Dissecting How Pitching Affects the Glenohumeral Joint

A new study has tackled the subtle, but no less important topic of baseball pitching stressors on the glenohumeral joint.

According to the study authors, “Long-term pitching activity changes the stress distribution across the glenohumeral joint surface; however, the influence of competitive level on stress-distribution patterns remains unclear.”  The study itself, titled “Stress-Distribution Pattern Across the Glenohumeral Joint in Collegiate and Professional Baseball Players: A Computed Tomography Osteoabsorptiometry” appears in the June 3, 2021 edition of the Orthopaedic Journal of Sports Medicine.

The research team used computed tomography (CT) osteoabsorptiometry to evaluate the distribution of subchondral bone density across the glenohumeral joint in collegiate and professional baseball players as well as to determine the effects of pitching activity on the articular surfaces.

Overall, the authors collected CT data from 50 baseball players and 73 of their shoulders. Specifically, the team took CT scans of the dominant-side shoulder for 12 professional pitchers, 15 professional fielders, and both shoulders of 12 asymptomatic collegiate pitchers and 11 collegiate fielders.

The data showed that stress-distribution patterns over the articular surfaces differed between the dominant and nondominant sides in the collegiate pitcher group as well as between both collegiate groups versus the professional pitchers group.

In the collegiate pitcher group, the mean Hounsfield units of the humeral head surface were greater on the nondominant side compared to the dominant side (p = .035). On the dominant side, the mean Hounsfield units of the humeral head surface and glenoid were greater in the collegiate pitcher group versus the professional pitcher group (p = .001 and .027).

“Stress distribution on the articular surface of the glenohumeral joint was affected by pitching ability and competitive level. Our analysis indicates that the traction force on the glenohumeral joint surface might be greater than compression force during pitching.”

“The present findings suggest that pitching activity results in low stress to the articular surfaces of the glenohumeral joint. This supports the notion that mechanical conditions play a crucial role in the etiology of disorders specific to pitching activity.”