The low medial horizontal osteotomy in patients with atypical ramus morphology undergoing sagittal split osteotomies

Abstract Background The sagittal split osteotomy (SSO) of rami with fused or no marrow space above the lingula may increase the risk for an unfavorable osteotomy split of the proximal ramus. To reduce the risk of a proximal segment fracture, a recent modification of the SSO places the medial horizontal osteotomy below the lingula. The purpose of this work was to evaluate outcomes in consecutive SSOs with a low medial horizontal osteotomy in patients with increased risk for unfavorable osteotomies. Methods This was a prospective series composed of patients with atypical proximal ramus anatomy undergoing SSOs. All patients had bilateral SSO (BSSO) for correction of mandibular deformities, with the horizontal ramus osteotomy placed at or slightly above the mandibular occlusal plane due to atypical ramus morphology (thin ramus with no appreciable marrow space at or above the lingula and/or narrow retromolar ramus width). The outcome variables were unfavorable splits of the proximal or distal segments, nerve location following the SSO (proximal or distal segment), and neurosensory recovery of the inferior alveolar nerve (IAN). Results The sample included 25 patients who underwent 50 SSOs using a low medial horizontal osteotomy. The sample’s mean age was 19.6 + 3.2 years; 14 subjects were female. Twenty-two subjects had a primary diagnosis of craniofacial anomaly. Twenty-three subjects had bimaxillary surgery; 6 patients had concomitant genioplasties. There were no unfavorable fractures of the proximal segment. There were no intra-operative IAN injuries; the IAN was contained within the proximal segment 52% of the time. All subjects achieved functional sensory recovery of the IAN bilaterally by 1-year post-operatively; the mean time to FSR was 116 days. Conclusion The low medial horizontal osteotomy is an effective technique for reliable execution of SSO in morphologically atypical mandibles.