Preserved Active Spin and Reduced Workload After Ulnar Collateral Ligament Reconstruction in Major League Baseball Pitchers: A Propensity-Matched Analysis of 8 Pitch Types
Dustin J. Kress, Cole S. Garrett, James Lee, Kyle Cantave, Carissa Zhu, Julia R. Hong, Ajith MaligeBackground:
Prior studies report preservation of total spin rate after ulnar collateral ligament reconstruction (UCLR). Total spin includes a gyroscopic component that generates no pitch movement, and the movement-producing fraction varies by pitch type. Direct measurement of that fraction became possible only in 2020, and no prior study has quantified active spin rate after UCLR.
Purpose/Hypothesis:
The purpose was to determine whether active spin rate is preserved after UCLR across the pitching arsenal, using data restricted to the optical tracking era and propensity-matched controls. The authors hypothesized that preservation would extend across pitch types rather than being confined to the fastball.
Study Design:
Cohort study; Level of evidence, 3.
Methods:
The authors identified 456 professional pitchers who underwent primary UCLR between 2020 and 2024 and linked each to major league pitch-tracking data by player identifier. Pitchers required at least 100 tracked pitches in a qualifying index and postreturn season. Active spin percentage was taken from the directly measured 3-dimensional spin vector, and active spin rate was derived as its product with total spin for 8 pitch types. Controls without recorded UCLR were matched on age, Major League Baseball experience, index expected fielding independent pitching, and 4-seam velocity, with exact constraints on hand, role, and season.
Results:
Sixty-one pitchers met inclusion criteria, and 52 were matched to 153 controls. Four-seam active spin rate did not differ between groups (2094 vs 2078 rpm;
Conclusion:
Active spin rate was preserved after UCLR across all 8 pitch types examined, and neither fielding independent pitching nor earned run average differed from uninjured peers in the same seasons. The first-season deficit was confined to workload and resolved by the second season.