How to Prevent Mandibular Lower Border Notching After Bilateral Sagittal Split Osteotomies for Major Advancements: Analysis of 168 Osteotomies

Abstract

Mandibular ramus bilateral sagittal split osteotomy (BSSO) has been the most commonly used technique in orthognathic surgery for mandibular advancement. However, a common complication of BSSO has been the occurrence of visible and palpable osseous defects at the inferior border of the mandible. The aim of the present study was to determine whether bone grafting of the osseous defect at surgery would reduce the defect at 1year postoperatively compared with no bone grafting. The present retrospective cohort study evaluated patients who had undergone mandibular ramus BSSO for 10mm or more of advancement. The primary predictor variable was BSSO surgery with bone grafting of the defect (graft group [GG]) versus no bone graft (no graft group [NGG]). The size of the mandibular ramus inferior border defect was the outcome variable considered within the framework of a 1-year postoperative cone beam computed tomography (CBCT) analysis. Gender, age, and the amount of advancement were also considered in the multilevel regression analyses. From January 2012 to November 2016, 84 patients (168 osteotomies) had undergone BSSO surgery with 10mm or more of mandibular advancement at the Facesurgery Center (Parma, Italy). Their mean age was 27.4years (range, 17 to 44years). Of the 84 patients, 40 had undergone BSSO with bilateral bone grafts (GG). The monocortical block of the iliac crest bone was used as the bone homograft. The final residual defect was measured at 1year postoperatively on CBCT scans. The GG and NGG had presented with a mean final defect of 0.7mm (range, 0 to 4.5mm) and 3.0mm (range, 0 to 5.5mm), respectively. Complete absence of the defect was achieved in 72% of the osteotomies in the GG and 9% of the osteotomies in the NGG. The use of an iliac crest bone allograft block in the gap between 2 segments during mandibular advancement of 10mm or more substantially reduced the size and incidence of inferior border defects.