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Baseball players with UCL tears had increased humeral torsion in nondominant arm
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Recently published results showed greater nondominant limb humeral torsion values and greater humeral retrotorsion side-to-side limb differences among high school and collegiate baseball players with an ulnar collateral ligament tear of their dominant arm.
Researchers measured dominant arm humeral retrotorsion and nondominant arm humeral retrotorsion in 112 male competitive high school and collegiate baseball players. According to researchers, 56 participants with a clinical and MRI-confirmed diagnosis of a throwing-arm ulnar collateral ligament (UCL) tear were matched for age, experience and position with 56 healthy baseball players who no history of an elbow injury. Researchers measured dominant arm humeral retrotorsion and nondominant arm humeral retrotorsion in the supine position using a previously validated ultrasound method and calculated the humeral retrotorsion side-to-side difference.
Results showed significantly more humeral torsion in the nondominant arm of baseball players with a UCL tear vs. healthy baseball players. However, researchers noted no differences in dominant arm humeral retrotorsion between players with a UCL tear and healthy baseball players. Both groups had significant side-to-side differences in humeral retrotorsion, according to results. – by Casey Tingle
Disclosures: Meyer reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.
Perspective
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Peter N. Chalmers, MD
The extreme shoulder external rotation required for pitching is acquired developmentally partially through increasing retroversion of the humerus during growth. In this recently published study by Dr. Conway’s group in Fort Worth, Texas, humeral version was measured bilaterally in matched cohorts of adolescent pitchers with and without ulnar collateral ligament (UCL) tears. In this study, there were no differences in humeral retroversion in the dominant arms of injured and noninjured pitchers. However, pitchers with UCL injuries had significantly less humeral retroversion in their nondominant arms. These findings suggest that those who start with a less retroverted humerus must go through a great degree of remodeling to reach the necessary retroversion to achieve external rotation. During this remodeling process, pitchers with less starting retroversion place more stress on the upper extremity, which in turn leads to UCL tears.
In addition to aiding in the understanding of the pathophysiology of UCL tears, this study helps to identify an additional risk factor for injury — decreased non-dominant humeral retroversion. Future work will be necessary to understand how to mitigate this anatomic risk factor, as well as the importance of this risk factor relative to previously described risk factors, such as pitch counts and pitch velocity.
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