ Menton (soft tissue) N Nasion N’ Nasion (soft tissue) Ns Nasale Or Orbita Pog Pogonion Pog’ Pogonion (soft tissue) S Sella Sn Subnasale Spa Spina nasale anterior Spp Spina nasale posterior Sto Stomion Tr Trichion

B Pog' Pog Me Me'

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3.5 Models

4

The examination is continued by examining models of the patients’ teeth which should be mounted in a semiadjustable articulator after face-bow transfer. Crowding, both absolute and relative, and transverse discrepancies are noted. A relative transverse discrepancy is present when the models are moved in a model operation and the apparent cross bite is resolved. The casts should be examined for steps in the plane of the occlusion. This is done by placing the occlusal surfaces of the models on a flat surface. If all the teeth do not touch the flat surface, there is a step in occlusion. The mounted casts serve as a basis for model operations and the fabrication of intraoperative splints or wafers (Figs 7.1-4 , 7.1-5).

Classification

4.1 Mandibular excess

Horizontal excess in the mandible is usually called mandibular prognathism or hyperplasia. It is frequently a combination of an anomaly of the dental arch, mandibular excess, and macrogenia. However, the patient can have dentoalveolar horizontal excess and genial deficiency. Additionally, there may be a vertical component of alveolar mandibular hyperplasia. The combination of discrepancies will determine the ultimate treatment plan. Clinically the patient will present with a strong lower jaw, a long chin-throat angle, and will usually have difficulty with some aspects of speech and incising food. 4.2 Mandibular deficiency

Horizontal deficiency in the mandible is often called mandibular retrognathism or hypoplasia. It is frequently a combination of an anomaly of the dental arch, microgenia, and mandibular alveolar hypoplasia. As with mandibular excess, each component must be examined as part of the treatment plan. Clinically the patient will present with a soft or weak chin with a poor chin-throat angle or a “double chin.” Frequently these patients habitually posture their jaws in order to function better. Sometimes it is difficult to determine

Fig 7.1-4 Mounted casts of a patient with mandibular prognathism in the preoperative class III situation.

326


Fig 7.1-5 Backward movement of the mandible cast in the articulator into the desired class I situation.


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where the correct position of the mandible is, due to their habit. Sleep apnea may be an issue, especially in patients who are very deficient or have combined maxillary deficiency states and obesity. 4.3 Mandibular asymmetry

Mandibular asymmetry may be seen in isolation or in combination with either excess or deficiency states of the mandible. Depending on how much the mandible is shifted to one side, the soft tissue of the lips may be distorted. This can make assessment of dental and facial midlines difficult. A simple tool to assess dental midlines in a patient with severe asymmetry is to have them align their dental midlines. This will usually correct any soft-tissue distortion. 4.4 Vertical discrepancies of the mandible

Vertical discrepancies with asymmetry of the mandible are usually due to deficiency or excess discrepancies of the condyle(s) or ramus. The etiology should be assessed as to whether it is an active process or a burned-out process. If there is an overgrowth as in condylar hyperplasia the chin point will be canted away from the site of increased growth. Depending on how active the condyle is growing, there may or may not be a posterior open bite on the same side. In addition, the mandibular midline will usually be shifted to the opposite side with a dental class III malocclusion. In contrast, a patient with progressive condylar resorption may have the chin canted to the side of the deficiency, a class II malocclusion, and with the midline shifted to the side of the deficiency. Patients with asymmetric deficiency states frequently posture their jaws forward in order to function better. It is recommended to carefully examine these patients in order to document and accurately record occlusal shifts. It is important in both active growth and deficiency states to determine whether and how active the process is. This can be done by radionucleotide imaging. Clinically, patients may be followed by serial cephalometric examinations, with x-rays in centric relationship. An active growth process can be diagnosed with radionucleotide imaging. When active growth or resorption is occurring, surgery may need to be delayed or modified to address the active state. Passive or inactive processes such as old condylar fractures or hemifacial microsomia can be treated without these measures if it has been determined that normal growth is completed and there are no functional issues that need to be addressed before surgery.

4.5 Maxillary hyperplasia

Maxillary hyperplasia has three component subsets that must be assessed. These are vertical, horizontal, and transverse. The patient may have anterior and/or posterior vertical maxillary excess. Clinically, in addition to a long middle third of the face, if the patient has anterior vertical maxillary excess, they will show more than 2–5 mm of their central incisors at rest. Excessive tooth show at rest is only a sign of vertical excess if the upper lip length is normal. In both vertical and horizontal maxillary excess the patient may show excess amounts of central incisors with animation. In the horizontal maxillary excess tooth show at rest will be normal. In anterior vertical maxillary excess there will be excessive tooth show at rest. If a patient has posterior maxillary hyperplasia without anterior maxillary hyperplasia, tooth show at rest will be normal but the patient will have a long lower face height with an open bite. 4.6 Apertognathia (open bite)

Apertognathia or open bite has several different causes. The most frequent is posterior maxillary excess often associated with a transverse discrepancy of the maxilla. However, it may also occur in patients with macroglossia and in those patients with short posterior facial heights. All patients with anterior open bite usually have lip strain in an attempt to achieve closure of the lips. Patients with macroglossia tend to have the tongue frequently between the teeth. In these cases the patients usually have a component of the open bite in both the upper and lower jaws. In the lower jaw, there will be a reverse curve of Spee, frequently with flaring and splaying of the lower incisors. Patients with short posterior facial height usually have a steep mandibular plane and crowding of dentition. 4.7 Maxillary hypoplasia

Maxillary hypoplasia also has three component subsets of vertical, horizontal, and transverse. Patients with horizontal and vertical deficiency will have deep nasolabial folds in the frontal view and an obtuse nasolabial angle in profile. Clinically, it is common to find both horizontal and vertical deficiency together, especially in patients with a history of cleft lip and palate. Occlusally, they will have a class III dental relationship. Absolute transverse discrepancies will be present in some patients; they are often seen in patients with cleft lip and palate. For more detailed classifications see Table 7.1-1.

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Sagittal disturbances (mandible) Diagnosis

Definition

Symptoms

Mandibular prognathism (hyperplasia)

Anterior position of mandible in relation to correct position of maxilla

Reverse dental overjet, mesial interdentation, anterior overprojection of chin (increased chin prominence), protruding lower lip, Angle Class III

Mandibular retrognathism (hypoplasia), mandible too short in sagittal direction (mandibular anteroposterior deficiency)

Posterior position of mandible in relation to correct position of maxilla

Large overjet, posterior position of chin, short, normal or long lower face, distal interdentition (laterally) Angle Class II

Diagnosis

Definition

Symptoms

Maxillary retrognathia

Maxilla in posterior position in relation to regular position of mandible and skull base

Reversed frontal overjet, protruding lower lip, mesial interdentation, Angle Class III

Maxillary prognathia

Maxilla in anterior position in relation to regular position of mandible to skull base

Large overjet, distal interdentation laterally, lip incompetence, Angle Class II

Maxillary alveolar protrusion

Isolated anterior position and/or tilting of anterior alveolar process

Protrusion of maxillary teeth, lip incompetence, dental procumbency

Maxillary alveolar retroposition

Alveolar process in posterior position in relation to regular position of maxillary base

No or negative overjet, prominent lower lip

Diagnosis

Definition

Symptoms

Vertical hypoplasia of mandible

Shortness of either the ascending ramus, the mandibular body, or the chin

Depending on the affected part of the mandible, findings may include an anterior open bite, excessive occlusal and mandibular plane angles, a long anterior facial height, a flat face or a flat chin may occur

Vertical hyperplasia of mandible

Elongation of either the ascending ramus, the mandibular body, or the chin

Depending on the affected part of the mandible, elongation of posterior lower face (rare), low (flat) occlusal, and mandibular plane angle. If the mandibular body or chin is concerned, sagittal elongation of the lower face or chin is the consequence

Mandibular hypoalveolism

Alveolar process does not reach the occlusal plane

Partial open bite or vertical deviations from occlusal plane

Mandibular hyperalveolism

Rare pathology, mostly in connection with bony pathology like fibrous dysplasia

Isolated elevation of parts of the alveolar process with occlusal disturbances occurring

Sagittal disturbances (maxilla)

Vertical discrepancies (mandible)

Table 7.1-1 Symmetric and asymmetric dysgnathias.

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Vertical discrepancies (maxilla) Diagnosis

Definition

Symptoms

Vertical hyperplasia of the maxilla

Long face deformity, increased vertical height

Elongated midface, short upper lip, gummy smile, lip incompetence. When only occurring posteriorly, an anterior open bite may occur.

Vertical maxillary hypoplasia

Maxilla too short

Short midface, elongated upper lip, upper frontal teeth invisible, even in motion, large distance between rest position and centric occlusion

Maxillary hyperalveolism

Caudal elongation at least of parts of the maxillary alveolar process

Occlusal disturbances

Maxillary hypoalveolism

Cranial position of parts of the maxillary alveolar process, possibly due to growth disturbances

Open bite in disturbed regions, sometimes elongation of alveolar process of opposite area of the mandible

Diagnosis

Definition

Symptoms

Transverse hypoplasia of the mandible

Narrow lower jaw (mandible)

Buccal crossbite, pointed mandible in chin area

Transverse hyperplasia of the mandible

Wide lower jaw (mandible)

Lingual crossbite, chin appears wide

Transverse hypoplasia of chin

Chin appears narrow and pointed

Narrow lower facial third with narrow chin

Transverse hyperplasia of chin

Wide base at the chin area

Wide chin

Transverse hypoplasia of maxilla

Maxilla too narrow at its base

Bilateral lingual crossbite, often associated with crowding

Transverse hyperplasia of maxilla (rare)

Maxilla too wide at its base in relation to mandible

Lateral overjet

Diagnosis

Definition

Symptoms

Laterognathia (hemimandibular elongation)

Asymmetric size of mandibular halves in the sagittal plane

Midline deviation of mandible in relation to correct position of maxilla, lingual crossbite on one side (short mandible) and buccal crossbite on opposite side (long side of mandible)

Hemimandibular hyperplasia

Three-dimensional (sagittal, vertical, transverse) enlargement of one mandibular half

Facial asymmetry (oversized lower face on one side), oblique occlusal plane

Condylar hyperplasia

Isolated unilateral enlargement of condylar neck

Oblique occlusal plane, asymmetry of lower facial third, sometimes posterior open bite

Isolated unilateral hyper- or hypoalveolism

Unilateral over- or undersized sections of alveolar process

Alterations in occlusal plane, open bite

Unilateral mandibular hypoplasia

Hypoplasia or aplasia of condylar process and parts of the ascending ramus

Facial asymmetry, short lower facial third or facial half on one side, high occlusal plane angle with elevation towards diseased side

Unilateral vertical elongation of maxilla

Unilateral elongation of maxilla, mostly to compensate mandibular hypoplasia

Facial asymmetry, oblique occlusal plane

Unilateral shortening (hypoplasia) of the maxilla

Unilateral hypoplasia usually due to restricted growth of the mandible on the same side

Facial asymmetry, oblique occlusal plane angle

Transverse discrepancies

Asymmetric discrepancies

Table 7.1-1 (cont) Symmetric and asymmetric dysgnathias.

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5

Treatment planning

5.1 General considerations

Once the diagnosis is established, a number of decisions must be taken as to how to best treat the patient. These decisions include considering the needs of the patient, timing of the procedure, the stability of the move, and type of surgery. As discussed, timing of the surgical procedure will vary with the underlying skeletal discrepancy, growth potential of the patient, and functional needs of the patient. In addition, most orthognathic surgical procedures are performed in close cooperation with an orthodontist and within a complex combined treatment concept. The stability of the individual move can dictate which procedure to use.

Fig 7.1-6 Tracing of lateral cephalometric x-ray. Vertical maxillary excess with open bite (apertognathia), mandibular excess (prognathism), steep mandibular plane, two steps in the maxillary occlusal plane.

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For example, a patient with a large maxillary transverse discrepancy with vertical maxillary excess may be best treated by a surgically assisted rapid palatal expansion to correct the transverse discrepancy, followed by a Le Fort I osteotomy with ostectomy to correct the vertical component of the problem. A large mandibular advancement may be best accomplished by distraction rather than a bilateral sagittal split. How much the jaws are moved is dictated by the clinical examination, the discrepancy of the patient from the norm, and the orthodontic treatment concept. Cephalometric tracings are used to predict the amount of movement based on the needs of the clinical examination (Figs 7.1-6 , 7.1-7). Model surgery is performed based on the cephalometric tracings and in cooperation with the orthodontist (Fig 7.1-5 , page 326).

Fig 7.1-7 Postoperative lateral cephalometric x-ray. Situation after moving the anterior portion of the maxilla with the central incisor 2 mm down and 3 mm forward, leveling the maxillary occlusal plane, mandibular setback of 7 mm, closing the open bite, altering the mandibular occlusal plane. 6 weeks postoperatively.


