Motion analysis assessment of alterations in the scapulo-humeral rhythm after throwing in baseball pitchers

Purpose: Throwing a baseball requires a coordinated sequence of scapula and humerus movements also called scapulo-humeral rhythm (SHR). Fatigue associated with repetitive throwing can lead to scapular dyskinesia, a recognized cause of shoulder disability in pitchers and overhead athletes. We introduce a novel device, the Xbus Kit, which can objectively assess scapular biomechanics and the effect of pitching on SHR. Methods: SHR was studied using the Xbus Kit (Xsens Technologies B.V., NL). Thirteen collegiate baseball pitchers (aged 20 \ub1 2.6) were studied, evaluating SHR in forward elevation and abduction in three sessions: before throwing (S1), after 60 pitches (S2) and 24 h after a pitching session (S3). Results: SHR changes were found in 85 % of pitchers (11 cases), and no changes were observed in 2 cases (15 %). We were able to subdivide pitchers into four groups, based on their response to pitching. Conclusion: Repetitive movement of pitching leads to SHR changes and sometimes, incomplete restoration of normal shoulder biomechanics. \ua9 2013 Istituto Ortopedico Rizzoli