Orientation feedback during simulated simple translation tests has little clinical significance on the magnitude and precision of glenohumeral joint translations

Abstract

The repeatability of shoulder instability clinical examinations has been reported to be poor, producing a large range of translations. The objective of this study was to determine the effect of providing the clinician with joint orientation feedback on the magnitude and precision of glenohumeral joint kinematics. A 6-degree of freedom magnetic tracking system was used to determine the kinematics of the humerus with respect to the scapula (n=8 cadaveric shoulders). The joints were preconditioned with simple loading tests five times. At 60 degrees of glenohumeral abduction and 0 degrees of flexion/extension, a clinician then applied an anterior and posterior load to the humerus until a manual maximum simulating a simple translation test (STT) was achieved at 0, 30, and 60 degrees of external rotation with and without angular orientation feedback of the humerus with respect to the scapula. The precision for the external rotation was within 4.3 degrees for the feedback group and 17.5 degrees for the no feedback group over all external rotations. For achieving the target external rotation of 30 degrees , there was a significant difference in precision between the feedback and no feedback groups (p<0.05). The magnitudes of the anterior translations were 18.2+/-5.3, 15.5+/-5.1, and 9.9+/-5.5 mm for the feedback group and 19.3+/-6.6, 17.5+/-4.9, and 11.5+/-5.3 mm for the no feedback group, at 0, 30, and 60 degrees of external rotation, respectively. There was a significant difference in the precision of anterior translation at 30 and 60 degrees of external rotation for 4 of 8 specimens (p<0.05). Significant differences in the precision of the posterior translation was only detected at 0 degrees of external rotation for 3 of 8 specimens (p<0.05). Based on the data obtained, providing orientation feedback to a clinician performing a simulated STT results in increased precision for not only the target external rotations but also the resulting glenohumeral translations. While providing feedback may be a necessary step to achieving precise results for experimental studies, the magnitudes of translations in the anterior and posterior directions were relatively similar for the feedback and no feedback states indicating little benefit for clinical examinations.