Evaluating a modified proximal segment manipulation technique in sagittal split osteotomy for correcting facial...

To evaluate the effectiveness and stability of a modified overlap method for manipulating proximal segments (PSs) during bilateral sagittal split osteotomy for correcting facial asymmetry and to identify risk factors contributing to Menton horizontal relapse.

This retrospective cohort study involved 62 consecutive adults with class III asymmetry who underwent bimaxillary surgery. Patients were classified in two groups according to surgical techniques: the overlap group (n = 31), in which the non-deviated PS was flared outward before aligning with the distal segment (DS), and the conventional group (n = 31), in which the PSs and DS were aligned in maximum contact. Computed tomographic scans were taken before surgery (T0), postoperative 1 week (T1) and 1 year (T2). Transverse ramus measurements and maxillo-mandibular segments movements were intergrouply compared. Correlations of Menton horizontal relapse with preoperative and intraoperative factors were also assessed.

From T1-T0, the overlap group showed greater reductions in discrepancies for gonial width (4.09 ± 3.49 mm) and coronal ramus angle (3.67° ± 3.44°) compared to the conventional group (1.76 ± 2.55 mm; 1.70° ± 3.16°) (p = 0.004, 0.023). From T2-T1, relapses in both groups were ≤ 2 mm and ≤ 2°. No correlation was found between surgical techniques and Menton horizontal relapse.

The overlap method demonstrates effectiveness in correcting facial asymmetry, resulting in greater reductions in ramus discrepancies while maintaining mandibular stability one year postoperatively.

For severe facial asymmetry, clinicians may consider using the overlap technique to enhance postoperative facial appearance.