Arthroscopic anatomy medial to the coracoid: an anatomic study of the axillary and musculocutaneous nerves
The purpose of this study was to provide arthroscopic measurements and orientations of the axillary and musculocutaneous nerves medial to the coracoid.
A retrospective chart review of 29 patients undergoing arthroscopic subscapularis repair and arthroscopic cadaveric dissection of 23 shoulders was used to analyze neuroanatomical distances to arthroscopic landmarks and to document the orientations of the axillary and musculocutaneous nerves using a clock face analogy. The clock face data was analyzed by separating the clock face into four quadrants and the frequency of any crossing nerve within each of the four quadrants was then determined.
In vivo, the axillary nerve was found 1.5 ± 0.5 cm medial to the coracoid tip and the musculocutaneous nerve was found 1.6 ± 0.6 cm medial to the coracoid tip. In cadavera, the axillary nerve was found 2.0 ± 0.6 cm medial to the coracoid tip and the musculocutaneous nerve was found 1.5 ± 0.5 cm medial to the coracoid tip. The posterosuperior quadrant of the subcoracoid space contained a crossing nerve in 4 of 29 (13.8%) patients undergoing arthroscopic rotator cuff repair medial to the coracoid, compared to 9 of 23 (39.1%) cadavera undergoing arthroscopic dissection medial to the coracoid. The posteroinferior quadrant contained a crossing nerve in 16 of 29 (55.2%) patients compared to 17 of 23 (73.9%) cadavera.
The axillary and musculocutaneous nerves run in close proximity to the coracoid tip and coracoid arch, most consistently within 1–2 cm medial to these structures, which is closer than has been previously documented in the literature. Crossing nerves are least frequently encountered within the posterosuperior quadrant of the subcoracoid space medial to the coracoid, followed by the posteroinferior quadrant. Arthroscopic dissection of this space should begin in the posterosuperior quadrant and carefully progress to the posteroinferior quadrant to decrease the risk of intraoperative nerve injury. Given the close proximity and frequently encountered nerves in this area, extreme caution must be exercised when working arthroscopically within the subcoracoid space.
KeywordsAxillary nerve Musculocutaneous nerve Coracoid Anatomy Arthroscopic subscapularis repair Arthroscopic Latarjet
The authors would like to thank the contributions made by Dr. Denis Clohisy and the Department of Orthopaedic Surgery at the University of Minnesota for the provision of funds and for the acquisition of materials and cadavera for this study. The authors would also like to thank Dr. Jason C. Hibbard and Dr. Michal P. Zlowodzki for their contributions in the assistance of data collection for this study. Lastly, the authors would like to thank Kellie A. Knudsen for her line drawing contributions for this study.
No external funding sources were used in the development of this study.
Compliance with ethical standards
Conflict of interest
Dr. Braman serves as a paid consultant of Zimmer Biomet, unrelated to the subject of this work. Dr. Knudsen does not receive anything of value and does not own any stock in a commercial company or institution related directly or indirectly to the subject of this article.
This study was approved by the University of Minnesota Institutional Review Board.
Supplementary material 1 Video 1 This video demonstrates a right shoulder while utilizing an anterolateral viewing portal and an anteroanterolateral working portal. Dissection has already been performed in the subcoracoid space using a combination of sharp and blunt techniques. The dissection was carried down along the anterior surface of the torn subscapularis tendon and under the coracoid arch. The axillary and musculocutaneous nerves are identified medial to the coracoid arch in this video. The strap muscles, or conjoint tendon, are seen to the right of the video and determine the vertical axis of the scope and the apex of the coracoid arch relative to this is considered the 12:00 position. This dissection was performed in a standardized beach chair position with the arm in 60 degrees of forward flexion and 20 degrees of lateral deviation (MP4 14175 KB)
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