Does the amount of mandibular setback during bimaxillary surgery correlate with the degree of surgical relapse?

Objective. The aim of this study was to investigate postoperative horizontal relapse of the mandible in terms of the effects of the magnitude of mandibular setback movement and ramus inclination after LeFort I osteotomy and sagittal split ramus osteotomy. Study Design. A retrospective study of patients who underwent orthognathic surgery for mandibular prognathism was performed. Postoperative relapse at point B was analyzed with regard to the magnitude of mandibular setback and the ramus inclination. Serial cephalograms were used to measure surgical changes and evaluate postoperative relapse. Results. Nineteen men and 31 women (mean age 23.1 years) were retrospectively enrolled. Mean surgical backward movement of the mandible at point B was 8.2 mm, mean ramus inclination was 3.56 degrees, and mean relapse 1 year postoperatively was 0.95 mm (11.6%). Horizontal relapse of the mandible was significantly correlated with the magnitude of mandibular setback (r = -0.52; P = .007) and ramus inclination (r = 0.48; P = .014). Conclusions. Increased horizontal mandibular relapse after bimaxillary surgery was associated with greater mandibular setback movement and increased proximal segment clockwise rotation. Mandibular relapse after bimaxillary surgery may be minimized via adequate control of intraoperative clockwise rotation of the proximal segment.