Effect of Wrist Angle on Median Nerve Appearance at the Proximal Carpal Tunnel

<div><p>This study investigated the effects of wrist angle, sex, and handedness on the changes in the median nerve cross-sectional area (MNCSA) and median nerve diameters, namely longitudinal diameter (D1) and vertical diameter (D2). Ultrasound examination was conducted to examine the median nerve at the proximal carpal tunnel in both dominant and nondominant hands of men (n = 27) and women (n = 26). A total of seven wrist angles were examined: neutral; 15°, 30°, and 45° extension; and 15°, 30°, and 45° flexion. Our results indicated sexual dimorphism and bilateral asymmetry of MNCSA, D1 and D2 measurements. MNCSA was significantly reduced when the wrist angle changed from neutral to flexion or extension positions. At flexion positions, D1 was significantly smaller than that at neutral. In contrast, at extension positions, D2 was significantly smaller than that at neutral. In conclusion, this study showed that MNCSA decreased as the wrist angle changed from neutral to flexion or extension positions in both dominant and nondominant hands of both sexes, whereas deformation of the median nerve differed between wrist flexion and extension.</p></div

Demographic data of participants (n = 53).

<p>Demographic data of participants (n = 53).</p

Deformation percentage of median nerve longitudinal diameter at different wrist positions compared with at neutral.

<p>Dom = dominant hand; Non-Dom = nondominant hand; Flex = flexion; Extn = extension; NA = Not applicable</p><p>Deformation percentage of median nerve longitudinal diameter at different wrist positions compared with at neutral.</p

Median nerve vertical diameter (D2) at different wrist angles.

<p>(A) Male dominant hand. (B) Male nondominant hand. (C) Female dominant hand. (D) Female nondominant hand. Extn = extension, Flex = flexion.</p

Inter- and intrarater reliability.

<p>MNCSA = median nerve cross-sectional area</p><p>D1 = median nerve longitudinal diameter</p><p>D2 = median nerve vertical diameter</p><p>Inter- and intrarater reliability.</p

Median nerve cross-sectional area at different wrist angles.

<p>(A) Male dominant hand. (B) Male nondominant hand. (C) Female dominant hand. (D) Female nondominant hand. Extn = extension, Flex = flexion.</p

Normality test for median nerve cross-sectional area.

<p>M = mean; SE = standard error</p><p>Normality test for median nerve cross-sectional area.</p

Median nerve longitudinal diameter (D1) at different wrist angles.

<p>(A) Male dominant hand. (B) Male nondominant hand. (C) Female dominant hand. (D) Female nondominant hand. Extn = extension, Flex = flexion.</p

Comparison between male and female participants.

<p>MNCSA = median nerve cross-sectional area</p><p>D1 = median nerve longitudinal diameter</p><p>D2 = median nerve vertical diameter</p><p>Comparison between male and female participants.</p

Deformation percentage of median nerve cross-sectional area at different wrist positions compared with at neutral.

<p>Dom = dominant hand; Non-Dom = nondominant hand; Flex = flexion; Extn = extension; NA = Not applicable</p><p>Deformation percentage of median nerve cross-sectional area at different wrist positions compared with at neutral.</p