Transverse change of the proximal segment after bilateral sagittal split ramus osteotomy in mandibular prognathism using computed tomography

ABSTRACT

PURPOSE: This study was performed to evaluate transverse changes of proximal segment after bilateral sagittal split ramus osteotomy (BSSRO) using 3-D CT in mandibular prognathism.PATIENTS AND METHODS: Twenty-two patients who underwent BSSRO for mandibular set-back in class III malocclusion without facial asymmetry were examined. Miniplates were used for the fixation after BSSRO. Facial CT was taken before and after BSSRO within 3 months. Frontal-ramal inclination (FRI), intergonial width (IGW) and intercondylar width (ICW) were measured in 3-D CT images using V-works 4.0(TM) program. Student t-test was used to compare the changes between pre- and post-operative measurements using SPSS 10.0 program.RESULTS: 1. Mean peroperative FRI value (12.87 +/- 3.43degrees) was slightly increased to postoperative value (14.13 +/- 3.72degrees) (p < 0.05). The average FRI increased 10.42 percent and the range was from -2.46degrees to 3.34degrees.2. Mean peroperative IGW (99.01 +/- 5.36) was slightly decreased to postoperative IGW (96.51 +/- 5.88 mm) (p < 0.05). The average IGW decreased 2.52 percent and the range was from -6.61degrees to 0.91 mm.3. Mean preoperative ICW (125.01 +/- 5.30 mm) was slightly decreased to postoperative ICW (125.40 +/- 5.45 mm) (p < 0.05). There is no significant difference between pre- and post-operative ICW.4. There was significant correlationship between FRI difference and IGW difference (p < 0.05).CONCLUSIONS: These results indicate that the lower ramus of the proximal segment is moved inward after BSSRO procedure for mandibular set-back.