Quantification of Ulnar Nerve Elastic Modulus Using Shear Wave Elastography: A Study of Sex Differences in Healthy Adults

Background: In recent years, there has been a growing interest in the use of shear wave elastography (SWE) to evaluate neuromuscular lesions and follow-up treatment progress. SWE is a technique used to measure tissue stiffness; however, the factors influencing the elastic modulus obtained by SWE, as well as the reliability of the measured values, have not been sufficiently examined. This study introduces a reproducible SWE protocol for assessing the ulnar nerve in healthy adults and investigates differences in elastic modulus by sex, side (left/right), measurement site and the presence or absence of ulnar nerve dislocation. Methods: A total of 48 ulnar nerves of 24 healthy adults were evaluated. The elastic modulus was measured using SWE. The elastic modulus was measured at two locations with the elbow in full extension (0°): 5 cm proximal to the medial epicondyle (ME; upper arm) and 5 cm distal to the ME (forearm). Results: The coefficient of variance for the elastic modulus was <0.05, indicating stable measurement. No significant differences or interactions were observed based on side (left/right), measurement site or ulnar nerve dislocation status. However, a significant sex difference in the ulnar nerve elastic modulus was found (F = 47.74, p < 0.001), indicating that the nerve was stiffer in males than in females. In the elastic modulus distribution, males tended to have a higher median value in the right forearm, whereas females showed significant asymmetry between the left and right forearms. Conclusions: This study established a reproducible SWE protocol and explored sex-based and anatomical differences in ulnar nerve elastic modulus, providing foundational data for future cubital tunnel syndrome (CuTS) diagnostics.