Effect of Counterclockwise Mandibular Autorotation on Temporomandibular Joint Spaces and Condylar Morphology After Bimaxillary Orthognathic Surgery: A CBCT-Based Study

Background/Objectives: Mandibular counterclockwise (CCW) autorotation following maxillary repositioning is a common biomechanical consequence of bimaxillary orthognathic surgery. However, its effect on temporomandibular joint (TMJ) morphology remains controversial. This study aimed to evaluate whether condyle-centered CCW mandibular autorotation influences postoperative TMJ spaces and condylar morphology using cone-beam computed tomography (CBCT). Methods: A total of 24 patients who underwent combined Le Fort I osteotomy and bilateral sagittal split ramus osteotomy were included in this retrospective analysis. Patients were divided into two groups based on virtual surgical planning: those with condyle-centered CCW autorotation (4–7°) and those without autorotation. Preoperative and one-year postoperative CBCT images were analyzed. Sagittal and coronal joint spaces, condylar dimensions, and glenoid fossa thickness were measured. Intra- and intergroup comparisons were performed using nonparametric statistical tests (α = 0.05). Results: Both groups demonstrated significant postoperative reductions in condylar height, width, and depth, reflecting adaptive bone remodeling. Joint space changes were limited overall. A significant intergroup difference was observed only in the change in the right superior joint space (p = 0.024), which decreased in the non-autorotation group but was preserved or slightly increased in the autorotation group. No other joint space or fossa parameter showed significant between-group differences. Conclusions: Condyle-centered CCW mandibular autorotation during bimaxillary orthognathic surgery does not induce adverse TMJ morphological changes beyond physiological adaptation. Preservation of the superior joint space suggests that autorotation may contribute to maintaining a more favorable condyle–fossa relationship. Incorporating controlled mandibular autorotation into surgical planning may support TMJ biomechanical balance and postoperative joint stability.