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About this Article
Written by: Melissa Price
Written on: September 1st, 2000
Tags: biomedical engineering, health & medicine, ergonomics
Thumbnail by: Skoivuma/Wikimedia Commons
About the Author
In the fall of 2000, Melissa Price was a senior pursuing a Bachelors degree in Industrial & Systems Engineering. She is now pursuing a career in human factors.
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Volume IV Issue I > Carpal Tunnel Syndrome: Are You at Risk?
Ergonomics and human factors are major fields within industrial engineering. By studying the human body and its measurements and variations, it's possible to create an ideal tool for any function. In recent years, as people utilize high technology more in their everyday lives, the focus has moved strongly toward ergonomically-sound computer workstations. Though ergonomics may just seem to be a popular trend, it stems from scientific background.

Introduction

More and more people today, college students in particular, log several hours per day sitting at a computer. Whether working, checking email, surfing the web, or chatting, they're using the mouse and keyboard. Considering that people do this every day, for hours at a time, is it possible they could actually be harming themselves? Unfortunately, it's entirely possible.
Carpal tunnel syndrome (CTS) is a cumulative trauma disorder that affects the wrist and hand. CTS is caused by trauma to the median nerve. Such trauma is something such as frequent repetitive motions, either heavy or light, especially while the hand or wrist is in an unnatural position. Symptoms of CTS include numbness in the thumb and first two and a half fingers, followed by pain or stiffness in the wrist and hand. To better understand how damage occurs to the median nerve, it is important to be familiar with the anatomy of the human wrist.

Wrist Anatomy

Let's look at a cross section of the wrist with the palm of the hand facing upward. Along the dorsal part of the wrist (away from the palm), there are tendons running along the length of the arm, and the pisiform (P), triquetrum (T), hamate (H), capitate (C), and navicular (N) bones running alongside the tendons. On the thumb side of the wrist are the radial artery and nerve, and on the opposite side are the ulnar artery and nerve. Along the top of the wrist on the palmar side are transverse carpal ligaments creating an upper boundary. In the center is a small canal called the carpal tunnel, which contains the median nerve and various other muscles and tendons.
With frequent repetitive motion, or crooked positioning of the wrist, the available space becomes smaller, and tissues begin to swell. Together, this causes extreme pressure on the blood vessels and the median nerve, thus reducing blood flow and nerve functionality. Ultimately, this impairs use of the affected joints [1].

How The Wrist Moves

The natural position of the human wrist (if the arms are extended straight out in front of the body) is perfectly horizontal, and straight out, with no bending to the side. When the wrist is bent upward (but not to the right or left), it is experiencing dorsiflexion, and downward but still straight is called palmar flexion. When the wrist is out straight from the arm, but is bent to the left, it is experiencing radial deviation, and if bent to the right, ulnar deviation [2]. Trauma to the median nerve can be caused by any deviation from the neutral position.