Modified internal mandibular distraction osteogenesis in the treatment of micrognathia secondary to temporomandibular joint ankylosis: 4-year follow-up of a case.

Micrognathia and obstructive sleep apnoea syndrome (OSAS) are problems subsequent to temporomandibular joint ankylosis (TMJa) in growing patients. For patients with micrognathia and OSAS secondary to TMJa, it is important to restore proper mandibular form and dimension, achieve occlusal stability and recover satisfactory joint movement. We report a 4-year follow-up of a patient with micrognathia and OSAS secondary to bilateral TMJa. The treatment of this patient involved (1) a modified internal mandibular distraction osteogenesis without altering the pre-existing occlusion; (2) TMJ arthroplasty in which the dislocated disc was found and repositioned and the shape of the glenoid fossa and articular head was formed without removing bone in vertical dimension; (3) passive mouth-opening exercise with an individualized occlusal pad postoperatively for one month; and (4) orthodontic treatment for the occlusal disturbance and active mouth-opening exercise for one year. After the treatment the micrognathia was corrected; the oropharyngeal airway was increased significantly; mouth-opening increased to 40mm intraoperatively was maintained at 36.66mm 4 years after surgery. Satisfactory occlusion was achieved after orthodontic treatment. Through the 4-year follow-up, no signs of reankylosis were found. In conclusion, this new clinical protocol is a safe, effective and quick way to treat micrognathia and OSAS secondary to TMJa.