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

Abstract

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 25 y 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 mobilephone keying for 5 min, indicated by a significant increase in the cross-sectional area from 6.05 ± 0.97 mm 2 to 7.56 ± 1.39 mm 2 . Passive longitudinal excursion was observed at the median nerve when the students performed mouse-clicking (2.4 ± 1.0 mm) and mobile-phone keying tasks (1.7 ± 0.6 mm), 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.

Effect of Bilateral Versus Unilateral Use of Smartphone on Cross Sectional Area of Median Nerve

“…The results of the present study can be explained 0.582 0.091 by the finding of Lai et al, who suggested that the median nerve became swollen after the students performed rapid mobile phone keying for 5min, indicated by a significant increase in the crosssectional area [14] .…”

“…All participants were requested to sit on a chair facing the examiner with shoulder slightly abducted, the elbow of dominant hand flexed approximately at 90, forearm rested on the table in partially supinated (approximately 45º) to enable them to assume a posture generally applied when using a smartphone for text messaging. During the ultrasound examination, participants were instructed to move their thumb and keep other parts of the hand still when writing on smartphone [13,14] .…”

Ergonomics standards and guidelines for computer workstation design and the impact on users’ health – a review

“…Simoneau and Marklin (2001) recommended that typing with the keyboard at 5cm above elbow height is beneficial compared with placing the keyboard toward the user's lap, because wrist extension can be limited to 15° or less, which would theoretically reduce the risk of carpal tunnel syndrome. Compression of the median nerve at the wrist was also the least when wrist extension was below 15° (Lai et al, 2014).…”

Development of Kinematic Graphs of Median Nerve during Active Finger Motion: Implications of Smartphone Use

“…Indeed, smartphone brings us many conveniences. However, increasing evidence shows that prolonged use of a smartphone, together with inappropriate wrist position, may lead to repetitive strain injury of the wrist, especially when fingers, hands and wrists are overused [ 1 ].…”