Neurosensory deficits after bilateral sagittal split ramus osteotomy of the mandible--influence of soft tissue handling medial to the ascending ramus.

Deficits in the neurosensory function (NF) of the inferior alveolar nerve (IAN) are often encountered after bilateral sagittal split osteotomy of the mandible. A prospective follow-up study was performed to examine the long-term effect of especially gentle handling of the soft tissues on the medial side of the ascending ramus. After the initial incision, the soft tissues of the ramus were either retracted extremely gently and minimally (test side) or, as was the earlier routine, more widely (contralateral control side). NF was tested with 2-point discrimination (2-PD) and vitality scanner tests (VST) preoperatively and four times postoperatively up to 1 year. Patients' subjective sensations were also assessed. The results showed a difference between the sides, which was most distinct at the 6-month follow-up (P=0.028) measured with VST, while 2-PD did not show any statistical differences. Our findings support the earlier intraoperative neurophysiologic reports that dissection trauma to the IAN around the mandibular foramen may cause NF deficits in the IAN even before the actual splitting of the mandible. Therefore, minimal distraction of the soft tissues in the ramus is indicated. Higher age is an evident risk factor, and subjective sensation correlates with 2-PD in the lower lip.