Using Stress Ultrasonography to Understand the Risk of UCL Injury Among Professional Baseball Pitchers Based on Ligament Morphology and Dynamic Abnormalities

BACKGROUND: Ulnar collateral ligament (UCL) injury of the elbow is a common and debilitating problem seen frequently among elite baseball pitchers. Ultrasound is a useful diagnostic tool in evaluating UCL injuries. HYPOTHESIS: Evaluation with stress ultrasound of the elbow to measure the morphology of the UCL and the ulnohumeral joint space gapping is indicative of higher risk of UCL injury among professional baseball pitchers. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Ultrasound imaging was used to assess the medial joint laxity of the elbow of 70 asymptomatic professional baseball pitchers during spring training. Medial joint laxity and UCL morphology were assessed with OsiriX imaging software under 2 conditions—gravity valgus load and 5.5 lb of valgus load per a handheld dynamometer—with the shoulder in the maximal cocking position and the elbow in 90° of flexion. Two trials of resting position, elbow gapping, and UCL thickness were collected, measured, and averaged for data analysis. Intra- and interrater reliabilities were established and maintained, with intraclass correlation coefficients in the acceptable range for all measures (0.84-0.99). One-way analysis of variance was used to compare dominant variables between those pitchers who sustained a subsequent UCL injury and those who did not. A receiver operating curve was used to identify pitchers who, based on elbow gapping measures (by cut score), were at high risk versus low risk for UCL injury. RESULTS: Players who went on to injure the UCL (n = 7) displayed a significantly wider opening under 5.5 lb of applied stress (6.5 ± 1.2 vs 5.3 ± 1.2 mm, P = .01) when compared with pitchers without UCL injury history (n = 63); they also presented a trend toward wider dominant arm resting joint opening (4.9 ± 1.2 vs 4.0 ± 1.1 mm, P = .07). Professional pitchers with valgus stress ulnohumeral joint gapping ≥5.6 mm (area underneath the curve, 0.77; P = .02) of the dominant arm were at a 6-times greater risk of sustaining a UCL tear requiring reconstruction within a season. CONCLUSION: Our data suggest that ultrasound evaluation of UCL morphology may be indicative of pitchers who are at risk of sustaining UCL injury and that it may improve player assessment.