Effects of age, amount of advancement, and genioplasty on neurosensory disturbance after a bilateral sagittal split osteotomy

Purpose: There are numerous risks for developing neurosensory deficits after a bilateral sagittal split osteotomy (BSSO). The purpose of this study was to evaluate the effects of genioplasty, length of advancement, and age and their interactions in a group of patients undergoing BSSO advancement and followed up for 2 years. Materials and Methods: Patients were examined at multiple time intervals during the 2 years. Measuring in the mental nerve distribution assessed damage. 127 subjects were divided into the following 3 age groups: younger than 24 years, 24 to 35 years, and older than 35 years old. They also were divided into small (≤7 mm) and large (>7 mm) advancements and genioplasty and no genioplasty. Change in tactile sensitivity from presurgical to the subsequent time periods is reported as a function of these variable and interactions among the variables. Data were analyzed using the Kruskal-Wallis test and the Friedman test, all at an a level of 0.05. Results: Older subjects had greater sensory losses than younger subjects. Patients with a genioplasty had a greater loss of sensation initially. For all subjects, the sensory function of those receiving large and small advancements was not significantly different. Among subjects receiving small advancements there was no significant difference among the 3 age groups. However, among patients receiving advancements greater than 7 mm, older patients did worse. Among patients not receiving genioplasty, there was no significant difference among the 3 age groups. In contrast, older subjects with a genioplasty had significantly greater sensory deficits. Conclusions: Age at the time of surgery and addition of a genioplasty increases the risk of a neurosensory injury. Large advancements further increase the risk of injury in older patients.