Reliable Method of Radial and Ulnar Nerve Identification During the Posterior Approach to the Humerus: A Clinical and Cadaveric Correlation Study

OBJECTIVE: To determine the reliability of using "fingerbreadths" and anatomic landmarks as reference points for predictable identification of the radial and ulnar nerves when using the posterior approach to the humerus. METHODS: A systematic approach using "fingerbreadths" to mark and measure the skin before incision. Two markings were made: the first 4 fingerbreadths proximal to the lateral epicondyle (radial nerve location) and the second 2 fingerbreadths proximal to the medial epicondyle (ulnar nerve location). Once the posterior approach was made, the same fingerbreadths were used on the radial and ulnar sides to identify the radial and ulnar nerves within the deep interval. Measurements were taken at each stage in cadaveric specimens. Clinical correlations followed. Statistical analysis was performed comparing measurements (outer vs. inner) in both cadaveric and clinical specimens. RESULTS: Thirty-two elbows evaluated in this study, 20 patients and 12 cadaveric specimens. In the cadaveric specimens, the mean distance of the radial nerve was 7.59 cm from the lateral epicondyle, SD ± 0.17 cm (P = 0.55), and the ulnar 3.68 cm from medial epicondyle, SD ± 0.63 cm (P = 0.302). In the clinical measurements, the radial nerve was 7.46 cm, SD ± 0.48 cm, never within 7.0 cm (P = 0.425), and the ulnar nerve was 3.14 cm, SD ± 0.31 cm (P = 0.051). Statistical analysis yielded no difference between skin marking and actual location in the deep interval, between cadaveric and clinical specimens, observer fingerbreadth widths, or between left or right arms. CONCLUSIONS: Use of "fingerbreadths" is a reliable, efficient, and reproducible method of identifying both the radial and ulnar nerves during the posterior approach to the humerus.