The repeatability of scapular rotations across three planes of humeral elevation

Measurement of scapular kinematics is an important component in the assessment of shoulder function; however, repeatability of these measurements has not been established. The purpose of this study, therefore, was to determine the repeatability of scapular rotation measures for different humeral elevation planes between trials, sessions, and days. Three-dimensional scapular rotations were collected using an electromagnetic tracking system in three planes of humeral elevation. Coefficient of multiple correlation (CMC) values were calculated between trials, sessions, and days for curves of scapular rotations. CMC values were compared with repeated measures analysis of variance (ANOVAs) and Tukey's post-hoc procedures. Tests of simple main effects were performed for significant interaction effects. Our results suggest that scapular rotation measures are repeatable between trials within the same testing session, but less repeatable between testing sessions and days. Sagittal plane elevation consistently yielded the highest CMC values for all scapular rotations. These results suggest sagittal plane elevation should be considered to evaluate differences in scapular rotations.