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Determining the Relationship of the Axillary Nerve to the Shoulder Joint Capsule from an Arthroscopic Perspective
Matthew R. Price, Edward D. Tillett, Robert D. Acland, and G. Stephen Nettleton
Abstract
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.
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'key-hole' surgery. Surgery performed via small incisions, using special instruments and a viewing scope.. at the botom; towards the feet at the side or outer aspect A tough band of connective tissue that connects two bones to each other. "Ligament" is a fitting term; it comes from the Latin "ligare" meaning "to bind or tie."
References
J Bone Joint Surg Am. 2004;86:2135-2142
Comments
Summary:
1. The axillary nerve was closest to the glenoid and to the joint capsule at the 6 o'clock position, at a mean of 12.4 mm (range, 12.2 to 14 mm) from the glenoid, and a mean of 2.5 mm from the inferior glenohumeral ligament complex.
2. The branch of the axillary nerve that innervates the teres minor was closest to the glenoid rim. It arose from the posterior deltoid branch at the 6 o'clock position together with the superior lateral brachial cutaneous branch.
It is unfortunate that only the lateral decubitus position was studied, as this allows us only to speculate on the location of the axillary nerve when the patient is placed in the beach-chair position.
The joints were not distended with fluid as they are during arthroscopic surgery, although it would be expected that distention would result in an added margin of safety.
While the specimens in this study were normal shoulders, the most common reasons for surgery in the axillary pouch are instability or stiffness, where a patulous axillary capsule or a scarred shortened pouch would be expected. How these conditions affect the course of the axillary nerve remains open to interpretation.
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