Workshop
Planning Orthognathic Surgery 2010
Kamal F. Busaidy, BDS, FDSRCS, Associate Professor, Dept. Oral and Maxillofacial Surgery.
Overview of the Workshop •
•
•
•
•
•
•
•
•
•
•
•
Setting goals Clinical evaluation Radiographic evaluation Cephalometric tracing and analysis Photographs Mounting of models Formulating Formulating the surgical plan Performing prediction tracings (The VTO) Model surgery and constructing constructing splints The TMJ and orthognathic Surgery Surgery Planning for stability Pitfalls in planning and execution KB 2010
1
•
Primary references: –
–
Modern Practice in Orthognathic Reconstructive Reconstructive Surgery (Edited (Edited by William H. Bell) Bell ) Essentials of Orthognathic Surgery (Johan Reyneke)
KB 2010
Goals in Orthognathic Surgery
KB 2010
2
•
Primary references: –
–
Modern Practice in Orthognathic Reconstructive Reconstructive Surgery (Edited (Edited by William H. Bell) Bell ) Essentials of Orthognathic Surgery (Johan Reyneke)
KB 2010
Goals in Orthognathic Surgery
KB 2010
2
The Key to Successful Planning
•
Find out where you are
•
Determine your destination
•
Plan your journey
•
Allow for contingencies contingencies
•
Communicate with the team
KB 2010
What problem are we addressing? •
•
•
•
Inability to incise or chew Speech impediment Oral health (dental, periodontal) Poor esthetics •
•
•
•
•
•
•
Facial soft tissue Facial hard tissue Dental
OSA TMJ Primary versus secondary growth disturbance Psychological Psychological issues KB 2010
3
What is success? •
In the eyes of the patient success is measured by –
Addressing the original complaint
–
Absence of adverse outcomes
–
Stability of result
Assuming there is no underlying psychiatric issue!
KB 2010
Clinical Evaluation of the Orthognathic Surgery Patient
KB 2010
4
The Team Approach •
•
•
•
•
•
•
•
•
Orthodontist OMS General Dentist ENT Plastic surgeon Periodontist Prosthodontist Psychiatrist Pulmonologist/Sleep physician
KB 2010
OMFS Evaluation •
Stage 1
Initial evaluation/Feasibility
•
Stage 2
Pre surgical evaluation
•
Stage 3
Post surgical evaluation
(Long term)
KB 2010
5
Coordination of Care
Referring Practitioner
OMFS:1st Evaluation
Ortho:1st Evaluation
ENT / PRS etc
Ortho Treatment OMFS: 2nd Evaluation
OMFS: Surgery Ortho 2nd Evaluation Ortho Treatment Finalization
OMFS: 3rd Evaluation
Ortho 3rd Evaluation
Perio / Pros etc KB 2010
Patient Evaluation 1. Complaint + History 2. Health Status 3. Assessment of Facial Esthetics 4. Routine Dental Examination 5. Orthodontic Evaluation 6. Cephalometric Evaluation 7. Photos 8. Dental casts * Psychological Assessment
KB 2010
6
Facial Esthetics
KB 2010
Facial Esthetics 1/3
1/3
1/3
KB 2010
7
Facial Esthetics ULL 21mm (+/- 2 mm) Men ULL 19 mm (+/-2 mm) Women
Incisor Show at Rest 2 - 4 mm
Note lip-tooth relationships at rest and when active!
