Morphological and positional changes of the carpal arch and median nerve during wrist compression

- Carpal arch and median nerve changes were examined during radioulnar wrist compression.
- Wrist compression decreased the carpal arch width and increased the carpal arch area.
- The median nerve displaced volarly and became more circular under wrist compression.
- Radioulnar wrist compression augments available carpal arch space, potentially alleviating compression of the median nerve.

BackgroundThe carpal tunnel is a fibro-osseous structure containing the median nerve and flexor tendons. Its cross-sectional area has been shown to increase during compressive force application to the carpal bones in modeling and in vitro studies. The purpose of this study was to investigate the morphological and positional changes of the carpal arch and median nerve while in vivo compressive force was applied in the radioulnar direction across the wrist.MethodsUltrasound images of the carpal tunnel and its contents were captured for 11 healthy, female volunteers at the distal tunnel level prior to force application and during force application of 10 and 20 N.FindingsWith applied force, the carpal arch width significantly decreased, while the carpal arch height and area significantly increased (P < 0.001). The median nerve shape became more rounded as the compressive force magnitude increased, reflected by decreases in the nerve's flattening ratio and increases in its circularity (P < 0.001). The applied force also resulted in nerve displacement in the radial-volar direction.InterpretationThis study demonstrates that noninvasively applying radioulnar compressive force across the wrist may potentially provide relief of median nerve compression to patients suffering from carpal tunnel syndrome.