Surgical anatomy of the axillary nerve.

Any surgical approach that splits the deltoid puts the axillary nerve at risk secondary to extension from traction or sharp dissection. Standard texts an anatomy and chapters on surgical approaches frequently state the axillary nerve comes to lie approximately 2 inches from the acromion. However, a large series of cadavers of varying sex and size on which these measurements had been obtained could not be found in an extensive literature search. Fifty-one embalmed cadaveric specimens representing 102 shoulders were dissected in the static portion of this study. In nearly 20% of cadavers the nerve at some point along its course around the humerus in the deltoid muscle was less than 5 cm from the palpable edge of the acromion. This was especially true of female cadavers with short arm spans; in one cadaver the nerve was 3.1 cm from the acromial edge. Abducting the shoulder to 9cr decreases the distance from the nerve to the palpable edge of the acromion nearly 30%. Five centimeters does not describe an absolute safe zone for the axillary nerve. Furthermore, abduction of the arm brings the nerve even closer to commonly used bony landmarks.