Posterior Shoulder Capsules Are Thicker and Stiffer in the Throwing Shoulders of Healthy College Baseball Players A Quantitative Assessment Using Shear-Wave Ultrasound Elastography

Background:Posterior and posteroinferior capsulesin the shoulder jointsof throwing athletes have been reported to be thicker in throwing than nonthrowing shoulders, and this has a relationship to glenohumeral internal rotation deficit (GIRD). However, the stiffness of these thickened capsuleshas not been reported. Shear-wave ultrasound elastographyis a new technology that can measure tissue elasticity quantitatively.Hypothesis:The posterior and posteroinferior capsulesare stiffer as well as thicker in the throwing shouldersof baseball players than in their nonthrowing shoulders. The thickness and elasticity of these capsulesare inversely correlated with glenohumeral internal rotation.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Forty-five male college baseball players were examined. The thickness and elasticity of the posterior capsulebeneath the infraspinatus and the posteroinferior capsulebeneath the teres minor were measured using an ultrasonic device equipped with shear-wa...