The deformation and longitudinal excursion of median nerve during digits movement and wrist extension

The use of electronic devices, such as mobile phones and computers, has increased drastically among the young generation, but the potential health effects of carpal tunnel syndrome (CTS) on university students has not been comprehensively examined. Thirty-one university students aged 18 to 25y with no symptoms of CTS were successfully recruited in this study. By using noninvasive ultrasonography, the morphological characteristics of the median nerve of each volunteer, and the extent of its longitudinal excursion movement under experimental conditions, in which a real operating environment of electronic devices was simulated, were quantified. The results demonstrated that the median nerve at the carpal tunnel inlet was flattened during wrist extension: the flattening ratio increased from 3.40±0.91 at the neutral position to 4.10±1.11 at the angle of 30° and 4.09±1.11 at the angle of 45°. In addition, the median nerve became swollen after the students performed rapid mobile-phone keying for 5min, indicated by a significant increase in the cross-sectional area from 6.05±0.97mm2to 7.56±1.39mm2. Passive longitudinal excursion was observed at the median nerve when the students performed mouse-clicking (2.4±1.0mm) and mobile-phone keying tasks (1.7±0.6mm), with the mouse-clicking task generating a greater extent of longitudinal excursion than the mobile-phone keying task did. In conclusion, the findings of the present study verify the potential harm caused by using electronic devices while maintaining an inappropriate wrist posture for a substantial period.