Association of shoulder girdle function and glenohumeral joint alignment with pain during throwing in cases of shoulder posterosuperior impingement.

Background: No study has compared shoulder girdle function or glenohumeral joint alignment during shoulder abduction and external rotation in baseball players with posterosuperior impingement (PSI) with and without pitching-related shoulder pain. This study aimed to clarify factors associated with shoulder pain during throwing in players with PSI. Methods: This retrospective observational study enrolled 53 professional or nonprofessional baseball players who visited our orthopedic department for a checkup. The upper thoracic movement, scapular upward rotation angle, humeral elevation angle, glenohumeral joint horizontal abduction angle in the shoulder abduction/external rotation position, and the presence/absence of shoulder pain during throwing were examined. The presence/absence of PSI was assessed using oblique axial magnetic resonance images during shoulder abduction and external rotation. Data were compared between the pain and no-pain groups. Factors associated with shoulder pain during throwing were identified using logistic regression analysis. Results: All participants had PSI findings on magnetic resonance images (pain group, n = 34; no-pain group, n = 19). The pain group showed lesser upper thoracic movement than no-pain group ( Conclusion: Among baseball players with PSI findings, decreased upper thoracic movement may be associated with shoulder pain during throwing, whereas the association with increased glenohumeral horizontal abduction is more suggestive and should be interpreted cautiously.