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

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.

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

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.

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.

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.