Osseous Adaptation and Range of Motion at the Glenohumeral Joint in Professional Baseball Pitchers

Crockett HC, Gross LB, Wilk KE, Schwartz ML, Reed J, O’Mara J, Reilly MT, Dugas JR, Meister K, Lyman S, Andrews JR. Osseous Adaptation and Range of Motion at the Glenohumeral Joint in Professional Baseball Pitchers. The American Journal of Sports Medicine 30(1): 20-26, 2002

The throwing shoulder in pitchers frequently exhibits a paradox of glenohumeral joint motion in which excessive external rotation (rotation of the axis of the shoulder away from the midline of the body) is present at the expense of decreased internal rotation (rotation of the axis of the shoulder toward the midline of the body). The purpose of this study was to determine the role of humeral head retroversion (displaced or bent backward) in relation to increased glenohumeral external rotation.

Methods

Glenohumeral joint range of motion and laxity along with humeral head and glenoid retroversion of the dominant versus nondominant shoulder were studied in 25 professional pitchers and 25 nonthrowing subjects. Each subject underwent a computed tomography scan to determine bilateral humeral head and glenoid retroversion.

Results

The throwing group demonstrated a significant increase in the dominant shoulder versus the nondominant shoulder. Increased values included humeral head retroversion, glenoid retroversion, external rotation at 90º, and external rotation in the scapular plane. Internal rotation however decreased in the dominant shoulder. Total range of motion, anterior glenohumeral laxity, and posterior glenohumeral laxity were found to be equal bilaterally. Both humeral head retroversion, and external rotation at 90º were significantly greater in the dominant shoulder of the throwing group.