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° (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° (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.