1/3 2/3
KB 2010
Facial Esthetics •
Nasofacial Angle
o
30 - 40 o
•
Nasomental Angle 120 -132
•
Mentocervical Line to Vertical
100
o
•
o
80 – 95 o
o
o
Mentocervical Line 110 – 120 to Nasomental Line
•
o
Nasolabial Angle
o
100 - 110
o
Powell and Humphreys: Proportions of the Aesthetic Face. New York, Thieme-Stratton, 1984 KB 2010
8
Dental Esthetics Tooth Location (Midline) Tooth Size Tooth Shape Tooth Number Tooth Orientation Emergence Tooth Color KB 2010
Dental Esthetics Arch Form Occlusal Plane Occlusal Level Overbite Overjet Buccal Corridor Surrounding Tissues KB 2010
9
KB 2010
Case Example
KB 2010
10
Case Example SMILE
REST
12 mm
9 mm KB 2010
Case Example
KB 2010
11
Case Example
KB 2010
Case Example Class II Skeletal Pattern (*mandible) Increased incisal show No increased LFH! Close bite (?traumatic) Maxillary cant Ocular dystopia Unstable occlusion. Poor bridges (shape/color) KB 2010
12
Radiographic Evaluation of the Orthognathic Surgery Patient
KB 2010
Radiographs •
Lateral Cephalogram
•
Panoramic Dental Xray
•
Periapicals
•
SMV
•
PA Cephalogram
•
Others (MRI/CT/Bone scan/Wrist Films)
KB 2010
13
MRI/CT/Bone scan/Wrist Films •
•
•
•
•
•
•
TMJ meniscus position OSA Complex craniofacial deformities Local growth disturbance (Condylar Hyperplasia) Systemic growth disturbance (Excess growth hormone) Autoimmune arthritis Assessment of completion of growth
KB 2010
PA Cephalogram •
Symmetry (particularly gonial angles, symphysis)
•
Position of proximal segment post op
•
Position of internal fixation post op
KB 2010
14
SMV •
Thickness of mandible (Superseded by CBCT!)
•
Flaring of rami (vertical ramus osteotomy)
•
Position of proximal segment post op
•
Position of internal fixation post op
KB 2010
Periapicals •
Periodontal bone loss
•
Proximity of apices (multi-piece segments)
•
Periodontal bone loss post op
KB 2010
15
Panoramic Radiograph •
Third Molars
•
Inferior alveolar nerve position
•
Intraosseus pathology (best screening tool)
•
Position of fixation post op
•
Position of condylar head post op
KB 2010
Lateral Cephalogram •
•
•
•
•
•
•
Skeletal proportions Growth prediction Cessation of growth Soft tissue measurements Planning (primary tool) Position of fixation post op Baseline post op status*** KB 2010
16
Cone Beam CT
Dolphin Imaging
KB 2010
Lateral Cephalogram
What is wrong with this Lateral Ceph? KB 2010
17
Lateral Cephalogram Nasion
Pt point Porion Basion
Orbitale PNS
ANS A Point
Xi Point Gonion Pm Point Pogonion Gnathion Menton
KB 2010
•
•
•
• • •
• •
• • • • •
• •
Ba- Basion: the lowest point on the anterior margin of the foramen magnum, at the base of the clivus Po-Porion : the midpoint of the upper contour of the external auditory canal (anatomic porion); or, the midpoint of the upper contour of the metal ear rod of the cephalometer (machine porion) Pt- the point at about 11 0’clock on the outline of the pterygomaxillary fissure adjacent to the foramen rotundum Or-Orbitale: the lowest point on the inferior margin of the orbit ANS-anterior nasal spine: the tip of the anterior nasal spine Point A: the innermost point on the contour of the premaxilla between the anterior nasal spine and the incisor tooth Pog-Pogonion : the most anterior point on the contour of the chin Pm-Suprapogonion : the point where the anterior curvature of the mandible changes from concave to convex Me- Menton: the most inferior point on the mandibular symphysis Na-Nasion: the anterior point of the intersection between the nasal and frontal bones Go- Gonion: the midpoint of the contour connecting the ramus to the body of the mandible Gn-Gnathion: the most outward and everted point on the mandibular symphysis PNS-Posterior nasal spine: the tip of the posterior nasal spine of the palatine bone, at the junction of the hard and soft palate Xi- The point in the middle of the ramus, approximately in line with the occlusal plane FH-Frankfort Plane: the horizontal reference plane in the heads natural position extending from the porion to orbitale KB 2010
18
Hands-on Exercise Lateral Ceph Pencil Protractor/Ruler
•
•
•
Identify the points marked in the previous slides, (then trace the outlines of the skeleton as described), and start measuring the pertinent angles using Rickett’s analysis.
