Summary

There have been various reports about shoulder injuries of young baseball players, however few reports focusing on the gender differences. This is the first report based on a large-scale survey.

Abstract

Aim

There have been various reports about injuries of young baseball players. However few reports focusing on the gender differences. It has been reported that there are differences in some sports injuries between male and female players. The purpose of this study was to assess the injuries of young baseball players focusing on the gender differences. Subjects were 3188 young baseball players aged 7 to 12 years (mean, 10.3±1.3 years) who participated in medical check-ups from 2010 to 2018. 3067 (96.2%) were male and 121 (3.8%) were female. We compared the rates of injuries between male and female players using a questionnaire, physical examination and ultrasonography.

Results

There were significant differences in the age introduced to baseball (male, female; 8.1y, 8.5y), the duration of competitive play (29.6m, 21.9m) and the weight (34.6kg, 32.5kg). Regarding the position, the rate of fielder was higher in female (88.4%) than in male (69.5%). Male and female players had shoulder pain while pitching at present (3.7%, 3.3%), shoulder pain in the past (10.4%, 9.8%), tenderness of the proximal humeral physis (4.8%, 4.1%), Hyper external rotation test (2.7%, 3.3%), elbow pain while pitching at present (4.3%, 1.6%), elbow pain in the past (15.0%, 13.9%), restricted ROM of elbow (10.7%, 9.1%), tenderness of the medial epicondyle (7.9%, 9.8%), valgus test (8.0%, 11.5%), osteochondritis dissecans (1.4%, 0.0%) respectively, and there were no significant differences. However, there were significant differences in morphological irregular of the medial epicondyle (24.5%, 9.8%) and in softball throwing distance (35.3m, 28.1m). Multivariate analysis of these variables showed that only softball throwing distance 30m (Odds ratio, 4.83; 95% CI, 1.53-15.2) was risk factor significantly associated with morphological irregular of the medial epicondyle.

Conclusion

This study clarified that there are no significant differences between male and female players and suggested that overlord of the elbow was the most important factor of injuries regardless of gender.