Effect of Glenohumeral Abduction on Supraspinatus Tendon Strain: A Cadaveric Study

Objectives Rotator cuff tears are among the most common causes of shoulder pain and loss of function in adults. The supraspinatus tendon plays a crucial role in shoulder abduction, where a better understanding of the mechanical environment could lead to more informed clinical decisions. This study aimed to examine the heterogeneous nature of the supraspinatus tendon to understand the differences in regional strain patterns. Methods Five fresh frozen cadaveric shoulders were abducted from 60° to 90°. The supraspinatus tendon was loaded at 30 newtons to simulate motion in a subject operating at roughly 26% of the maximum glenohumeral abduction force. The surface strain at the supraspinatus tendon insertion, where tears most commonly occur, was evaluated in the tendon’s anterior, middle, and posterior regions to identify the heterogeneous deformation during abduction. Results Surface strain increased with increasing abduction angle (R2 = 0.697, P < 0.001). The posterior regions exhibited larger strains compared to the anterior regions at 70° (P = 0.037), 75° (P = 0.028), and 90° (P = 0.011) of abduction. Conclusion During abduction, the strain on the bursal surface of the supraspinatus tendon insertion increases with increasing abduction angle, and the posterior region experiences the largest strains.