Increased Tendon Thickness in Healthy Collegiate Baseball Pitchers Is Associated With Fewer Years of Pitching and Less External Rotation Motion Adjusted for Humeral Torsion.

backgroundMechanistic models of rotator cuff (RC) tendinopathy implicate repetitive loading as a driver of tendon structural changes. Baseball pitchers experience repetitive loading and physical adaptations in shoulder range of motion (ROM) and humeral torsion (HT) that may affect tendon structure and lead to tendinopathy. PURPOSE: To (1) characterize the effect of repetitive loading by determining dominant-to-nondominant arm differences in shoulder ROM, HT, and RC tendon thickness in healthy collegiate pitchers and (2) determine whether side-to-side differences in tendon thickness are associated with shoulder ROM, HT, and self-reported years of pitching experience. STUDY

designCross-sectional. LEVEL OF EVIDENCE: Level 3.

methodsA total of 71 healthy, Division I pitchers were assessed bilaterally for shoulder internal rotation (IR), external rotation (ER), and flexion. HT and RC tendon thickness were measured via ultrasound. ROM measures were adjusted for HT to account for individual differences in bony morphology. Years of pitching was recorded. Paired

resultsAim 1: dominant arms showed greater tendon thickness and ER, and less IR, flexion, and HT (greater retrotorsion) (

conclusionThere are ROM, tendon structure, and HT adaptations in pitchers' dominant arm. Greater tendon thickness was moderately associated with fewer years of pitching and was not significantly associated with less difference in ER ROM-adjusted for HT. CLINICAL RELEVANCE: These findings are hypothesis-generating and support future longitudinal work incorporating exposure to pitching with bony morphology to understand their combined relationship with tendon morphology and potential injury risk.