Characterization of glenoid bone remodeling in professional baseball pitchers

Objective To characterize the appearance, location, severity, and prevalence of focal glenoid retroversion on shoulder MRI in professional baseball pitchers versus age-matched controls. Materials and methods In this retrospective review, two musculoskeletal radiologists evaluated shoulder MRI examinations from 40 professional baseball pitchers and 40 age-matched controls. Images were scored for the presence of a focal posterior glenoid convexity and the clock face positions involved. A consensus interpretation was also performed. A third reader identified the presence of additional shoulder abnormalities. Results After consensus, 60% (24/40) of pitchers were found to have focal glenoid retroversion versus 20% (8/40) of controls ( p = 0.001). The most apparent location was posterior or posterior-superior, from 7.75 o’clock to 10.5 o’clock (median, 9.75 o’clock; interquartile range, 9.25–10 o’clock). The median clock angle of involvement was greater in pitchers than in controls (30° vs. 0°; p < 0.001). Interreader agreement regarding the presence or absence of focal glenoid retroversion was moderate (Cohen’s kappa, 0.49). Focal glenoid retroversion was more prevalent among subjects with additional shoulder abnormalities ( p = 0.014). Conclusions Glenoid remodeling occurs in the throwing shoulder of professional baseball pitchers and manifests as focally convex morphology of the posterior or posterior-superior glenoid. This type of remodeling does not appear to be associated with a lower prevalence of injuries related to posterior-superior impingement.