Internal rotation resistance test at abduction and external rotation: a new clinical test for diagnosing subscapularis lesions

Abstract

A new clinical test for evaluating subscapularis (SSC) integrity was described, and its diagnostic value was compared with the present SSC tests (the lift-off, belly-press, IRLS and bear-hug tests). The new test is called internal rotation resistance test at abduction and external rotation (IRRT). The test is performed at maximal 90° of abduction and maximal external rotation. Two hundred and thirty-five consecutive patients suffering from rotator cuff injury were evaluated preoperatively. Six tests were performed to assess the function of the SSC: the lift-off, belly-press, IRLS, the bear-hug, IRRT at 0° abduction and 0° external rotation (IRRT0°) and IRRT at maximal 90° abduction and maximal external rotation (IRRTM). Arthroscopic findings were the reference for diagnosing of SSC lesions. The IRRTM test showed the greatest sensitivity (76.5%), and IRLS (31.6%) test had the lowest sensitivity. The IRRTM had the highest accuracy (79.0%), and lift-off had the lowest accuracy (65.3%). Positive IRRTM, bear-hug, belly-press, IRRT0° tests indicate that about one-third of the SSC is torn, and a positive lift-off and IRLS tests predict a severe tear at least two-thirds of the SSC. The IRRTM represents a sensitive diagnostic test for SSC lesions and improves the chance of finding the upper part of the SSC tears. When the IRRTM is positive, the surgeon should pay particular attention to detecting the SSC tendon during arthroscopy. Diagnostic study, Level I.