Do patients treated with bimaxillary surgery have more stable condylar positions than those who have undergone single-jaw surgery?

PURPOSE: Because condylar positioning after sagittal split ramus osteotomy of the mandible has been known to affect postoperative skeletal stability, accurate positional assessment of the temporomandibular joint after orthognathic surgery is vital to maximize stability of the surgery. The purpose of this study was to evaluate condylar changes after single-jaw and double-jaw surgeries in mandibular prognathism patients by comparing 3-dimensional angular and positional changes of the condylar heads in groups of patients receiving combined maxillary posterior impaction and mandibular setback and those undergoing only mandibular setback surgeries.

PATIENTS AND METHODS: We assessed condylar changes of patients who have been diagnosed with mandibular prognathism and underwent either bimaxillary surgery or isolated mandibular surgery at Kangdong Sacred Heart Hospital and SmileFuture Orthodontic Clinic, Seoul, South Korea, from August 2008 to February 2011. Condylar angulation, intercondylar distance, and amount of condylar displacement were examined based on the 3-dimensional reconstructed images. Preoperative and postoperative changes within each group were assessed by paired t test. Differences between the groups were determined by independent t test.

RESULTS: A total of 43 skeletal Class III patients were included in this retrospective, multicenter study. After single-jaw surgery, condylar angulations in all dimensions did not change. In contrast, those who received double-jaw surgery showed forward rotation of 1.93° (P = .027) and medial rotation of 1.48° (P = .032) in the sagittal and axial planes, respectively. The mean distances of condylar displacements were 0.28 ± 0.44 mm in the single-jaw group and 0.31 ± 0.51 mm in the double-jaw group, but there was no statistically significant difference.

CONCLUSIONS: Condylar angulations are more stable after sagittal split ramus osteotomy of the mandible as an isolated procedure than in combination with the posterior maxillary impaction in treatment of skeletal Class III malocclusion patients. Condylar displacements in both the single-jaw and double-jaw groups are clinically insignificant.