Hands-on Exercise Lateral Ceph Pencil Protractor/Ruler
•
•
•
Identify the points marked in the previous slides, (then trace the outlines of the skeleton as described), and start measuring the pertinent angles using Rickett’s analysis. KB 2010
Lateral Cephalogram Nasion
MARK THESE POINTS ON YOUR CEPHALOGRAM Porion Basion
Pt point Orbitale PNS
ANS A Point
Xi Point
Gonion Pm Point Pogonion Gnathion Menton
KB 2010
19
o
Facial Depth (Angle) 87 +/- 3 Nasion
Frankfort Horizontal o
Porion
87
Orbitale
Pogonion KB 2010
o
Mandibular Plane Angle: 26 +/- 4
o
26
Mandibular Plane Gonion Pogonion Menton KB 2010
20
o
Facial Axis: 90 +/- 3
o
90
Basion
Skull Base
KB 2010
o
Maxillary Depth: 90 +/- 3
o
90
A point
KB 2010
21
Convexity at point A: 2mm +/- 2 mm
A point
KB 2010
Lower incisor to APog: 1mm +/- 2 mm
A point
Pogonion KB 2010
22
Xi Point and Functional Occlusal Plane
Xi
KB 2010
o
Lower Face Height : 47 +/- 4
ANS Xi
o
47
Pm Point KB 2010
23
o
Interincisal Angle: 130
o
130 +/-6
KB 2010
Other Analyses
o
32 +/-5
o
Approximately Parallel
112 +/-6
o
112 +/-6
o
130 +/-6
o
90 +/- 7
KB 2010
24
Evaluation of Soft Tissue on Lateral Ceph 30-40
o
UFH: 130
o
100-110
o
LFH: 120-132
o
85-95
o
CHECK THAT THE PATIENT IS IN REPOSE, KB 2010 WHICH THIS PATIENT IS NOT
Clinical Photography
KB 2010
25
Clinical Photographs
KB 2010
Clinical Photographs
KB 2010
26
Mounting the Case
KB 2010
•
Take the impressions
•
Interocclusal records
•
Face bow record
•
Mount the casts
•
Measuring in 3 planes of space
KB 2010
27
Impressions •
2 sets of upper impressions
•
2 sets of lower impressions
•
•
Block out brackets with wax to prevent distortion of the impression Avoid bubbles/voids in pour-up
KB 2010
KB 2010
28
Interocclusal Record •
Record occlusion in centric relation
(Potential
disparity with centric relation when asleep) •
Avoid displacement from premature contacts (Wax is not ideal for occlusal records)
•
Alternatives: •
Record occlusal relationship supine
•
Deprogramming
•
Short general anesthetic!
KB 2010
Facebow Recording •
Find Frankfort Horizontal (Easier said than done!)
KB 2010
29
A Common Reference Plane
The Frankfort plane identified clinically should correlate with the Frankfort plane on the articulator AND the lateral Ceph
KB 2010
True Frankfort versus Clinical
KB 2010
30
Radiographic Frankfort
Projected Frankfort Clinical Frankfort
KB 2010
Identifying True Frankfort
J Oral Maxillofac Surg. 2001 Jun;59(6):635-40; discussion 640-1. KB 2010
31
Identifying True Frankfort
KB 2010
A Common Reference Plane
KB 2010
32
Facebow Recording •
•
•
Find Frankfort Horizontal (Easier said than done!) Ensure the facebow is centered on the face Lock down the hinges to prevent distortion of record
KB 2010
Midlines and occlusal angulations/cants are consistent with clinical picture
KB 2010
33
Mount Two Sets of Casts
A
B KB 2010
Erickson Model Block and Platform
KB 2010
34
KB 2010
3 Planes of Measurement
KB 2010
35
3 Planes of Measurement
RIGHT SIDE DOWN! KB 2010
3 Planes of Measurement
KB 2010
36
3 Planes of Measurement
KB 2010
Formulating the Surgical Plan and the VTO
KB 2010
37
When I hand articulate the models can I get a good occlusion? No
Segmental maxilla / (Segmental mandible) / More Ortho
Yes
Proceed to Next
Is the position of the anterior maxilla acceptable? No
Maxillary osteotomy
Proceed to Next
Yes
Mandible acceptable? No Yes
Mandibular osteotomy
No
Genioplasty
No. There is an AOB
Is the position and form of the chin acceptable?
