The Low Medial Horizontal Osteotomy in Patients With Atypical Ramus Morphology Undergoing Sagittal Split Osteotomy

Purpose Sagittal split osteotomy (SSO) of rami with fused cortices or minimal marrow space above the lingula can increase the risk of 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 the present study was to evaluate the outcomes of SSOs utilizing a low medial horizontal osteotomy in patients with atypical ramus morphologies. Patients and Methods The present study was a prospective series composed of patients with atypical proximal ramus anatomy undergoing SSOs. All patients had undergone bilateral SSO for correction of mandibular deformities. The horizontal ramus osteotomy had been placed at or slightly above the mandibular occlusal plane because of 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 an unfavorable split of the proximal or distal segments, nerve location after SSO (proximal or distal segment), and neurosensory recovery of the inferior alveolar nerve (IAN). Results The sample included 25 patients who had undergone 50 SSOs using a low medial horizontal osteotomy. Their mean age was 19.6 ± 3.2 years; 14 patients were female. Of the 25 patients, 22 had a primary diagnosis of craniofacial anomaly; 23 had undergone bimaxillary surgery and 6 had received concomitant genioplasty. No unfavorable fractures of the proximal segment occurred. No intraoperative IAN injuries occurred. The IAN was contained within the proximal segment in 52% of the cases. All the patients achieved functional sensory recovery of the IAN bilaterally by 1 year postoperatively. The mean interval to functional sensory recovery was 116 days. Conclusions The low medial horizontal osteotomy is an effective technique for reliable execution of SSOs in morphologically atypical mandibles.