Evaluation of post-surgical outcomes in mandibular asymmetry with three-dimensional cephalometric analysis

Facial asymmetry is common among orthognathic patients, particularly in Southern Chinese populations. Mandibular asymmetry is a prominent manifestation of facial asymmetry and is frequently observed in skeletal Class III patients. Various three-dimensional (3D) imaging techniques, such as cone beam computed tomography (CBCT), are utilized to evaluate skeletal asymmetry. Orthognathic surgery is the definitive treatment for the correction of facial asymmetry; however, the positions of vital structures may constrain surgical access to certain anatomical regions, resulting in residual asymmetry. A 3D analysis - RBC cephalometric analysis - categorizes mandibular asymmetry based on a severity grading across three distinct anatomical regions: ramus (R), body (B), and chin (C). This analysis was applied to the data of 57 patients, and their preoperative and postoperative CBCT scans were compared. The findings indicated significant corrections in height at ramus and chin, while asymmetry in height and width at the mandible body could not be adequately corrected. No significant difference in the degree of mandibular asymmetry correction achieved was observed between intraoral vertical ramus osteotomy and sagittal split ramus osteotomy. Through the application of the RBC cephalometric analysis, this study identified and evaluated the limitations of orthognathic surgery in the context of asymmetry correction.