Maxillary osteotomy +/Mandibular osteotomy
Yes
Finished
KB 2010
Prediction Tracing: Exercise One Visualized Treatment Objective (VTO) for Mandibular Sagittal Split Osteotomy Osteotomy
KB 2010
38
Exercise 1: VTO for BSSO Setback
Trace the cephalogram and indicate in the mandible where the osteotomy will be placed
Trace the cephalogram and indicate in the mandible where the osteotomy will be placed
KB 2010
Take a new piece of tracing paper and trace over the original: only trace structures in the maxilla and above. Trace the soft tissues of the nose and upper lip.
KB 2010
39
Reposition the prediction tracing on the original such that the maxillary teeth of the prediction tracing meet the mandibular teeth on the original tracing in class 1 Trace the mandible ANTERIOR to the osteotomy line, including the teeth. Trace the soft tissues of the lower lip and chin.
KB 2010
Reposition the prediction tracing such that the skull bases and orbits coincide. Rotate the prediction tracing around the axis of rotation in the condylar head until the inferior border of the proximal mandibular segment seems aligned with the inferior border of the distal segment. Trace the proximal mandibular segment. Note the degree of overlap. This corresponds to the amount of mandibular setback. KB 2010
40
Exercise 2: VTO for Le Fort 1
Prediction Tracing: Exercise Two Visualized Treatment Objective (VTO) for Maxillary Le Fort 1 Osteotomy
Prediction Tracing: Exercise Two Visualized Treatment Objective (VTO) for Maxillary Le Fort 1 Osteotomy
KB 2010
Trace the cephalogram and indicate in the maxilla where the osteotomy will be placed
KB 2010
41
Take a second piece of tracing paper and trace again all the structures that will NOT move during the osteotomy (i.e. above the osteotomy cut). Stop tracing the soft tissue of the nose at the supra-tip break. Mark a horizontal line that corresponds to the level of desired maxillary incisal vertical height
KB 2010
Rotate the top sheet around the axis of rotation in the condylar head until the tip of the lower incisors protrude above the horizontal line by 2 to 3 mm. This represents the overbite. Trace the entire mandible and the soft tissue of the neck and chin up to the labiomental fold.
KB 2010
42
Reposition the top tracing over the original such that the maxillary dentition occludes with the new mandibular dentition in class 1. Pay particular attention to the incisal relationship. Trace the maxilla and the maxillary teeth. Trace the remainder of the nose and upper lip, then complete the tracing of the lower lip.
KB 2010
Reorient the prediction tracing on the original such that the skull bases and orbits coincide. Examine the degree of movement of the maxilla in 2 planes. Make a note of these measurements. Examine the degree of autorotation of the mandible. Examine also the effect on the chin prominence and assess whether a genioplasty is required.
KB 2010
43
Exercise 3: VTO for 2-Jaw Surgery
Prediction Tracing: Exercise Three Visualized Treatment Objective (VTO) for Bimaxillary Osteotomy (Le Fort 1 and BSSO)
Prediction Tracing: Exercise Three Visualized Treatment Objective (VTO) for Bimaxillary Osteotomy (Le Fort 1 and BSSO)
KB 2010
Trace the cephalogram and indicate in the maxilla AND mandible where the osteotomies will be placed
KB 2010
44
Take a new sheet of tracing paper and trace over the original: only trace structures that will NOT move in either the maxillary or mandibular osteotomies. Stop tracing the soft tissue of the nose at the supra-tip break Indicate the desired vertical height of the incisal edges of the maxillary teeth with a horizontal line. Indicate with a vertical line the desired AP position of the incisal edge of the maxillary incisors KB 2010
Rotate the top sheet around the axis of rotation in the condylar head until the tip of the lower incisors protrude above the horizontal line by 2 to 3 mm. This represents the overbite. Trace the mandible.
KB 2010
45
The degree of reverse overjet indicates the amount the mandible must be set back.
Reposition the prediction tracing such that the maxillary incisal edge rests in the indicated ideal position. Align the maxillary occlusal plane with the occlusal plane of the mandibular teeth on the prediction tracing. (Note that the maxillary teeth NEED NOT be in class 1 occlusion with the mandibular teeth at this point!) Trace the maxilla and the maxillary teeth. Trace the remainder of the nose and the upper lip. KB 2010
Your prediction tracing should look like this now. Label this tracing “IPT” (Intermediate Prediction Tracing)
KB 2010
46
Take a new sheet of tracing paper and trace over all hard structures on the first prediction tracing except the mandible. It is recommended that you use a different color pencil. Trace soft tissues down to and including the upper lip. Label this tracing “FPT” (Final Prediction Tracing)
KB 2010
Place the Final prediction tracing (FPT) over the Intermediate Prediction Tracing (IPT) in such a way that the maxillary teeth on the FPT meet the mandibular teeth on the IPT in class 1. Trace the mandible ANTERIOR to the mandibular osteotomy line. Trace the mandibular teeth.
