Planning Orthognathic Surgery 2010
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Planning Orthognathic Surgery 2010

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Planning Orthognathic Surgery 2010 Planning Orthognathic Surgery 2010 Document Transcript

  • 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 the surgical plan• Performing prediction tracings (The VTO)• Model surgery and constructing splints• The TMJ and orthognathic Surgery• Planning for stability• Pitfalls in planning and execution KB 2010 1
  • • Primary references: – Modern Practice in Orthognathic Reconstructive Surgery (Edited by William H. 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• 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 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
  • Referring PractitionerCoordination ofCare 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 2010Facial Esthetics 1/3 1/3 1/3 KB 2010 7
  • Facial EstheticsULL 21mm (+/- 2 mm) MenULL 19 mm (+/-2 mm) WomenIncisor Show at Rest 2 - 4 mmNote lip-tooth relationships atrest and when active! 1/3 2/3 KB 2010 Facial Esthetics o o • Nasofacial Angle 30 - 40 o o • Nasomental Angle 120 -132 o o • Mentocervical Line 80 – 95 to Vertical o o 100 • Mentocervical Line 110 – 120 to Nasomental Line o o • Nasolabial Angle 100 - 110 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 2010Dental Esthetics Arch Form Occlusal Plane Occlusal Level Overbite Overjet Buccal Corridor Surrounding Tissues KB 2010 9
  • KB 2010Case Example KB 2010 10
  • Case ExampleSMILE REST12 mm 9 mm KB 2010 Case Example KB 2010 11
  • Case Example KB 2010 Case ExampleClass II Skeletal Pattern(*mandible)Increased incisal showNo increased LFH!Close bite (?traumatic)Maxillary cantOcular dystopiaUnstable occlusion. Poorbridges (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 CTDolphin Imaging KB 2010 Lateral Cephalogram What is wrong with this Lateral Ceph? KB 2010 17
  • Lateral Cephalogram Nasion Pt point Porion Orbitale ANS Basion PNS A Point Xi Point Gonion Pm Point Pogonion Menton Gnathion 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/RulerIdentify the points marked in the previous slides,(then trace the outlines of the skeleton asdescribed), and start measuring the pertinentangles using Rickett’s analysis. KB 2010 Lateral Cephalogram Nasion MARK THESE POINTS ON YOUR CEPHALOGRAM Pt point Porion Orbitale PNS ANS Basion A Point Xi Point Gonion Pm Point Pogonion Gnathion Menton KB 2010 19
  • o Facial Depth (Angle) 87 +/- 3 NasionFrankfort Horizontal o Porion 87 Orbitale Pogonion KB 2010 o Mandibular Plane Angle: 26 +/- 4 o26 Mandibular Plane Gonion Pogonion Menton KB 2010 20
  • o Facial Axis: 90 +/- 3 o 90 BasionSkull 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 2010Lower incisor to APog: 1mm +/- 2 mm A point Pogonion KB 2010 22
  • Xi Point and Functional Occlusal Plane Xi KB 2010 oLower Face Height : 47 +/- 4 ANS Xi o 47 Pm Point KB 2010 23
  • o Interincisal Angle: 130 130 +/-6 o KB 2010 Other Analyses o o32 +/-5 Approximately 112 +/-6 Parallel o 112 +/-6 130 +/-6 o o 90 +/-7 KB 2010 24
  • Evaluation of Soft Tissue on Lateral Ceph o 30-40 UFH: o 130 o 100-110 LFH: o o 120-132 85-95 CHECK THAT THE PATIENT IS IN REPOSE, WHICH THIS PATIENT IS NOT KB 2010 Clinical Photography KB 2010 25
  • Clinical Photographs KB 2010Clinical 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 2010True Frankfort versus Clinical KB 2010 30
  • Radiographic Frankfort Projected FrankfortClinical 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 2010A 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 2010Erickson Model Block and Platform KB 2010 34
  • KB 20103 Planes of Measurement KB 2010 35
  • 3 Planes of Measurement RIGHT SIDE DOWN! KB 20103 Planes of Measurement KB 2010 36
  • 3 Planes of Measurement KB 2010Formulating the Surgical Plan and the VTO KB 2010 37
