The purpose of this study was to assess the postoperative stability of the distal segment and the condylar head of the mandible in eleven follow-up patients after intraoral vertical ramus osteotomy (IVRO). Retrospective radiographic assessments of horizontal and vertical changes of point B on distal segment and preoperative amount of overbite were performed based on lateral cephalograms. In addition, the position of the condylar head and the inclination angle of the condylar process were also analyzed by lateral panoramic temporomandibular joint projection photographs and computer tomography.
The results were as follows:
1. The distal segment of the mandible tended to move in the postero-inferior direction in five cases, four of which were open-bite.
2. The five cases tended to show a delay in adaptation of the condylar head in the grenoid fossa postoperatively. In particular, two cases in whom the distal segment showed large clockwise rotation, possessed a shallow inclination angle of the condylar process.
The results of this study suggest that the stability of the distal segment after IVRO depends on the preoperative amount of overbite before operation. The relation between the inclination angle of the condylar process and postoperative stability, however, was not elucidated.
