Background:&nbsp;Carpal tunnel syndrome is an entrapment neuropathy at the wrist associated with compromised median nerve longitudinal mobility. The wrist flexion or extension could increase carpal tunnel pressure which was known as one of the key factors that lead to the damage of median nerve. However, there was little literature showing whether wrist position could change the median nerve longitudinal mobility. The purpose of this study was to investigate the effects of wrist flexion or extension on the median nerve longitudinal mobility. We hypothesized that wrist flexion or extension could compromise the median nerve mobility during finger flexion compared to the wrist neutral position.Methods:&nbsp;Dynamic B mode ultrasound images (10 MHz) with 15 Hz frame rate captured longitudinal median nerve motion in the carpal tunnel from 10 healthy subjects with an average age of 24 and standard deviation of 2.3. We obtained the B mode ultrasound images of subjects’ longitudinal median nerve during natural finger flexion at a frequency of 0.5 Hz under wrist neutral position, 30-degree wrist flexion, and 30-degree wrist extension. Longitudinal median nerve displacement of region of interests tracking along the centerline of median nerve between two consecutive frames was calculated in thee ultrasound image sequences using speckle cross-correlation algorithm. Linear regression was conducted on the relationship of accumulative median nerve displacement and time, and the slope was defined as the nerve mobility. One-way analysis of variance (ANOVA) with Tukey’s post-hoc test was used to show the significant difference of median nerve longitudinal mobility among the wrist neutral position, wrist extension and wrist flexion.Results:&nbsp;We found that median nerve longitudinal mobility were significantly different under different wrist positions (p&lt;0.05). The median nerve mobility under wrist neutral position was 2.62 (standard deviation 0.7) mm/s, which was 28 % higher than the nerve mobility 2.03 (standard deviation 0.9) mm/s under wrist extension (p&lt;0.05). And the median nerve longitudinal mobility under wrist extension was 1.21 (standard deviation 0.16) mm/s, 54% lower than the nerve mobility under wrist neutral position (p&lt;0.05).Discussion:&nbsp;The results of this study showed that the wrist extension or flexion can significantly decrease the median nerve longitudinal mobility during natural finger extension. The carpal tunnel pressure was the least under wrist neutral position compared to wrist extension or flexion. The increase of the tunnel pressure under wrist extension or flexion might be the reason of compromised median nerve longitudinal mobility. The study also implied the use of computer mouse when wrist was in extension position could cause potential mechanical damage to the median nerve, which might induce carpal tunnel syndrome. The approaches to increase the median nerve longitudinal mobility during wrist extension or flexion might benefit to the prevention of carpal tunnel syndrome.

The Effects of Wrist Position on the Median Nerve Longitudinal Mobility During Finger Flexion

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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