Non-surgical risk factors for condylar resorption after orthognathic surgery

Abstract

Background: Condylar resorption following orthognathic surgery is an important cause of late skeletal relapse. However, its pathogenesis is not well understood. The purpose of this study was to find non-surgical risk factors for condylar resorption after orthognathic surgery. Patients: In this retrospective study, 17 patients (Group I) who developed postoperative condylar resorption were selected. These patients were compared with 22 patients (Group II) without postoperative condylar resorption, but who showed mandibular hypoplasia with a preoperative high mandibular plane angle of more than 40°. Methods: Possible non-surgical risk factors were sought by analysing clinical and radiological data collected preoperatively and immediately, 6 weeks, and 1 and 2 years postoperatively. Results: There was no significant difference of gender distribution between the two groups. Patients in Group I were significantly younger ( p=0.02) than those in Group II. The incidence of temporomandibular joint dysfunction in both groups was similar preoperatively, but was significantly higher ( p=0.001) postoperatively in Group I. The posterior inclination of the condylar neck in Group I was also significantly greater ( p<0.001). The preoperative mandibular plane angle in Group I (mean value: 49.4°) was significantly greater ( p=0.005) than in Group II (mean value: 44.9°). The preoperative SNB angle, overbite, and posterior facial height and ratio (posterior/anterior facial heights) in Group I were significantly smaller ( p<0.05). Conclusion: The present study suggests that the posteriorly inclined condylar neck should be considered as a relevant non-surgical risk factor.