KB 2010
47
Reposition the FPT on the IPT such that the skull bases and orbits coincide. Rotate the FPT around an axis of rotation on the condylar head until the inferior border of the proximal mandibular segment aligns with the inferior border of the distal mandibular segment. Trace the proximal mandibular segment. The overlap indicates the amount of mandibular setback. KB 2010
Place the FPT on the original tracing of the cephalogram such that the lower incisor and symphysis of both coincide. Estimate the predicted chin and lower lip shape.
KB 2010
48
Your FPT should now look like this. Measure the vertical and AP predicted movement of the maxilla and mandible and record the measurements. Note that the post-surgical occlusal plane in this example was determined by the occlusal plane of the mandible after rotation; however the occlusal plane can be adjusted (within limits) to fit the needs of the individual case.
KB 2010
Soft Tissue Predictions Mandible
•
•
Advancement –
Chin 100%
–
Lower Lip 70%
Setback –
Chin 90%
–
Lower Lip 90%
–
Upper Lip 20% KB 2010
49
Soft Tissue Predictions Maxilla Advancement
•
–
–
–
Nasal Tip 30% Upper Lip 50% at incisor level (70% - 90% with VY closure) Upper lip shortens 1-2 mm
Setback
•
–
–
–
Upper Vermillion 50% - 60% (Less with VY) Subnasale 30% (Less with VY) Upper Lip 10% KB 2010
Soft Tissue Predictions Maxilla
•
Inferior –
•
Lip length increases 10-15%
Superior –
Subnasale
20% up
–
Nasal Tip 20% up
–
Lip
10% up (Less if VY)
KB 2010
50
Predicting Chin Position Horizontal distance to 0-Meridian 0-Meridian
0-Meridian: Perpendicular to FH from soft tissue forehead. Chin should be 0-3mm ahead of this line
KB 2010
Predicting Chin Position FH to Z Line Z Line
o
78 +/- 10
Z Line: Tangent to most protrusive lip and soft tissue chin
KB 2010
51
Predicting Chin Position H Line to NB H Line
H Line: Tangent to most protrusive lip and soft tissue chin
o
8 +/- 2
KB 2010
Review of Process in Planning. Start with the Maxilla 1. 2. 3. 4. 5. 6.
Predict ideal A.P. position of maxilla form lateral ceph Predict ideal superior/inferior position of anterior maxilla from clinical incisal show Set occlusal plane: Use Xi point, Frankfort Horizontal and mandibular occlusal plane as primary guides Find required lateral repositioning of maxilla from clinical assessment of midlines Assess cant from clinical measurement and mounted casts Assess maxillary arch width from models
KB 2010
52
Detailed Process in Planning (continued) 7.
Trace the new maxilla and mandible positions (VTO) as we did in the exercises.
8.
Re-analyze using Ricketts to compare the VTO to cephalometric norms.
9.
Record the intended changes in vertical, transverse, AP and arch width dimensions of the posterior and anterior maxilla and the intended amount of set back/push forward at the mandibular osteotomy.
KB 2010
Detailed Process in Planning (Step Back) 10.
Are the movement planned so far reasonable. If not start again and redistribute the movements between the maxilla and mandible, or change the plan entirely, (SARPE or more orthodontics)
KB 2010
53
Detailed Process in Planning (Chin and Profile) 11.
Assess the projected soft tissue profile, particularly the chin
12.
Proceed to model surgery
13.
Verify on the models that the movements are surgically feasible
KB 2010
Model Surgery and Splint Construction
KB 2010
54
Model Surgery 1.
Calculate the new measurements that would give the desired new maxillary cast position (AP, Vertical and Transverse).
2.
Segmentalize the upper segment if necessary and make occlusal adjustments to give best intercuspation
3.
Mount maxillary model to new position using the Erickson model block and platform
4.
