Is the Low and Short Medial Horizontal Osteotomy a Predictive Factor for Bad Splits in Sagittal Split Osteotomies?

Abstract

Statement of the problemThe purpose of this study is to determine whether a low and short medial horizontal osteotomy is a predictive factor for determining bad splits in non-syndromic patients undergoing sagittal split osteotomies for dentofacial disorders. Materials and methodsA retrospective cohort analysis was conducted on subjects who received orthognathic surgery from 2017 to 2019 at Parkland Memorial Hospital. Inclusion criteria were a traditional osteotomy defined by Hunsck and Epker or a low and short osteotomy defined by Posnick.1,2 Exclusion criteria were the diagnosis of a syndromic condition, repeat surgery, or concomitant temporomandibular joint surgery. The predictor variable was the type of osteotomy performed, defined as either a low and short or traditional osteotomy. The primary outcome variable was the occurrence of a bad split. Secondary predictor variables were age and sex, defined as male or female, and faculty side (right side) versus resident side (left side). Descriptive, bivariate, and multiple logistic regression analyses were performed with P < .05 used to determine statistical significance. Results and outcomesFifty-nine patients met the defined inclusion criteria. The average age at the time of surgery was 21 years old. The cohort consisted of 27 males and 32 females. Thirty-six patients were treated with bilateral low and short osteotomies, and 23 patients were treated with bilateral traditional osteotomies. Of the 118 total osteotomies performed, there were a total of 9 bad splits (7.6%). There were 3 right-side bad splits and 6 left-side bad splits. The occurrence of a right-side bad split was 3 for the low and short group and 0 for the traditional group. The occurrence of a left-side bad split was 4 for the low and short group and 2 for the traditional group. There were no significant differences between the type of osteotomy performed and the occurrence of a right-side bad split (P = .1607) or a left-side bad split (P = .7695). There was no significant difference between sex and occurrence of a right-side bad split (P = .6640) or a left-side bad split (P = .2862). There was no significant difference between age and occurrence of a right-side bad split (P = .5233) or a left-side bad split (P = .4492). There was no significant difference between faculty side and resident side with regards to bad splits (P = .4903). Discussion and conclusionThe sagittal split osteotomy (SSO) was first reported by Trauner and Obwegeser in 1955, with the horizontal medial osteotomy further modified by Hunsuck to terminate superior and posterior to lingula.1 Posnick developed an additional modification of the SSO to reduce the frequency of unfavorable splits toward the condyle by modifying the medial horizontal osteotomy to terminate below lingula at the level of the mandibular occlusal plane (low) and anterior to lingula (short).2 The occurrence of bad splits using the traditional osteotomy ranges from 1% to 23%, while the incidence of bad splits reported by Posnick in his retrospective analysis was 0%. The results of the present study suggest a low and short osteotomy is at least as reliable as the traditional osteotomy with regards to intraoperative bad splits. Future prospective studies, including split-mouth study designs by this group, will further elucidate the low and short osteotomy as a reliable alternative to the traditional osteotomy.1.The low medial horizontal osteotomy in patients with atypical ramus morphology undergoing sagittal split osteotomy2.Occurrence of a ‘bad’ split and success of initial mandibular healing: a review of 524 sagittal ramus osteotomies in 262 patients