Influence of Inferior Alveolar Nerve Exposure During Sagittal Split Osteotomy on the Rate and Timing of Baseline Sensory Recovery

Abstract

Neurosensory disturbance is the most common consequence of sagittal split osteotomy (SSO). The purpose of this study is to quantitatively assess neurosensory deficiency and recovery to the preoperative status when the inferior alveolar nerve (IAN) was exposed versus unexposed during SSO. This is a single-center, prospective, cohort study of all patients undergoing bilateral SSO between August 2018 and July 2019. Patients were included in the study sample if they underwent bilateral SSO with an intact intraoperative IAN and were received follow-up assessment for at least a year. The predictor variable was the intraoperative IAN status (exposed vs unexposed). The outcomes of interest were the rate and timing of recovery to the preoperative status. The covariates were age, sex, and the magnitude and direction of surgical movements. Neurosensory function was quantitatively evaluated using the Semmes-Weinstein monofilament test at follow-up intervals of 1, 3, 6, and 12months. Descriptive statistics, bivariate statistics, Cox proportional hazards regression, and Kaplan-Meier analyses were performed. P value <.05 was considered statistically significant. Of 90 patients, 86 patients who underwent 172 SSOs were included in this study. The mean age was 22.95±3.34years (range, 17 to 30), 65 were women, and the range of surgical movements was 3 to 8.3mm of advancement and 2 to 12mm of setback. Eighty-five nerves (49.4%) were allocated to the unexposed group, and 87 (50.6%) to the exposed group, with statistically significant differences in the rate and timing of recovery (hazard ratio= 2.368; 95% confidence interval, 1.662 to 3.376; P<.001). Among those with recovered nerves, the median time to recovery was 90days in the unexposed group and 364days in the exposed group (P<.0001). IAN exposure during SSO is associated with an increased risk of neurosensory deficiency and an increased time of sensory recovery to the baseline threshold in patients aged 17 to 30years. When the IAN remained fully enclosed in the canal of the distal segment, only 11% of patients had a measurable sensory deficit 1year after surgery. In those patients with any degree of IAN exposure, 36% had a residual sensory deficit 1year after surgery.