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Published 11/21/2020
Kerri Fitzgerald

Limiting Pitch Count Reduces Elbow Injuries in Young Pitchers

Editor’s note: The following content was originally scheduled for the AAOS Now Daily Edition, which publishes each year onsite at the AAOS Annual Meeting, but this year’s meeting in March was canceled due to COVID-19. Despite the cancellation, members can access virtual content from the Annual Meeting by visiting the Academy’s Annual Meeting Virtual Experience webpage at aaos.org/VirtualAAOS2020.

Limiting pitch count in youth baseball pitchers resulted in decreased elbow injuries, according to a paper that was presented by Tetsuya Matsuura, MD, a professor in the Department of Orthopaedics at Tokushima University in Japan, as part of the Annual Meeting Virtual Experience.

High pitch counts, pitch velocity, pitching year-round, geography, loss of shoulder motion, elbow torque, sports specialization, and other factors have been associated with increased risk of injury for pitchers. With the incidence of elbow injuries increasing, pitch limits have been implemented in various countries to prevent throwing injuries.

In 2018, the local baseball federation in Japan made a rule that the number of pitches per day must be limited to 70 for players aged 12 years or younger. To assess the effectiveness of the rule, researchers enrolled 719 youth baseball pitchers (aged 9–12 years) in a study, including 352 pitchers from before introduction of the rule and 367 pitchers from after the rule’s implementation. No pitchers had thrown curveballs or sliders, and all had thrown fastballs or changeups.

Participants completed a questionnaire that asked whether they experienced any episodes of elbow pain during the season, as well as data on age, length of baseball experience, height, weight, and pitch counts per week. They also underwent physical examination, which encompassed range of motion (ROM), tenderness, and valgus stress test.

Elbow pain occurred in 31.9 percent of players following the rule change compared to 40.9 percent of players before the rule change, representing a significant difference (P ˂ 0.05). Limitation of flexion also improved from 19.0 percent to 10.6 percent after the rule change (P ˂ 0.01). Researchers observed no significant between-group differences in limitation of extension, tenderness, or valgus stress test. The researchers noted their surprise that the pitch-count limitation did not decrease positive valgus stress testing.

Prior to the rule change, the following risk factors were significantly associated with elbow pain: 12 years of age (odds ratio [OR], 2.05; 95 percent confidence interval [CI], 1.12–3.49) and baseball experience of ≥ 54 months (OR, 2.25; 95 percent CI, 1.20–4.28). Tables 1 and 2 show outcomes before and after the rule change.

“In this study, the physical examination did not include factors such as glenohumeral internal rotation deficit, loss of full ROM at the shoulder, humeral retroversion, scapular dysfunction, muscle tightness in the lower extremities, and balance deficits when standing on one leg,” Dr. Matsuura told AAOS Now. “Greater emphasis is now placed on variations in these physical factors as potential contributors to an increased risk of injury,” and he said these might be important factors to study further.

The study is limited by its retrospective cohort design and use of patient-reported information. In addition, the exact causes of elbow pain could not be objectively confirmed.

Dr. Matsuura’s coauthors of “Pitch Count Limitation in Youth Baseball Pitchers Decrease the Elbow Injuries” are Toshiyuki Iwame, MD; and Koichi Sairyo, MD.

Kerri Fitzgerald is the managing editor of AAOS Now. She can be reached at kefitzgerald@aaos.org.