The course of the inferior alveolar nerve in the normal human mandibular ramus and in patients presenting for cosmetic reduction of the mandibular angles

This study was undertaken to quantify the path of the inferior alveolar ner ve in the normal human mandible and in the mandibles of patients presenting for cosmetic reduction of the mandibular angles. The goals were: (1) to pr ovide normative information that would assist the surgeon in avoiding injur y to the nerve during surgery; (2) to characterize gender differences in th e normal population; and (3) to compare the course of the nerve in the norm al population to its course in a group of patients who presented with a com plaint of "square face." The study was based upon the computerized tomographic scans of 10 normal pa tients (six men, four women) and 8 patients tall women) complaining of "squ are face." Using AnalyzePC 2.5 imaging software, the mandibles were segment ed and the position of the nerve was recorded within its osseous canal in t he mandibular ramus on each axial slice in which it was identifiable. Dista nces were calculated between the nerve and the anterior, posterior, lateral , and medial cortices. The positions of the lateral ramus prominence and th e lowest point on the sigmoid notch were also recorded. The position of the mental foramen was recorded in relation to the nearest tooth, and the thre e-dimensional surface distances from the foramen to the alveolar bone, the inferior border of the mandible, and the mandibular symphysis were determin ed. The distances from the entrance of the nerve into the mandible to the l ateral ramus prominence and the lowest point on the sigmoid notch were calc ulated. Summary statistics were obtained, comparing differences in gender. The nerve was identifiable in each ramus over a mean distance of 12.7 mm. O n average, the lateral ramus prominence was 0.3 mm higher on the caudad-cep halad axis than the point at which the nerve entered the bone, whereas the location of the lowest point on the sigmoid notch was 16.6 mm above the ner ve. The average distances from the nerve to the anterior, posterior, medial , and lateral cortices were 11.6, 12.1, 1.8, and 4.7 mm, respectively. Gend er differences were significant for all of these except the medial cortex t o nerve distance. On average, the mental foramen exited the body of the man dible immediately below the second premolar and the average surface distanc es from the foramen to the symphysis, the most cephalad alveolar bone, and the inferior border of the body were 30.9, 14.2, and 19.3 mm, respectively. With regard to the patients presenting for mandibular angle reduction, the re were a few statistically significant but small scalar differences from n ormal controls.