Risk factor for elbow symptom manifestation in young baseball players with asymptomatic medial elbow abnormalities: a prospective cohort study.

Asymptomatic elbow abnormalities are relatively common in young baseball players, but the factors responsible are unclear. To prospectively identify risk factors related to symptom manifestation in asymptomatic elbow abnormalities, we recruited 573 baseball players (age: 7-14 years) at a pre-participation medical/physical examination in the preseason who were right-handed and had asymptomatic medial elbow abnormalities on ultrasound (US). Baseline preseason and postseason participant characteristics were assessed. A "symptomatic" elbow was defined as an elbow with medial elbow joint problems that prevented ball throwing for ≥ 8 days. After exclusions, 82 players were enrolled, of whom 22 (26.8%) developed a symptomatic elbow. In univariate analyses, the external and internal rotation strengths of the dominant shoulder were significantly greater in the symptomatic group than in the asymptomatic group (P = 0.021). Multivariate logistic regression analysis showed that the internal rotation strength of the dominant shoulder was a significant independent risk factor (odds ratio = 1.091, P = 0.027) for developing a symptomatic elbow. In young asymptomatic baseball players with abnormalities in the medial elbow region of the dominant arm on US, stronger preseason internal rotation strength of the dominant shoulder was a significant independent risk factor for the development of a "symptomatic" elbow.