Contribution of the supraspinatus to the external rotator lag sign: kinematic and electromyographic pattern in an in vivo model

Hypothesis: This study reassessed the sensitivity and the specificity of the external rotator lag sign (ERLS) for diagnosis of supraspinatus tears in a large cohort of patients. Materials and methods: The ERLS was used to assess 401 consecutive patients with 406 painful shoulder conditions. The clinical diagnosis was controlled either arthroscopically or by open surgery. Results: For isolated full-thickness supraspinatus tears, the ERLS had a sensitivity of 56% and a specificity of 98%. When the lesion involved the infraspinatus and the teres minor the sensitivity improved substantially. There was a strong correlation between the extension of the tear and the amount of the lag. The lag increased from 7for an isolated rupture of the supraspinatus tendon to 26 in case of extension to the teres minor. Conclusion: The ERLS is highly specific and acceptably sensitive for diagnosis of full-thickness tears, even in case of an isolated lesion of the supraspinatus tendon. Level of evidence: Level 2; Prospective cohort treatment study.