Mount mandibular model to new position (in occlusion with upper model) on the articulator
5.
Verify movements correlate with intention
6.
Note magnitude of movements in all planes
7.
Verify movements are surgically feasible
8.
Construct splints
KB 2010
Adjust Occlusal Surfaces Segment maxillary cast at this stage to achieve best occlusion if performing multipiece Le Fort 1
Record where occlusal adjustments are made so that they can be duplicated intraoperatively KB 2010
55
Remount Upper Cast to Desired Position in Space
KB 2010
Maxillary Post op cast with Mandibular Post op cast
Final splint ONLY
CONSTRUCT FINAL SPLINT FIRST
KB 2010
56
Maxillary Post op cast with Mandibular Pre op cast
Final splint AND Intermediate splint
CONSTRUCT INTERMEDIATE SPLINT SECOND
KB 2010
Final Splint
Final Splint capable of being wired into maxillary dentition to support maxillary fixation KB 2010
57
Intermediate Splint
Intermediate Splint should locate positively in Final Splint
KB 2010
Summary •
Take the records meticulously
•
Verify that the “A” casts match the “B” casts
•
•
•
Verify that the mounted casts match the clinical picture Perform the model surgery on one set of casts
Construct the splints in correct sequence for the planned surgery.
KB 2010
58
TMJ Considerations in Orthognathic Surgery
KB 2010
The “Normal” TMJ •
What does a normal TMJ look like and how do we identify it? –
Clinically
–
Radiographically
–
MRI
KB 2010
59
KB 2010
KB 2010
60
KB 2010
Goals of Orthognathic Surgery as Relate to the TMJ •
Restore/maintain “normal” range of opening
•
Eliminate/avoid joint pain and noises
•
•
Achieve stable condyle and meniscus position in fossa when teeth are in centric occlusion Where is the ideal
location for the condyle?
KB 2010
61
Condylar Malposition •
Condylar sag: Inferior displacement of the condylar head within the glenoid fossa
KB 2010
Central Condylar Sag •
•
•
Condyle is positioned inferiorly in the fossa No contact between condylar head and articular fossa in centric occlusion Immediate malocclusion on release of fixation (assuming no hemarthrosis or joint edema is present)
KB 2010
62
Central Condylar Sag
KB 2010
Peripheral Condylar Sag •
•
•
Contact between condylar head and articular fossa may support the inferiorly positioned condylar head Immediate or late relapse Late relapse associated with condylar resorption
KB 2010
63
Peripheral Condylar Sag
KB 2010
Condylar Resorption
KB 2010
64
Other Causes of Condylar Malposition •
•
Posterior positioning of condyle is associated with increased risk of post-operative symptoms of popping and locking. Limit that the condyle may be posteriorly positioned increased by –
–
–
Supine, paralyzed state Improper surgical technique Condylar sag
KB 2010
Other Causes of Condylar Malposition •
Uneven contacts between the proximal and distal segments may cause the condyle to become laterally or medially displaced when fixation is applied
KB 2010
65
KB 2010
KB 2010
66
Minimizing Condylar Malposition •
Avoid creating intrarticular edema or hemarthrosis –
–
–
Support during split Support during mobilization Avoid rotating the condyle around its long axis
KB 2010
Minimizing Condylar Malposition •
Avoid bad splits; they complicate condylar positioning!
KB 2010
67
Minimizing Condylar Malposition •
•
Ensure adequate stripping of medial pterygoid to eliminate interference to distal movement of distal segment. Reduce bony interferences, especially on mandibular setback.
KB 2010
Minimizing Condylar Malposition •
Eliminate uneven contact between osteotomized segments that prevent passive, even and stable apposition
KB 2010
68
Minimizing Condylar Malposition •
Gentle use of clamps to hold segments whilst placing fixation
KB 2010
Minimizing Condylar Malposition •
Use shims of bone to eliminate intersegmental gaps
KB 2010
69
Minimizing Condylar Malposition •
•
Avoid lag screw fixation Positional screws are fine
KB 2010
Minimizing Condylar Malposition •
Plates can be adapted in order to provide passive fixation. More difficult to achieve with positional screws.
