The surgical anatomy of the radial nerve around the humerus.

Twenty-four cadaveric arms were dissected to determine the position of the radial nerve on the posterior aspect of the humerus relative to the posterior tip of the acromion, the medial and lateral epicondyles, the division between the lateral and long heads of the triceps, and the triceps aponeurosis. The radial nerve passed anterior to the long head of triceps and cross onto the posterior shaft of the humerus an average of 124 mm below the posterior tip of the acromion. It was never closer than 97 mm. The nerve usually lies on the medial head of the triceps as it courses posteriorly around the humerus and then leaves the posterior shaft of the humerus an average of 126 mm above the lateral epicondyle and 131 mm above the medial epicondyle. It was never within 100 mm of either epicondyle. The surgeon can use these landmarks as guidelines to avoid the radial nerve during operative intervention on the humerus.