Clinical Study of Incidence and Relating Factors on Neurosensory Disturbances after Sagittal split Ramus Osteotomy

Abstract

Sagittal split ramus osteotomy(SSRO)is an effective orthognathic surgery used to correct mandibular deformity. Neurosensory disturbance(NSD)of the inferior alveolar nerve(IAN)is a common complication after SSRO. This clinical study aimed to evaluate NSD after SSRO using a tactile-threshold test by SemmesWeinstein monofilaments(SW test)and an interview about the subjective symptoms(Subjective test)and to analyze several factors regarding their possible influence on NSD. A total of 80 patients(160 sides) who underwent SSRO were examined before surgery and at 7 days, 4 weeks, 3 months and 6 months after surgery. The incidence of NSD was found in 35.0% by the SW test and in 29.4% by the Subjective test at 7 days after surgery. These were classified into four levels(Normal, Level 1 to 3)by the SW test and two groups(Light/Severe group)by the Subjective test. Each level and group gradually returned to normal by 6 months after surgery. 25% of the Severe group presented NSD on all of 3 evaluated zones of the mental nerve at 7 days after surgery and 50% of the Severe group still showed relatively wide zones at 4 weeks after surgery. A significantly higher incidence of NSD at 7 days after surgery was observed on intraoperative nerve encounter in the SW test and mandibular advancement in the Subjective test. The comparison between gender, age and osteotomy method did not show any significant difference. The results suggest that SSRO has the disadvantage of temporary NSD. However, when patients are considered and that the Severe group still showed NSD on a wide zone at 4 weeks after surgery, the delay in recovery should be kept in mind. Our study concluded that NSD after SSRO is strongly associated with IAN nerve exposure and mandibular advancement.