  • When I hand articulate the models can I get a good occlusion? No Yes Segmental maxilla / Proceed to Next (Segmental mandible) / More Ortho Is the position of the anterior maxilla acceptable? No Yes Proceed to NextMaxillary osteotomy Mandible acceptable? No No. There is an AOBMandibular Yes Maxillary osteotomy +/-osteotomy Mandibular osteotomy Is the position and form of the chin No acceptable? YesGenioplasty Finished KB 2010 Prediction Tracing: Exercise One Visualized Treatment Objective (VTO) for Mandibular Sagittal Split Osteotomy KB 2010 38
  • Exercise 1: VTO for BSSO Setback
  • Trace the cephalogram andindicate in the mandiblewhere the osteotomy will beplaced KB 2010Take a new piece of tracingpaper and trace over theoriginal: only trace structuresin the maxilla and above.Trace the soft tissues of thenose and upper lip. KB 2010 39
  • Reposition the predictiontracing on the original suchthat the maxillary teeth of theprediction tracing meet themandibular teeth on theoriginal tracing in class 1Trace the mandible ANTERIORto the osteotomy line,including the teeth.Trace the soft tissues of thelower lip and chin. KB 2010Reposition the predictiontracing such that the skullbases and orbits coincide.Rotate the prediction tracingaround the axis of rotation inthe condylar head until theinferior border of the proximalmandibular segment seemsaligned with the inferiorborder of the distal segment.Trace the proximal mandibularsegment. Note the degree ofoverlap. This corresponds tothe amount of mandibularsetback. KB 2010 40
  • Exercise 2: VTO for Le Fort 1
  • 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 tracingpaper and trace again all thestructures that will NOT moveduring the osteotomy (i.e.above the osteotomy cut).Stop tracing the soft tissue ofthe nose at the supra-tipbreak.Mark a horizontal line thatcorresponds to the level ofdesired maxillary incisalvertical height KB 2010Rotate the top sheet aroundthe axis of rotation in thecondylar head until the tip ofthe lower incisors protrudeabove the horizontal line by 2to 3 mm. This represents theoverbite.Trace the entire mandible andthe soft tissue of the neck andchin up to the labiomentalfold. KB 2010 42
  • Reposition the top tracingover the original such that themaxillary dentition occludeswith the new mandibulardentition in class 1. Payparticular attention to theincisal relationship.Trace the maxilla and themaxillary teeth.Trace the remainder of thenose and upper lip, thencomplete the tracing of thelower lip. KB 2010Reorient the prediction tracingon the original such that theskull bases and orbitscoincide.Examine the degree ofmovement of the maxilla in 2planes. Make a note of thesemeasurements.Examine the degree ofautorotation of the mandible.Examine also the effect on thechin prominence and assesswhether a genioplasty isrequired. KB 2010 43
  • Exercise 3: VTO for 2-Jaw Surgery
  • Prediction Tracing: Exercise ThreeVisualized 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 tracingpaper and trace over theoriginal: only trace structuresthat will NOT move in eitherthe maxillary or mandibularosteotomies.Stop tracing the soft tissue ofthe nose at the supra-tipbreakIndicate the desired verticalheight of the incisal edges ofthe maxillary teeth with ahorizontal line.Indicate with a vertical linethe desired AP position of theincisal edge of the maxillaryincisors KB 2010Rotate the top sheet aroundthe axis of rotation in thecondylar head until the tip ofthe lower incisors protrudeabove the horizontal line by 2to 3 mm. This represents theoverbite.Trace the mandible. KB 2010 45
