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Randomized Controlled Trial
. 2017 Sep 28;59(5):408-417.
doi: 10.1539/joh.17-0058-OA. Epub 2017 Jul 13.

Impact of keyboard typing on the morphological changes of the median nerve

Ping Yeap Loh  1   2 , Wen Liang Yeoh  3 , Hiroki Nakashima  3 , Satoshi Muraki  1
Affiliations
Randomized Controlled Trial

Impact of keyboard typing on the morphological changes of the median nerve

Ping Yeap Loh et al. J Occup Health. .

Abstract

Objectives: The primary objective was to investigate the effects of continuous typing on median nerve changes at the carpal tunnel region at two different keyboard slopes (0° and 20°). The secondary objective was to investigate the differences in wrist kinematics and the changes in wrist anthropometric measurements when typing at the two different keyboard slopes.

Methods: Fifteen healthy right-handed young men were recruited. A randomized sequence of the conditions (control, typing I, and typing II) was assigned to each participant. Wrist anthropometric measurements, wrist kinematics data collection and ultrasound examination to the median nerve was performed at designated time block.

Results: Typing activity and time block do not cause significant changes to the wrist anthropometric measurements. The wrist measurements remained similar across all the time blocks in the three conditions. Subsequently, the wrist extensions and ulnar deviations were significantly higher in both the typing I and typing II conditions than in the control condition for both wrists (p<0.05). Additionally, the median nerve cross-sectional area (MNCSA) significantly increased in both the typing I and typing II conditions after the typing task than before the typing task. The MNCSA significantly decreased in the recovery phase after the typing task.

Conclusions: This study demonstrated the immediate changes in the median nerve after continuous keyboard typing. Changes in the median nerve were greater during typing using a keyboard tilted at 20° than during typing using a keyboard tilted at 0°. The main findings suggest wrist posture near to neutral position caused lower changes of the median nerve.

Keywords: carpal tunnel syndrome; keyboard typing; median nerve; ultrasound.

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Conflict of interest statement

Conflicts of interest: The authors declare that there are no conflicts of interest.

Figures

Fig. 1.
Fig. 1.
Quantification of the (a) median nerve cross-sectional area using the tracing method and (b) median nerve diameter using the minimum bounding rectangle method.
Fig. 2.
Fig. 2.
Wrist kinematic changes in all the conditions. (a), (c): right wrist; (b), (d): left wrist. Flex: flexion, Extn: extension; RD: radial deviation; UD: ulnar deviation. The mean wrist angle is presented at 10-min intervals.
Fig. 3.
Fig. 3.
Median nerve cross-sectional area (MNCSA) changes in all the conditions. (a) right wrist; (b) left wrist.
Fig. 4.
Fig. 4.
Median nerve diameter (D1 and D2) changes in all the conditions. (a), (c) right wrist; (b), (d) left wrist.
See this image and copyright information in PMC

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