Pre-arthroplastic mandibular distraction osteogenesis for the correction of OSA in TMJ ankylosis: a prospective observational study of 25 cases.

INTRODUCTION: In severe TMJ ankylosis cases, the lack of growth of the mandible creates an anatomically narrow airway with a reduced pharyngeal airway space [PAS] which predisposes these patients towards obstructive apnoea [OSA]. There is evidence in the literature that such patients experience severe discomfort during physiotherapy if such airway abnormalities are not corrected prior to ankylosis release. This eventually leads to non-compliance towards physiotherapy and increases the risk of re-ankylosis.

OBJECTIVE: In our study, pre-arthroplastic mandibular distraction osteogenesis [DO] was used to increase the PAS and resolve the underlying OSA prior to releasing the ankylosis.

MATERIALS AND METHODS: Twenty-five cases of TMJ ankylosis with micrognathia and OSA were included in this prospective observational sleep study. They were further divided into a paediatric group [14 subjects] and an adult group [11 subjects]. All cases presented with a history of onset of ankylosis during childhood [before the completion of craniofacial growth] as result of which there was a lack of forward growth of the mandible. Subjects included in our study underwent initial DO of the mandible followed by a second procedure for distractor removal and ankylosis release. Questionnaires, lateral cephalograms and sleep studies were taken pre-operatively (T0), immediate post-distraction to the desired length (T1) and 12 months post the distractor removal and ankylosis release (T2). The parameters studied were PAS width, apnoea hypopnea index [AHI], O2 saturation, mouth opening and mandibular advancement.

RESULTS: The paediatric group variables were as follows: mean PAS width which increased from 3.5 mm [T0] to 9 mm [T2], mean AHI which decreased from 48.04 [T0] to 3.60 [T2], mouth opening which increased from 4.5 mm [T0] to 34 mm [T2] and mean O2 saturation which increased from 89.86% [T1] to 96.88% [T2]. The adult group variables were as follows: mean PAS width which increased from 5 mm [T0] to 11 mm [T2], mean AHI which decreased from 31.45 [T0] to 1.43 [T2], mouth opening which increased from 5 mm [T0] to 34 mm [T2] and mean O2 saturation which increased from 92.01% [T0] to 96.84% [T2]. Statistical analysis revealed that DO of the mandible significantly improved OSA by increasing the PAS which was evident by the lower AHI score. Mouth opening was also significantly improved post ankylosis release and maintained at the T2 interval. Ten subjects followed up beyond the T2 interval [mean 28 months post ankylosis release] and their data also revealed positive compliance towards physiotherapy, adequate mouth opening and maintenance of normal AHI.

CONCLUSION: Pre-arthroplastic mandibular DO has proved to be a successful modality for treatment of OSA in TMJ ankylosis patients with stable results at 12 months. By resolving the narrow airway and OSA, compliance towards physiotherapy was improved thus reducing the risk of re-ankylosis in the long term.