Humeral Retroversion and Injury Risk After Proximal Humeral Epiphysiolysis (Little Leaguer's Shoulder)

Background: The increased humeral retroversion on the dominant side of throwing athletes is thought to result from repetitive throwing motion. Little Leaguer's shoulder-a rotational stress fracture of the proximal humeral epiphyseal plate-may influence the risk of humeral retroversion and injury of the shoulder or elbow joint.

Purpose: To investigate the effect of Little Leaguer's shoulder on humeral retroversion and the rates of shoulder and elbow injuries.

Study design: Cohort study; Level of evidence, 3.

Methods: 10 high school baseball players (average age, 16.6 years; range, 16-18 years) who had experienced Little Leaguer's shoulder during elementary or junior high school (average age, 12.6 years; range, 11-15 years) were enrolled in the study. As a control group, 22 high school baseball players (average age, 16.9 years; range, 16-18 years) who had never had any shoulder or elbow injury during elementary and junior high school were included. Humeral retroversion on ultrasonographic measurement, shoulder range of motion, and rates of shoulder and elbow injuries were evaluated.

Results: Humeral retroversion was significantly greater on the dominant side than on the nondominant side in both players with Little Leaguer's shoulder (dominant, 104°± 8°; nondominant, 84°± 12°; P < .001) and controls (dominant, 91°± 13°; nondominant, 81°± 10°; P < .001). In the dominant shoulder, humeral retroversion was greater in the Little Leaguer's shoulder group than in the control group (P = .008). When the effects of humeral retroversion were excluded, maximal external rotation was significantly less in the dominant shoulder than in the nondominant shoulder in the Little Leaguer's shoulder group (by 11°± 12°, P = .02), whereas no significant difference was found between dominant (110°± 11°) and nondominant (111°± 13°) shoulders in the control group (P = .64). The rates of shoulder and elbow pain were significantly higher in the Little Leaguer's shoulder group (shoulder pain 80%, elbow pain 70%) than in the control group (shoulder pain 9%, P < .001; elbow pain 32%, P = .04).

Conclusion: Humeral retroversion was increased in baseball players without any history of shoulder or elbow injury during elementary and junior high school and was further increased in players who had had Little Leaguer's shoulder. Increased humeral retroversion after Little Leaguer's shoulder may be a risk factor for future shoulder or elbow injury.