Ultrasound Shear Wave Elastography for Assessing Ulnar Nerve Stiffness During Elbow Valgus Stress: Cross-Sectional Study

Understanding the relationship between valgus stress on the medial elbow and ulnar nerve strain during shoulder external rotation is essential for preventing and managing ulnar neuropathies, particularly in athletes. This observational cross-sectional study aimed to assess ulnar nerve stiffness changes under varying levels of valgus stress at two primary nerve entrapment sites. Twenty healthy baseball players participated, with stiffness measured on the throwing side at two locations: the arcade of Struthers (proximal site) and Osborne’s ligament (distal site). Measurements were taken at elbow flexion angles of 0°, 60°, and 90° using shear wave elastography with a 10-MHz linear transducer. To simulate increasing levels of valgus stress, a Telos stress device was applied at 0, 30, 50, and 70 N to the medial elbow. Results showed that at all measured flexion angles, ulnar nerve stiffness significantly increased as valgus stress intensified, with the greatest stiffness observed under 70 N stress. Notably, the proximal site (arcade of Struthers) exhibited higher stiffness compared to the distal site (Osborne’s ligament), suggesting that the nerve at the proximal site may be more susceptible to strain under valgus stress. These findings highlight the impact of valgus stress on ulnar nerve stiffness, with increased stress correlating to heightened stiffness, particularly at the proximal entrapment site. This information may be valuable in the development of targeted training or rehabilitation techniques for athletes exposed to repetitive valgus stress, as well as in the early identification of potential risk factors for ulnar neuropathies. Overall, this study underscores the importance of shear wave elastography as a precise, non-invasive tool for evaluating ulnar nerve biomechanics under stress, offering insights into both prevention and management strategies for elbow-related nerve injuries.