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Modern computer-based planning programs help to visualize the position of the bones, the teeth, and the soft tissue profile. They allow to simulate a movement of fragments, in this case a Le Fort I osteotomy and advancement, and to predict the postoperative position of teeth and the expected soft-tissue profile (Fig 7.1-8). Combined movements of jaws

and teeth can be simulated by combining an articulator based orthognatic surgery and an orthodontic setup. For an orthodontic setup the teeth are subsequently mobilized in the Plaster of Paris models. After that a simulation of the estimated orthodontic movements is done by reassembling the teeth in a wax socket (Fig 7.1-9).

Fig 7.1-8 Computerized prediction of profile, jaw and teeth position. A Le Fort I osteotomy and advancement is simulated for a patient with maxillary retrognathia.

Fig 7.1-9 Combined orthognatic and orthodontic setup. A Le Fort I osteotomy and maxillary advancement in combination with a mandibular setback is simulated in the orthognatic setup. In addition an orthodontic setup is done by moving multiple single teeth Plaster of Paris blocks in a wax socket.

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5.2 Orthognathic surgery versus distraction osteogenesis

Orthognathic surgery (osteotomies, positioning, and fixation) has been used for decades to treat patients with skeletal discrepancies. In contrast, distraction osteogenesis is a relatively new technique that has gained popularity in the treatment of skeletal discrepancies in the maxillofacial complex. While some authors suggest that distraction may replace routine orthognathic procedures, it should be viewed as an alternative technique that can be used to correct discrepancies in the maxilla and mandible. Both distraction and orthognathic surgery have strengths and weaknesses, and points where one is indicated over the other. Orthognathic surgical techniques are much more versatile and precise. A maxilla may be canted, rotated, advanced, setback, impacted, brought down, or segmented after a Le Fort I osteotomy. In contrast, with distraction a maxilla is often advanced, brought down, and with some difficulty it can be simultaneously widened. The surgeon is much more dependent on the patient's compliance when doing distraction and it frequently requires more office visits to see the patient than with orthognathic surgery. Orthognathic surgery is much more predictable than distraction. For instance, moving a maxilla or mandible forward five or six millimeters into exact interdigitation of the teeth with the opposite jaw is very predictable with a Le Fort I osteotomy of the maxilla or a bilateral sagittal split of the mandible. However, when it is necessary to advance the maxilla or mandible extensively, orthognathic surgery is difficult to perform and less stable, especially when the patient has had previous surgeries. In contrast, with distraction it is possible to advance the maxilla or mandible great distances with confidence, but precise interdigitation of the teeth can be problematic. Finally, distraction offers the possibility of creating inter-arch space through the use of interdental osteotomies and gradual expansion.

5.3 Stability

An important consideration in treatment planning is the concept of stability of the planned surgical moves. Stability of the surgical procedure is dependent on multiple factors including the direction of the move, the fixation technique, and the procedures chosen. It could be shown that stability of surgical moves can be grouped into four categories: Most stable

Maxillary impaction, mandibular advancement less than 10 mm and clockwise rotation

Stable

Maxillary advancements less than 10 mm

Less stable

Mandibular setbacks

Least stable

Downward rotation of the maxilla, widening of the maxilla

The surgical moves in the most stable category have a less than 10% chance of significant post-treatment change. Stable procedures have a less than 20% chance of significant post-treatment change. The most stable surgical procedure is the superior repositioning of the maxilla followed by mandibular advancement. Both of these moves have more than a 90% chance of less than 2 mm change of landmarks. Mandibular advancement, especially with moderate moves and rigid internal fixation in patients with short or normal facial height and less than 10 mm of advancement, has an excellent record of stability. Maxillary advancement falls into the second category of a stable move. With advancements of up to 8 mm there is an 80% chance of less than 2 mm change of landmarks. Twojaw surgeries with the maxilla up and the mandible forward, or the maxilla forward and the mandible back, are less stable than the above moves. These surgeries and the correction of asymmetry are stable only if rigid internal fixation is used. Less stable procedures have a 20-40% chance and least stable procedures a chance of 50% and more of two to four millimeters postsurgical change. These include moving the mandible back, the maxilla down, and widening of the maxilla. By understanding the stability of surgical moves, the surgeon and orthodontist may be able to alter the treatment plan to include the possibility of more stable and predictable moves. Alternatively, if the treatment cannot be altered to include more stable moves the surgeon and the orthodontist should be aware of the potential problems and the patient should be informed.

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5.4 Treatment

5.5 Morbidity of surgical procedures

As discussed in the previous chapter, the patient’s diagnosis and treatment is established from the clinical examination, dental model exam, and cephalometric evaluation. Table 7.1-2 oversimplifies the treatment planning process but will give the novice a good starting point.

Every orthognathic procedure has potential complications and pitfalls (chapter 7.6 Complications and pitfalls). Especially when small skeletal discrepancies are treated, a procedure with less specific complications may be used if there are alternatives. For instance a mandibular prognathism with mild skeletal discrepancy may be treated with a Le Fort I advancement instead of a bilateral sagittal split osteotomy (BSSO) to avoid inferior alveolar nerve damage.

How much the maxilla or mandible are moved is based on the clinical examination, cephalometric x-ray evaluation, model surgery, and orthodontic planning aspects. Models are mounted on a semi-adjustable articulator and are moved so that they interdigitate with the opposing arch. Measurements are made in the laboratory from the model surgery. A splint is fabricated from the interdigitated models to be used to accurately position the maxilla or mandible. For 2-jaw surgery typically two splints are made, one for intermediate and one for final positioning.

Diagnosis

Treatment

Vertical maxillary excess

Maxillary impaction

Vertical maxillary deficiency

Maxillary downgraft

Maxillary constriction

idening of the maxilla (Le fort I in W s egments or surgically assisted rapid palatal expansion)

Mandibular constriction

andibular widening (distraction M osteogenesis)

Apertognathia

ifferential maxillary impaction or D mandible osteotomies

Maxillary retrognathia

Maxillary advancement

Mandibular retrognathia

Mandibular advancement

Mandibular prognathism

andibular setback or maxillary M advancement in mild forms

Microgenia

A dvancement genioplasty

Macrogenia

Reduction genioplasty

Table 7.1-2 Simplified treatment planning process.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.2 Standard osteotomies in the mandible

1

Angle and ramus osteotomies

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1.1 Bilateral sagittal split ramus osteotomy (BSSO)

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1.2 Vertical ramus osteotomy

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1.3 Inverted L-osteotomy

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2

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Osteotomies of the mandibular body

2.1 Osteotomy of the lateral body

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2.2 Subapical (block) osteotomies

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3

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Genioplasty

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Authors Christian Lindqvist, Tanja Ketola-Kinnula

7.2 Standard osteotomies in the mandible

Prior to the decision to start the treatment, patients should always meet both orthodontist and surgeon to receive as broad information as possible. Preoperative orthodontic care takes on average 1.5 years and, when the patients are ready for surgery, they meet the surgeon again to get further information. It must be kept in mind that the inclusion of patients in decision making increases their awareness and also acceptance of the result. Postsurgical support is also mandatory. Several procedures have been described for correction of deformities of the mandible. For osteotomies aiming to change the position of the mandibular base, the main idea is to get a moveable/slideable distal fragment apart from the proximal fragments, which contain the condyles and, therefore, should stay as precisely as possible in the preoperative position. Many anatomical and functional reasons have guided the development of procedures as we know them today. In 1957, Trauner and Obwegeser introduced the step-shaped sagittal split osteotomy for correction of both the prognathic and retrognathic mandible. The original osteotomy has subsequently been modified by numerous authors in an effort to increase the areas of bone contact, minimize the need for dissection of soft tissues, avoid nerve injuries, and prevent relapse. The sagittal split technique today is widely accepted as the method of choice for correcting a variety of mandibular anomalies. The distal segment of the mandible can be positioned in almost all planes. The vertical ramus osteotomy can be used especially when correcting asymmetry of the mandible. The standard way is to make a sagittal split osteotomy at the side which rotates forward and the vertical ramus osteotomy at the side which rotates backwards. There is usually no need to internally fix the vertical osteotomy line, but mandibulomaxillary fixation (MMF) for 2-3 weeks is required. Sometimes this type of osteotomy is also used for surgical treatment of temporomandibular joint (TMJ) dysfunction and pain. The goal

is to decrease the pressure of the condyle against the retrodiscal ligament (caused by occlusion) in cases where the disc is anteriorly displaced. Advancement of the mandible is also possible after vertical ramus osteotomies, but here bone grafts need to be positioned between the fragments. Fixation of the fragments is required. When an increase of ramus height is indicated, the inverted L-osteotomy can be used. Bone grafts may be positioned in the line of osteotomy when additional height is needed. In those cases the osteotomy line should be perpendicular to the surface of the lateral cortex and is performed through a retromandibular transcervical incision. “Bird face” deformities have been corrected by this procedure. When only a slight increase of height is needed and the anatomy of the ramus is favorable, an oblique line of osteotomy can be made and correction achieved by sliding the fragments towards each other. This procedure is usually performed transorally. Bilateral mandibular body osteotomy is not often used nowadays. Previously, it was more often performed in cases of prognathism, especially when the body was long and one tooth was missing on each side, or in case of an anterior open bite with first contacts in the premolar or molar region. This osteotomy is performed via a transoral or a combined transoral-transcutaneous approach. Extra care should be taken to avoid injuries to the inferior alveolar nerve. Subapical osteotomies are also used in orthognathic surgery. They may be total, including the complete alveolar process or partial (block or segmental) osteotomies. They are mostly performed to correct an anterior open bite and are then restricted to the area between the mental foramina. This type of osteotomy can also be used for patients with severely compromised lower anterior teeth (eg, deep fillings, root resorption), making orthodonthic moves impossible. The procedure can be combined with other osteotomies, ie, the sagittal split osteotomy.

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To harmonize the profile and to make the face look more favorable, a genioplasty can be performed. It can be combined with some other type of osteotomy and done simultaneously or at a second stage. Following the osteotomy, the chin can be positioned in almost every vector in space. Reduction genioplasties usually need bone removal; elongation or augmentation genioplasties especially need an increase in height and perhaps a bone graft. Bone grafts can be positioned between the fragments or on top of them. The chin fragment can be split vertically and used to correct the mediolateral dimension as well.

a

a

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1

Angle and ramus osteotomies

1.1 Bilateral sagittal split ramus osteotomy (BSSO)

The original bilateral sagittal split osteotomy as described by Trauner and Obwegeser was placed in the ramus of the mandible (Fig 7.2-1a–b). Dal Pont et al changed the lower horizontal osteotomy to a vertical osteotomy in the posterior body of the mandible. The ramus was split all the way to the posterior border. Hunsuck recommended that the medial cortical osteotomy should be extended just posterior to the mandibular foramen. Epker stated that stripping of the pterygo-masseteric sling from the ramus is unnecessary. The sagittal split osteotomy is nowadays usually carried out taking into account these modifications (Fig 7.2-2a–b).

b

Fig 7.2-1a–b Horizontal step-shaped osteotomy (Trauner/Obwegeser). a Lingual side. b Buccal side.

b

Fig 7.2-2a–b Sagittal split osteotomy according to Obwegeser/Dal Pont. a Lingual side horizontal cut of lingual cortex above the mental foramen. Vertical cut of buccal cortex just posterior to second molar. A piece of bone is marked that needs to be removed prior to retropositioning of the distal tooth-bearing fragment. b Buccal side after mandibular setback.


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The osteotomy lines can first be marked with a round burr. After that, the drill holes are connected with a fissure burr involving the whole thickness of the cortex. A saw, a piezoelectric device, or a burr are used for the medial horizontal and lateral vertical osteotomies (Fig 7.2-3). Any unnecessary stretching of tissues on the medial region of the ramus should be avoided while carrying out the medial osteotomy and

identifying the nerve bundle. The splitting is finalized using thin, narrow osteotomes, slowly advancing from thinner to thicker (Fig 7.2-4a–c). The splitting can also be made with special separation forceps. It should be undertaken with extra care to avoid fractures of the buccal plate (bad split). Piezoelectric cutters can be used instead of saws and burrs for better soft-tissue and nerve protection.

Fig 7.2-3 Connecting the initial burr holes with a Lindemann drill.

b

a

c

Fig 7.2-4a–c a Splitting of the ramus with a thin narrow osteotome strictly alongside the inner aspect of the outer cortex in order to avoid damage to the mandibular nerve. b Osteotome gliding down alongside the inner aspect of the outer cortex. c Final split laterally from the nerve bundle.

