Impact of changes in pitch limit guidelines on position distribution and capitellar OCD in youth baseball: A 6-year cohort study.

OBJECTIVES

To evaluate changes in position distribution and capitellar osteochondritis dissecans detected at annual screening before and after the 2019 introduction of pitch limit guidelines, focusing on dual-role players.

DESIGN

Retrospective observational study using an interrupted time series design.

METHODS

Annual ultrasonography screening was performed from 2017 to 2023 in 1576 players aged 10-12 years. Players were classified as pitcher, catcher, or dual-role. Position distribution was analyzed using interrupted time series binomial models; chi-square tests were used for supplementary comparisons. Osteochondritis dissecans was analyzed using interrupted time series Poisson regression with an offset for the annual number screened and 95% confidence intervals. Worst-case sensitivity analyses assumed all missing confirmatory examinations were osteochondritis dissecans; analyses were repeated in males only.

RESULTS

Catcher proportion decreased from 21.2% to 15.6% in a supplementary pre-post comparison (p = 0.011). Dual-role players accounted for 18.1% pre-guideline and 22.3% post-guideline and increased from 17.4% in 2017 to 26.1% in 2023 (p = 0.040). Overall osteochondritis dissecans was 3.6% pre-guideline and 1.8% post-guideline (p = 0.055); among dual-role players, 6.7% and 1.9% (p = 0.083). In Poisson interrupted time series using confirmed cases only, no significant level change was detected (incidence rate ratio 0.53, 95% confidence interval 0.09-3.00). Under the worst-case assumption, guideline introduction was associated with an immediate decrease in overall osteochondritis dissecans (incidence rate ratio 0.15, 95% confidence interval 0.035-0.64). Findings were consistent in males only.

CONCLUSIONS

Guideline introduction coincided with fewer catchers and more dual-role players, while osteochondritis dissecans detected at annual screening did not show evidence of an increase among dual-role players.