  • 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 withThe degree of the mandibular teeth at thisreverse overjet point!)indicates theamount the Trace the maxilla and themandible must be maxillary teeth.set back. 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 tracingpaper and trace over all hardstructures on the firstprediction tracing except themandible. It is recommendedthat you use a different colorpencil.Trace soft tissues down to andincluding the upper lip.Label this tracing “FPT” (FinalPrediction Tracing) KB 2010Place the Final predictiontracing (FPT) over theIntermediate PredictionTracing (IPT) in such a waythat the maxillary teeth on theFPT meet the mandibularteeth on the IPT in class 1.Trace the mandible ANTERIORto the mandibular osteotomyline. Trace the mandibularteeth. KB 2010 47
  • Reposition the FPT on the IPTsuch that the skull bases andorbits coincide.Rotate the FPT around an axisof rotation on the condylarhead until the inferior borderof the proximal mandibularsegment aligns with theinferior border of the distalmandibular segment.Trace the proximal mandibularsegment.The overlap indicates theamount of mandibularsetback. KB 2010Place the FPT on the originaltracing of the cephalogramsuch that the lower incisorand symphysis of bothcoincide. Estimate thepredicted chin and lower lipshape. 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-Meridian0-Meridian:Perpendicularto FH fromsoft tissueforehead.Chin shouldbe 0-3mmahead of thisline KB 2010 Predicting Chin Position FH to Z Line Z Line o 78 +/- 10Z Line:Tangentto mostprotrusivelip andsoft tissuechin KB 2010 51
  • Predicting Chin Position H Line to NB H LineH Line:Tangentto most oprotrusive 8 +/- 2lip andsoft tissuechin KB 2010 Review of Process in Planning. Start with the Maxilla 1. Predict ideal A.P. position of maxilla form lateral ceph 2. Predict ideal superior/inferior position of anterior maxilla from clinical incisal show 3. Set occlusal plane: Use Xi point, Frankfort Horizontal and mandibular occlusal plane as primary guides 4. Find required lateral repositioning of maxilla from clinical assessment of midlines 5. Assess cant from clinical measurement and mounted casts 6. 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 chin12. Proceed to model surgery13. 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 SurfacesSegment maxillarycast at this stage toachieve bestocclusion ifperforming multi-piece 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 2010Maxillary Post op cast with Mandibular Post op cast Final splint ONLYCONSTRUCT FINALSPLINT FIRST KB 2010 56
  • Maxillary Post op cast with Mandibular Pre op cast Final splint AND Intermediate splintCONSTRUCT INTERMEDIATESPLINT SECOND KB 2010 Final Splint Final Splint capable of being wired into maxillary dentition to support maxillary fixation KB 2010 57
  • Intermediate SplintIntermediate 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 2010KB 2010 60
  • KB 2010Goals 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 2010Other 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 2010KB 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 inter- segmental 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 • Large mandibular• Age 15-30 advancement• Pre-op TMJ disease • Counterclockwise rotation• Mandibular hypoplasia • IMF• High mandibular plane angle • Posterior repositioning of• Small posterior face height condylar head in fossa• Posterior inclination of • Increase in ramus length condylar neck 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 • ImpactionSTABLE • Setback • Advancement • Downgraft LESS • Expansion (**SARPE)STABLE • Advancement with downgraft KB 2010 Long Term Stability in Mandibular Osteotomies MORE • Advancement***STABLE (Proportional to advancement) • Setback LESSSTABLE ***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
  • Pitfalls in Planning and Execution (continued)• Compromising blood supply – Gingivae during flap for segmental osteotomy – Over-ambitious advancement Le Fort 1 level• Tear of palatal mucosa during segmentalization• Condylar sag (very difficult to plan for)• Failure to check condylar position post-op• Setback of mandible in presence of a flat chin-throat angle• Planning for >6mm posterior maxillary impaction• Weak brackets/hooks at time of surgery KB 2010 81