Influence of unfavourable osteotomy on skeletal stability and temporomandibular joint symptoms in sagittal split ramus osteotomy

This study was performed to investigate the impact of the split line on postoperative stability and temporomandibular joint (TMJ) disorders (TMD) after sagittal split ramus osteotomy. Skeletal Class III malocclusion patients who underwent mandibular osteotomy with/without plate fixation between August 2008 and March 2023 were enrolled retrospectively. The osteotomy lines were divided into original sagittal split ramus (SSRO), short lingual (SLO), and short buccal (SBO) osteotomies. Skeletal stability was evaluated, and TMDs were assessed preoperatively. Overall, 135 patients (270 TMJs) (87 female, 48 male; mean age 23.7 +/- 7.8 years) were included. Mean mandibular setback was 6.2 +/- 2.9 mm. Skeletal stability was observed in all patients. TMD were recorded in 47 joints (17.4%) preoperatively and 15 joints (5.6%) postoperatively. When TMD were compared between joints with and without plate fixation, preoperative TMD was found to be improved in non-fixed joints (P = 0.004). On multivariate analysis, segment fixation (P = 0.040), the osteotomy line (SBO vs SLO/SSRO, P = 0.043), and preoperative TMD (P = 0.030) were associated with postoperative TMD. The results of this study suggest that no plate fixation after mandibular osteotomy may be beneficial when the split line is SBO or preoperative TMD is observed.