The impact of bilateral sagittal split osteotomy on mandibular width and morphology

Purpose: In this study, we examined mandibular width before and I year after bilateral sagittal split osteotomy. Patients and Methods: Forty-two patients (28 females and 14 males) underwent bilateral sagittal split osteotomy. Fifty-six points or angles on the lateral cephalogram and 15 points or angles in the posteroanterior cephalogram were obtained before surgery and I year after surgery. Mandibular width was measured on the posteroanterior cephalogram (from gonion to gonion [Go to Go]). Changes in mandibular width were also measured by monitoring changes in an angle formed between a constructed line along the outside of the left and right ascending rami of the mandible and the facial midline. Association of the mandibular width with a variety of standard skeletal parameters was calculated. Results: Mandibular width increased from 99.7 +/- 7.2 mm (mean +/- SD) to 101.1 +/- 6.1 mm. It remained unchanged in 17 patients, increased in 23 patients, and decreased in 2 patients. Analysis revealed a significant inverse correlation of the changes in mandibular width with the changes in posterior facial height (P = .05) and a significant positive correlation with the angle formed by the facial midline and the left ascending ramus (P > .005). All other changes were not significantly correlated with the changes in mandibular width. Multiple regression analysis revealed that the change in posterior facial height is an independent parameter for the changes in mandibular width (P = .041 for mandibular width at Go-Go). Conclusions: This study establishes a clinically important association between frontal view parameters with parameters derived from lateral view analysis. (C) 2002 American Association of Oral and Maxillofacial Surgeons.