IAN disturbance is believed to be caused by iatrogenic injury to the nerve including excessive nerve manipulation, nerve laceration, fixation of segments by incorrect placement of position screws, large mandibular movement and bad splits. Identification of risk factors for IAN disturbance after BSSO can help clinician to prevent it and raise the satisfaction level of patients. It is generally thought that the injury to IAN inside the mandibular ramus and body during surgery are highly correlated to variations in preoperative anatomy (ie, patient-related factors). Previous computed tomography (CT) studies have reported the anatomical variations including the thickness and length of ramus, the position and bone density of inferior alveolar nerve canal (IAC) and thickness of buccal and lingual cortical plate. However, few studies tried to identify surgery-related factors such as types of BSSO, extent of surgical correction, extent of split, concomitant genioplasty or third molar extraction. Furthermore, most of the studies were retrospective in design or had limited number of patients to conduct multivariate analysis to recognize the influences of patient- and surgery-related risk factors on IAN disturbance. Moreover, heterogeneity of the assessment timing and methods for IAN disturbance in previous studies prevented from overall assessment of the degree of IAN recovery. We therefore aim to (1) determine the incidence of IAN injury after BSSO, (2) identify the risk factors associated with such injuries, and (3) understand the consequences of such injuries including the degree of neurologic recovery by performing a prospective, longitudinal study.