KB 2010
70
Minimizing Condylar Malposition •
Positioning the condyle prior to fixation –
Direction of force
–
Magnitude of force
KB 2010
KB 2010
71
Minimizing Condylar Malposition •
Ensure adequate bone removal at posterior of maxilla in Le Fort 1 osteotomy
KB 2010
KB 2010
72
Minimizing Condylar Malposition •
Avoid heavy post-op elastics as the effect on the occlusion may be more temporary than you think!
KB 2010
Idiopathic Condylar Resorption •
•
Progressive alteration of the condylar shape with decreased mass bilaterally, in temporomandibular joints that previously exhibited normal growth patterns AICR (Adolescent Internal Condylar Resorption)
KB 2010
73
Risk Factors for ICR •
Female
•
Age 15-30
•
Pre-op TMJ disease
•
Counterclockwise rotation
•
Mandibular hypoplasia
•
IMF
•
High mandibular plane angle
•
•
Small posterior face height
•
Posterior inclination of condylar neck
•
•
Large mandibular advancement
Posterior repositioning of condylar head in fossa Increase in ramus length
KB 2010
Idiopathic Condylar Resorption
KB 2010
74
Idiopathic Condylar Resorption
KB 2010
Treatment and Prognosis •
•
•
•
Re-osteotomy alone has 50-100% failure rate Stabilization of occlusion with occlusal splint prior to re-osteotomy has similar failure rate Orthodontic occlusal compensation and stabilization achievable in some Advanced cases require condylectomy and joint reconstruction (alloplastic or costochondral)
KB 2010
75
Effect of Orthognathic Surgery on the Symptomatic TMJ Patient •
Lack of consistency in terminology used to categorize TMJ disease
•
Populations are often poorly described
•
Outcomes are poorly defined
•
Lack of information on the post-op condylar position in patients studied
KB 2010
Concomitant TMJ and Orthognathic Surgery for Symptomatic TMJ Patients •
•
•
Pts without symptoms from TMJ pathology can become symptomatic after orthognathic surgery Pts with anterior disc displacement prior to BSSO will most likely not improve, and may get worse IVRO in a pt with ADD improves disc-condyle relationships and pain KB 2010
76
Concomitant TMJ and Orthognathic Surgery for Symptomatic TMJ Patients •
Goncalves et al (JOMS April 2008). Retrospective cohort study, looking at 51 pts with pre-op TMJ symptoms and compared concomitant TMJ + orthognathic surgery to orthognathic surgery alone. Demonstrated improved stability and relief of symptoms in the former group after 31 months follow up
KB 2010
Summary •
•
•
•
•
Perform a baseline TMJ exam on every patient Avoid intra-operative trauma to the TMJ that might cause intra-articular edema Take care with positioning and fixation of the segments Orthognathic surgery may induce symptoms from the TMJ Consider treating the TMJ first if disease is present
KB 2010
77
Stability Issues
KB 2010
Instability •
Early:
From the time of surgery up to week 8
•
Late:
After 8 weeks
KB 2010
78
Long Term Stability in Maxillary Osteotomies MORE STABLE
LESS STABLE
•
Impaction
•
Setback
•
Advancement
•
Downgraft
•
Expansion (**SARPE)
•
Advancement with downgraft KB 2010
Long Term Stability in Mandibular Osteotomies MORE STABLE
•
(Proportional to advancement)
•
LESS STABLE
Advancement***
Setback
***Idiopathic Condylar Resorption KB 2010
79
Limiting Long Term Instability •
•
•
•
Bone grafting especially when downgrafting a maxilla by 5mm or more Conservative moves, not ambitious. (*Cleft cases) Overcorrection especially when doing a mandibular setback (easier to correct a relapsing class II with ortho than a relapsing class III) ? Rigid fixation versus IMF. ? Positional Screws versus miniplates
KB 2010
Pitfalls in Planning and Execution •
Leaving appliance activated at time of surgery
•
Inadequate strength of arch wire at surgery
•
Inadequate incisor decompensation (leads to inappropriate incisal relationship)
•
Inaccurate pre-op occlusal record (condylar position)
•
Inadequate root divergence before segmentalizing
•
Hasty split (fracture or nerve damage)
•
Occlusal splint too thick
•
Poor condylar position during application of fixation
•
Excessive torque on proximal segment during fixation KB 2010
80
