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Abstract Presented at the 26th Annual Meeting of the Arthroscopy Association of North America| Volume 23, ISSUE 6, SUPPLEMENT , e2-e3, June 2007

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Arthroscopic Perspective of the Axillary Nerve in Relation to the Glenoid and Arm Position: An Anatomic Study (SS-04)

      Summary

      We performed real arthroscopic simulation using cadaveric shoulder specimens to describe the morphologic feature and relatioship of the axillary nerve, and thus determined changes depending on different arm position commonly used for arthroscopy.

      Purpose

      Although the anatomy of the axillary nerve is relatively well described in literatures, true arthroscopic perspective has been seldom reported. The aim of this study was to describe the morphologic features of the axillary nerve and its anatomical relationship to the glenoid under true arthroscopic setup. Also, we wanted to determine the practical aspect of the nerve position and its changes in relation to different arm positions during cadaveric arthroscopic simulation.

      Methods

      Eighteen paired fresh-frozen cadaveric shoulder specimens were used for evaluations. None of specimens had previous history of shoulder surgery or scar. Identical shoulder arthroscopic setup was applied to all the specimens, which was the same as the operating room (Lateral decubitus with posterior tilt 30° and 6-8lb traction with 20° flexion and 30° abduction, and pump pressure 80mmHg). Careful removal of capsule and soft tissue revealed the main trunk of the axillary nerve or with some of its branches. The axillary nerve morphologic description and documentation from the anterior and posterior portals were performed in all cases. The nearest distance from the glenoid rim was measured using the Neviaser portal with probe. Finally, the nerve was documented of its changes in the distance and its relationship from the glenoid rim depending on four different arm positions (Neutral meaning original traction setup, Abduction, Abduction-IR, and Abduction-ER). At the end of arthroscopic simulation, the nerves were marked and verified by open dissections to see if they were actually true axillary nerve.

      Results

      The axillary nerve almost always appeared in sight of the joint space around inferior edge of the subscapularis muscle after releasing an anterior bundle of inferior gleno-humeral ligament and seemed to be closest to glenoid rim at 5 o‘clock (right) or 7 o‘clock (left). With reference to the glenoid horizontally the main trunk appeared with mean angle of 29.3° (range, 15-35°) in neutral traction. Thereafter the nerve went away from the inferior glenoid rim and disappeared from the joint heading toward the quadrilateral space. The nearest distances from the glenoid rim to the nerve were 10-15mm in 1 shoulder, 15-20mm in 9 shoulders, 20-25mm in 7 shoulders, and 25-30mm in 1 shoulder with neutral arm positions. The four different arm position showed that abduction was helpful for moving the axillary nerve away from the glenoid most. The other two positions, ABD-IR and ABD-ER, did not change much of its relationship than abduction itself, furthermore, obstructed the visual field, which made arthroscopic surgery neither practical nor useful.

      Conclusions

      This study gives arthroscopic view of the main trunk of the axillary nerve. Between 4-8 o‘clock position the nerve appeared, passed through inferior joint with average angle of 29.3° and the nearest distance of 15-20mm most commonly, and then disappeared. Slight abduction and neutral position may be most practical in performing arthroscopic anterior and/or inferior capsular procedures, which made the axillary nerve far distant from the glenoid and provided maximum intraarticular space.