Sliding genioplasty, avoiding mental nerve injuries.

Mental nerve injuries have been inculcated in sliding genioplasty. An anatomical study was completed (and published) that demonstrated a surgical approach that would, it was hoped, prevent such nerve injuries. A prospective clinical study to test this hypothesis has now been completed. On the basis of the anatomical finding mentioned previously, fifty consecutive sliding genioplasties were compared with the immediate 50 consecutive sliding genioplasties preceding the anatomical finding. Sensation testing was based on multiple finger touches on both sides of the lower lip and chin in both groups. The anatomical finding was that in none of the mandibles studied did the inferior alveolar nerve canal dip more than 5.5 mm below the inferior border of the mental nerve canal. All the osteotomies in the prospective study were completed with at least 6 mm between the most proximal osteotomy and the inferior border of the mental nerve canal. In the retrospective cases, the distance between the canal and the osteotomy was generally not recorded. Surgery was completed on a broad spectrum of aesthetic and congenital-developmental deformities. In the 50 prospective cases, there were no permanent mental nerve injuries. There were three permanent injuries (one bilateral complete numbness, one unilateral complete numbness, and one unilateral partial numbness). Although keeping 6 mm or more between the inferior border of the mental nerve canal and the proximal osteotomy during sliding genioplasty does not absolutely rule out or prevent an injury to the inferior alveolar nerve within the bony canal, it seems that by not keeping the 6 mm the chances of a nerve injury would be greatly increased. It seems advisable to always keep 6 mm as a minimal distance because avoiding a nerve injury should be an obligatory goal of this surgery. If a greater distance can be kept without decreasing the aesthetic result, it should be considered.