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Axillary Nerve Injury Following Reverse Total Shoulder Arthroplasty: An Anatomical Study
Sebastian D. Arango, B.S.
1,2; Jason C. Flynn, B.S.
1,3; Charles J. Nessralla, M.D.
1; Jacob Zeitlin, B.A.
1,4; Johannes B. Roedl, M.D., Ph.D.
5; Kenneth A. Kearns, M.D.
1; Matthew S. Wilson, M.D.
1; Adam B. Strohl, M.D.
11Philadelphia Hand to Shoulder Center, Philadelphia, PA; 2University of Miami Miller School of Medicine, Miami, FL; 3Sidney Kimmel Medical College, Philadelphia, PA; 4Weill Cornell Medical College, New York, NY; 5Thomas Jefferson University Hospital, Philadelphia, PA
Introduction: Reverse total shoulder arthroplasty (rTSA) is associated with a greater risk of nerve injury compared to anatomic total shoulder arthroplasty. The aim of this study was to characterize the structural changes occurring to the axillary nerve (AN) and quadrangular space (QS) during the rTSA procedure.
Materials & Methods: A single cadaver with two shoulders was used in this study. Each shoulder was dissected via a posterior and anterior deltopectoral approach. Six metal clips were placed 1 cm apart along each AN starting at the QS posteriorly moving anteriorly (Figure 1). A rTSA was performed on the right shoulder in the standard fashion. A rTSA was performed on the left shoulder following tethering of the AN at the superior border of the QS to simulate scar tissue formation. Following rTSA, metal clip position was measured in neutral and stressed (90° abduction, 45° external rotation) positions. Ultrasonography was employed to measure changes to QS volume and AN cross sectional area (CSA) in neutral and stressed positions (Figure 2).
Results: The right, non-tethered AN was lengthened by 5 mm and the left, tethered AN by 2 mm. In the stressed position, both nerves were stretched 11 mm. The average CSA of the right AN along the course of our measured length was 2.22 mm
2. After rTSA, the CSA decreased to 2.13 mm
2 in neutral and 1.92 mm
2 in the stressed position. On the left, the CSA was 3.12 mm
2 prior to rTSA, 3.05 mm
2 after rTSA, and 2.95 mm
2 after rTSA in the stressed position. The right QS measured 9 cm
3 prior to rTSA in neutral, 7.59 cm
3 after rTSA in neutral, and 6.61 cm
3 after rTSA in the stressed position. Following tethering, the left QS measured 13.8 cm
3 prior to rTSA in neutral, 9.83 cm
3 after rTSA in neutral, and 6.86 cm
3 after rTSA in the stressed position.
Conclusions: In the setting of trauma and subsequent fibrosis, tethering and stretching of the nerve does likely contribute to postoperative nervous complications. The QS also appears to become constricted following rTSA, impeding the AN's course and contributing to the risk for injury.
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