The Relationship Between Mandibular Angle Morphology and Unfavorable Fractures in Sagittal Split Ramus Osteotomy: A Retrospective Case-Control Study

Unfavorable buccal cortical plate fracture, as one of the most severe complications of mandibular sagittal split ramus osteotomy (SSRO), has not yet been fully elucidated in terms of its risk factors, which urgently require further investigation. This retrospective study aimed to evaluate the relationship between mandibular angle morphology and unfavorable buccal cortical plate fractures during SSRO. A total of 20 patients with buccal cortical plate fractures during SSRO were included. The cleavage line of the mandibular ramus was extracted from immediate postoperative computed tomography (CT) 3-dimensional (3D) reconstruction images. Four key anatomic points and a virtual plane were defined to characterize the mandibular angle. Among patients undergoing SSRO, 23 mandibles with buccal cortical plate fractures were assigned to the case group, while the remaining served as the controls. Statistical analysis revealed a significant association between mandibular angle morphology and fracture risk (P<0.001). Specifically, 21 cases (91.3%) in the fracture group exhibited an introversive mandibular angle pattern, whereas only 1 case (5.9%) in the control group showed this pattern. These findings suggest that an introversive mandibular angle constitutes a significant risk factor for buccal cortical plate fractures. The results underscore the importance of preoperative evaluation of mandibular angle morphology and highlight the potential of digital surgical planning to optimize operative strategies, enhance safety, and reduce the incidence of unfavorable fractures.