A 24-Year-Old With Class III, Facial Asymmetry, a Cant, and an Eroded Condyle: How Much Decompensation and How Many Jaws?
A 24-year-old woman is referred for Class III correction. She has a concave profile, a 3 mm anterior open bite, overjet −3 mm, overbite −2 mm, and her chin is deviated 6 mm to the left. The maxillary occlusal plane is 3 mm lower on the left. Cephalometrics: SNA 79°, SNB 85°, ANB −6°, Wits −8 mm, SN-MP 38°, upper incisor to SN 112°, IMPA 82°, nasolabial angle 92°. She had four first premolar extractions with fixed appliances for 22 months between ages 13 and 15 in another city; records are unavailable. Clinically there is 2 mm residual space in the upper arch, none in the lower, thin gingiva with 1-2 mm recession on 41 and 31, and a 2 mm buccal corridor asymmetry. The left TMJ clicks, without pain or locking. Cone-beam CT shows condylar volumes of 1,050 mm³ on the right and 880 mm³ on the left, with cortical erosion on the left condyle and a steep articular eminence. She is a non-smoker with a customer-facing job and says she cannot face two more years in braces.
1. State your orthodontic objectives before surgery, quantify the decompensation you need, and identify what limits you in this particular patient.
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The principle is that the teeth must be moved to their ideal position relative to their own jaws before surgery, even though this makes the skeletal discrepancy look worse. Here the dentition is already heavily compensated: U1-SN at 112° is proclined and IMPA at 82° is retroclined, which is exactly the dentoalveolar masking of a Class III, compounded by the earlier camouflage.
Targets: bring U1-SN from 112° to about 102-104° and IMPA from 82° to about 90-92°. Because the upper incisors are retroclined, the overjet will move from −3 mm to roughly −9 or −10 mm. That number, not the initial −3 mm, defines the surgical correction required, and it must be calculated now so the surgeon plans the correct magnitude.
The constraint is space. The upper arch has 2 mm residual; the lower has none. Retroclining the upper incisors by 8-10° needs approximately 4 mm, so the residual space plus interproximal reduction can supply it. Proclining the lower incisors by 10° needs about 4-5 mm that does not exist. Options are interproximal reduction of up to 0.5 mm per contact (about 2 mm over four contacts), accepting partial decompensation with IMPA to 86-88° and a correspondingly smaller setback, or considering a different surgical plan that needs less dental change.
The second constraint is periodontal. There is already 1-2 mm of recession on 41 and 31 with thin gingiva. Proclination moves the incisor roots lingually but the crowns labially, which thins the labial plate and typically worsens recession. Obtain a periodontal opinion and consider a connective tissue graft before or during decompensation, limit the proclination, and use torque-controlled mechanics rather than simple tipping. Also assess symphyseal thickness on the CBCT; a narrow symphysis with a thin labial plate is a reason to under-treat the decompensation rather than force the numbers.
Other preparatory steps: do not attempt to correct the 3 mm occlusal cant orthodontically. Bracket placement should build a level archwire, and the cant is corrected surgically. Plan the case on a CBCT-based 3D virtual surgical plan with model surgery, and record the CR position, because all cephalometric and occlusal planning depends on it.
2. Choose the surgical plan. Justify the number of jaws, the direction and magnitude of movement, and how you would manage the asymmetry and the open bite.
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Bimaxillary surgery is the correct choice; single-jaw mandibular setback would compromise her.
Why not setback alone: she has maxillary retrusion (SNA 79°) and an already flat nasolabial angle of 92°. A setback of the magnitude required to correct a 9-10 mm decompensated overjet would push the midface further back relative to the chin, flatten the profile and deepen the labiomental fold. It would not correct the 3 mm cant, which is a maxillary problem. It would also be a large mandibular rotation with a long mandibular plane (38°), which loads the condyles asymmetrically and makes the soft-tissue result unpredictable.
Why bimaxillary: a Le Fort I advancement of about 3-4 mm corrects the midface; differential posterior impaction (more on the left, to bring the 3 mm low left maxilla up) levels the occlusal cant; and the posterior impaction closes the anterior open bite by allowing the mandible to autorotate. Then a mandibular setback of roughly 4-6 mm with an asymmetric component (more setback on the right, less on the left, with a midline correction) addresses the remaining sagittal and transverse discrepancy. The 6 mm chin deviation is best managed by combining the asymmetric setback with an asymmetric genioplasty, which gives direct control of the chin point in three planes and reduces how much the mandible itself must be moved-important for condylar loading. A 2 mm buccal corridor asymmetry will partly resolve with the transverse correction; assess it on the 3D plan rather than promising correction.
The condyle is the part of the plan that matters most. A young woman with a high mandibular plane angle, reduced posterior facial height, condylar volume asymmetry, cortical erosion on the left, and a steep eminence is in the recognised risk group for progressive condylar resorption, which is a leading cause of late relapse and of the "surgery didn't hold" complaint. Mitigations: minimise the mandibular setback and the counterclockwise rotation; avoid over-rotation of the proximal segment; seat the condyles passively in the fossa during fixation, using a repositioning splint or navigation, and verify position intraoperatively; consider a period of observation with serial CBCT before operating if there is any suspicion that the erosion is active; and consent her explicitly for condylar change and relapse as a known risk rather than as a complication. With this much decompensation needed, a surgery-first approach is not appropriate here-the dental movements required are too large for a short pre-surgical phase.
3. Does the left TMJ click change your plan? What would you do before, during, and after surgery regarding the joint?
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A painless click on its own does not change the surgical plan and is not a contraindication to orthognathic surgery. It is common, often unrelated to the skeletal problem, and noise alone does not warrant treatment. What matters is not the click but the cortical erosion and the reduced condylar volume on the same side, because that combination is what predicts resorption and relapse rather than the click itself.
Before surgery: take a full baseline. Document pain on a numeric scale, maximum opening, deviation on opening, joint noises, and locking history at every visit; these become your outcome measures. Do not order MRI routinely for a painless click in a patient with a stable occlusion, but do order it if pain, locking, or a change in the click develops, and to assess disc position and joint effusion if you are considering active joint treatment. Obtain a baseline CBCT for condylar volume and cortical integrity. If the erosion looks active-pain, effusion on MRI, or progressive volume loss on serial imaging 6-12 months apart-defer surgery and observe, because operating on an actively resorbing condyle is the scenario most likely to produce a poor long-term result. Counsel her that correcting the occlusion does not treat TMJ disorders and that the click may persist after surgery.
During surgery: minimise loading of the left joint. That means less setback, no aggressive counterclockwise rotation, passive seating of the condyle, stable internal fixation, and intraoperative verification of condylar position. If the left joint is the limiting factor, a slightly less ambitious sagittal correction with a genioplasty for the profile is a better trade than a large setback to hit a cephalometric number.
After surgery: early controlled mobilisation, a soft diet, guided physiotherapy, and short-course NSAIDs rather than prolonged splint therapy. Review clinically at 1, 3, 6, 12, and 24 months, with CBCT at 6-12 months and again at 2 years to detect condylar change and skeletal relapse. Warn her in writing that late relapse after mandibular surgery is most often condylar, and that a second procedure may be required if that happens. Night-time splint use to control parafunction is reasonable given her reported clenching, but it is adjunctive, not a substitute for careful surgical planning.