Assessment of temporomandibular joint morphological alterations after bilateral sagittal split ramus osteotomy - A systematic review and meta-analysis

Background Orthognathic surgery corrects skeletal deformities and restores facial and functional balance. This systematic review evaluated the effects of bilateral sagittal split ramus osteotomy (BSSRO) on temporomandibular joint (TMJ) morphology, including joint spaces, condylar height, axial angle, disc position, and muscle changes. Methods Following PRISMA guidelines, a comprehensive search of PubMed, Scopus, Cochrane Library, and Google Scholar was conducted. Two authors independently performed critical appraisal and data extraction. Standardized mean differences with 95% confidence intervals were used to evaluate surgical effects on TMJ morphology. Results A total of 26 studies were included, with ten contributing to meta-analysis. Most studies showed no significant postoperative changes in joint spaces in either malocclusion group. Two long-term studies showed a significant reduction in posterior joint space in Class II patients [SMD: 0.97 (95% CI 0.61, 1.33)], with no change in Class III patients. In Class III cases, two studies showed a significant long-term decrease in condylar height [SMD: 0.37 (95% CI 0.08, 0.66)], and three studies demonstrated a reduction in axial condylar axis angle [SMD: 0.77 (95% CI 0.44, 1.10)]. Non-pooled studies reported largely unchanged disc positions, occasional improvement in Class III cases, and inconsistent postoperative changes in masseter and pterygoid muscle morphology. Conclusions BSSRO produces malocclusion-specific TMJ adaptations, with posterior joint space reduction in Class II, condylar remodeling in Class III, and stable disc position in both groups.