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According to the correct osteotomy technique, the inferior alveolar nerve should be situated totally in the distal fragment. In many cases the nerve can, however, be identified between the fragments and sometimes even to some extent be attached to or indented into the outer cortex of the proximal fragment. Releasing should be carried out with extra care. The looseness and mobility of the fragments is checked bimanually. Thereafter, the acrylic splint is applied and the anterior segment of the mandible is placed in the planned relation to the maxilla. Mandibulomaxillary fixation is carried out tightly with wires or with an orthodontic “power chain.”

a

In case of advancing the tooth-bearing fragment, the convergence of the mandible should be kept in mind. The osteotomy lines are usually also convergent, and sliding the distal fragment anteriorly may make the proximal fragments flare medially (Fig 7.2-5a–b). When correcting a class II malocclusion by advancement, the convergence leads to anterior gap formation. If this gap is eliminated by compression, the condyles tend to move outward (Fig 7.2-6). In mandibular setback, a cortical fragment from the anterior part of the proximal fragment should be removed to allow the mandible to move posteriorly.

b

Fig 7.2-5a–b a Marking of the osteotomy for sagittal split osteotomy of the mandibular ramus. b Possible medial condylar displacement with mandibular advancement.

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The most important phase of the fixation procedure is keeping the proximal fragments in the correct position within the glenoid fossa. Several devices and methods have been developed to achieve this, but manual seating by the surgeon is probably the most extensively used method. Earlier, when wire osteosynthesis was used, the position was not that critical because the flexibility of the system allowed slight movements of the condyle into a favorable position prior to healing of the osteotomies. Rigid fixation methods, though, are unforgiving and do not allow this adjustment (Fig 7.2-7).

Fig 7.2-6 Possible outward rotation of condyle if anterior gap after mandibular advancement is closed by lag screw fixation.

Fig 7.2-7 Correct fixation of sagittal split osteotomy and mandibular advancement. Anterior gaps are kept and stabilized with position screws. Posterior natural contact area is stabilized with a lag screw.

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A 1.5 or 2.0 adaptation or Matrix plate can be used as a “prefixation” plate to define and later maintain the positions of the proximal fragments. Before performing the osteotomies, MMF is applied in the preoperative centric occlusion using a splint/wafer in the preoperative position. Transoral approaches are made and miniplates are attached bilaterally from the lateral side of the ramus to the retromolar area of the maxilla with two screws on either sides of the plates. In the maxilla the screws can be inserted through the mucosa. MMF is released and stability is controlled. Positioning plates are removed and bilateral osteotomies are performed. After that, the anterior segment of the mandible is positioned

a

into the splint, MMF is performed, and the prefixation plates are reattached using the same burr holes. Now stable internal fixation can be performed, while the proximal fragments are maintained in their preoperative position (Fig 7.2-8a–e). However, it must be noted that there is no evidence confirming that the prefixation technique leads to improved condyle positions over manually positioned condyles. Therefore, many surgeons prefer to position the small proximal fragments manually by pushing the mandibular angles upwards and backwards. Intraoperative position control with surgical navigation is also possible.

b Fig 7.2-8a–e Fixation procedure for keeping the proximal fragment in correct position for mandibular setback. a Marking of the osteotomy line on the bone surface. b Fixation of the ascending ramus fragment to the maxilla with the help of a plate and transbuccal instrumentation. This is done before the BSSO is performed. c Completion of the osteotomy with a Lindemann burr after removal of the fixation device for the positioning of the proximal fragment.

c

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d

e

Fig 7.2-8a–e (cont) Fixation procedure for keeping the proximal fragment in correct position for mandibular setback. d Completion of the osteotomy with an osteotome. e After completion of the osteotomy, the distal tooth-bearing fragment is positioned with the splint and MMF, while the condyle-bearing fragment is positioned with the prefixation plate. Position screw osteosynthesis is performed using transbuccal instrumentation.

An altered position of the condyle can lead to postoperative resorption, other joint complications, and/or relapse of the position of the mandible. The placement of the condyle is anatomically guided by the shape and the position of the disc and by the shape of the glenoid fossa. The direction and magnitude of forces applied are critical. General anesthesia, relaxation, and the supine position of the patient tend to seat the condyle posteroinferiorly. This should be remembered while attempting to achieve the correct, uppermost position of the condylar head in the center of the glenoid fossa. Condylar resorption is an irreversible cause of late relapse. Mandibular hypoplasia with a high mandibular plane angle, huge advancement, TMJ dysfunction, long period of MMF,

and counterclockwise rotation of the proximal fragment, especially when connected with a posteriorly inclined condylar neck, are regarded as risk factors for this condition. After seating of the proximal fragments, fixation of the osteotomies can be initiated. Historically, fixation was done with wires. After that, a long period of MMF was necessary and the union of the fragments was sometimes poor. Lag screw fixation gives excellent stability and good conditions for primary healing of the osteotomy. The nerve could, however, be injured by the screw itself or by compression of the fragments. When gaps exist between the osteotomy fragments, compression may cause unwanted torque of the proximal fragment with the consequences previously mentioned. Screw fixation requires minimal hardware.

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To avoid the previously mentioned consequences, position screws are introduced to fix the fragments. With these, the gap between the fragments can be maintained. Bone grafts may be positioned between the fragments to avoid compression and movement of the proximal fragment. Sometimes it is indicated to use lag screws in combination with position screws (Fig 7.2-9a–b). When advancing the mandible, the lag screw is used to stabilize the posterior natural contact area and the anterior area is fixed with position screws which can be placed through a sandwiched bone graft, if necessary. It should be noted that in setbacks, the natural contact area is situated in the front allowing lag screw fixation. Typically two or three 2.0 mm titanium screws are used in a linear or triangular fashion (Fig 7.2-10a–c).

Monocortically fixed miniplates are an alternative to stabilize fragments. The stability is adequate and predictable. 2.0 mandibular or Matrix plates can be used, usually with six holes (Fig 7.2-11a–b). There is also a specially designed 2.0 plate with an adjustable slider (SplitFix) for sagittal split osteotomies (Fig 7.2-12). Injuring the nerve by the screws and by compression can be avoided because the fragments are not pressed against each other. The plate can be bent according to the anatomical situation and flaring of the anterior end of the proximal fragment can be maintained. Thus, the unwanted torque and the movement of the condyle are avoided. The application of a plate requires the vertical osteotomy to be seated further anteriorly, sometimes between the first and second molars, thus increasing the risk of buccal plate fractures (bad split) and nerve injury.

a

b

Fig 7.2-9a–b Correct fixation of sagittal split osteotomies, for mandibular advancement (a) or mandibular setback (b) with position screws and lag screws.

a

b

c

Fig 7.2-10a–c The possible placements of either lag or positioning screws: a Along the superior rim. b Triangular with one screw superiorly. c Two screws superiorly, one screw caudally.

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a

b

Fig 7.2-11a–b Monocortical fixation of sagittal split osteotomies with either one (a) or two (b) 2.0 mandibular or Matrix plates.

Fig 7.2-12 Fixation of sagittal split osteotomy with an adjustable slider fixation device. Fixation is done with monocortically placed screws.

For fixation, an adequate plate is selected and bent according to neutral positions of fragments, holding the proximal fragment in the correctly seated position. At least two screws should be inserted in the proximal and two in the distal fragment. The neurovascular bundle is identified at the mental foramen. Nerve injury must be avoided. The plates are fixed transorally, and placement of the proximal screws rarely requires transbuccal instrumentation or the use of an angulated screwdriver. After fixation of both sides, MMF is released. The occlusion is checked making sure that the condyles are correctly placed within the fossae. In case of occlusal problems, MMF should be reapplied. Removing the screws at the distal fragment only is sufficient in the majority of those cases. The proximal fragment is seated again with extra care and the plate is again adjusted. New holes are drilled and screws inserted. Rechecking is performed after releasing the MMF. The patients are not kept in postoperative MMF, but the splint is usually fixed to the brackets in the maxilla with thin wire ligatures.

Light guiding elastics are often used at least until the splint is removed, approximately 2–4 weeks postoperatively. Policies with splints and guiding elastics differ a lot between centers, but rigid MMF is usually not required. Fixation with bioresorbable osteosynthesis material is an option in sagittal split osteotomies. When bioresorbable plates are used, 2.0 mm screws are preferred. The plate should not be placed directly under the incision. The area under the attached gingiva should be avoided to enable good softtissue coverage. Being situated lower, the plate will not be palpable and a proper soft-tissue coverage makes undisturbed degrading possible. At least three screws should be placed in each fragment to provide adequate stability. In some cases formation of granulation tissue occurs. Surgical treatment is needed only if there is loose material palpable. Wound dehiscence may occur in rare cases. If a plate is exposed immediately after the operation, revision and wound closure should be done. If that happens 2 months postoperatively or later, the plate and screws can be removed. These problems are rare and occur similarly when other materials are used.

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1.2 Vertical ramus osteotomy

Historically, vertical ramus osteotomies were widely used in cases with Class III malocclusion and prognathic mandibles. The method was preferred to BSSO for the lower incidence of nerve injuries. The fragments were usually left without any fixation and a long period of MMF was used. Nowadays, the operation is rarely performed, but may be useful in cases with asymmetry and if vertical movement of the ascending ramus is needed. It can be used in combination with some other type of osteotomy, ie, body step osteotomy on the same side or sagittal osteotomy on the other side. If the planned retrusion is very large, the coronoid process may hit the condyle, and coronoidectomy should be carried out. The whole surface of the lateral cortex of the ramus is exposed, usually from a transoral incision, and a 6–7 mm deep cut is performed with an angle-bladed oscillating saw. The cut is made posterior to the mandibular foramen, keeping the antilingula of the buccal plate as an anatomical landmark (Fig 7.2-13a–b). The cut is completed from the posterior aspect of the sigmoid notch to the ante-

a

gonial notch area at a distance of 7 mm anterior and parallel to the posterior border of the ramus. After the osteotomy is completed, the proximal fragment is usually displaced laterally. It can be pulled more laterally with an elevator, and the medial pterygoid muscle and the periosteum are stripped from the most anterior part of the medial surface to allow the fragments to overlap and have bone-to-bone contact. It should be remembered that the remaining part of the muscle acts as a pedicle to the proximal fragment and maintains the superior seating of the condyle and should not be totally stripped. After the osteotomy is made, some interference between the two fragments can usually be observed. A good approximation is ensured by smoothening the interfering areas with a large rounded burr. The soft tissues are protected. A gap of more than 1 mm leads to fibrous tissue formation between fragments. Bony union is more likely to occur if decortication of the gap areas and rigid fixation is used. If rigid fixation is performed, a percutaneous trocar should be

b

Fig 7.2-13a–b a Marking of vertical ramus osteotomy posterior to the mandibular foramen and parallel to the posterior border. b Mandibular setback after a vertical ramus osteotomy. The proximal fragment is displaced laterally. Fixation with screws.

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used for appropriate screw placement. Two or three screws can be applied in a linear fashion. The osteotomy is performed like previously mentioned. Correct seating of the condyle in the glenoid fossa may be difficult. Instead of screws, L- or T-shaped miniplates can be used. The demand for rigidity is obvious when vertical movements of the distal fragments are produced. The placement of any fixation hardware should be passive to avoid unwanted movements of the condyle. It should be remembered that the buccal plate in the area of the nerve entrance can be extremely thin, and the nerve can easily be injured. 1.3 Inverted L-osteotomy

The inverted L-osteotomy is carried out in the same way as the vertical ramus osteotomy. It can be approached transorally. The lower cut is made with an oscillating saw with angled blade. The lower part of the cut is exactly the same as in the vertical ramus osteotomy, but the upper cut is bent anteriorly in the horizontal plane above the mandibular foramen and is performed with a reciprocating saw. Care

a

should be taken when separating the segments to avoid fracturing the cut into the sigmoid notch. In that case, the situation would be the same as carrying out a vertical ramus osteotomy with coronoidectomy. The indications for this procedure are the same as for the vertical ramus osteotomy. When retruding the mandible, the proximal segment is pulled laterally to allow overlapping of the segments. The segments can be left without any fixation but a long period (6–8 weeks) of MMF is then required. Some anterior movement by sliding is possible without any bone grafting. Miniplates can be used with transbuccal screw placement (Fig 7.2-14a–b). A bone graft can be positioned between the segments at the horizontal or at the vertical osteotomy, depending on which dimension needs to be increased. If an increase is needed in both dimensions, eg, in case of a “bird face,“ L-shaped or multiple bone grafts can be positioned between the segments. The procedure is then approached trancutaneously and rigid fixation is performed.

b

Fig 7.2-14a–b a Marking of an inverted L-osteotomy-vertical cut as for the vertical ramus osteotomy. Horizontal cut above the mandibular foramen and below the sigmoid notch. b Situation after mandibular setback. The proximal fragment is displaced laterally and fixation is done with two miniplates.

