Humeral Retroversion and Its Relationship to Glenohumeral Rotation in the Shoulder of College Baseball Players

Background: Previous studies have documented changes in musculature, bony anatomy, and glenohumeral rotation in the dominant shoulder of baseball players. Hypothesis: In a group of asymptomatic college baseball players the total range of motion in the dominant and nondominant shoulders will be similar. Any measured increase in external rotation and decrease in internal rotation occurring between the two sides will be consistent and directly correlate with an increased angle of humeral retroversion in the dominant extremity. Study Design: Descriptive anatomic study. Methods: Fifty-four asymptomatic college baseball players were examined. Standard measurements of glenohumeral range of motion were made and humeral retroversion was determined radiologically. Results: Total rotational motion, measured at 90° of glenohumeral abduction, was 159.5° for the dominant shoulders and 157.8° for the nondominant shoulders. Mean differences in external and internal rotation in the dominant versus nondominant extremities were 9.7° and 8.2°, respectively. Humeral retroversion measured 36.6° ± 9.8° in the dominant and 26° ± 9.4° in the nondominant extremity. The mean difference in retroversion correlated significantly by Pearson’s product moment with the difference in external ( P = 0.001) and internal ( P = 0.003) rotation measurements. Conclusions: There is a pattern of increased external rotation and decreased internal rotation in the dominant extremity that significantly correlates with an increase in humeral retroversion. The loss of internal rotation and gains in external rotation may be more strongly related to adaptive changes in proximal humeral anatomy than to changes in the soft tissues.