Carpal Tunnel Syndrome (CTS) is a painful condition that occurs when the median nerve, which runs from the forearm into the hand, becomes pressed, squeezed, or repeatedly stressed over time.
The most common cause of CTS is keyboard and mouse use, and the onset of symptoms makes it painful to use a computer at all, which can have devastating consequences for employment options. My Aunt got CTS as a result of non-stop typing at her job, and was forced to make a total career change.
The chances of women being at risk for carpal tunnel syndrome are three times higher than men.
- Women have smaller, square-shaped wrists and a narrower carpal tunnel passage.
- With a lower average body temperature, women often have cooler hands and decreased blood flow.
- Hormonal changes during pregnancy, menopause, or even from the use of birth control pills can result in swelling of the wrists increasing the chances of developing CTS.
What are the implications of this? Are women at a disadvantage career-wise because of a higher risk of computer-related injury?
group of human factors and ergonomics researchers from the University of California at San Francisco and McMaster University in Ontario, Canada, have conducted the first study that systematically identifies how one contributor to carpal tunnel syndrome–carpal tunnel pressure–can be examined in detail to establish limits on how much a wrist can be flexed before nerve damage sets in. The researchers believe their findings could be used to create simple guidelines to help workers avoid wrist postures that are likely to cause nerve trauma. The findings from their study appear in a paper, “Guidelines for Wrist Posture Based on Carpal Tunnel Pressure Thresholds,” in the February issue of Human Factors: The Journal of the Human Factors and Ergonomics Society.
The research team studied the pressure that is placed on the nerve in the carpal tunnel in various wrist postures in 37 healthy men and women between the ages of 22 and 50. Wrist postures that are not neutral (that is, bent or flexed) causes increased pressure on the nerve. The researchers concluded that when sustained pressure on the carpal tunnel reaches 30 mmHG, injury is likely to occur.
In order to keep the pressure below 30 mmHg, it is recommended that sustained wrist extension (bending the hand back) should not exceed 32.7 degrees, wrist flexion (bending the wrist toward the palm) should not exceed 48.6 degrees, ulnar deviation (sideways toward the small finger) should not exceed 14.5 degrees, and radial deviation (sideways toward the thumb) should not exceed 21.8 degrees.
The researchers believe that a set of guidelines could be developed from their data guidelines that could, if applied by engineers and designers during the design of work and tools, protect workers. Such guidelines could also be used to identify tasks that may put workers at risk for developing or aggravating CTS.