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2

Osteotomies of the mandibular body

2.1 Osteotomy of the lateral body

Osteotomies of the lateral body of the mandible for mandibular setback were once widely used, especially when premolars or molars were missing. By this technique prosthetic reconstructions with bridges can be avoided by eliminating the areas of missing teeth. Osteotomies of the mandibular body with ostectomies are also indicated in cases with extreme mandibular prognathism with marked discrepancies between mandibular and maxillary arch lengths. An extremely deep curve of Spee can be corrected, too. Some correction of the transversal dimensions is also possible. The osteotomy cuts can be linear or stepwise, and the inferior alveolar nerve must be preserved. Piezoelectric saws are helpful to avoid nerve damage. Blocks of bone are removed from the area of

a

the missing teeth and from the inferior part of the body. In step osteotomies the segments are connected by a horizontal osteotomy line which extends anteriorly above the nerve canal. The apices and lateral surfaces of roots should not be injured (Figs 7.2-15a–b, 7.2-16a–b). When the osteotomy is completed and the bone blocks are removed, an acrylic splint is placed and the segments moved to the planned occlusion with the maxilla. MMF is carried out. The vertical osteotomies are fixed with miniplates, typically with one being positioned above and another below the nerve canal. 2.0 plates or Matrix plates with four holes can be used, fixed by monocortical screws, two at the distal and two at the proximal segment for each plate. Injuring the nerve and roots of the teeth must be avoided.

b

Fig 7.2-15a–b a Marking for a linear ostectomy of the lateral body of the mandible. The inferior alveolar nerve must be freed (neurolysis). b Fixation of mandible setback after linear osteotomy with two mandibular miniplates.

a

b

Fig 7.2-16a–b a Marking for a stepwise ostectomy in the lateral body of the mandible. The horizontal cut is performed above the mental foramen. The width of one premolar is removed. b Setback of anterior mandible after stepwise ostectomy in the premolar area. Fixation with two miniplates.

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In a chin osteotomy with transversal expansion for patients with narrow mandibles and anterior crowding, transversal mandibular expansion is an alternative for extraction therapy. Mandibular expansion is usually done from a vertical midline or a paramedian osteotomy with a bone-anchored distractor (Fig 7.3.2-3, page 364). 2.2 Subapical (block) osteotomies

Subapical osteotomies are indicated when the basal skeletal relationships are good and the malocclusion is of alveolar origin and cannot be treated by orthodontic methods only. They can be restricted to certain segments (block or segmental osteotomies) or extended even to the whole dental arch (Fig 7.2-17). The osteotomies are typically performed from an intraoral vestibular approach. Care must be taken

to avoid unnecessary soft tissue stripping. Soft tissues must remain attached to the lingual aspect of the mobilized segment. The creation of small segments containing only one or two teeth should be avoided, in order not to compromise viability of the segments. The segments can be moved in any direction. Anterior open bite can in some cases be treated by moving the segment upwards. Bone grafts should then be positioned into the gap area. The method is extremely suitable for correcting the superior position of anterior teeth. In these cases a section of bone should be removed inferiorly (Fig 7.2-18a–b). The method can be combined with other types of osteotomies and carried out in the same session.

Fig 7.2-17 Circumferential subapical block osteotomy in the mandible. The osteotomy is performed above the canal of the inferior alveolar nerve and below the tooth roots.

a

b

Fig 7.2-18a–b a Subapical osteotomy in the chin area. The ostectomy zone is marked for ostectomy and subsequent downward movement of the anterior block. b The anterior block is fixed in the new position after downward setting. Fixation of the bony part with two crosslike miniplates and fixation in the dental area with a splint.

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The interdental osteotomies are performed with a fissure burr or a piezoelectric saw, directed perpendicular to the dental arch. If the dentoalveolar segment is moved cranially, the lines should not be convergent. In cases with convergent dental roots, a special orthodontic pretreatment must be performed to allow for safe interdental osteotomies. The mental nerves are identified and protected. The horizontal cut is made using a reciprocating saw and is situated 3–5 mm inferior to the dental apices. Thin osteotomes are used to mobilize the block.

3

When the dentoalveolar segment is mobile, the acrylic splint is placed, the segment is gently moved to the planned position, the bone graft is positioned and MMF is carried out, if necessary for fixation. X-, T-, L-, H-shaped 2.0 or 1.5 or Matrix miniplates can be used. Two 4-hole plates are enough to stabilize most bone blocks. Vertically positioned plates are stable and tilting movements are well prevented. Injuring the dental roots should again be avoided.

From a transoral incision the bone surface is exposed to the inferior border of the mandible from first molar to first molar. Most surgeons prefer to cut in the mobile mucosa. The mentalis muscles are exposed and dissected separately. The periosteal attachment at the anterior inferior border is maintained to have the soft tissue contour unchanged. The midline is marked before the osteotomy. The osteotomy is performed with a reciprocating saw and a chisel (Fig 7.2-19a–b). The angle of the osteotomy is planned according to the planned movement of the fragment (Fig 7.2-20 a–d). When increasing the vertical dimension, a bone graft can be positioned into the gap. When increasing the width, the fragment can be split in two or more pieces and bone grafts can be positioned between the fragments (Fig 7.2-21).

a

Genioplasty

To harmonize the profile and to make vertical dimensions of the face more favorable, a genioplasty may be indicated. It can be combined with some other type of osteotomy and can be performed simultaneously in the same session or at the second stage. When advancing a mandible with a huge distal bite by BSSO, the stretching forces of soft tissues can cause a relapse of genioplasty performed in the same session. Any dimension of the chin can be adjusted by this method.

b

Fig 7.2-19a–b a Horizontal osteotomy for a genioplasty. Note marking of the midline which is done before the osteotomy. b After completion of the osteotomy the lower segment is grasped and moved into the desired position.

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a

b

c

d

Fig 7.2-20a–d

Various markings for osteotomies in the chin area for the various desired movements of the chin.

Fig 7.2-21 Genioplasty after increasing the vertical dimension with a bone graft in the osteotomy gap.

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Stability of the fragments is achieved by fixation with miniplates 1.5, 2.0, or corresponding Matrix plates. As a rule, two screws should be placed in each fragment. Fixation can be performed by using straight Y- or X-shaped plates (Fig 7.2-22a–b). Monocortical screws offer sufficient stability. The plates should be bent to lie passively on the fragments to avoid dislocating forces and to avoid sharp edges that postoperatively can be felt through the skin. Lag screw fixation

a

c

350


is also an option because the screws cannot be felt through the skin and the stability is excellent. Two or more lag screws can be placed (Fig 7.2-22c). This is also a good indication for bioresorbable fixation. During wound closure care must be taken to suture the mentalis muscle, thus resuspending the soft tissues to avoid a drooping chin.

b

Fig 7.2-22a–c a Genioplasty with advancement of lower segment and fixation with two X-shaped 2.0 plates. b Genioplasty with setback of lower segment and fixation with two X-shaped 2.0 plates. c Fixation of lower segment after advancement with two lag screws. Care must be taken not to damage the tooth roots.


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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.3 Standard osteotomies in the maxilla

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Planning

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Surgical access

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Osteotomies and fragment fixation

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Author Gerson Mast

7.3 Standard osteotomies in the maxilla

Maxillary osteotomies can be performed at different anatomical levels. They are currently described according to the Le Fort trauma classification. Whereas Le Fort II and III level osteotomies are almost exclusively used for corrections of craniofacial deformities, the so-called Le Fort I osteotomy has become a workhorse of orthognathic surgery. The total basal maxillary osteotomy (Le Fort I osteotomy) has a wide range of applications. Maxillary block and segmental osteotomies, either in combination with total osteotomies or isolated, are also possible, but play only a subordinated role today due to the progress in orthodontics. The anatomical structure of the maxilla with its characteristic thin bone layers in between facial buttresses, the neighboring nasal cavity, and the maxillary sinuses, as well as bone areas with a variety of thicknesses requires special considerations in planning, soft-tissue access, techniques of osteotomy and fixation, as well as additional tissue handling.

1

2

Surgical access

All basal maxillary procedures can be performed by transoral approaches. Even with the vascularization of the maxillofacial region being outstanding compared to the rest of the human skeleton, it must be taken into account that only a thin soft-tissue layer covers the maxilla and provides blood supply to the bone. Therefore, care must be taken to preserve the soft-tissue lining of the fragments after an osteotomy by limited exposure and periosteal stripping. Total and combined segmental osteotomies are mostly performed following a slightly curved horizontal vestibular incision from molar 6 to 6 (Fig 7.3-1). Block and segmental osteotomies can safely be performed following limited horizontal and vertical incisions. The general rule, that smaller fragments are more easily detached from soft tissues with the consequence of compromised blood supply and a higher risk for complications, such as necrosis, must be considered.

Planning

The three-dimensional movement of the maxilla, in total or in parts, has functional and esthetic implications. Functionally, maxillary osteotomies allow for an enlargement of the oral space (tongue space) by impaction or advancement of the maxilla, which for instance is of major importance in open bite deformities. A transversal widening of the maxilla can prevent tooth extractions, a concept that very often leads to a better and more stable dentoalveolar correction of skeletal disorders. The surgical correction of the dental axis in skeletal and dentoalveolar deformities, especially in the frontal part, can be faster and more stable than orthodontic corrections and, therefore, prevent relapse. Esthetically, maxillary osteotomies are important to improve midfacial projection, to correct the transverse plane, the facial midline, the lip-to-tooth relationship, the support of the upper lip, and to influence the position of the nose.

Fig 7.3-1 Slightly curved incision line from 6 to 6 for the exposure of the maxilla. Marked osteotomy line in the Le Fort I plane.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.3 Standard osteotomies in the maxilla

3

Osteotomies and fragment fixation

Maxillary osteotomies, with their long tradition, have seen several modifications over the years and have become generally accepted, standardized, and safe procedures. The intention of all procedures is the preservation of the blood supply, proper positioning and sufficient fixation of the fragments, and the prevention of relapse. Usually the osteotomies are performed with burrs, osteotomes, reciprocating saws, or piezoelectric devices. New technologies which employ navigation or endoscopic approaches are already in clinical use. The use of plates and screws for internal fixation was revolutionary. Patient comfort has increased dramatically with stable internal fixation, and the risk for relapse has significantly diminished. Today, adaptation plates 1.5, 2.0, or Matrix plates are most used for maxillary fixation. Special plate configurations, such as L-plates, help to simplify the osteosynthesis technique and to save time. It is of major importance to realize that the plates must be bent accurately (“passive”) to the bone surface without any “active” influence to the fragment position. Therefore, compression plate osteosynthesis is not indicated in fixation of maxillary osteotomies. If internal fixation is carried out properly, no additional mandibulomaxillary fixation is required in the postoperative phase. Sometimes training elastics are used to guide the patient into the desired postoperative position.

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Author Gerson Mast

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.3 Standard osteotomies in the maxilla 7.3.1 Le Fort I

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Technique

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Internal fixation

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Soft-tissue considerations

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Authors Carlos Ries Centeno, Gerson Mast

7.3.1 Le Fort I

Le Fort I osteotomy was first reported by Cheever (1865) for access to a sinus tumor. In 1927, Wassmund described it as a procedure for open bite correction. Obwegeser popularized this technique for maxillary advancement. The “down fracture” terminology and the biological basis of the technique were introduced by Bell et al in 1975. This osteotomy’s versatility allows moving the maxilla in all possible directions, however, the extent varies due to anatomical reasons. For example, the setback or retroposition of the maxillary unit has some limitations because of the pterygoid plates. A maxillary vertical elongation leads to loss of bone contact and makes bone grafting of the defects a requirement. Since the osteotomy line is not truly horizontal, care must be taken because total advancement may cause changes to the final vertical position of the maxilla. In order to avoid this ramping effect, a step osteotomy is an option for a proper horizontal movement.

1

Technique

In single-jaw surgery one interocclusal wafer or splint is needed and two splints are necessary for double jaw surgery. These splints are the key to positioning. Prior to surgery, it is necessary to check whether they fit to both dental arches correctly. It is important to measure the vertical position of the maxillary incisor edge in a reproducible way. Depending on the esthetic goals of surgery one may decide to leave this unchanged, or to superiorly reposition the incisor teeth, or to achieve less incisor exposure, or to inferiorly reposition the incisal edge for greater incisor exposure. A vertical distance from a fixed reference point to the edge of the central incisors must be measured and recorded. Some surgeons prefer to temporarily anchor a screw into the glabella to establish a firm reference. A U-shaped incision from first to first superior molars (Fig 7.3-1, page 353), 3 or 4 mm above the attached gingiva is performed, and subperiosteal dissection is done to expose the inferior aspects of the maxilla, the infraorbital nerve, the zygomaticoalveolar buttress, and the piriform aperture on both sides. Bone markers (guidelines or holes) may be applied across the line of osteotomy to check or control maxillary movements.

