Short-term changes of condylar position after sagittal split osteotomy for mandibular advancement

Objective. The goal of this study was to quantify condylar position changes after mandibular advancement surgery with rigid fixation (screws). Radiographic changes in condylar position were determined in all planes (X, Y, and Z). Computed tomography with image reconstruction was used. Study design. A consecutive population of patients who elected to have rigid fixation for surgical stabilization method were studied (n = 21). Computed tomography data were acquired in the axial plane through use of abutting 1.5-mm-thick slices. Data acquisition occurred 1 week preoperatively and 8 weeks postoperatively. Measurements were made from 2-dimensional reconstructions. Results. The averages were as follows: lateral displacement from midline, 1.2 mm (55% of patients); medial displacement from midline, 1.5 mm (45% of patients; range, 3.2 mm); condyle angle increase from coronal plane, 3.5 degrees (60% of patients); condyle angle decrease from coronal, 4.3 degrees (40% of patients; range, 8.5 degrees); superior rotation of proximal segment, 3.2 degrees (39% of patients); inferior rotation of proximal segment, 8.6 degrees (61 % of patients; range, 15.6 degrees); superior displacement, 1.2 mm (60% of patients); inferior displacement, 1.0 mm (40% of patients; range, 2.5 mm); anterior displacement, 1.6 mm (33% of patients); posterior displacement, 1.6 mm (67% of patients; range, 2.8 mm). Conclusions. Changes occurred in all planes, but the most common postoperative condyle position was more lateral; with increased angle, the coronoid process was higher and the condyle was more superior and posterior in the fossa.