An ultrasound study of the mobility of the median nerve during composite finger movement in the healthy young wrist

Introduction/Aims There is a lack of consensus regarding median nerve movement in the carpal tunnel during composite finger flexion in healthy individuals. In this study we examined the amount and direction of median nerve movement and differentiate nerve mobility between dominant and nondominant sides in a large, healthy, young adult cohort. Methods Sonographic videos of the median nerve during composite finger motion from extension to full flexion were analyzed in 197 participants without median nerve pathology. Displacement of the nerve's centroid was calculated based on a change in the relative location of the nerve. Longitudinal nerve sliding was categorized as none, independently from the tendons, or with the tendons. Results In short axis, median nerves moved within 1 mm vertically and 3 mm horizontally; no direction was predominant. About half of the nerves (52.5%) slid independently while 26.9% slid with the tendons; 21.3% did not slide at all. On the nondominant side, median nerves that slid with the tendons had a larger absolute vertical displacement than nerves that slid independently or did not slide at all (P < .01). Nerves on the dominant side moved in a radial direction more frequently than on the nondominant side (P = .02). Discussion Transverse nerve movement during composite finger flexion in healthy individuals varies widely with no clear pattern in the direction of transverse movement or amount of longitudinal sliding. These data provide a foundation for future research to better understand the biomechanical contribution of nerve movement to median nerve pathologies.