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Before the osteotomy is performed the nasal mucosa is mobilized from the floor and lateral walls of the nasal cavity. Additionally, the posterior aspect of the maxilla is dissected with curved elevators, and special retractors are inserted for soft-tissue protection. Afterwards, the maxillary osteotomies are performed including the lateral nasal walls. The septal base is detached from the maxilla with chisels or nasal septal osteotomies. The location of the osteotomy should allow for placing screws at a safe distance (a few millimeters) from the apices of the teeth. The osteotomy is best

a

performed with a reciprocating saw passing through previously designated landmarks made with a fissure burr on the piriform margins and the zygomaticoalveolar buttress to perform a precise and symmetrical osteotomy as planned (Fig 7.3.1-1a–b). Additional osteotomies must be placed above the previous ones, in a parallel fashion if the maxilla needs a total shortening, or modified if anterior, posterior, or transverse corrections of the occlusal plane are going to be performed (Figs 7.3.1-2, 7.3.1-3). The pterygopalatine junction is now the

b

Fig 7.3.1-1a–b a Osteotomy with a reciprocating saw in the Le Fort I plane. The nasal mucosa is mobilized and protected with a periosteal elevator. b Possible lower or higher osteotomy lines.

Fig 7.3.1-2 Marking of parallel osteotomy lines for a symmetrical shortening of the maxilla.

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Fig 7.3.1-3 Marking of an asymmetrical Le Fort I osteotomy for a shortening in the vertical plane on the right.


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remaining attachment of the maxilla and is easily sectioned with a curved osteotome introduced through the buccal incision (Fig 7.3.1-4). This osteotomy should be performed before mobilizing the maxilla anteriorly downward (so-called down fracture), because dividing the pterygomaxillary junction makes down fracturing easier. For maximum release, traction can be applied with a transosseous wire through the anterior nasal spine. In addition, irregular fractures in the posterior aspect of the maxilla that may extend into the posterior orbit and may be associated with the rare complication of postoperative blindness may less likely occur. After down fracturing, bleeding from the pterygoid plexus or great palatine artery can be controlled with pressure or electrocautery. No special attempt to preserve greater palatine vessels is necessary. The principal blood supply to the osteotomized fragment is through the soft tissues of the intact palate.

With the maxilla in the down-fractured position, excellent exposure is obtained, and the bony interferences to the movements of the maxilla can be eliminated with a rongeur or a high-speed burr, eg, posterior maxillary walls, nasal septum, floor, and lateral walls, until the maxilla can be completely mobilized and passively placed in the desired new position without interference (Fig 7.3.1-5).

Fig 7.3.1-4 Osteotomes for the horizontal separation and curved osteotome for the separation of the pterygopalatine junction.

Fig 7.3.1-5 After down fracturing the nasal septum, nasal walls, and maxillary walls can be trimmed, if needed, with a high-speed burr.

Next, the splint is inserted and temporary mandibulomaxillary fixation (MMF) is performed with wires or elastics. It must be noted that after maxillary osteotomy, the mandible and the basal segment of the maxilla can be moved en bloc. Therefore, proper seating of the condyles within the glenoid fossae is checked and confirmed. They should be seated passively posteriorly and superiorly in the fossae. After moving the newly positioned maxilla upwards, the contact zone between upper and lower maxilla is checked and final interferences at the posterior medial sinus walls are removed, especially in the thick bone of the vertical process of the palatine bone and vomer. Extended superior movements may require turbinate reduction as well.

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Vertical downward positioning of the maxilla results in a bone gap between upper and lower part of the maxilla creating the need for bone grafts. These grafts are placed at the piriform rim and zygomaticoalveolar buttress areas. Bone grafts can also be applied in large advancements of 10 mm or more to decrease the gap, increase the bone-to-bone contact surface, and to help project midfacial soft tissues. Vertical movement of the maxilla always introduces mandibular positional changes by autorotation. Maxillary downward positioning elongates the face, rotates the chin point downwards and backwards, and rotates the condyles anteriorly. In contrast, maxillary impaction rotates the mandible upwards while shortening the lower face and brings the chin upward and forward. In cases where rotational movements of the mandible should be avoided, bimaxillary osteotomies (combining a Le Fort I with an osteotomy in the ascending rami of the mandible) are indicated.

2

Internal fixation

Fixation is typically performed with four miniplates, which must be placed along the four anterior maxillary buttresses and correctly adapted to the osteotomized segments. Typically, L- or Y-shaped plates (right and left) are ideal because they fit the anatomy very well. Internal fixation is performed with the splint and MMF in place (Fig 7.3.1-6). Miniplates 1.5 or corresponding Matrix plates are strong enough for internal fixation. However, in cases with large movements and in cases with preexisting scars (cleft cases, secondary osteotomies after trauma) 2.0 plates or stronger Matrix plates and screws are recommended. Placement of screws must avoid tooth roots, and placement of plates must not interfere with dental prostheses, because compression of mucosa between plate and prosthesis may cause discomfort, pain, and finally hardware exposure.

Before internal fixation is performed it is important to ensure: • Passive placement of the teeth into occlusal splint • Centric position of the condyles • Correct vertical position of the maxilla through bone-to-teeth measurement

Fig 7.3.1-6 Correct fixation of a Le Fort I osteotomy with L- and Y-plates along the anterior and anterolateral maxillary buttresses.

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3

Soft-tissue considerations

The upper lip

It is of major importance to realize that the outcome of orthognathic surgery does not rely only on the movement and fixation of bone fragments. A multitude of changes in the surrounding tissues need consideration to achieve the desired functional and esthetic result. The nose

Functional restrictions may follow the reduction of the nasal space by impaction of the maxilla. To prevent deviation, the nasal septum must be reduced in height in the same amount as the maxilla is moved cranially. The space between the inferior turbinates and the nasal floor may change, causing airway obstruction. Reduction of the turbinates can help to prevent airway compromise. The bony nasal aperture will become smaller after impaction. Modeling osteotomies may be needed to correct this.

The length of the upper lip can be influenced by additional soft-tissue procedures, typically by V-Y plasty. Short lips, especially after advancements, may need lengthening to achieve a good lip-to-tooth relationship. The cheeks

Resuspension of the soft tissues may be necessary to prevent sagging, especially in complex (high Le Fort I, Le Fort II, Le Fort III) upper facial osteotomies.

Therefore, esthetically the advancement of the maxilla tends to flatten the nose by widening the nasal base. The use of the alar base cinch suture (Fig 7.3.1-7a–c) is helpful to prevent flaring of the alar base and flattening of the nose.

a

b

c

Fig 7.3.1-7a–c Alar base cinch suture for the control of the nasal width after Le Fort I impaction or advancement of the maxilla. a The alar bases are incised and the nostril sill portions are de-epithelized. A tunnel is dissected through the base of the columella through which afterwards the denuded flaps are passed. b Diagram showing the alar base cinch suture. c Final position of alar base and nasal tip after correct closure.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.3 Standard osteotomies in the maxilla 7.3.2 Surgically assisted rapid palatal expansion (SARPE)

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Author Michael Ehrenfeld

7.3.2 Surgically assisted rapid palatal expansion (SARPE) The terms “surgically assisted rapid palatal expansion (SARPE)” and “surgically assisted rapid maxillary expansion (SARME)” are used synonymously for a surgical procedure which is one of the most frequently performed orthognathic operations. It is indicated for adult patients with fused midline palatal sutures, to allow for a gradual transverse expansion of the lower midface including the dental arch. Before fusion of the palatal suture transversal expansion of the dental arch is performed with tooth-anchored orthodontic appliances. After bony fusion of the suture which is completed after the age of 20, the attempt to expand the dental arch with orthodontic appliances alone does not widen the palate and the lower maxilla, but will lead to a lateral flaring of the canines, premolars, and molars, which is usually neither desired nor part of the orthodontic treatment concept. In patients with fused palatal sutures, a widening of the dental arch without tilting of the above mentioned teeth is only possible after a surgical intervention with the aim to reopen the midline palatal suture.

a

Historically, only an osteotomy of the midline palatal suture was performed for this purpose, either from an anterior superior vestibular approach or a palatal approach. However, in some adult patients the anterior and lateral vertical midfacial buttresses (paranasal and zygomaticoalveolar buttresses) are so strong that the alveolus including the teeth tends to flare out laterally during a widening procedure. In addition, it is important to completely detach the basal nasal septum during this procedure to avoid basal septum deviations to one side during rapid palatal expansion. To avoid these problems and to make expansion easier it is recommended to perform a subtotal Le Fort I osteotomy. As in a Le Fort I osteotomy (chapter 7.3.1 Le Fort I) the surgical approach is a high vestibular approach (often a hockey stick approach) from first molar to first molar. Exposure of the lower maxilla, pterygomaxillary junction, and basal parts of the septum are identical to the exposure performed for a Le Fort I osteotomy. The vertical bone cut is similar to a low Le Fort I osteotomy; a pterygomaxillary disjunction is only done in posteriorly very narrow palates (Fig 7.3.2-1a–b). After that a sagittal osteotomy is performed

b

Fig 7.3.2-1a–b Typical bone cuts for a surgically assisted rapid palatal expansion. a Separation of the anterior facial buttresses and vertical osteotomy between the central incisions. b Midline osteotomy of the palate. The pterygomaxillary disjunctions are optional.

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from the anterior alveolus to the posterior palate with a thin osteotome, with a starting point between the central incisors (Fig 7.3.2-2). Care should be taken not to perforate the palatal mucosa. To avoid perforations the submucous chisel position can be controlled with a palpating finger. Some surgeons prefer to do two osteotomies, one on each side of the basal nasal septum, to avoid a basal septal deviation

through the widening process. The anterior osteotomy of the alveolus between the two middle front teeth must be performed very carefully to avoid damage to the tooth roots. It is recommended to perform an incomplete osteotomy of the anterior alveolus and finally do a gentle maneuver with a chisel to crack it open. Mobility of the two palatal halves and the attached lower maxillary components is checked. This osteotomy in the end creates two fragments containing the two halves of the palate and the lateral and anterior lower parts of the maxilla. Therefore, the terminology of “surgically assisted rapid palatal expansion (SARPE)” and “surgically assisted rapid maxillary expansion (SARME)” are both inaccurate, because the former does not mention the lower parts of the maxilla, and the latter does not mention the palatal halves. To avoid a wider maxilla exposure, endoscopically assisted SARPE procedures have been described as a minimally invasive alternative.

Fig 7.3.2-2 Midline osteotomy of the hard palate, osteotome in place.

The transverse expansion is done with the help of either a tooth- or bone-anchored distraction device according to the preferences of both surgeon and orthodontist (Figs 7.3.2-3a–o, 7.3.2-4a–b). Only a bone-anchored device does not direct

a

b

c

d

Fig 7.3.2-3a–o Transverse expansion of both maxilla and mandible with tooth-anchored (maxilla) and bone-anchored distraction devices. a Narrow maxilla and mandible with crowding. b Tooth-anchored maxillary distractor before SARPE. c Bone-anchored distraction device for SARPE. d Maxillary width after SARPE and retention. e Midline osteotomy of the mandible.

e

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f

g

i

j

k

l

m

n

o

h Fig 7.3.2-3a–o (cont) Transverse expansion of both maxilla and mandible with tooth-anchored (maxilla) and bone-anchored distraction devices. f Positioning of a bone-anchored mandible distractor. g Distractor in place, stabilized with monocortical mini screws. Initial activation to check functionality of the device. h Situation after closure of the mucosa. I Tooth-anchored maxillary and boneanchored mandible distractor in place, midline mandible gap after activation of the distractor. j Midline mandible gap, endpoint of activation. k Situation after distractor removal, consolidated bone in the chin area. l Narrow mandible before midline distraction. m Mandible after midline distraction in the retention phase of orthodontic treatment. n Oblique view of the occlusion before treatment. o Oblique view of the occlusion after treatment.

