Infralingular Versus Supralingular Medial Osteotomy in Sagittal Split Osteotomy of the Mandible: A Randomized Control Study.

Purpose: A recently proposed modification of the sagittal split osteotomy (SSO) of the mandible places the horizontal medial cut 'low and short' of the lingula. The purpose of the study was to answer the following clinical question: Among patients undergoing mandibular setback procedures (≤ 8 mm) via SSO, does the placement of the medial horizontal osteotomy below the lingula (infralingular), when compared to placement above the lingula (supralingular), results in different neurosensory, bite force, and range of motion outcomes?

Materials And Methods: This was a single-center, double-blind, parallel-group study among patients undergoing mandibular setback by SSO (≤ 8 mm), between January 2021 and September 2022. Patients were randomly allocated in a ratio of 1:1 to the supralingular (control) and the infralingular (study) group. Primary outcome variables included neurosensory disturbance of the inferior alveolar nerve based on clinical neurosensory testing and severity graded using Zuniga and Essick's protocol, bite force, and maximum mouth opening evaluated postoperatively during the first week (T1), first month (T2), and third month (T3) of follow-up. Secondary outcome measures included the incidence of a bad split and distal segment interferences intraoperatively. Association between the variables was assessed using Pearson chi-squared test or Fisher's exact test based on the expected observations. A P value of ≤.05 was considered statistically significant.

Results: A total of 29 patients (58 osteotomies) were included in the study. Group 1 consisted of 15 patients (9 females and 6 males) with a mean age of 26.4 years. Group 2 consisted of 14 patients (8 females and 6 males) with a mean age of 25.9 years. Patients with severe neurosensory disturbance of the inferior alveolar nerve were more common in group 2 (n = 15, 53.6%) than group 1 (n = 4, 13.3%) at T1 (P value = .0001) and insignificant between the two groups at T2 (P value = .63) and T3 (P value = .99). Comparison of maximum mouth opening between the two groups at T1 (P value = .535), T2 (P value = .934), and T3 (P value = .703) and bite force at T1 (P = .324), T2 (P = .113), and T3 (P = .811) was not significant.

Conclusion: Both SSO techniques have similar clinical outcomes among patients having mandibular setbacks (≤ 8 mm) for the variables studied.