Comparison of acromiohumeral distance and glenohumeral internal rotation angle between the empty can test and modified empty can test: “thumb pointing down” versus “elbow pointing laterally”

During the empty can test, the direction of the thumb (downward) has been widely used as an instruction for producing glenohumeral internal rotation. However, the combination of forearm pronation and thumb motion as a compensatory movement could contribute to the lack of glenohumeral internal rotation during the empty can test. This study aimed to compare the glenohumeral internal rotation angle between the conventional empty can (with thumb direction) and modified empty can tests (with elbow direction), as well as the acromiohumeral distance between the full can, conventional empty can, and modified empty can tests. In this laboratory study, we measured the glenohumeral internal rotation angle using a motion sensor and the acromiohumeral distance using ultrasonography during the following tests: full can test (thumb pointing up), conventional empty can test (thumb pointing down), and modified empty can test (elbow pointing laterally) in 20 healthy subjects. Compared with the conventional empty can test, the glenohumeral internal rotation angle was significantly greater during the modified empty can test (p