Transverse displacement of the proximal segment after bilateral sagittal split osteotomy advancement and its effect on relapse.

PURPOSE: To evaluate the transverse displacement of the proximal segment and its association with horizontal relapse post-treatment.
METHODS: Retrospective study of 25 patients (10 males, 15 females) who underwent bilateral sagittal split osteotomy (BSSO) advancement and Le Fort I osteotomy with rigid internal fixation (RIF) using bicortical lag screws. Posteroanterior and lateral cephalograms obtained preoperatively (T1), early postoperatively (T2), and after orthodontic treatment completion (T3) were used to assess: the angulation of each proximal segment relative to the upper orbital margin line and obtain the sum of both angles (total angle), mandibular intergonial width (IGW), mandibular length (Ar-B), B point position, and condylion position. Paired t tests were used to determine statistically significant (P < .05) changes within the variables between various time points (T2-T1; T3-T2; T3-T1). Correlations between variables were estimated by calculating Pearson's correlation coefficients.
RESULTS: T2-T1 findings: all 25 patients showed an increase in IGW with a mean of 6.5 +/- 2.5 mm and the angulations of the proximal segments increased 3.2 +/- 2.6 degrees (total angle change). Ar-B increased 3.8 +/- 3.4 mm. B point moved anteriorly 4.8 +/- 2.9 mm. T3-T2 findings: IGW decreased 1.8 +/- 1.5 mm; angulation of the right and left proximal segments decreased 1.2 +/- 2.8 degrees (total angle change). Condylion moved superiorly 1.5 +/- 2.0.
CONCLUSIONS: Statistically significant changes occurred in transverse width and angulation of proximal segments of patients who underwent BSSO advancement with Le Fort I osteotomy. No clinically significant associations were found between transverse displacement of the proximal segments and horizontal relapse.