The Curse of the All-Star Team: A Single-Season Prospective Shoulder MRI Study of Little League Baseball Players.

Background: Throwing guidelines have been implemented in Little League baseball in an attempt to minimize injuries in young baseball players. We hypothesized that playing pitcher or catcher and increased innings played during the season would result in dominant shoulder magnetic resonance imaging (MRI) abnormalities.

Methods: A prospective evaluation of Little League players aged 10 to 12 years was performed. Players recruited before the start of the season underwent bilateral preseason and dominant shoulder postseason MRI, physical examination, and questionnaires addressing their playing history and arm pain. Innings played, player position, pitch counts, and all-star team selection were recorded.

Results: In total, 23 players were enrolled. The majority (19/23, 82.6%) were right-handed and 16 of 23 (69.6%) played at least 10 innings as pitcher or catcher. Sixteen were selected for the all-star team. Fourteen players (60.9%) had positive dominant shoulder MRI findings not present in their nondominant shoulder. Eight players (34.8%) had new or worsening postseason MRI findings. Thirteen players (81.3%) selected to the all-star team had abnormal MRI findings whereas only one (14.3%) player not selected as an all-star had MRI abnormalities (P=0.005). Year-round play (P=0.016), innings pitched (P=0.046), innings catcher (P=0.039), and number of pitches (P=0.033) were associated with any postseason MRI abnormality, but not for new or worsening MRI changes. Single sport athletes and players playing for multiple teams were significantly more likely to have abnormal MRI findings (P=0.043 and 0.040, respectively) when compared with multisport athletes playing on a single team.

Conclusions: MRI abnormalities involving the dominant shoulder are common in Little League baseball players and often develop or worsen during the season. Contrary to our hypothesis, MRI abnormalities were not associated with player position and pitch counts. Instead, they were most closely associated with year round play, single sports participation, and all-star team selection. The increased demands required for all-star selection comes at a price to the young athlete as the majority of players selected for this honor had abnormal MRI findings in their throwing shoulder while few non all-stars demonstrated such pathology.

Level Of Evidence: Level II.