Effective glenoid version in professional baseball players

The pathomechanics of the throwing shoulder have yet to be fully elucidated. The focus of this study reported here was to further characterize the morphology of the glenoid in a population of elite throwing athletes. We obtained magnetic resonance imaging scans of 38 professional baseball players (dominant shoulders) and of 35 age matched nonthrowing control patients (17 dominant and 18 nondominant shoulders). Seven measurements were made by 3 blinded reviewers on 3 axial images per patient: version of superior glenoid, middle glenoid, inferior glenoid, superior capsulolabral junction, middle capsulolabral junction, inferior capsulolabral junction, and depth of concavity of glenoid in a middle slice. Mean age of the 38 players (24 pitchers, 14 fielders) was 26.8 years, and mean age of the 35 control patients was 27.6 years. Intraclass correlation coefficients ranged from .55 to .84 for the version measurements. There were no statistically significant differences between the pitchers and the fielders on any of the 7 measurements, but such differences were found between the throwers and the dominant-shoulder control patients on all 7 measurements. There were only 2 differences (version of superior glenoid, depth of concavity of glenoid in a middle slice) between dominant- and nondominant- shoulder control patients. There was significantly more retroversion in the osseous and soft tissues of the elite throwing athletes than in the nonthrowing control patients. This increased retroversion may play a role in development of internal impingement in the overhead athlete.