Background: The axillary nerve is out of the field of view during shoulder arthroscopy, but certain procedures require manipulation of capsular tissue that can threaten the function or integrity of the nerve. We studied fresh cadavers to identify the course of the axillary nerve in relation to the glenoid rim from an intra-articular perspective and to determine how close the nerve travels in relation to the glenoid rim and the inferior glenohumeral ligament.

Methods: We dissected nine whole-body fresh-tissue shoulder joints and exposed the axillary nerve through a window in the inferior glenohumeral ligament. Then we cut coronal sections through the glenoid fossa of ten unembalmed, frozen shoulder specimens after the axillary nerve had been stained with Evans blue dye. All specimens were studied with the joint secured in the lateral decubitus position used for shoulder arthroscopy.

Results: Microsurgical dissection through the inferior glenohumeral ligament from within the joint capsule revealed the axillary nerve as it traversed the quadrangular space. In each dissection, the teres minor branch was the closest to the glenoid rim. The coronal sectioning of the unembalmed shoulder specimens demonstrated that the closest point between the axillary nerve and the glenoid rim was at the 6 o'clock position on the inferior glenoid rim. At this position, the average distance between the axillary nerve and the glenoid rim was 12.4 mm. The axillary nerve lay, throughout its course, at an average of 2.5 mm from the inferior glenohumeral ligament.

Conclusions: We used two novel approaches to map the axillary nerve from an intra-articular perspective. Our analysis of the position of the nerve with use of these methods provides the shoulder arthroscopist with essential information regarding the location, route, and morphology of the nerve as it passes inferior to the glenoid rim and shoulder capsule.

Clinical Relevance: Orthopaedic surgeons have long known that the axillary nerve is vulnerable to damage during repair of the shoulder joint capsule. Knowledge of the precise relationship of the axillary nerve and its branches to the inferior glenohumeral ligament can be of benefit in shoulder arthroscopy.