A new pathophysiology of atraumatic rotator cuff tears: adduction restriction of the glenohumeral joint

BACKGROUND: The pathophysiology of atraumatic rotator cuff tears (ATTs) has not been fully understood. Adduction restriction of the glenohumeral joint can cause pain and disability in patients with ATTs. We aimed to use our adduction test (pushing the humerus toward the side in the coronal plane with scapular fixation) to fluoroscopically measure the glenohumeral adduction angle (GAA) and to assess the effectiveness of adduction manipulation. MATERIALS AND METHODS: Fifty-five patients with ATTs were included in the study. The GAAs of the patients vs. healthy subjects without ATTs were measured fluoroscopically and compared. During the test, patients showed restriction and expressed pain. The visual analog scale (VAS) score, passive range of motion (ROM), and the American Shoulder and Elbow Surgeons score at the initial visit were compared with those after adduction manipulation. RESULTS: Of the patients, 41 (75%) had positive adduction test results. A higher percentage of positive adduction test results was observed in smaller tears. The average GAA was –21.4° on the affected side, which was smaller than that on the unaffected side, at –2.8° (P < .001), and that in healthy subjects, at 4.8° (P < .001). After manipulation, the GAA was –0.8° (P < .001) and the VAS score, the American Shoulder and Elbow Surgeons score, and all ROM values significantly improved up to the level on the unaffected side. CONCLUSION: Adduction restriction of the glenohumeral joint was identified in 75% of all the patients with ATTs. Adduction manipulation significantly reduces the VAS score and restores the ROM. Adduction restriction is considered a crucial pathophysiology of ATTs.