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Predicting Rotator Cuff Tears

Doctors need an easy, inexpensive, and accurate way to tell if a patient has a rotator cuff tear (RCT). Efforts have been made to find a physical test, X-ray, or other means of identifying RCTs. In this study, a handheld dynamometer for shoulder strength testing is used.

A dynamometer is a small device used to test muscle strength. It can be used to measure rotator cuff strength in healthy adults with an intact rotator cuff. By measuring 100 patients with full-thickness RCTs and comparing the results with 100 subjects who had excellent rotator cuff function, researchers hoped to develop a functional index. The functional index would be used to predict which patients have a RCT.

Four tests to assess shoulder force were done on each person. Each test was described in detail. The four muscles of the rotator cuff were included: supraspinatus, infraspinatus, teres minor, and subscapularis. Adduction strength (moving the arm away from the body) was also tested.

The results showed that supraspinatus and adduction tests can be used to predict RCTs. These tests do not predict the size of the tear. The tests weren't 100 percent though. Sensitivity was 83 percent and specificity was 79 percent. These results are considered "relatively high" by the authors.

Sensitivity reflects the test's ability to show a true positive for RCT. This means that 83 percent of the time it was accurate and 17 percent of the time, it was wrong. Specificity reflects the test's ability to tell a true negative test (no RCT tear). In this case, 79 percent of the time the test was negative and the patient didn't have a RCT. But 21 percent of the time, the person did have a RCT and the test didn't show it.

References: Daryl C. Osbahr,MD and George A. C. Murrell, MBBS, DPhil. The Rotator Cuff Index. In The American Journal of Sports Medicine. June 2006. Vol. 34. No. 6. Pp. 956-960.

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