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any forces against the teeth, but is much more costly than a tooth-anchored device. A tooth-anchored device can be cemented on the teeth before, and timewise completely independent from the surgical procedure in the orthodontists office or intraoperatively after completion of the osteotomy. A bone-anchored device is typically inserted after the osteotomy. Some bone-anchored distractors are modular with removable foot-plates. If this is the case, the foot-plates may be fixed (screwed) to the palate prior to the start of the osteotomy. The operation finishes with suturing the mucosa.

a

The widening procedure per se is a distraction osteogenesis: 1 mm transversal expansion per day is the usual and accepted rate. The distraction devices are activated two to four times a day according to their construction. After the desired expansion is reached, a long retention phase of 3 months or more is mandatory, because of high relapse rates for transverse expansions and the time needed for complete mineralization and remodelling of the callus. For retention purposes the relatively big and uncomfortable bone-anchored devices may be replaced by slim, low-profile tooth-anchored orthodontic appliances.

b

Fig 7.3.2-4a–b a Lower facial width before distraction. b Lower facial width after distraction and orthodontic treatment.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.3 Standard osteotomies in the maxilla 7.3.3 Subapical (block) and segmental maxillary osteotomies

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Historical background

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Indications

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Planning aspects

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Preoperative preparations

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Surgical technique

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5.1 Isolated block or segmental osteotomies

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5.2 Segmental osteotomies as part of total osteotomies

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Author Gerson Mast

7.3.3 Subapical (block) and segmental maxillary osteotomies Subapical (block) and segmental osteotomies can be performed either as an isolated procedure or as part of a total jaw osteotomy. The maxilla can be segmented anteriorly, or laterally, or in combinations of both (multi-segments). Theoretically, the blocks or segments can be moved in all three dimensions but practically, the movement is limited by the elasticity of the attached soft tissues which are essential for blood supply to the bone. Generally, elongation and widening of the dental arch is more difficult than impaction and narrowing. The maximum range of movement is difficult to predict while a case is planned, however, movements are usually possible for corrections in a range of around 5–10 mm. The size of the blocks or segments depends on the individual situation and planning. Typically, a block or segment contains a couple of teeth. A reduction of fragment size to only one or two teeth can be critical with regard to blood supply.

1

Historical background

Subapical and segmental osteotomies to correct orthognathic problems were developed in a period when surgical skills and anesthesia allowed for this kind of surgery. Whereas orthodontic techniques, especially with fixed appliances for adults, were not routinely part of the combined treatment. A new dimension of segmentation of the maxilla was reached in the 1970s and later, after Bells method of maxillary “down fracture” had become standard. As part of a total osteotomy, segmental osteotomies were performed with up to twelve pieces. Today, with the advances in orthodontic treatment, the indications for segmental osteotomies in orthognathic surgery have substantially decreased. It can be an alternative if ortho dontic treatment is not available, not desired by the patient, or for shortening of treatment. Nowadays, there is again a tendency towards subapical and segmental osteotomies because of the advent of distraction osteogenesis.

When performing a block or subapical osteotomy the continuity of the mandible or maxilla is maintained. A segmental osteotomy separates the mandibular or maxillary continuity (Fig 7.3.3-1a–b).

a

b

Fig 7.3.3-1a–b a Block or subapical osteotomy in the mandibular front. b Segmental osteotomy in the mandibular front.

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2

Indications

Subapical and segmental osteotomies can be useful for the correction of skeletal and dentoalveolar deformities without, or in combination with, orthodontic treatment. Typical indications for isolated segmental osteotomies are found: • In vertical dentoalveolar and/or skeletal disorders, such as frontal open bite deformities and deep bites • In sagittal dentoalveolar disorders, such as dentoalveolar prognathism

Elongation procedures can be done using the same type of osteotomies. In case of an intramaxillary block osteotomy, mobilization of the tooth-bearing fragment creates an intramaxillary gap which needs to be filled with a bone graft or bone replacement material, especially if the gap exceeds 1–2 mm. The correction of sagittal disorders of the dental arch requires ostectomies in dentate areas together with the removal of teeth (unless teeth are missing) or osteotomies and the insertion of a bone graft in case of an advancement. Lateral maxillary blocks or segments

Typical indications for subapical and segmental osteotomies as part of total osteotomies are present when vertical, sagittal, and transverse dentoalveolar problems need to be corrected in addition to basal skeletal disorders.

3

Planning aspects

The typical indication for osteotomies of lateral maxillary blocks or segments is the correction of vertical disorders, mostly through impaction. Very often the question arises if transverse deficiencies can be corrected at the same time. This is feasible but only to a very limited degree, because widening of the maxillary arch with lateral subapical osteotomies mostly needs a corporal movement and not a lateral “swing” and is limited by stretchability of the palatal mucosa.

Anterior maxillary blocks or segments

The correction of vertical disorders needs either impaction or elongation of the anterior block or segment. Impaction can be achieved either by resecting a slice of bone between the apices of the tooth roots and the nasal floor in a block osteotomy, or by moving the nasal floor cranially in a segmental osteotomy. The advantage of the first variation is no change in the position of the anterior nasal spine, and therefore, only little influence on nasal shape. The disadvantages are a greater risk for devitalization of the teeth, especially for the canine tooth, and a more demanding surgical technique. The second variation is technically simpler, but there will be a reduction of airway space and the nasal septum usually must be shortened to prevent deviation. Therefore, an individual decision is needed, depending on the amount of bone and the expected movement in the region of interest.

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4

Preoperative preparations

Preoperative orthodontic treatment can be very helpful to open interdental spaces at the sites of the osteotomies. Adjacent teeth should receive a dental root torque away from the osteotomy line. The orthodontic arch wires must be cut at the osteotomy sites to allow the blocks or segments to be mobilized. Based on the preoperative planning, occlusal splints should be available to align the fragments into the desired new position.


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Author Gerson Mast

5

Surgical technique

5.1 Isolated block or segmental osteotomies Anterior maxillary segment

Although the procedure is typically performed under general anesthesia, local anesthetics with vasoconstriction are applied prior to incision to prevent excessive bleeding. If preoperative planning includes removal of a tooth, typically a premolar, the tooth extraction is performed first. The soft-tissue access is chosen according to the planned osteotomy lines. Vertical vestibular incisions are placed in the region of the planned bone cuts. Ideally, the cuts should spare the papillae to prevent gingival recession. If the plan is to include the nasal floor, thus performing a segmental osteotomy, an additional midline incision is frequently necessary to obtain access to the anterior septal base. Careful subperiosteal soft-tissue tunnelling gives access to the alveolar ridge, the anterior antral wall, and the bony nasal aperture.

a

It is advisable to mark the planned osteotomy lines for symmetry and protection of the dental roots with a small round burr or chisel according to the information on the length of the tooth roots provided by a preoperative panoramic x-ray. The osteotomies are performed with a microsaw, a piezoelectric device, a burr, a chisel, or with a combination thereof (Fig 7.3.3-2a). Care must be taken not to damage the tooth roots and not to cut through the palatal mucosa. It is technically demanding to connect both premolar osteotomies precisely in the palatal midline and to mobilize the anterior segment. To complete the mobilization, it is necessary to sever the nasal septum at its base with the help of an osteotome or scissors (Fig 7.3.3-2b). If a corporal movement and a rotation of the fragment are planned simultaneously, full fragment mobilization is mandatory. Only then will proper positioning with use of an acrylic splint be successful. With the acrylic splint in place, occlusion will be stabilized with mandibulomaxillary wires.

b

Fig 7.3.3-2a–b Anterior maxillary osteotomy. a After marking of the osteotomy lines the osteotomy is performed with a microsaw. b Completion of the palatal osteotomy after L-shaped ostectomy of the facial bony wall.

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Fragment fixation is performed with adaptation plates 1.5, 2.0, or corresponding Matrix plates. L-plates on the nasal buttresses are typically used (Fig 7.3.3-3a–b). Before fixation, the plates must be precisely bent and passively adapted to the bone surface to prevent secondary movements through attraction of a fragment to the plate. Compression osteosynthesis is not indicated to stabilize small fragments in corrective bone surgery. For stabilization of segmental osteotomies it is recommendable not to rely solely on internal fixation devices such as plates and screws because of the long lever arm between the insertion point of the plate at the upper border of the fragment and the point of load at the occlusal plane, but to additionally use dental arch fixation with orthodontic devices. The use of a splint gives additional postoperative stability. Lateral maxillary subapical osteotomies

A lateral maxillary block typically includes premolars and molars. It is used for frontal open bite correction through bilateral impaction of the lateral blocks. Patient preparation is the same as for anterior segment surgery. The soft-tissue access can be performed either by a horizontal vestibulary incision from region 3 to 8, or, with regard to a safer blood supply, by vertical vestibulary incisions not directly above the planned osteotomy line in region 4 and 7/8 and subsequent tunnelling under the mucosa. Again, the vertical cuts should not extend into the interdental pa-

a

pillae to prevent gingival recessions after healing. Subperiosteal dissection then provides access to the alveolar process and the anterior-lateral antral wall. The planned osteotomy lines are marked with a small round burr (Fig 7.3.3-4a). The osteotomy is carried out with burrs, piezoelectric devices, microsaw, and/or osteotomes. The horizontal ostectomy is performed at a safe distance, typically 5 mm or more from the apices of the teeth. The width of the ostectomized bone strip must correspond to the amount of the planned impaction (Fig 7.3.3-4b–c). The anterior vertical osteotomy divides the alveolar ridge between two teeth, mostly canine and first premolar. The posterior osteotomy can either split the pterygomaxillary junction or run through the alveolar ridge, sometimes after removal of the wisdom tooth. The palatal osteotomy finally is performed transantrally with a burr through the previously created gap in the antral wall (Fig 7.3.3-4d). Care must be taken not to damage the palatal soft-tissue cover and to preserve the palatal vessels. Otherwise, excessive bleeding can be a problem. However, there seems to be no evidence for blood supply problems if the descending palatine vessels are transsected. Even after full mobilization of the segment, impaction can be a difficult procedure. It is achieved either manually or with careful use of a blunt osteotome. Finally, the occlusal splint is inserted and the segment position controlled. Mandibulomaxillary fixation is done with wire ligatures.

b

Fig 7.3.3-3a–b Anterior maxillary osteotomy according to Schuchardt/Köle. a Schematically drawn is the bony part which has to be removed together with the first premolar. b The frontal segment in its new position, stabilized with an L-plate.

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Fragment fixation is performed with adaptation plates 1.5 or Matrix plates (Fig 7.3.3-4e). Again, the plates must be perfectly adapted to the bone surface to avoid positional changes while tightening the screws. Especially in the lateral part of the maxilla plate fixation alone tends to produce an outward rotation of the segments. Therefore, additional dental fixation

a

with arch bars or orthodontic devices is recommended. Mandibulomaxillary fixation can be removed after stable fixation. The occlusal splint is fixed with two or three wire ligatures to brackets in the upper jaw. It stays in place for approximately two weeks.

b

c

d

e

f

Fig 7.3.3-4a–f Lateral maxillary block osteotomy. a Marking of the osteotomy zone. b Horizontal osteotomy performed with a microsaw. Vertical vestibulary incision with small horizontal extension. c Osteotomy of the palatal process with an osteotome. Protection of the palatal mucosa through the surgeon’s finger. d Shortening of the bony lamella on the palatal side after caudal mobilization of the lateral segment. e Fixation of the lateral segment with cross-shaped plates after repositioning with the help of an occlusal splint. f Position of lateral segment after correction.

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5.2 Segmental osteotomies as part of total osteotomies

Maxillary segmentation as part of a total osteotomy has become an accepted method to correct sagittal, transverse, and vertical problems in a one-step procedure. The widely used “3-piece-maxilla” combines one anterior and two lateral segments. The soft-tissue access is a horizontal, dorsally slightly curved, vestibular incision as performed in total osteotomies. At the site of the planned segmentation, the remaining vestibular mucoperiosteum is undermined towards the attached gingiva. The planned osteotomy lines are marked on the level of Le Fort I and the alveolar ridge. It is advisable to start the procedure with incomplete osteotomies of the alveolar ridge using a burr, a piezoelectric device, or a reciprocating microsaw (Fig 7.3.3-5a). Then, the Le Fort I osteotomy is performed. Following the regular down fracture, the segmental osteotomies can be complet-

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ed with a diamond-coated drill, piezoelectric device, and/ or an osteotome under direct visual control from the maxillary base (Fig 7.3.3-5b–c). Care must be taken to preserve the soft-tissue layer on the palatal aspect, especially when starting to mobilize the segments. The more segments are created, the more difficult it is to position them as desired in the occlusal splint. To achieve the desired inclination of the segments it can be helpful to use splints with palatal shields. Depending on the size and number of fragments, fragment fixation can be demanding. A well-established technique is to start with the intersegmental fixation similar to a fracture simplification. For this, adaptation plates 1.3 or 1.5 can be used. The plates are initially fixed with one screw per segment to allow for “corrective molding.” Only when the desired position is precisely reached, additional screws are inserted. Care must be taken not to damage the tooth roots and not to strip the segments excessively. Finally, the reassembled tooth-bearing part of the maxilla is anchored to the facial buttresses using adaptation plates of convenient shapes (eg, straight, L-shape, Y-shape). If required, additional bone grafting is performed.


