Vertical ramus versus sagittal split osteotomies: comparison of stability after mandibular setback. Changes in condyle position after bilateral vertical ramus osteotomy with and without osteosynthesis.
Intraoral vertical ramus osteotomy (IVRO) offers some advantages over sagittal split ramus osteotomy (SSRO) for treatment of the prognathic patient. The purpose of this study was to compare the postoperative changes of proximal and distal segments after IVRO and SSRO with semirigid internal fixation.
                Thirty Japanese adults with a diagnosis of prognathic mandible were randomized to undergo either IVRO (n = 15) or SSRO (n = 15) according to an adaptive random assignment procedure. The postoperative changes of the proximal and distal segments were assessed with posteroanterior and lateral cephalograms.
                Compared with the SSRO group, the B-point and pogonion moved significantly posteriorly and inferiorly in the IVRO group from 1 month to 3 months after surgery. At 1 year after surgery, there was no significant difference between the 2 groups in the horizontal and vertical stability of the B-point and the pogonion. In the IVRO group, the gonion deviated significantly laterally from 1 week until 1 month after surgery as compared with that of the SSRO group. There was a significant correlation between the amount of setback and the amount of lateral gonial deviation in the IVRO group from 1 week to 1 year after surgery.
                Although in IVRO cases, distal segments moved posteriorly and inferiorly immediately after the release of maxillomandibular fixation, the stability after IVRO is equal to that after SSRO with semirigid internal fixation. The purpose of the present study was to elucidate the importance of ramal osteosynthesis and evaluate postoperative condylar movements. The right temporomandibular joints of 53 patients with mandibular prognathism were examined by linear tomography the day before, 1 week after, and 1 year after surgery. During surgery the patients were randomly allocated to two groups: one with (n = 26) and one without (n = 27) osteosynthesis. It was found that osteosynthesis did not influence condyle position (p greater than 0.3). The two groups were thereafter pooled. Radiographic measurements of the posterior and anterior interarticular space revealed that condyle position 1 week postoperatively was forward and downward in relation to the preoperative position (posterior fossa, p less than 0.001; anterior fossa, p less than 0.01). One year later the condyle position demonstrated a tendency to approximate the preoperative position, especially with respect to the posterior part, but there was still a significant (p less than 0.01) difference when related to the original position. In conclusion, osteosynthesis after ramus osteotomy seems to be of no importance when healing and postoperative condyle position are considered. Furthermore, 1 year after surgery the condyles were not reestablished in their preoperative positions.