Incidence and Characteristics of Elbow Injury in Japanese Youth Baseball Players: Comparison Between 2011 and 2021

Background: Little League elbow, including humeral epicondylitis and osteochondritis dissecans, is a severe throwing injury in school-aged pitchers. Recent rule revisions have been implemented, and thus, prevention awareness may have increased.Purpose: To compare the incidence of elbow injury in 2011 from a previous study with that in 2021 and examine changes in the incidence and characteristics of players with elbow injuries.Study Design: Cross-sectional study; Level of evidence, 3.Methods: A survey based on the 2011 survey was conducted from September 1 to December 31, 2021, among 4060 third- to sixth-grade Little League players belonging to 203 teams in Kyoto, Japan. This survey included a 23-item checklist on physical condition and injury. The participants were classified into 2 groups according to the presence or absence of an elbow injury in the dominant arm during the season. The Wilcoxon rank-sum test was conducted to compare differences in basic information between the 2 groups. We also compared the differences in the 23 checklist items between the 2 groups using the chi-square or Fisher exact probability test.Results: Overall, 98 teams (1335 players; age range, 8-12 years) returned the questionnaires (collection rate, 32.9%). The final analysis population (excluding incomplete questionnaires) was 678 (mean age, 10.6 +/- 1.1 years). Elbow injuries accounted for 30.7% of all injury sites in the players. Overall, 61 players (9.0%) reported elbow injuries in 2021 compared with 19.1% of the players in the 2011 survey (P < .01) A significantly higher percentage of players with elbow injuries had elbow pain in extension (item 2 on the survey checklist, P < .001) and flexion (item 4, P < .0024), were regular players (item 5, P = .0288), played baseball under fatigue (item 8, P = .0028), and had lower and upper limb inflexibility (item 17, P = .0379; item 18, P = .0146; and item 22, P = .0085).Conclusion: Study findings indicated that the incidence of elbow injuries has decreased significantly over the past 10 years, although the elbow joint still accounted for almost one-third of all injuries in Japanese youth baseball players.