Prediction of neurosensory alterations after sagittal split ramus osteotomy

Prediction of neurosensory deficit in the lower lip and chin after sagittal split ramus osteotomy (SSRO) is challenging. This study aimed to elucidate factors related to the development and improvement of neurosensory disturbance (NSD) after SSRO with respect to surgical procedure and the anatomical and structural characteristics of the craniomaxillofacial skeleton. Subjects comprised 50 patients treated by a single experienced surgeon. Anatomical data and landmarks were obtained by computed tomography (CT) imaging. There was a significant difference between patients with or without NSD for the surgical space on the medial side of mandibular ramus 1 week after SSRO (P = 0.006). Less than 15.0 mm between the lingula and mandibular notch (relative risk, 6.7; 95% CI, 1.7–33.8) and 195.0 mm2 or more space on the medial side of the mandibular ramus (relative risk, 17.2; 95% CI, 3.9–100.4) indicated a significant risk of NSD development at 6 months postoperatively. These results suggested that the development of NSD is related to the surgical space on the medial side of the mandibular ramus and subsequent manipulation of the inferior alveolar nerve (IAN) in that region. Limited periosteal degloving prevents excessive stretching of the IAN during SSRO, thus lowering NSD incidence.