Arthroscopic perspective of the axillary nerve in relation to the glenoid and arm position: a cadaveric study

The purposes of this study were to examine the morphologic features of the axillary nerve and its relation to the glenoid under an arthroscopic setup, and to determine the changes in nerve position according to different arm positions.

Twenty-three fresh-frozen fore-quarter cadaveric shoulder specimens were used for evaluations in an arthroscopic setup with the lateral decubitus position. The main trunk of the axillary nerve with or without some of its branches was exposed after careful arthroscopic dissection. Morphologic features and the course of the axillary nerve from the anterior and posterior portals were documented. The closest distances from the glenoid rim were measured with a probe by use of a distance range system. The changes in nerve position were determined in 4 different arm positions. At the end of arthroscopic examination, the nerves were marked and verified by open dissections.

The axillary nerve appeared in the joint near the inferior edge of the subscapularis muscle. With reference to the inferior glenoid rim horizontally, the nerve had a mean running angle of 23 degrees (range, 14 degrees to 41 degrees; SD, 8 degrees ). The closest points from the glenoid were between the 5:30- and 6:00-o'clock position (right) or 6:00- and 6:30-o'clock position (left). The closest distance range varied from 10 to 25 mm in the neutral arm position. The abduction-neutral position resulted in the greatest distance between the inferior glenoid and the nerve.

The abduction-neutral rotation position was the optimal position for minimizing axillary nerve injuries, because it resulted in the greatest distance between the inferior glenoid and the nerve.

Knowledge of the anatomy of the axillary nerve aids the shoulder surgeon in avoiding nerve injury during arthroscopic procedures. Abduction-neutral rotation may be more helpful for arthroscopic surgeons performing procedures in the anteroinferior glenoid with the nerve being farther away from the working field.