Correlation of Torque and Elbow Injury in Professional Baseball Pitchers

Background: During the pitching motion, velocity is generated by the upper extremity kinetic chain on internal rotation of the shoulder and trunk translational/rotational motion. This generation of power places significant forces and torques on the elbow and shoulder. Elbow valgus torque and shoulder rotational torque are theoretically linked to elbow injury. Hypothesis: Pitchers experiencing higher levels of elbow valgus torque and shoulder external rotation torque throughout the pitching motion are more likely to suffer elbow injury than pitchers with lower levels of torque. Study Design: Cohort study; Level of evidence, 3. Methods: With an established biomechanical analysis model, 23 professional baseball pitchers were videotaped during spring training games and followed prospectively for the next 3 seasons for elbow injury. A mixed statistical model using differences of least squares means and analysis of variance was used to analyze the association between elbow injury and torque levels throughout the pitching motion as well as at each major event within the pitching motion. Results: There were overall statistical trends relating elbow injury with both higher elbow valgus torque (P=.0547) and higher shoulder external rotation torque (P=.0548) throughout the entire pitching motion. More importantly, there was an individual significant correlation of elbow injury with both higher elbow valgus torque (P=.0130) and higher shoulder external rotation torque (P=.0018) at the late cocking phase (pitching event of maximum external rotation of the shoulder). Conclusion: This study provides information that supports existing theories about how and why certain injuries occur during the throwing motion in baseball. The late cocking phase appears to be the critical point in the pitching motion, where higher levels of torque at the shoulder and elbow can result in increased risk of injury. Manipulation of pitching mechanics to alter these torque levels or using these measures to identify pitchers at risk may help decrease injury rates.