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Author Gerson Mast

a

b

c

Fig 7.3.3-5a–c a Osteotomy in the Le Fort I level with a microsaw. Additionally, a midline osteotomy is performed. b Shortening of the nasal septum and nasal crest if cranial positioning is planned. c Markings for possible additional segmentations.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.4 Special considerations and sequencing in 2-jaw osteotomies

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Author Carlos Ries Centeno

7.4 Special considerations and sequencing in 2-jaw osteotomies Technically, 2-jaw surgery is the combination of a mandibular and a maxillary osteotomy or osteotomies. In 1-jaw surgery the occlusal plane of the non-osteotomized jaw may be used as a reference for positioning, as only one jaw is going to be mobilized. Whereas in 2-jaw surgery, as both jaws are moved, a new occlusal plane is created in most cases. The potential creation of a new occlusal plane is the key element in double-jaw procedures. A three-dimensional change of major portions of the facial skeleton may result. The new occlusal plane is transferred to the patient with the help of an intermediate occlusal splint. Double-jaw surgery is usually required for facial asymmetries, combined anterior-posterior problems involving both jaws, vertical deformities and/or transverse discrepancies, eg, apertognathia, open bite (dentoalveolar, skeletal base, combination of both), as well as severe one-vector anomalities such as extreme class III cases, and crossbites. The evaluation of the deformity is made as previously described by clinical examination, cephalometric and articulated model analysis mounted after a face bow transfer. Based on this analysis, the position of the new occlusal plane is determined. Some points must be considered: • The new position of the maxilla is planned based on cephalometric and clinical analysis. • Clinical analysis is more important than cephalometrics. • The anterior vertical position of the maxilla is essentially determined by the desired amount of incisor show, usually about 3–4 mm. • The occlusal plane should be parallel to the bipupillary line. • The dental midline should be congruent to the facial midline. • The occlusal plane angle relative to the Frankfurt horizontal should be in between +8 and – 4.

In most 2-jaw osteotomy cases, the first osteotomy and movement is performed in the maxilla. The desired movements of the maxilla are performed first on the articulated model (model surgery) and an intermediate acrylic intraocclusal wafer is made with the maxilla in the new position and the mandible in its original (unmodified) position. With the maxilla in the desired new position the mandible model osteotomy is performed and the final acrylic wafer is constructed. The intermediate wafer or splint is the key for the new maxilla position and all desired movements of the osteotomized segment are transferred by it. The teeth must passively fit in the splint when the mandibulomaxillary fixation is established. In addition, intraoperative bone-to-teeth measurements are performed, the same way as in maxillary surgery alone, to confirm the desired jaw and tooth position. After internal fixation of the maxilla in the desired new position temporary MMF and the intermediate splint are removed and the mandible osteotomy is performed. The mandible is positioned with the help of the second splint. Internal fixation for the mandibular is performed again with the patient in temporary MMF. Hardware selection is done identically as it is done for single-jaw surgery in each location. The desired occlusion must be checked after releasing MMF, with and without the final splint. If the position is not the desired one, osteosynthesis has to be redone. For correction of facial asymmetries, 2-jaw osteotomies may be combined with bone grafts (Fig 7.4-1a–d).

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.4 Special considerations and sequencing in 2-jaw osteotomies

a

c

b

d

Fig 7.4-1a–d a Facial asymmetry with deviation of the occlusal plane due to shortness of the mandibular ramus and reduced maxillary height on the right side. b T he correction consists of a Le Fort I osteotomy, a sagittal split osteotomy on the left, a step-like osteotomy on the right, the transplantation of a costochondral graft, and a chin osteotomy. All osseous gaps are filled with bone grafts. c–d Orthopantomogram and posterior anterior view of the described correction.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.5 Perioperative and postoperative management

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Postoperative x-ray control

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Implant removal

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Occlusal splints

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Medication

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Local treatment

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Pain control

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Diet

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7.5 Perioperative and postoperative management Nasal intubation is standard in orthognathic surgery. Hypotension must be guaranteed via deep anesthesia. Local infiltration with epinephrine 1/100.000 is injected submucosally for hemostasis.

1


Postoperative mandibulomaxillary fixation after internal fixation is not necessary in cases where correct stable internal fixation has been applied. Elastics for functional training are recommended to achieve neuromuscular adaptation.

2

Occlusal splints

After internal fixation with plates and screws and before wound closure, the occlusal splint is removed and the achieved position is checked and compared to the planning models. If there are discrepancies, the reason must be determined and corrections must be undertaken, for instance new positioning of the osteotomized segments. In case the postsurgical occlusion is as desired, the splint is reinserted and fixed with two or three wire ligatures to brackets of upper teeth for postoperative neuromuscular adaptation. In the early postoperative situation with swelling and restricted mouth opening, it is helpful to keep the splint in place up to 2 weeks to secure the occlusion before orthodontic treatment continues.

Postoperative x-ray control

X-rays in two planes are taken immediately after surgery and before the patient is allowed to return to full function.

3

4

A good interdisciplinary coordination between the surgeon and the orthodontist is essential to achieve good results. The orthodontist must be informed when the splint is going to be removed and when the postoperative orthodontic treatment can be started. There should be no prolonged time gap between surgical and orthodontic treatment.

Implant removal

After uneventful healing, the removal of pure titanium plates is usually not necessary.

5

Medication

Antibiotic prophylaxis is used by the majority of surgeons performing jaw osteotomies. The argument is that in elective bone surgery in a contaminated area, such as the oral cavity, the patient should have only a minimal risk for infections. With antibiotics an infection rate below 5% can be achieved. Nevertheless, the application of antibiotics in that field, as in others, is part of controversial discussions. Astringent nose drops and disinfectant mouth-washes are part of the postoperative care during the first days. The prevention or reduction of postoperative edema by the use of steroids is widely discussed for its clinical evidence.

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Local treatment

Cooling the face after osteotomy, sometimes with the help of special devices (cooling masks), reduces swelling and postoperative pain.

7

8

Diet

The use of internal fixation with adaptation miniplates leads to a stable result under reduced function. It is recommended to stay on a soft diet for 4 to 6 weeks until bone consolidation allows for full function.

Pain control

For pain control non-steroidal pain killers are usually sufficient.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.6 Complications and pitfalls

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Intraoperative complications

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Early postoperative complications

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Late postoperative complications

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Rare complications

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Several publications dealing with complications and pitfalls show that orthognathic surgery is generally safe and predictable, but associated with risks for typical complications. With the exception of damage to the inferior alveolar nerve in sagittal split osteotomies of the mandible, which is described to be as high as 28%, the statistical risk for other complications stays well below 10%. Since these procedures are elective, a major concern must be to prevent and minimize complications and pitfalls and to inform patients about potential risks. The prevention of complications starts with a careful patient selection. It is of paramount importance to understand the patient’s motivation. The surgeon needs to get an impression of his patient’s personality. This is not possible with a single short appointment which is focussed on planning and technical aspects only. If there are doubts on the patient’s or on the surgeon’s side about the treatment indication, or if there is a suspicion for any psychological condition of the patient with tendency to dysmorphophobia, it is advisable to clarify the situation first and not to operate. Complications and pitfalls can happen preoperatively (patient selection, diagnosis, surgical preparations), intraoperatively, and postoperatively. Several retrospective studies have evaluated the incidence of potential complications. Because of the great variety of possible complications and different recording protocols in various centers, the results can only serve as an orientation. In addition, a large number of case reports demonstrate rare and unusual complications. This chapter focuses on intraoperative and postoperative complications.

1

Intraoperative complications

Bleeding

Especially maxillary osteotomies can be accompanied by severe bleeding, usually from branches of the maxillary artery or the pterygopalatine venous plexus, which may even create a need for transfusion. Severe bleedings may require intraoperative compression with packs, vessel ligation such as the maxillary artery, or arteriographic embolization procedures. As part of the preoperative preparation acute normovolemic hemodilution (ANH) or the provision of self-donated or crossmatched blood may be considered. Airway obstruction

In almost all procedures, the airway is manipulated and a potential for airway obstruction produced by swelling or hematoma formation is possible. Before extubation, the airway conditions must be checked and, depending on the type and severity of the operation, the airway needs to be monitored postoperatively. The discussion about immediate extubation after surgery or prolonged postoperative intubation is controversial and influenced by medical, legal, and economic aspects. In 2-jaw surgery, it is common practice to leave the patient intubated until the swelling has reached its maximum during the first 4–12 hours postoperatively and to then decide, whether extubation can be performed. Nerve damage

Due to its location in the mandibular bone and the specific technique of the sagittal split osteotomy, injuries of the inferior alveolar nerve occur with a high incidence, in some series up to 28%. The majority of neurosensory deficits is temporary, but permanent damage may occur. The infraorbital nerve and in very rare cases the lingual and facial nerves may be injured as well. Nerve injuries (neurapraxy, axonotmesis, neurotmesis) can occur as a result of direct trauma by instruments used for dissection, osteotomy, and soft-tissue retraction, as a consequence of placement of osteosynthesis or intermaxillary fixation (IMF) screws, or as a result of interfragmentary compression. If neurotmesis becomes clinically evident, microsurgical nerve exploration and, if needed, repair may be considered.

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Initially incomplete neurosensory deficiencies are not specifically treated, but observed and documented. In case of a complete sensory deficit, there should be a reevaluation of the situation 2–4 weeks after surgery, because a decision needs to be made to wait for regeneration or to attempt repair or decompression, for instance in the case of a rare complete lingual nerve deficiency. Motor nerve injuries associated with facial nerve palsy or weakness are looked at differently because of their devastating effect on the patient. Depending on the degree of the damage and the suspected reason an individual decision is necessary, whether close observation, or exploration with possible nerve repair, or even facial reanimation is indicated. Tooth injuries

Especially segmental and subapical osteotomies bear a risk for tooth injuries. They can be caused by direct trauma with osteotomes, saws, drills, or osteosynthesis screws leading to a root injury with or without devitalization. Obviously, devitalized teeth need endodontic treatment as soon as the patient’s mouth opening capacity will allow for that to prevent further problems, such as infections or tooth resorption. Small defects in the root area without transsection of the neurovascular bundle normally do not affect the prognosis of the tooth, whereas large defects, for example longitudinal cuts due to reciprocating saws may induce devitalization and root resorption. Clinical and experimental studies using laser Doppler flowmetry have shown that necrosis and sensitivity disorders of the dental pulp and periodontium due to reduced blood supply following osteotomies may occur. In those cases, there is a risk for infection and tooth loss. However, it should be recalled that especially after maxillary osteotomies in the Le Fort I level transient loss of sensivity of upper teeth is quite common, but as a rule it will return spontaneously after several weeks or months.

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“Bad splits”

Unfavorable osteotomies or “bad splits” are another potential complication, especially in sagittal split mandibular ramus osteotomies according to the original technique, when large spreading osteotomes for dissection of the mandibular ramus are used. Modifications of this technique and the use of smaller osteotomes can reduce the risk for bad splits and comminution, especially in class II patients with their typical thin and compact ascending ramus. Once an unfavorable split has occurred, it must be checked first, whether the split is complete or can be completed to allow for the desired movement of the fragments, and whether there is a possibility to position and to internally fix the fragments for a stable result. If so, a simplification of the fractured area by repositioning and fixation of the fragments is advisable. Then, an individual decision is needed about how to perform stable internal fixation with respect to size and position of bone fragments. Depending on the case, it can be necessary to apply plates and/or lag screws transorally or transbuccally with the use of load-sharing or load-bearing osteosynthesis material. Keeping a patient postoperatively in mandibulomaxillary fixation (MMF) is also an option after “bad splits.” Instrument fractures, foreign bodies

A rare intraoperative complication is the fracture and loss of instrument, osteosynthesis material, or orthodontic appliances (brackets) with displacement into soft tissues. This can happen with tips of burrs, screw heads, blades of selfretaining screw drivers, etc. First, it is important to realize that such a problem has occurred. Then, the lost material must be located clinically or by intraoperative x-ray examination. The indication for removal depends on the location, the size, and the kind of material, as well as the operative risk and the calculated time for the procedure. If the removal is necessary, but not possible in the same operation, the patient must be informed about the problem and the need for a secondary procedure.


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2

Early postoperative complications

Bleeding and swelling

After surgery, complications are often related to secondary bleeding with gross swelling and edema causing airway obstructions. In these cases monitoring, local physical treatment with cold dressings, and the application of steroids are mostly sufficient. Revision surgery is usually not needed. The use of intraoral drains in mandibular osteotomies can help to reduce the risk for airway obstruction, but then the infection rate rises. In acute and severe cases, reintubation or even tracheostomies may become necessary to solve an airway problem. Wound healing disturbances including infection

Wound healing disturbances and infections are rare complications in orthognathic surgery, despite the fact that transoral approaches with wound contamination and facultative pathogenic bacteriae are the norm. Infections occur most often in the angular region of the mandible following sagittal split procedures. Studies reveal that they may be related to the duration of surgery. Beside purulent infections, which are treated by incision and drainage, rare cases of osteomyelitis and cervicofacial actinomycosis have been reported.

