Ultrasound Shear Wave Elastography of the Elbow Ulnar Collateral Ligament: Reliability Test and a Preliminary Case Study in a Baseball Pitcher

Abstract

Overhead throwing athletes are at high risk of the elbow ulnar collateral ligament (UCL) injury, and there is a need for clinical tools to objectively diagnose severity of injury and monitor recovery. Mechanical properties of ligaments can potentially be used as biomarkers of UCL health. The objectives of this study are to evaluate the reliability of shear wave ultrasound elastography (SWE) for quantifying UCL shear modulus in 16 healthy nonthrowing individuals and use this technique to evaluate the difference in UCL shear modulus between the injured and uninjured elbows in a baseball pitcher with UCL tear. In the reliability test, the UCL shear modulus of both elbows of each participant was evaluated by SWE for five trials. The same procedures were repeated on two different days. The intra-day and day-to-day reliabilities were determined by the five measurements on the first day and two averages on the two days, respectively. In the case study, each elbow of the baseball pitcher with UCL tear was tested for five trials, and the average was calculated. The intra-day (intraclass correlation coefficient (ICC) = 0.715, Cronbach's alpha = 0.926) and day-to-day (ICC = 0.948, Cronbach's alpha = 0.955) reliabilities were found to be good. There was no difference between both sides. In the case study, the UCL shear modulus of the injured elbow (186.45 kPa) was much lower than that of the uninjured elbow (879.59 kPa). This study shows that SWE could be a reliable tool for quantifying the mechanical properties and health status of the UCL.