Morphological study of the changes after sagittal split ramus osteotomy in patients with facial asymmetry: measurements of 3-dimensional modelling

The effects of bilateral sagittal split ramus osteotomy (BSSRO) on the temporomandibular joint (TMJ) are still not well understood. The aim of this study was to compare the morphological differences among unaffected subjects on the one hand, and patients with facial asymmetry before and after BSSRO on the other. Ten Chinese patients (preoperative and postoperative groups, mean (SD) age 25 (5) years) diagnosed with facial asymmetry and 10 unaffected subjects (control group, mean (SD) age 27 (5) years) were recruited prospectively. The 3-dimensional morphological measurements made on 3-dimensional models in each group were assessed by analysis-of-variance (ANOVA) and Student’s t test, and probabilities of <0.05 were accepted as significant. The horizontal condylar angle (HCA), coronal condylar angle (CCA), sagittal ramus angle (SRA), medial joint space (MJS), lateral joint space (LJS), and superior joint space (SJS) differed significantly between the preoperative and control groups (HCA: p = 0.000, CCA: p = 0.000, SRA(left/undeviated side): p = 0.002, MJS(left/undeviated side): p = 0.000, MJS(right/deviated side): p = 0.007, LJS(right/deviated side): p = 0.000, SJS(left/undeviated side): p = 0.000, SJS(right/deviated side): p = 0.000). The SRA, MJS, LJS, and SJS differed significantly between the preoperative and postoperative groups (SRA(left/undeviated side): p = 0.012, MJS(left/undeviated side): p = 0.002, LJS(right/deviated side): p = 0.021, SJS(left/undeviated side): p = 0.000, SJS(right/deviated side): p = 0.001), And the SRA, MJS, and LJS in the preoperative group differed significantly between the deviated and undeviated side (SRA: p = 0.006; MJS: p = 0.003; LJS: p = 0.011). However, there were no significant differences in the postoperative and control groups between the deviated and undeviated sides. BSSRO improved the asymmetrical morphology of the TMJ and alleviated the symptoms.