Epidemiology of shoulder injuries in young baseball players and grading of radiologic findings of Little Leaguer’s shoulder

Relatively few epidemiological studies have examined shoulder injuries. This study aimed to investigate the epidemiology of such injuries in young baseball players. A total of 2,055 players aged 9-12 years who participated in a regional championship between 1983 and 1985 were the subjects of this investigation. They were assessed by questionnaire and radiographic examination. Prevalence of shoulder pain was determined according to position, years of baseball playing experience, and training hours per week. Radiographic examination was recommended to all players who complained of shoulder pain. Of the 2,055 subjects, 275 (13.4%) reported episodes of pain in the throwing shoulder. Years of baseball experience, but not player position or training hours per week, was significantly associated with shoulder pain. Forty-one of the 275 subjects reporting shoulder pain agreed to undergo radiography and 15 exhibited findings of Little Leaguer’s shoulder. Their lesions could be classified into three distinct grades based on radiographic findings : grade I, widening of the epiphyseal plate in the lateral area (n=9) ; grade II, widening at all areas of the epiphyseal plate and demineralization of the metaphysis (n=5) ; and grade III, a slipped epiphysis (n=1).