Is it necessary to free the inferior alveolar nerve from the proximal segment in the sagittal split osteotomy?

Purpose When the inferior alveolar nerve (IAN) is contained within the proximal segment after a mandibular sagittal split osteotomy (SSO), conventional teaching is to release the nerve so that it freely enters the distal segment. However, manipulation of the IAN may cause further injury. The purpose of this study was to measure IAN neurosensory recovery in SSOs when the nerve was not freed from the proximal segment. Materials and Methods This was a prospective split-mouth study of patients undergoing bilateral sagittal split osteotomy (BSSO). The sample was composed of patients who underwent a BSSO in which the IAN was intact bilaterally but freely entering the distal segment on one side (IANDI) and contained within the proximal segment on the other (IANPR). The outcome of interest was time to functional sensory recovery (FSR) of the IAN, measured in days. Descriptive, bivariate, and Kaplan-Meier statistics were computed. P ≤ .05 was considered statistically significant. Results Twenty patients undergoing 40 SSOs were included as study patients. The sample's mean age was 19.0 ± 2.4 years (range, 15 to 26 years); there were 13 female patients. Of these patients, 15 underwent BSSO whereas 5 underwent BSSO plus genioplasty. The planned mean composite 3-dimensional mandibular movements for IANDI and IANPR were 6.3 ± 2.8 mm (range, 2.5 to 12.3 mm) and 6.3 ± 2.3 mm (range, 2.7 to 10.8 mm), respectively (P = .96). All patients achieved FSR in the bilateral IAN distributions within 1 year of surgery (range, 34 to 284 days). The median times to FSR were 100 days for IANDI and 101 days for IANPR (P = .64). Conclusions In patients undergoing SSOs, maintaining the IAN within the proximal segment of the mandible may not affect neurosensory recovery.