Identifying the underlying mechanisms responsible for glenohumeral internal rotation in professional baseball pitchers

• Published in: JSES international 2023-01, Vol.7 (1), p.138-142
• Main Authors: Paul, Ryan W., Erickson, Brandon J., Cohen, Steven B., Ciccotti, Michael G., Hefta, Michael, Buchheit, Paul, Rauch, Joseph, Fcasni, Shawn, Plum, Alex, Hoback, Aaron, Thomas, Stephen J.
• Format: Article
• Language: English
• Subjects: Injury prevention; Internal rotation; Pitching; Rotator cuff; Shoulder; Ultrasound
• ISSN: 2666-6383; 2666-6383
• DOI: 10.1016/j.jseint.2022.09.005

Glenohumeral internal rotation deficit has been identified as a significant risk factor for upper-extremity injuries in pitchers across all ages. Humeral retroversion (HR), posterior capsule thickness (PCT), and posterior rotator cuff muscle pennation angle (PA) have been independently associated with internal rotation range of motion (IR ROM); however, these anatomic structures have not been collectively measured in baseball pitchers to determine the underlying mechanisms responsible for IR ROM. Therefore, the purpose of this study was to determine the contributions of HR, PCT, and posterior rotator cuff PA on IR ROM during a preseason evaluation in healthy professional baseball pitchers. The authors hypothesized that HR, PCT, and posterior rotator cuff PA would have a significant contribution to IR ROM. This is a cross-sectional study. Healthy professional pitchers from a single organization were recruited at the beginning of the 2021 Major League Baseball Spring Training. Participants received bilateral IR ROM assessment while laying supine with the shoulder at 90 degrees of abduction and the scapula stabilized. Ultrasound imaging was also performed bilaterally to assess HR, PCT, infraspinatus (superficial + deep) PA, and teres minor (superficial + deep) PA. All ultrasound imaging processes were performed utilizing previously published, highly reliable techniques. A stepwise regression was performed, which included both arms to determine the mechanisms of IR ROM. Overall, 49 pitchers (88 shoulders) with an average age of 22.5 ± 2.2 years were included in the final data analysis. Stepwise linear regression found that only HR and PCT were associated with the preseason IR ROM. There was a moderate relationship between HR and PCT relative to IR ROM (R = 0.535, P