Stability after vertical subcondylar ramus osteotomy for correction of mandibular prognathism.

A cephalometric analysis of the positional changes of the mandible and the upper and lower incisors following vertical subcondylar ramus osteotomy was performed on 80 patients. The patients were prognathic without laterognathism or open bite and all the patients had preoperative orthodontic treatment. 40 patients were operated with an intraoral (IVSO) and 40 with an extraoral approach (EVSO). Both groups showed postoperatively posterior rotation of the mandible, shortening of the posterior facial height, increase in anterior facial height and extrusion of the incisors in both jaws. A significantly greater reduction of posterior facial height was observed in the EVSO-group, but otherwise the 2 groups did not reveal any statistically significant positional differences. The material was sub-divided into 2 groups 1 with (n = 32) and one group without (n = 48) extra skeletal (nasomandibular) fixation in addition to the intermaxillary fixation. Significantly less positional changes of the incisors and less increase of anterior facial height was found in the group with skeletal fixation, but the influence on other skeletal alterations was limited. After release of the intermaxillary fixation, the only difference between the groups was intrusion of the earlier extruded incisors, most pronounced in the group without skeletal fixation.