Analysis of abduction moment arms after rotator cuff tear and acellular dermal matrix allograft reconstruction

Pranav Krishnan; Jason Koh; Sonia Pradhan; Aimee Bobko; Aravind Athiviraham; Farid Amirouche

doi:10.1016/j.jse.2023.04.031

Analysis of abduction moment arms after rotator cuff tear and acellular dermal matrix allograft reconstruction

J Shoulder Elbow Surg. 2023 Nov;32(11):2207-2213. doi: 10.1016/j.jse.2023.04.031. Epub 2023 Jun 3.

Authors

Pranav Krishnan¹, Jason Koh², Sonia Pradhan³, Aimee Bobko³, Aravind Athiviraham⁴, Farid Amirouche⁵

Affiliations

¹ Pritzker School of Medicine, The University of Chicago, Chicago, IL, USA. Electronic address: pranavkrishnan23@gmail.com.
² Department of Orthopaedic Surgery, NorthShore University Health System, Chicago, IL, USA.
³ Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA.
⁴ Department of Orthopaedics, The University of Chicago, Chicago, IL, USA.
⁵ Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA; Department of Orthopaedic Surgery, NorthShore University Health System, Chicago, IL, USA.

PMID: 37276919
DOI: 10.1016/j.jse.2023.04.031

Abstract

Background: Biomechanical testing of abduction moment arms presents a useful method to assess the contributions of individual rotator cuff muscles to glenohumeral function. This study aimed to investigate the changes in abduction moment arms after the treatment of supraspinatus tears with superior capsular reconstruction (SCR), bursal acromial reconstruction (BAR), and a combined SCR-BAR procedure, all with human dermal allograft.

Methods: We tested 7 fresh-frozen cadaveric specimens under 6 conditions: (1) intact, (2) 50% supraspinatus tear (partial tear), (3) 100% supraspinatus tear, (4) SCR, (5) SCR combined with BAR, and (6) BAR. In each condition, the moment arms for the individual muscles of the teres minor, subscapularis, and infraspinatus were calculated throughout 90° of abduction using a motion capture system. Analysis of variance and post hoc Tukey testing were performed to determine significance.

Results: In the teres minor, the moment arms in the SCR (11.9 mm), BAR (10.1 mm), and SCR-BAR (11.9 mm) conditions were greater than those in the intact (8.5 mm; P = .001, P = .001, and P = .001, respectively), partial tear (9.1 mm; P = .001, P = .128, and P = .001, respectively), and complete tear (8.8 mm; P = .001, P = .011, and P = .001, respectively) conditions. Similarly, in the subscapularis, the moment arms in the SCR (13.4 mm), BAR (13.8 mm), and SCR-BAR (13.5 mm) conditions were greater than those in the intact (10.6 mm; P = .006, P = .001, and P = .003, respectively) and partial tear (10.4 mm; P = .006, P = .001, and P = .003, respectively) conditions. In the teres minor, the SCR (11.9 mm) and SCR-BAR (11.9 mm) conditions were also found to have significantly increased moment arms compared with the BAR condition (10.1 mm; P = .001 and P = .001, respectively). In the infraspinatus, the BAR condition (13.8 mm) was found to have a significantly decreased moment arm compared with the partial tear condition (15.8 mm, P = .026), with no other significant findings between conditions.

Conclusion: Our results suggest that the moment arm contributions of the individual muscles comprising the rotator cuff can change after reconstruction to compensate for tears. SCR and SCR-BAR increase the moment arms in the teres minor and subscapularis, potentially allowing for increased abduction ability.

Keywords: Moment arms; allograft; biomechanics; bursal acromial reconstruction; rotator cuff; rotator cuff tear; superior capsular reconstruction.