Identifying the axillary nerve during shoulder surgery: an anatomic study using advanced imaging

Michael E. Hachadorian, MD; Brendon C. Mitchell, MD; Matthew Y. Siow, MD, MBA; Wilbur Wang, MD; Tracey Bastrom, MA; T. Barrett Sullivan, MD; Brady K. Huang, MD; Eric W. Edmonds, MD; William T. Kent, MD

JSES International (Dec 2020)

Identifying the axillary nerve during shoulder surgery: an anatomic study using advanced imaging

Michael E. Hachadorian, MD,
Brendon C. Mitchell, MD,
Matthew Y. Siow, MD, MBA,
Wilbur Wang, MD,
Tracey Bastrom, MA,
T. Barrett Sullivan, MD,
Brady K. Huang, MD,
Eric W. Edmonds, MD,
William T. Kent, MD

Affiliations

Michael E. Hachadorian, MD: Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA
Brendon C. Mitchell, MD: Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA
Matthew Y. Siow, MD, MBA: Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA
Wilbur Wang, MD: Department of Musculoskeletal Radiology, University of California San Diego, San Diego, CA, USA
Tracey Bastrom, MA: Department of Orthopaedic Surgery, Rady Children's Hospital, San Diego, CA, USA
T. Barrett Sullivan, MD: Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA
Brady K. Huang, MD: Department of Musculoskeletal Radiology, University of California San Diego, San Diego, CA, USA
Eric W. Edmonds, MD: Department of Orthopaedic Surgery, Rady Children's Hospital, San Diego, CA, USA
William T. Kent, MD: Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA; Corresponding author: William T. Kent, MD, University of California San Diego, 200 W Arbor Dr. San Diego, CA 92103, USA.

Journal volume & issue: Vol. 4, no. 4
pp. 987 – 991

Abstract

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Background: The axillary nerve (AXN) is one of the more commonly injured nerves during shoulder surgery. Prior anatomic studies of the AXN in adults were performed using cadaveric specimens with small sample sizes. Our research observes a larger cohort of magnetic resonance imaging (MRI) studies in order to gain a more representative sample of the course of the AXN and aid surgeons intraoperatively. Methods: High-resolution 3T MRI studies performed at our institution from January 2010 to June 2019 were reviewed. Four blinded reviewers with musculoskeletal radiology or orthopedic surgery training measured the distance of the AXN to the surgical neck of the humerus (SNH), the lateral tip of the acromion (LTA), and the inferior glenoid rim (IGR). Intraclass correlation coefficient was calculated to assess reliability between reviewers. The nerve location was assessed relative to rotator cuff tear status. Results: A total of 257 shoulder MRIs were included. Intraclass correlation coefficient was excellent at 0.80 for the SNH, 0.90 for the LTA, and 0.94 for the IGR. All intraobserver reliabilities were above 0.80. The mean distance from the AXN to SNH was 1.7 cm (range, 0.7-3.1 cm; interquartile range, 1.38-2.00) and that from the AXN to IGR was 1.6 cm (range, 0.6-2.6 cm; interquartile range, 1.33-1.88). The mean AXN to LTA distance was 7.1 cm, with a range of 5.2-9.0 cm across patient heights; there was a large effect size related to the LTA to AXN distance and patient height with a correlation of r = 0.603 (P < .001). Rotator cuff pathology appears to affect nerve location by increasing the distance between the AXN and SNH (P = .027). Discussion/Conclusion: The AXN is vulnerable to injury during both open and arthroscopic shoulder procedures. This injury can be either a result of direct trauma to the nerve or secondary to traction placed on the nerve with reconstructive procedures that distalize the humerus. Our study demonstrates that the AXN can be found as little as 5.6 mm from the IGR and 6.9 mm from the SNH. In addition, we illustrate the relationship between patient height and the LTA to AXN distance and complete rotator cuff tears and the SNH to AXN distance. Our study is the first to demonstrate the nerve's proximity to important surgical landmarks of the shoulder using a large sample size of high-resolution images in living human shoulders.

Published in JSES International

ISSN: 2666-6383 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Medicine: Surgery: Orthopedic surgery; Medicine: Internal medicine: Specialties of internal medicine: Diseases of the musculoskeletal system
Website: https://www.journals.elsevier.com/jses-international

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