Effect of wrist angle on median nerve appearance at the proximal carpal tunnel.

Ping Yeap Loh,Satoshi Muraki,Luigi Cattaneo

doi:10.1371/journal.pone.0117930

Abstract

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.

Highlights

Over the past few decades, computers have become an essential tool in the workplace
The Shapiro-Wilk’s test (p > 0.05) [21,22] and visual inspection of histograms, normal Q-Q plots, and box plots showed that the median nerve cross-sectional area (MNCSA) were approximately normally distributed and slightly skewed and kurtotic (Table 3) for both male and female participants in both dominant and nondominant hands [23,24,25]
The results showed no significant interaction between wrist angle × handedness × sex for both D1 and D2 (D1: F [4.0, 202.8] = 0.704, p = 0.590; D2: F [4.6, 233.6] = 1.313, p = 0.262)

Summary

Introduction

Over the past few decades, computers have become an essential tool in the workplace. The increase in computer use in daily life has caused an increase in discomfort at the neck, shoulder, elbow, wrist, and hand due to repetitive and awkward joint positions [1]. 20% of computer users experience musculoskeletal disorders of the upper extremities, such as carpal tunnel syndrome (CTS) [2,3]. CTS—one of the most commonly reported work-related musculoskeletal disorders of the upper extremities—is a peripheral nerve compression syndrome affecting the median nerve at the wrist carpal tunnel region [4]. The etiology of CTS is multifactorial, with mechanical compression stress on the median nerve considered one of the relevant factors. Bonfiglioli et al [5] suggested that biomechanical stress and long hours of intensive manual work without adequate rest might cause impairment of the median nerve. The median nerve contributes to cutaneous sensation of the hand and fingers, as well as innervation to multiple hand muscles that control fine motor manipulation, including pinch and grip

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Discussion

Conclusion