Yoo HI, Hwang UJ, Jung SH, Weon YS, Kwon OY. 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".
J Orthop Sci 2023;
28:333-338. [PMID:
34969582 DOI:
10.1016/j.jos.2021.12.005]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 12/05/2021] [Accepted: 12/09/2021] [Indexed: 11/25/2022]
Abstract
BACKGROUND
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.
METHODS
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.
RESULTS
Compared with the conventional empty can test, the glenohumeral internal rotation angle was significantly greater during the modified empty can test (p < 0.05). Furthermore, the acromiohumeral distance measured in the modified empty can test was significantly less than that in the full can test (p < 0.001) and conventional empty can test (p < 0.001). However, there was no difference in the acromiohumeral distance between the full can test and the conventional empty can test (p > 0.017).
CONCLUSIONS
During the empty can test, the instructions should be given to patients based on the elbow direction (elbow pointing laterally). The modified empty can test can produce full glenohumeral internal rotation, compared with instructions based on the thumb direction (thumb pointing down). Consequently, the modified empty can test can produce a more decreased subacromial space.
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