Relationship between humeral retroversion and baseball positions during elementary and junior-high school

Abstract Background Humeral retroversion is greater in the dominant shoulder than in the non-dominant shoulder in baseball players. However, the effect of different baseball positions during childhood on humeral retroversion remains unknown. The purpose of this study was to investigate the following: 1) the relationship between humeral retroversion and baseball positions played during elementary and junior-high schools; 2) the association between humeral retroversion and the prevalence of pain during the medical check and self-reported history of injuries in the dominant shoulder or elbow. Methods We enrolled 149 male high-school baseball players who started playing baseball in elementary school. The subjects were classified into three groups according to their baseball positions in elementary and junior-high schools. All participants completed questionnaires regarding their current and past positions, current incidence and history of injuries in their shoulder or elbow joints, and the age they started playing baseball. Shoulder range of motion, humeral retroversion on ultrasonographic-assisted measurement, and the association between humeral retroversion and shoulder and elbow pain were evaluated. Results Humeral retroversion was significantly greater in the dominant shoulder than in the non-dominant shoulder in all groups (P Conclusion These results suggest that playing baseball as a pitcher during elementary school and junior-high school affects the increase in humeral retroversion in the dominant shoulder. Increased humeral retroversion in the dominant shoulder by repetitive throwing motion is an adaptive change, rather than a pathological change.