Wrist squareness and median nerve impairment.

Previous research indicated that a wrist-squareness ratio (thickness/width) greater than .7 is likely to indicate a median nerve sensory latency greater than 3.7 ms, usually a predictor of carpal tunnel syndrome (CTS). In this study, wrist thicknesses and widths were measured and wrist-squareness ratios were calculated for a sample of 417 railroad maintenance workers. Electrodiagnostic testing, in accordance with American Academy of Electrodiagnostics Medicine guidelines, was performed on both motor and sensory fibers of the median nerve to evaluate subjects for the presence of median nerve impairment typical of CTS. Results of this study indicate that wrist squareness is not a useful predictor of median nerve impairment typical of CTS in the railroad maintenance workers tested.