Little Leaguer’s Shoulder Caused Severe Humeral Retroversion: Ultrasonographic Analysis

Abstract

Objectives:The increased humeral retroversion on the dominant side in throwing athletes is thought to result from repetitive throwing motion. In the previous studies, the degree of increased humeral retroversion was various, suggesting that other factors may affect humeral retroversion. Little Leaguer’s shoulder, which is rotational stress fracture of the proximal humeral epiphyseal plate, may change humeral retroversion. The purpose of this study was to investigate effect of Little Leaguer’s shoulder on humeral retroversion.Methods:Ten high-school baseball players (average, 16.6 years; range, 16 to 18 years), who had had Little Leaguer’s shoulder during elementary or junior high schools (average, 12.6 years; range, 11 to 15 years), were enrolled in the study. As a control group, 22 high-school baseball players (average, 16.9 years; range, 16 to 18 years), who have never had shoulder or elbow pain, were included in this study. Humeral retroversion was ultrasonographically measured on the dominant and non-dominant sides. Humeral retroversion was compared between dominant and non-dominant shoulders with paired t-test. Side-to-side difference in humeral retroversion was compared between Little Leaguer’s shoulders and control group with unpaired t-test.Results:Humeral retroversion was significantly greater on the dominant side than on the non-dominant side in both Little Leaguer’s shoulder (Dominant, 104°±8°; Non-dominant, 84°±12°; P < .001) and control groups (Dominant, 91°±13°; Non-dominant, 81°±10°; P < .001). The side-to-side difference in humeral retroversion in Little Leaguer’s shoulder group (20°±10°) was significantly greater than that in control group (10°±10°, P = .02).Conclusion:Humeral retroversion was increased with repetitive throwing motion without any symptom in the shoulder and elbow joint. Additional increase in humeral retroversion was made when the players had had Little Leaguer’s shoulder in elementary or junior high school.