Intraoperative Inferior Alveolar Nerve Location following Low Medial Horizontal Sagittal Split Osteotomy

Abstract

PurposeThe purpose of this study is to evaluate the intraoperative location of the inferior alveolar nerve (IAN) after completion of a sagittal split osteotomy using a low medial horizontal (low and short) sagittal split osteotomy. MethodsThe authors designed and implemented a retrospective cohort study of patients who received orthognathic surgery from 2017 to 2019 at Parkland Memorial Hospital. Inclusion criteria was a traditional osteotomy defined by Hunsuck and Epker1,2 or a low and short osteotomy defined by Posnick.3 Exclusion criteria were the diagnosis of a syndromic condition, repeat surgery, or concomitant temporomandibular joint surgery. The predictive variable was the type of osteotomy performed, defined as either a low and short or traditional osteotomy. The primary outcome variable was the location of the IAN in either the proximal or distal segment, following completion of split. Statistical analysis was performed with P < .05 used to determine statistical significance. ResultsFifty-one patients met the defined inclusion and exclusion criteria. The average age at the time of surgery was 21 years. The cohort consisted of 26 males and 25 females. Thirty-six patients were treated with bilateral low and short osteotomies, and 15 patients were treated with bilateral traditional osteotomies. Of the 36 low and short osteotomies on the right side, 11 were located in the distal segment (30.5%) and 25 in the proximal (69.5%). Of 36 low and short osteotomies on the left side, 12 were located in the distal segment (33%) and 24 in the proximal (66%). Of the traditional osteotomies on the right side, 8 were located in the distal segment (53%) and 7 in the proximal (46%). Of 15 traditional osteotomies on the left side, 8 were located in the distal segment (53%) and 7 in the proximal (46%) There was no significant difference between the osteotomy performed and the location of the IAN on the right side (P = .1304) or the left side (P = .1897). DiscussionThere have been many modifications to the sagittal split osteotomy since the initial description by Trauner and Obwegeser in 1955. With each modification, the medial horizontal osteotomy has consistently remained superior to the lingula of the ramus. The more recent modification developed by Posnick places the medial horizontal osteotomy below and anterior to the lingula.3 With this modification, it makes anatomic sense that the IAN would be contained within the proximal segment. When the IAN is located within the proximal segment following traditional sagittal osteotomy, it is often teased out in an effort to prevent excessive stretching and damage to the nerve or limitation in the movement of the distal segment. The results of this present study show there is no significant difference in intraoperative nerve location after sagittal split when comparing the low and short osteotomy to the traditional osteotomy. Further prospective studies, including nerve testing following low and short osteotomy with the IAN located within the proximal segment, will further elucidate the low and short osteotomy as a viable alternative to the traditional osteotomy.