Summary

Increased contralateral trunk tilt among pitchers with an ulnar collateral ligament injury history may occur to increase pitch velocity at the expense of ball movement, while placing the pitching elbow in a potentially injurious position.

Abstract

Purpose

The anterior ulnar collateral ligament (UCL) bundle is the most important non-contractile elbow valgus stress stabilizer during pitching. The annual rate of UCL reconstruction is increasing, with up to 25% of major league baseball pitchers having undergone surgical repair or reconstruction. This study retrospectively compared the fastball profiles of pitchers who had sustained previous grade I or II ulnar collateral ligament (UCL) injuries, were rehabilitated, and released back to competition with pitchers that had no previous elbow injury history. The hypothesis was that pitchers with an injury history (Group 1) would display differing fastball velocity – ball movement relationships compared to those who did not (Group 2).

Methods

Eighteen pitchers from one NCAA Division III team participated in this study. Group 1 had a grade I or II UCL injury history (n = 8), and Group 2 (n = 10) did not. A computerized pitch tracking device (CPTD) analyzed ball movement and pitching mechanics during live pitching intra-squad games.

Results

Groups had similar height, weight, pitching experience, and arm slot positions at ball release. Pitching coach determined pre-injury arm slot position identification and post-injury CPTD measurements after return to competition displayed strong agreement (r = 0.83, p = 0.05) suggesting comparable pitching techniques before and after the index UCL injury. Group glenohumeral joint range of motion and fastball profiles were comparable with the exception of Group 1 releasing the ball at a 2.5 times lesser horizontal distance away from the pitching rubber center. Group 2 also displayed consistently more robust and more frequent fastball movement relationships with velocity, horizontal break, and vertical break than Group 1.

Conclusion

Reduced horizontal ball release distance at comparable vertical ball release height without arm slot position changes suggest that pitchers with a grade I or II UCL injury history had greater contralateral trunk tilt and greater elbow flexion at ball release. Increased contralateral trunk tilt may represent an attempt to increase pitch velocity at the expense of ball movement, while placing the pitching elbow in a potentially injurious position. Computerized fastball profile analysis using a CPTD in conjunction with coach pitching technique observation, and team medical staff clinical examination may help better identify pitchers who are at increased UCL injury risk so that preventative interventions can be initiated earlier.