Stress ultrasound in baseball players with ulnar collateral ligament injuries: additional value for predicting rehabilitation outcome

Abstract

The purpose of this study was to evaluate the additional value of stress ultrasound (US) for predicting rehabilitation outcome in baseball players with ulnar collateral ligament (UCL) injury. Stress US and magnetic resonance imaging (MRI) in 41 baseball players with UCL injury who received rehabilitation treatment for more than 6 weeks were retrospectively compared between the rehabilitation group (n = 23) and surgery group (n = 18). The MRI grade of UCL injury was assessed as intact continuity, low-grade partial tear, high-grade partial tear, and complete tear. To estimate sonographic joint laxity, we assessed 3 sonographic criteria as present or absent: ligamentous waviness, joint gapping, and intra-articular ring-down artifact. In addition, the presence of concomitant tenderness was checked during stress US. The diagnostic validity of MRI with and without stress US was analyzed as a predictor for the rehabilitation outcome. The MRI grade was higher in the surgery group than in the rehabilitation group (P < .001). Sonographic joint laxity showing the ring-down artifact and concomitant tenderness with stress were significantly more frequent in the surgery group (P = .024 and P = .006, respectively). Sensitivity, specificity, and accuracy were 61.1%, 86.9%, and 75.6%, respectively, for MRI alone and 83.3%, 56.5%, and 68.2%, respectively, for the combination of MRI with joint laxity showing the ring-down artifact. For MRI in combination with joint laxity and concomitant tenderness, these values were 72.2%, 82.6%, and 78.0%, respectively. The addition of stress US showing the ring-down artifact and concomitant tenderness was helpful for predicting the rehabilitation outcome of UCL injuries.