Obstructive sleep apnoea, a Class II skeleton and painful clicking joints: is this a surgical problem?
A 31-year-old woman with a BMI of 33 is referred for loud snoring and daytime sleepiness (Epworth 16). Polysomnography shows an apnoea–hypopnoea index of 34/h with oxygen desaturation to 78%. CPAP was abandoned after three months because of claustrophobia. Cephalometry and CT show ANB +9°, a mandibular plane angle of 42°, a posterior airway space of 6 mm and a narrow maxilla; the condyles are flattened bilaterally with disc displacement with reduction. She has chronic bilateral preauricular pain and clicks, managed with ibuprofen and tramadol, and she grinds her teeth at night. She had a tonsillectomy at 12. She asks whether 'breaking the jaw forward' will cure her and whether she can stop CPAP forever. She is a schoolteacher and can take six weeks off work.
1. Before committing to any operation, how do you decide whether this is a maxillofacial surgical problem or a sleep medicine one? Set out the work-up.
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The error to avoid is accepting the referral's premise - that a Class II skeleton with a high AHI automatically means maxillomandibular advancement. Sleep apnoea is a medical diagnosis with surgical options, not a surgical diagnosis.
Work-up.
- Confirm and characterise the sleep study. AHI 34 with nadir SpO₂ 78% is severe disease; confirm the study is recent, ideally with a Type 1 polysomnogram, and ask about central events and positional dependence.
- Re-establish medical therapy first. CPAP failure after three months is a trial failure, not a definitive one; a retrial with a different mask, humidification, desensitisation or auto-titrating device is the first step and should be documented. Mandibular advancement devices are a reasonable alternative for mild-to-moderate disease but are unlikely to control an AHI of 34 and can worsen TMJ pain.
- Weight and lifestyle. BMI 33 and a high AHI interact; weight reduction of 10% reduces AHI modestly but predictably, and any surgical plan must include it. Refer to a physician for metabolic assessment.
- Upper airway assessment. Drug-induced sleep endoscopy or awake endoscopy gives the level of collapse - retropalatal, retrolingual, lateral wall or epiglottic. A narrow maxilla with retropalatal collapse may respond to palatal expansion or uvulopalatopharyngoplasty; multiple-level collapse supports advancement.
- Orthognathic work-up. Photographs, model surgery, CBCT, and an honest assessment of the need for maxillary impaction or advancement with counterclockwise rotation.
Judgement. She is a candidate for surgery, but only after the non-surgical pathway has been revisited and the site of collapse documented - otherwise the operation is chosen for the cephalometric number rather than for the patient.
2. Compare maxillomandibular advancement with alternatives for her severe OSA, and justify what you would offer and what you would promise.
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Maxillomandibular advancement. Bimaxillary advancement of 10 mm or more, with counterclockwise rotation of the occlusal plane, enlarges the posterior airway at the retrolingual and retropalatal levels and is the most effective skeletal operation, with reported AHI reduction of roughly 60–70% and a surgical success rate (AHI <20 and >50% reduction) in the region of 80–90% in selected patients. It is also the operation with the greatest morbidity: bimaxillary osteotomies, a Class II to Class I or slightly overcorrected occlusion, potential need for a genioplasty, and a real risk of relapse, neurosensory deficit and airway swelling.
Why a single-jaw mandibular advancement is inadequate here. Advancing only the mandible in a patient with ANB +9° and a high mandibular plane produces an unaesthetic, prognathic profile, loads the TMJs unfavourably, and gives less airway gain than bimaxillary advancement. Distraction osteogenesis of the mandible is reserved for syndromic or severely hypoplastic cases, not for this profile. Tracheostomy is a last resort.
What to promise. Not a cure. She should be told that roughly 15–20% of patients remain with residual disease, that a post-operative sleep study is mandatory at 3–6 months, and that a residual AHI may require CPAP or a device to be resumed. She should also hear that 10% weight gain can undo much of the airway gain.
Sequencing. Correct the occlusion and the airway in one operation if the orthodontist can decompensate her dentition; document that the operation is being done for function (OSA) with an occlusal benefit, because the consent conversation differs.
3. How does her TMJ pain and disc displacement alter your plan, and how do you handle her request to stop CPAP?
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TMJ considerations. Bilateral disc displacement with reduction and chronic myofascial pain is common in this population and, on its own, is not a contraindication to orthognathic surgery - but it is a relative one if the pain is poorly controlled. The reasonable sequence is: (1) optimise conservative management for 3–6 months - a stabilisation splint, physiotherapy, jaw exercises, and a planned review of analgesics; (2) avoid a mandibular advancement device, which may aggravate her joint pain; (3) do not offer TMJ surgery (arthrocentesis, arthroscopy, disc repositioning) as a first step, since the evidence for prophylactic joint surgery before orthognathic correction is weak and her symptoms are currently manageable.
Radiographic flattening suggests remodelling or early degenerative change rather than active condylar resorption. If there is progressive resorption - young woman, steep mandibular plane, small posterior facial height - advancement can relapse; that risk should be discussed and the joints re-imaged before and after surgery.
Analgesia. Tramadol plus regular NSAIDs is a poor long-term regimen: it is opioid exposure for a non-malignant pain problem, it is compatible with central sensitisation, and it will complicate post-operative pain management. Taper to a structured regimen with paracetamol, topical NSAID and a limited course of a short-acting agent, and document a plan.
Her request to stop CPAP. She must be told explicitly that CPAP was never a cure and that surgery is also not a guarantee; the post-operative sleep study determines what happens next. Consent should record this conversation rather than a promise of cure. The medico-legal exposure in this case is the promise of cure, not the operation.