The Effect of Static Wrist Position on Median Nerve over Six Hours

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, caused by the compression of the median nerve in the carpal tunnel over the wrist. The purpose of this study is to demonstrate how different wrist positions change median nerve image and their corresponding results of nerve conduction study (NCS). In this study, we investigated 40 normal wrists and 32 wrists with CTS. In both groups, subjects were randomly assigned to wear a splint, and the wrist was placed at 0, 15, 30 and 45 degrees of extension. Ultrasonography was performed before splinting, immediately after splinting and repeated again 2, 4 and 6 hours later. Ultrasonographic examination evaluated the flattening ratio and cross-sectional area of the median nerve at carpal tunnel. NCS was performed before splinting and repeated again 2, 4 and 6 hours later. The motor and sensory components of nerve conduction over median nerve were tested. The results showed that the neutral position was associated with the lowest median nerve compression over time. All the extended wrist positions were associated with significant median nerve flattening at the proximal carpal tunnel level. But there were no significant electrophysiological differences between different wrist positions. The proper wrist position is a very important factor in preventing median nerve compression, and the ultrasonographic finding is more sensitive for earlier detection concerning median nerve compression.