Inferior alveolar nerve function after sagittal split osteotomy of the mandible: correlation with degree of intraoperative nerve encounter and other variables in 496 operations.

Dysfunction of the inferior alveolar nerve indicated by various degrees of numbness of the lower lip and chin is one of the few drawbacks of sagittal split osteotomy (SSO) of the mandible. Although it has been recorded throughout the history of this technique its true aetiology is poorly understood. In this study of 496 SSOs, we have evaluated possible correlations between neurosensory dysfunction and several variables that have been implicated, such as the age of the patient, mandibular movement, type of split technique and osteosynthesis, degree of intraoperative nerve encounter, and surgical skill. Nerve dysfunction developed after 200/496 SSOs (40%). The patient's age had a significant influence on the recovery of the neurosensory function. Intraoperative nerve encounter such as nerve manipulation correlated with dysfunction to a much lesser degree than expected. Surgical skill seemed to influence the recovery of neurosensory function after SSO, which is often referred to as a technique-sensitive procedure. We suggest that the dissection of the soft tissue on the medial aspect of the mandibular ramus might be partly responsible for nerve dysfunction of the lower lip and chin after SSO of the mandible.