Computed tomography morphology of the mandibular ramus in prognathism: effect on the medial osteotomy of the sagittal split ramus osteotomy.

PURPOSE: The purpose of this study was to investigate the distribution of cancellous bone relative to performance of the medial osteotomy of a sagittal split ramus osteotomy using computed tomography scanning. PATIENTS AND METHODS: Skeletal Class III patients consisted of 11 males and 22 females with a mean age of 23 years. The control patients without dentofacial deformity consisted of 10 males and 20 females with a mean age of 25 years. Scans were taken parallel to the mandibular occlusal plane, and morphologic measurements, including distribution of cancellous bone, were obtained. RESULTS: Compared with the control patients, the mandibular ramus of Class III patients was thinner with a more complicated and varied cancellous bone pattern, such as separate regions of cancellous bone and lack of cancellous bone posterior and anterior to the mandibular foramen. CONCLUSIONS: It was apparent that the safest region in which to establish the medial osteotomy line was just superior and 5 to 6 mm posterior to the lingula, directing the line slightly inferior.