Alterations in scapular kinematics in subjects with idiopathic loss of shoulder range of motion

STUDY DESIGN: Prospective cohort study. OBJECTIVE: To determine the effect of idiopathic loss of shoulder range of motion on scapular kinematics. BACKGROUND: Subjects with idiopathic loss of shoulder range of motion have difficulty performing activities of daily living. Previous investigations have focused on the glenohumeral component of shoulder complex motion. MATERIALS AND METHODS: Seventeen unilaterally impaired and 17 nonimpaired subjects. The 3-dimensional motion of the humerus, scapula, and trunk were measured withthe Fastrak electromagnetic motion-tracking system during humerus-to-trunk scapular plane elevation. An analysis of variance compared the impaired subjects noninvolved to the nonimpaired subjects' scapulae at 4 scapularplane elevation positions. A repeated-measures analysis of variance compared the impaired subjects' involved and noninvolved scapulae at 3 scapular plane elevation positions, and matched-pairs t test compared peak elevation values. RESULTS: The between-group ANOVAs demonstrated no difference in anterior tipping, internal rotation, or upward rotation. The repeated-measures ANOVAs demonstrated no difference in anterior tipping or internal rotation and a position-by-side interaction in upward rotation. The involved-side scapulae were more upwardly rotated (7.7 degrees) at peak humerus-to-trunk scapular plane elevation. DISCUSSION AND CONCLUSION: The impaired subjects' noninvolved scapular kinematics were not significantly different than the nonimpaired subjects, but were significantly different than their involved scapulae. The upward rotation differences may be a substitution pattern used to accomplish functional elevation.