OBJECTIVETo evaluate the clinical effect of distraction osteogenesis for patients with mandibular micrognathia secondary to temporomandibular joint (TMJ) ankylosis.

METHODS43 patients (aged from 2 to 61 years old) with mandibular micrognathia were treated with mandibular distraction osteogenesis. Two types of mechanical distraction were utilized in this study. Ten patients (age ranged from 2 to 16-years-old, mean age 7.6 years old) with severe micrognathia underwent bilateral mandibular distraction with rigid external distraction (RED) device. Other 33 patients were treated with unilateral(6 cases) or bilateral (27 cases) mandibular distraction using internal distraction device. Distraction was started on the 4th to 8th day after operation and distraction rate was 0.25 mm every time, four times a day. Distractor was removed after 3 to 6 months of consolidation period.

RESULTSEighty sides of mandible in 43 patients were lengthened. The mean distraction distance was 23.2 mm (ranged from 14 to 35 mm). After distraction, the average posterior airway space (PAS) was enlarged from 4.9 mm to 10.4 mm and average angle of sella-nasion-point B (SNB) was increased from 64.2 degrees to 74.5 degrees. The apnea hypopnea index (AHI) was decrease significantly. The profile was improved and OSA was improved effectively in each patient. No complication occurred during treatment. No persistent numbness of lower lip was observed. All patients were satisfied with the results. After a mean follow-up period of 20.3 months(5 to 103 months) , the result was stable and no obvious relapse of micrognathia was observed.

CONCLUSIONSDistraction osteogenesis is an effective way in correction of mandibular micrognathia secondary to TMJ ankylosis. RED is a new method for treatment of children and adolescence with severe mandibular micrognathia. The procedure is simple and safe with stable result.