Relationship Between Humeral Torsion and Injury in Professional Baseball Pitchers

Abstract

A strong relationship was found between lower degrees of dominant humeral torsion and more severe upper extremity injuries as well as a trend relating lower side-to-side differences in torsion with more severe dominant upper extremity injuries. In addition, there was a higher incidence of severe injuries in players with lower degrees of dominant torsion. If future studies confirm these results, humeral torsion measurements could play a role in risk assessment in pitchers.

A Proposal for Functional Screening of the Throwing Kinetic Chain in Baseball Pitchers to Assess Shoulder and Elbow Injury Risk

“…26 Polster, et al demonstrated a 30% reduction in injury risk for every 10° of humeral retroversion of the dominant arm compared to the non-dominant arm. 25 These results suggest that GIRD due to osseous torsion may be advantageous for pitchers as humeral retroversion will allow the thrower to move through a longer throwing arc and achieve greater throwing velocity without additional physical stress to the glenohumeral joint and its supporting structures. 25 Total Rotational Motion (TRM), defined as the sum of passive glenohumeral external rotation and internal rotation at 90° of abduction in the plane of the scapula, is considered deficient if there is a side-to-side difference of more than 5°.…”

“…25 These results suggest that GIRD due to osseous torsion may be advantageous for pitchers as humeral retroversion will allow the thrower to move through a longer throwing arc and achieve greater throwing velocity without additional physical stress to the glenohumeral joint and its supporting structures. 25 Total Rotational Motion (TRM), defined as the sum of passive glenohumeral external rotation and internal rotation at 90° of abduction in the plane of the scapula, is considered deficient if there is a side-to-side difference of more than 5°. 6 The odds ratio for the development of a shoulder or elbow injury in a pitcher with a TRM deficit was 2.5 and 2.6 respectively, and both were found to be statistically significant.…”

“…6,11,25 Historically, GIRD was thought to be a primary contributing factor to both shoulder and elbow injuries in overhead throwing athletes due to the concomitant hyperexternal rotation associated with the loss of internal rotation. GIRD has been attributed to tightness in the posterior glenohumeral joint capsule, myofascial restrictions, laxity of anterior glenohumeral joint capsule, and osseous changes that result in humeral retroversion.…”

“…Humeral retroversion is due to the torque placed on the humerus with throwing during skeletal maturity resulting in apparent increases in external rotation with loss of internal rotation without true changes at the glenohumeral joint. 25 Due to recent scientific evidence demonstrating that throwing athletes with GIRD do not exhibit capsular limitations, the latter theory has gained more popularity. 6,26 Humeral retroversion and GIRD is normal and advantageous for the overhead pitcher, and may not be an adequate predictor of injury.…”

“…25 Pitchers with GIRD are just as likely to develop an elbow injury as those without GRID (odds ratio=1.0).…”