Posterior approaches to the humerus: when should you worry about the radial nerve?

We used the olecranon osteotomy approach to the humerus on 75 cadaver arms and measured where the radial nerve pierced the intermuscular septum to determine the risk to that nerve during elevation of the triceps. We found the nerve an average of 10.0 cm from the distal articular surface in men and 9.4 cm in women; however, some cadavers had nerves as close as 7.5 cm. The humerus was also approached via a triceps split and the nerve located at the spiral groove. The distance from the articular surface to the nerve averaged 15.8 cm in men and 15.2 cm in women, with the minimum distance being 13 cm in one woman. When dissection beyond 7.5 cm laterally or 13.0 cm posteriorly is required, care should be taken to isolate and protect the radial nerve.