Glenohumeral Laxity in Professional Baseball Pitchers

Abstract

1405 Literature suggests that elite baseball pitchers develop acquired laxity as a result of adaptive changes to the shoulder joint capsule from throwing. Capsular laxity has been implicated in the etiology of micro-instability, mechanical impingement, rotator cuff tendinopathy, and scapular dyskinesis. PURPOSE: To quantify and compare glenohumeral (GH) laxity between the throwing and non-throwing shoulder in professional baseball pitchers. METHODS: Force-displacement measures were performed bilaterally in 33 asymptomatic professional baseball pitchers. Shoulders were positioned at 90° of abduction and 60° of external rotation and a 10-daN (100- N) anterior- and posterior-directed force was applied to the humerus. An ultrasound scanner with transducer was used to dynamically track GH motion during joint loading. Static images were captured at baseline (0-daN) and 10-daN force levels. Using selected bony landmarks measurements of bony position were taken directly from the images and the difference in humeral head displacement was recorded in mm. RESULTS: ANOVA revealed no significant differences (p = .14) in laxity between the throwing (global 7.25mm, anterior 2.39mm, posterior 4.87mm) and non-throwing shoulders (global 7.35mm, anterior 2.45mm, posterior 4.91mm). Posterior translation (4.89mm) was found to be significantly greater (p < .01) than anterior translation (2.39mm). CONCLUSION: We conclude that no significant difference in laxity (anterior, posterior or global) exists between throwing and non-throwing shoulders in professional baseball pitchers, however posterior translation was found to be significantly greater than anterior translation in both shoulders of professional baseball pitchers.Figure: No Caption available.