The Association between Excessive Glenohumeral External Rotation and Risk for Shoulder and Elbow Injury in Left-Handed High School Baseball Pitchers: A Prospective Cohort Study.

Background: Left-handed baseball pitchers exhibit unique throwing biomechanics, yet the risk factors for shoulder and elbow injuries in this population remain unclear.

Purpose: To prospectively investigate preseason risk factors for shoulder and elbow injuries in left-handed high school baseball pitchers.

Study design: Cohort study; Level of evidence, 2.

Methods: A total of 160 left-handed high school baseball pitchers were enrolled. Preseason evaluations included age, height, weight, shoulder muscle strength, and range of motion of the shoulder and elbow. Participants completed a self-recorded questionnaire on shoulder and elbow pain and associated pitching limitations during the subsequent season. Participants were categorized into the noninjured or injured group. The Mann-Whitney U test, chi-square test, logistic regression analysis, and receiver operating characteristic curve analysis were used to identify injury risk factors and cutoff values for shoulder and elbow injuries.

Results: Shoulder and elbow injuries occurred in 27 participants (16.9%). The injured group had significantly greater abduction-external rotation (ABER) in the dominant shoulder (114.8°± 11.9° vs 107.5°± 13.0°; P = .008) and a greater total arc of the dominant shoulder (166.4°± 25.1° vs 156.0°± 23.4°; P = .039). Logistic regression analysis showed that ABER in the dominant shoulder was an independent risk factor for injuries (P = .031; OR, 1.04). Receiver operating characteristic curve analysis determined that an ABER ≥109° predicted injury (P = .017). Pitchers with ABER ≥109° had a 3.3 times higher incidence of injury than those with ABER <109° (P = .005).

Conclusion: Increased shoulder ABER was significantly associated with shoulder and elbow injuries among left-handed high school baseball pitchers. Pitchers with ABER ≥109° are at higher risk.