Relapse

Early relapse with gross discrepancy between the planned and achieved occlusion is either the result of an inaccurate fragment positioning, dislocation of one or both condyles, inadequate fragment fixation, or failure of the osteosynthesis material (eg, fracture or loosening). A reoperation for correction is indicated after a diagnosis has been established. Nerve injuries

Intraoperative nerve injuries are mostly not detected during surgery, but become evident in the early postoperative phase. Depending on the procedure and the nerve branches involved, neurosensory dysfunction can be seen with various degrees of numbness of the lower lip and chin, the cheek area, the upper lip, the tongue and parts of the palate. The neurosensory function must be carefully assessed. The patient needs to be informed about the course of such a condition, its prognosis, and whether further treatment is needed. A regular recall should exist to document the course. Rarely, partial or complete facial palsy or weakness can be found following orthognathic surgery. Precise examination and review of the operation may help to find the most likely reason for and the severity of the damage. Based on the diagnosis a decision must be made together with the patient, whether to wait or to reexplore the nerve.

To reduce the risk of infection, stabilization of the osteotomized fragments with internal fixation devices and prophylactic application of antibiotics have proven to be effective. Controversial standpoints exist about the duration of the antibiotic prophylaxis. Duration of prophylaxis longer than 3 days does not reduce the rate of infections, even high-dose perioperative antibiotic administration seems to be sufficient. Amoxicillin-clavulanic acid, cefuroxime, and clindamycin are known to be effective.

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3

Late postoperative complications

Scar formation

Compromised soft-tissue healing can lead to excessive intraoral scar formation with restriction of soft-tissue motility as a very rare complication. If it occurs, it needs secondary intervention with scar excision and perhaps vestibuloplasty. Problems with bone healing

Bone healing can be disturbed following insufficient fragment fixation. Nonunion is a complication that can be found both in the mandible and the maxilla. To treat this problem the osteotomy site should be explored and the osteosynthesis material replaced if loose or fractured. Sometimes bone grafts are indicated. To prevent hardware overload, especially in patients suffering from bruxism, single tooth contacts should be avoided by using splints or occlusal stops during the healing period. Early removal of osteosynthesis material may be another reason for nonunion. Temporomandibular disorders (TMD)

The effect of orthognathic surgery on the temporomandibular joint (TMJ) is controversial with little consensus among surgeons. It is known that both a bite deformity and orthognathic surgery may adversely influence TMJ morphology and function. Prior to orthognathic surgery, TMJ function and morphology should be assessed and the patient should be asked about a history of TMJ pain or discomfort. If there is a preexisting dysfunction, a diagnosis regarding the TMJ needs to be established. Depending on the situation a TMJ specialist should be consulted. In some cases preoperative splint therapy is advisable. For evaluation it is helpful to classify the dysfunctions according to their origin into the subgroups myogenous, arthrogenous, or both. It is very important not to justify the indication for surgery by telling the patient that existing or potential TMJ problems can only be solved through an orthognathic surgical procedure. Orthognathic surgery may sometimes be helpful to improve TMJ dysfunction, but in some instances it may worsen the situation. Relapse

The outcome of orthognathic surgery, especially with regard to relapse, depends on various factors beginning with proper diagnosis, correct preoperative orthodontic treatment, precise planning and transfer to the clinical situation, correct surgical technique including fixation, the individual healing capacity and quality of bone, muscle tension, the cooperation of the patient, and many other factors.

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The key to prevent or minimize relapse is to form an experienced interdisciplinary team which is able to control the majority of those factors, to document the course of patients, and to evaluate and improve the result over time. From a surgical point of view, the amount and direction of the surgical movement, the type of fixation, and the surgical technique employed are of major concern. Rigid internal fixation techniques with metal implants have shown to improve long-term stability, especially after movements of the mandible. Condylar resorption

An important but rare cause of late skeletal relapse in connection with progressive condylar resorption has recently attracted attention. The pathogenesis is still not well understood, but etiopathogenic hypotheses and predisposing factors, such as a posteriorly inclined condylar neck and a high-angle mandibular retrognathia, are widely discussed. Hardware-related problems

In rare instances, the use of internal fixation devices may lead to local unpleasant sensations or discomfort in cold weather. In those cases, implant removal is indicated. Loose or fractured hardware should be removed as well. Persistent nerve damage

After a 2-year period, neurosensory and motor deficiencies can be classified as permanent. Compared to other cranial nerves at risk in orthognathic surgery, the inferior alveolar nerve has the highest incidence rate of permanent damage. Up to now, most neurosensory deficiencies have to be accepted by the patient without any treatment. In the rare case of disturbing dysesthesia or hyperesthesia an additional medical or surgical treatment, such as neurolysis or even nerve replacement or nerve grafting, may be considered. Nasal and sinus problems

Following maxillary osteotomies, restriction of the nasal airway may occur. Associated secondary problems such as maxillary sinusitis are rarely observed. The reason for nasal obstruction may be an insufficient resection of the nasal septum when the maxilla is impacted, with the consequence of a septal deviation and related problems. If the impaction is such that the nasal cavity will be significantly smaller, a reduction of the inferior turbinates must be considered. Deviations of the cartilaginous nasal skeleton may also happen. Persistant oro-antral fistulas after incomplete bone and softtissue healing can also lead to maxillary sinusitis. A careful examination including CT scans is needed to establish a diagnosis. Most cases require secondary surgery.


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4

Rare complications

Today in elective surgery a patient needs to be informed about all relevant risks, even if they are extremely rare.

Disturbed blood supply

Insufficient vascularity is mainly a problem following maxillary osteotomies, but there are also reports about aseptic necrosis following mandibular ostoeotomies, including those of the chin.

Eye complications

Potential complications after Le Fort type osteotomies include a decrease in visual acuity up to visual loss, extraocular muscle dysfunction with motility disorders and diplopia, neuroparalyitc keratitis, and nasolacrimal problems involving both a dry conjunctiva or epiphora. The pathomechanism for problems with visual acuity appears to be primarily mediated through indirect injuries to neurovascular orbital structures after traction, compression, or contrecoup injuries from forces transmitted during the pterygomaxillary dysjunction, or from fractures extending to the base of the skull or orbit associated with the pterygomaxillary dysjunction during maxillary down fracture. Surgical modifications of the maxillary osteotomy have been described to reduce the potential risks, eg, placing the posterior osteotomy more anteriorly into the maxillary tuberosity instead of dividing the pterygoid plates. In any case it is recommended to perform the pterygomaxillary dysjunction and down fracture with great care. Aside from this, unilateral blindness has been reported as a result of compromised perfusion of the optic nerve after hypotensive anesthesia. A decrease in visual acuity postoperatively may respond to aggressive treatment such as osmotic agents, steroids, lateral canthotomy, and optic nerve decompression. Even after therapy in most cases the visual loss is at least partially persistent, due to the extreme sensitivity of the optic nerve and the retina to hypoxemia, associated to injuries. CT scans are mandatory to document optic nerve pathology and to accurately exclude any intracranial lesion that could contribute to the altered visual acuity. Postoperative assessment of visual acuity should routinely be performed and documented.

The sequelae can vary and include loss of tooth vitality, periodontal defects, tooth loss, necrosis of the mucosa and underlying bone, as well as loss of major bone segments. These complications are more likely to occur after Le Fort I osteotomies done in multiple segments together with superior positioning and transverse expansion. If the problem is diagnosed at an early stage, medical treatment to improve perfusion and hyperbaric oxygen therapy can be considered. Major vascular complications

False aneurysms and arteriovenous fistulas are rarely seen following orthognathic surgery. The vessel most commonly involved with false aneurysms is the internal maxillary artery and its branches, after both mandibular or maxillary osteotomies. Arteriovenous fistulas are more often related to injuries of large vessels, especially the internal carotid artery. Patients complain of a sound and sometimes of hearing loss, potentially associated with tinnitus. Embolization procedures are the treatment of choice.

The list of papers identifying complications in orthognathic surgery is long and needs to be routinely reviewed and updated. Relevant complications should be published and made known to every surgeon practicing orthognathic surgery.

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7 Fixation techniques of standard osteotomies of the facial skeleton (orthognathic surgery) 7.7 References and suggested reading

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7.7 References and suggested reading Acebal-Bianco F, Vuylsteke PL, Mommaerts MY, et al (2000) Perioperative

complications in corrective facial orthopedic surgery: a 5-year retrospective study. J Oral Maxillofac Surg; 58(7):754–760. Altuna G, Walker DA, Freeman E (1995) Rapid orthopedic lengthening of the mandible in primates by sagittal split osteotomy and distraction osteogenesis: a pilot study. Int J Adult Orthodon Orthognath Surg; 10(1):59–64. Arnett GW, Tamborello JA, Rathbone JA

(1991) Temporomandibular joint ramifications of orthognathic surgery. Bell WH (ed) Modern practice in orthognathic and reconstructive surgery Vol 1. Philadelphia: WB Saunders, 522–594. Arnett GW, Milam SB, Gottesman L (1996) Progressive mandibular retrusion– idiopathic condylar resorption. Part I. Am J Orthod Dentofacial Orthop; 110(1):8–15. Baik HS, Han HK, Kim DJ, et al (2000) Cephalometric characteristics of Korean Class III surgical patients and their relationship to plans for surgical treatment. Int J Adult Orthodon Orthognath Surg; 15(2):119–128. Bailey LJ, Cevidanes LHS, Proffit WR (2004) Stability and predictability of orthognathic surgery. Am J Orthod Dentofacial Orthop; 126(3):273–277. Bailey LJ, Proffit WR, White JR (1999) Assessment of patients for orthognathic surgery. Semin Orthod; 5(4):209–222. Bell WH (1975) Le Fort I osteotomy for correction of maxillary deformities. J Oral Surg; 33(6):412–426. Bell WH, You ZH, Finn RA, et al (1995) Wound healing after multisegmental Le Fort I osteotomy and transection of the descending palatine vessels. J Oral Maxillofac Surg; 53(12):1425–1433. Booth DF (1981) Control of the proximal segment by lower border wiring in the sagittal split osteotomy. J Oral Maxillofac Surg; 9(2):126–128. Borstlap WA, Stoelinga PJ, Hoppenreijs TJ, et al (2004) Stabilisation of sagittal split

advancement osteotomies with miniplates: a prospective, multicentre study with two-year follow-up. Part I. Clinical parameters. Int J Oral Maxillofac Surg; 33(5):433–441. Boulétreau P, Frey R, Breton P, et al (2004) [Focus on the effect of orthognathic surgery on condylar remodeling.] Rev Stomatol Chir Maxillofac; 105(5):283–288. French. Buckley JG, Jones ML, Hill M, et al (1999) An evaluation of the changes in maxillary pulpal blood flow associated with orthognathic surgery. Br J Orthod; 26(1):39–45.

Burstone CJ, James RB, Legan H, et al

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Credits Chapter 1.3.1 Fig 1.3.1-4a–b Reprinted from Clinics in Plastic Surgery, 19(1), Rudderman RH, Mullen RL (1992) Biomechanics of the facial skeleton, p. 11–29. Copyright © 1992 by Elsevier, with permission from Elsevier.

Chapter 1.4.2 Fig 1.4.2-5 Pictures by Börje Müller Fotografie, CH-4056 Basel.

Chapter 1.4.3 Fig 1.4.3-1 Pictures of cruciform recess, PlusDrive, and Matrix recess by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-2 Pictures by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Table 1.4.3-3a–c Pictures of screws by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-5 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-6 Pictures of LC-DCP and MatrixMANDIBLE DCP by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-9, Figs 1.4.3-11–13 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-14 Picture by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Figs 1.4.3-15/16 Pictures of UniLOCK plates and MatrixMADNIBLE reconstruction plate with condylar head add-on: Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates.

Figs 1.4.3-17/18, Fig 1.4.3-19b–d, Fig 1.4.3-20 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-21a Pictures by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-21b Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Figs 1.4.3-22/23 Pictures by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-24, Fig 1.4.3-25a–b Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-25c–e Pictures by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-26 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-27 Pictures by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Figs 1.4.3-28–31 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-32a–b Pictures by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Fig 1.4.3-33 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-35a Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates. Fig 1.4.3-35b Picture by Börje Müller. Copyright © 2012 by Börje Müller Fotografie, CH-4056 Basel. Figs 1.4.3-36/37 Copyright © 2012 Synthes, Inc. or its affiliates. All rights reserved. Synthes is a trademark of Synthes, Inc. or its affiliates.

Chapter 7.1 Fig 7.1-8 Wolf (ed)/Wichelhaus: Farbatlanten der Zahnmedizin – Kiefer orthopädie/Therapie, Georg Thieme Verlag, Stuttgart, 2013. With kind permission from Georg Thieme Verlag. Fig 7.1.9 Wolf (ed)/Wichelhaus: Farbatlanten der Zahnmedizin – Kiefer orthopädie/Therapie, Georg Thieme Verlag, Stuttgart, 2013. With kind permission from Georg Thieme Verlag.

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