The subscapularis (SSC) provides 50 % of total rotator cuff strength and constitutes the anterior part of force couples of the glenohumeral joint. The advances in shoulder arthroscopy have resulted in improved detection and treatment of subscapularis tendon pathology. The prevalence is between 27 and 30 % in all shoulder arthroscopies and between 49 and 59 % in arthroscopic rotator cuff surgery .~It would be advantageous for the surgeon to be able to diagnose a SSC tear clinically before surgery is performed for rotator cuff tear. Magnetic resonance imaging (MRI) scans of the shoulder have been widely used as a diagnostic tool for predicting the rotator cuff injuries. But preoperative MRI scans do not reliably predict SSC tears, whether conventional MRI or MR arthrography is used. Many clinical tests have been published to evaluate the integrity of SSC. The first of these was the lift-off test by Gerber that was reported to be very reliable in patients with complete SSC tears. The internal rotation lag sign (IRLS) published by Hertel et al. was specific but more sensitive than the lift-off test for assessing the SSC. The belly-press test described by Gerber et al. was modified by other authors who called it the Napoleon sign or the modified belly-press test. Positive belly-press tests were found with upper-third SSC tears. More recently, the bear-hug test was published by Barth et al. and represented the most sensitive test compared with lift-off, belly-press and Napoleon tests. However, Yoon et al. found belly-press test was more sensitive compared with bear-hug test in the most recent study. In our institute, we also performed internal rotation resistance test (IRRT) at 0° abduction and 0° external rotation (IRRT0°, Fig. 1) and IRRT at maximal 90° abduction and maximal external rotation (IRRTM) to investigate the function of SSC. These tests use resisted internal rotation as the shoulder is at different abduction and external rotation degrees.~Although many of these tests are performed, SSC lesions are still underdiagnosed before operation. Because these 6 tests mentioned above have a distinct position and manner, the individual test might imply different severity of SSC lesions. The SSC is stretched out and more extension in the abduction and external rotation position compared with internal rotation position. The purpose of this study is to describe the new clinical test (IRRTM) for evaluating SSC integrity and to compare its diagnostic value with the present SSC tests (the lift-off, belly-press, IRLS and bear-hug tests). The hypothesis was that the IRRTM would be the most sensitive test for detecting tears of the SSC.
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, bellypress, 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.