Medial elbow joint space gapping associated with repetitive baseball pitching in preadolescent baseball players

The baseball pitching motion creates valgus stress to the medial elbow, which contributes to increased medial elbow joint space gapping. The musculoskeletal systems of preadolescent baseball players are immature compared with those of adults, but it is unclear whether the repetitive pitching action causes an increase in medial elbow joint space gapping. This study aimed to examine differences in medial elbow joint space gapping based on the pitch count of preadolescent baseball players compared with those of adult players.

The participants were 11 healthy preadolescent baseball players and 12 college students with baseball experience. They threw 60 maximal-effort pitches arranged into 4 sets of 15 pitches. The medial elbow joint space was measured ultrasonographically with the forearm weight before pitching and following every set of 15 pitches. Repeated-measures analysis of variance and the Bonferroni post hoc test were used to compare the medial elbow joint space among the 5 pitching sets (before pitching and after 15, 30, 45, and 60 pitches) and between the groups of preadolescent baseball players and college students.

There was no significant change in the medial elbow joint space gapping of the dominant elbow based on age/pitch count (F = 0.42, P = .796). There was a significant effect of pitch count (F = 30.28, P < .001) and between-group effects (F = 4.56, P = .045). The medial elbow joint space gapping increased significantly after 60 pitches in preadolescent baseball players (P = .023) and college students (P = .021). The medial elbow joint space gapping in preadolescent baseball players was significantly wider than that in college students (P = .007 before pitching, P = .027 at 15 pitches).

Sixty repetitive pitches contributed to an increase in the medial elbow joint space gapping, regardless of age. The results of this study provide further evidence when considering pitching limitations.