Can Handheld Dynamometers Diagnose Partial-thickness Rotator Cuff Tears?

Background Partial tears of the rotator cuff tendons of the shoulder are a common cause of significant pain and disability, yet are difficult to diagnose clinically. Handheld dynamometry has demonstrated good sensitivity and specificity in the diagnosis of full-thickness rotator cuff tears. The present study aimed to determine whether handheld dynamometer measurements could predict the presence of a partial-thickness rotator cuff tear among patients with shoulder pain. Methods Handheld dynamometer measurements and signs of impingement were collected before surgical evaluation in 450 patients with a partial-thickness rotator cuff tear ( n = 150), full-thickness rotator cuff tear ( n = 150) or nonrotator cuff pathology ( n = 150). Results Patients with partial-thickness tears did not have significantly different strength compared to patients without rotator cuff tears. Patients with full-thickness tears had a decrease in abduction and external rotation strength ( p < 0.001). Patients with any rotator cuff tear were more likely to have signs of impingement during internal rotation ( p < 0.001) and impingement during external rotation ( p = 0.004). Conclusions Handheld dynamometer measurements were unable to reliably distinguish patients with partial-thickness rotator cuff tears from patients with other causes of shoulder pain. The abduction and external rotation muscle strength tests demonstrated their usefulness when distinguishing partial-thickness rotator cuff tears from full-thickness rotator cuff tears.