Definition of a Risk Zone for the Axillary Nerve Based on Superficial Landmarks

BACKGROUND: The aim of this study was to investigate the axillary nerve's location along superficial anatomical landmarks, and to define a convenient risk zone. METHODS: A total of 123 upper extremities were evaluated. After dissection of the axillary nerve, the vertical distance between the upper border of the anterolateral edge of the acromion and the proximal border of the nerve was measured. Furthermore, the interval between the proximal border and the distal border of the axillary nerve's branches was evaluated. The interval between the distal border of the branches and the most distal part of the lateral humeral epicondyle was measured. The distance between the anterolateral edge of the acromion and the lateral humeral epicondyle was evaluated. Measurements were expressed as proportions with respect to the distance between the acromion and the lateral humeral epicondyle. RESULTS: The distance between the acromion and the proximal border of the axillary nerve's branches was at a height of 10 percent of the distance between the acromion and the lateral humeral epicondyle, starting from the acromion (90 percent when starting from the lateral humeral epicondyle). The interval between the proximal and distal margins of the axillary nerve's branches was between 10 percent and 30 to 35 percent of this interval, starting from the acromion (65 to 70 percent when starting from the lateral humeral epicondyle). CONCLUSIONS: The authors were able to locate the branches of the axillary nerve at an interval between 10 and 35 percent of the distance between the acromion and the lateral humeral epicondyle, starting from the acromion. This makes the proximal third of this distance an easily applicable risk zone during shoulder surgery.