A method to localize the radial nerve using the 'apex of triceps aponeurosis' as a landmark

Abstract

Background: The relationship of the radial nerve is described with various osseous landmarks, but such relationships may be disturbed in the setting of humerus shaft fractures. Alternative landmarks would be helpful to more consistently and reliably allow the surgeon to locate the radial nerve during the posterior approach to the arm.

Questions/purposes: We investigated the relationship of the radial nerve with the apex of triceps aponeurosis, and describe a technique to locate the nerve.

Materials and methods: We performed dissections of 10 cadavers and gathered surgical details of 60 patients (30 patients and 30 control patients) during the posterior approach of the humerus. We measured the distance of the radial nerve from the apex of the triceps aponeurosis along the long axis of the humerus in cadaveric dissections and patients. This distance was correlated with the height and arm length. For all patients, we recorded time until first observation of the radial nerve, blood loss, and postoperative radial nerve function.

Results: The mean distance of the radial nerve from the apex of the triceps aponeurosis was 2.5 cm, which correlated with the patients' height and arm length. The mean time until the first observation of the radial nerve from beginning the skin incision was 6 minutes, as compared with 16 minutes in the control group. Mean blood loss was 188 mL and 237 mL, respectively. With the numbers available, we observed no difference in the incidence of patients with postoperative nerve palsy: none in the study group and three in the control group.

Conclusion: The apex of the triceps aponeurosis appears to be a useful anatomic landmark for localization of the radial nerve during the posterior approach to the humerus.

Fig. 1A–C

Photographs of the cadaveric dissection (right arm) show (A) the apex of the triceps aponeurosis and anatomic details of the triceps aponeurosis, (B) the point 2.5 cm proximal to the apex of the triceps aponeurosis (exploration of that point will locate the radial nerve), and (C) the radial nerve on exploring the point in depth.

Fig. 2

A diagram shows how, during the posterior approach to the humerus, the radial nerve and accompanying vessels can be seen in the tunnel made approximately 2.5 cm proximal to the apex of the triceps aponeurosis. Point “A” denotes the apex of the aponeurosis, whereas point “B” denotes the most distal extent of the radial nerve along the long axis of the humerus in the plane between the long and lateral heads of the triceps.

Fig. 3

A diagram shows the anatomy of the triceps aponeurosis, the medial head of which is almost straight and the lateral border is curved proximally. The long and lateral heads of the triceps fuse to form the apex of the aponeurosis.

Fig. 4A–B

Perioperative clinical photographs of a patient with a distal third humerus fracture (left arm) show (A) anatomic details: two sutures placed in the deep fascia at the level of the apex of the triceps aponeurosis converge approximately 2.5 cm proximal to the apex; and (B) the radial nerve and accompanying vessels observed when exploring the point in depth.