On the kinematics of the cross body abduction and hand behind the back tests to assess osteoarthritis of the acromioclavicular joint

Abstract

Background: Osteoarthritis of the acromioclavicular joint is one of the most common sources of shoulder pain. One of the current standard clinical physical examination tests is the cross body adduction test which has been shown to signal the presence of osteoarthritis. Another test referred to as the hand behind the back test has been described to provide a more accurate diagnosis than the CBA test for some patients. Through this work, both the CBA and the HBB tests were modeled in order to determine if there is merit for the HBB test to be used as a diagnostic tool for clinicians. Methods: Both tests were modeled using the zygote solid 3D 50th percentile male human anatomy model and MSC-ADAMS Software to compile and run the simulations. Within MSC-ADAMS the bones were outfitted with joints. During simulation, the bones were moved from the anatomical position to the final position for each test and the corresponding minimum distances between the bones at the acromioclavicular joint were then determined. Results: It was found that the distance between the acromioclavicular joint articulating surfaces decreased by 0.3 mm from the anatomical position during the CBA test and by 1.65 mm from the anatomical position during the HBB. This shows that the minimum space decreased from the anatomical position by more than 5 folds during the HBB test than during the CBA test. Conclusions: These results indicate that the HBB test may be a better diagnostic test due to the greater stress and irritation it places upon the acromioclavicular joint.