Correlation of range of motion and glenohumeral translation in professional baseball pitchers

Background: Altered mobility patterns in the throwing shoulders of professional baseball pitchers have been reported. Most published reports examining glenohumeral laxity have not used an objective testing device. Objective: Quantify and compare glenohumeral translation and rotational range of motion between the throwing and non-throwing shoulders in professional baseball pitchers. Study Design: Descriptive laboratory study. Methods: Force-displacement and range of motion measures were performed bilaterally on 43 asymptomatic professional baseball pitchers. Ultrasound imaging was used to measure glenohumeral translations under stressed and unstressed conditions. Results: No significant difference in translation was found between the throwing and nonthrowing shoulders. For both shoulders, posterior translation (5.38 +/- 2.7 mm) was significantly greater (P < .001) than was anterior translation (2.81 +/- 1.6 mm). External rotation in the throwing shoulder was significantly greater than that in the nonthrowing shoulder (P < .001), whereas internal rotation in the throwing shoulder was significantly less than that in the nonthrowing shoulder (P < .001). The total arc of rotation for the throwing shoulder was not significantly different than that for the nonthrowing shoulder, and correlation coefficients were poor between rotational and translational range of motion in the throwing shoulder, ranging from r = 0.232 to 0.209 between variables. Conclusion: No significant difference in glenohumeral translation exists between the throwing and nonthrowing shoulders in asymptomatic professional baseball pitchers, posterior translation is significantly greater than anterior translation in the throwing shoulders of professional baseball pitchers, and glenohumeral translation is not related to rotational range of motion in the throwing shoulders of professional baseball pitchers. Clinical Relevance: Altered mobility patterns in asymptomatic professional baseball pitchers may be due to factors other than capsular adaptive changes.