Association of Strength Measurement with Rotator Cuff Tear in Patients with Shoulder Pain: The Rotator Cuff Outcomes Workgroup Study

Objective This study examines the association between strength measurements and supraspinatus tear in patients with shoulder pain. This study characterized determinants of abduction strength among patients with tears. Design A total of 208 patients with shoulder pain were recruited. Strength was tested using a handheld dynamometer. Supraspinatus tears were diagnosed by combination of clinical assessment and blinded magnetic resonance imaging review. Associations of supraspinatus tear with patient characteristics and strength measurements (abduction, internal rotation and external rotation) were assessed using multivariable logistic regression models. Results Patients with supraspinatus tear had decreased abduction strength (P = 0.02) and decreased external rotation strength (P < 0.01). When adjusted for age, sex, tear laterality, and body mass index, decreased abduction strength (odds ratio, 1.18/kg; 95% confidence interval, 1.06-1.32) and decreased external rotation strength (odds ratio, 1.29/kg; 95% confidence interval, 1.14-1.48) were associated with supraspinatus tear. In patients with tear, age 60 yrs or older, female sex, and visual analog scale pain score were significantly associated with decreased abduction strength but tear size, fatty infiltration, and atrophy were not. Conclusions Decreased abduction and external rotation strength were associated with supraspinatus tear in patients with shoulder pain. In this cohort, the abduction strength of patients with tears was influenced by demographic factors but not tear characteristics.