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

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.

Retrospective observational study using an interrupted time series design.

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.

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.

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.