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

Abstract

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.

Keywords: displacement; median nerve; movement; sonography.

Conflict of interest statement

Disclosure of Conflicts of Interest: None of the authors has any conflict of interest to disclose.

© 2021 Wiley Periodicals LLC.

Figures

Figure 1.

Two-dimension kernel density plots demonstrating distribution of endpoint displacement of the median nerves from rest to composite finger flexion for dominant (A) and non-dominant (B) hands. The (0,0) coordinate represents the location of the nerve at rest, and the colors represent the location of the nerve during composite finger movement based on the distribution across the two planes of motion and color intensity representing the density of individuals within a region across the sample (i.e., percentage). The direction and distance of nerve movement were fairly normally distributed around the group mode in the dominant side, whereas nerves on the non-dominant side had increased variability with an increased tendency for nerves to move in an ulnar direction.

Figure 2.

The absolute vertical and horizontal displacement for median nerves with no sliding, sliding independently from the tendons, and sliding with the tendons. The median is represented by the line subdividing the box, and the length of the box thus represents the interquartile range (IQR). *Post-hoc pairwise comparisons with p-value