Biomechanical Assessment of Graft-Augmented Fixation After Mandibular Advancement Following Sagittal Split Osteotomy

The success of bilateral sagittal split osteotomy (BSSO) depends on fixation stability, particularly in large mandibular advancements where conventional fixation methods may be insufficient and associated with lower border defects. Therefore, this study aimed to assess the stability of a graft-augmented fixation technique compared with conventional fixation methods for securing mandibular segments following the advancement of BSSO in cadaveric human mandibles.

Forty human hemimandibles underwent standardized sagittal split osteotomy with a 10 mm advancement and were stabilized using 3 bicortical screws, a single titanium plate with 4 screws, double titanium plates with 4 screws, or an allograft bone block combined with a single plate and 4 screws (experimental group). Nonoperated mandibles served as controls. The specimens were subjected to 3-point bending tests to evaluate their maximum load, flexural stress, load at maximum displacement, and modulus of elasticity.

The graft-augmented fixation demonstrated a significantly higher mean maximum load (928±414 N) compared with three-screw fixation (331.5±131 N), single-plate fixation (389.9±144 N), double-plate fixation (490±173 N), and controls (310±15 N). Flexural stress was also markedly higher in the grafted group (P<0.002).

Graft-augmented fixation significantly enhances biomechanical stability following mandibular advancement of BSSO and has the potential to decrease the risk of permanent lower border defects in larger advancement cases.