Carpal Tunnel and Typing: Does Use of a Keyboard Cause CTS

hands computer keyboard
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There is an ongoing and longstanding debate about the use of keyboards (or other technologies such as a computer mouse or smartphone) and the possible effects on developing carpal tunnel syndrome.  Many people with carpal tunnel blame their condition on these devices, but whether that is the actual cause is a subject of controversy.

The average person, including employers and employees, presume that work activities can lead to the development of carpal tunnel syndrome.

  While often people make this association, it has not been shown, despite many well-designed, large scientific studies, that carpal tunnel is caused by repetitive work activities.  In the Journal of the American Academy of Orthopedic Surgeons, a recent review of the best research on carpal tunnel stated:

"A direct relationship between repetitive work activity (eg, keyboarding) and CTS has never been objectively demonstrated."

Pressure in the Carpal Tunnel

Carpal tunnel syndrome occurs when the median nerve, one of the large nerves in the wrist, is pinched as it passes through the tight carpal tunnel.  The carpal tunnel is formed by the small wrist bones on the bottom, and a tight ligament on top.  If pressure builds up in the carpal tunnel, the nerve is pinched and begins to function abnormally.  When the nerve does not function properly, patients experience the typical symptoms of carpal tunnel, including pain, tingling, and numbness.

Pressure in the carpal tunnel is increased with certain positions of the wrist.  The basis for Phalen's test, one of the examination tests for carpal tunnel syndrome, is to forcefully bend the wrist to increase the pressure in the carpal tunnel to see if symptoms occur.  Similarly, the reason many people complain of carpal tunnel symptoms at night is they sleep with their wrists folded under their body.

  These positions can increase carpal tunnel pressure, exacerbating symptoms.

Repetitive Use

Some work-related activities can potentially cause similar effects of transient increases in pressure in the carpal tunnel.  Poorly designed work spaces can cause you to hold the wrist in a position that irritates the nerve causing you to experience symptoms of carpal tunnel syndrome.  Often wearing a splint, or redesigning your workspace can help to alleviate these symptoms. 

However, repetitive use (for example, prolonged typing or other repeated work-related tasks) has not been clearly shown to cause carpal tunnel syndrome. There have been numerous studies (a few of the best are listed below) comparing patients who have carpal tunnel syndrome, and those that do not, and no clear link between typing, or other repetitive work activities, has been shown to cause carpal tunnel syndrome.

It is certainly true that there have been other studies that do show a link between carpal tunnel and repetitive use at work.

  These studies generally show a weak link (meaning there may be a small effect), and generally these studies have been of inferior quality when compared to those listed below.  Most experts agree that there is no clear link between occupation and development of CTS, and any link that may exist is small.  Most data pointing to occupation as a risk factor for developing CTS comes from studies investigating the use of vibratory heavy machinery (including jackhammers), not from using a keyboard.

This is a subject of great controversy, and despite the best evidence there is an ongoing debate as many people attribute their symptoms to work activities.  I understand patients who are concerned the research may be flawed, and to them I would simply point out that the best research at this time points to no specific link between repetitive work activities and the development of carpal tunnel syndrome.  Certainly there will be more investigation in the future, and perhaps new information will emerge, but if there is a link it is not dramatic.

There Is A Difference Between Cause & Effect

While most research has been clear that typing and other work activities do not cause carpal tunnel, there is certainly a possibility that these activities could exacerbate symptoms of carpal tunnel.  Dr. Charles Eaton, a well known hand surgeon, used an excellent analogy on his web site explaining this concept: a job that requires you to go up and down stairs repeatedly may cause you to get short of breath, but that does not mean the job caused you to develop lung disease.  Similarly, it is possible that some work activities may cause you to notice symptoms of carpal tunnel syndrome, but it did not cause the problem. 

Bottom Line: No Link Between Computer Use and CTS

While some people find it hard to believe, the science has been clear.  There is very good data to show that keyboard use does not cause carpal tunnel syndrome.

Sources:

Cranford CS, et al. "Carpal Tunnel Syndrome" J Am Acad Orthop Surg September 2007 ; 15:537-548.

Slater RRS. "Carpal Tunnel Syndrome: Current Concepts" J South Orthop Assoc 8(3), 1999.

Dias JJ, et al. "Carpal tunnel syndrome and work" J Hand Surg [Br] 2004;29:329-333.

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