Mayo Study on Computers and Carpel Tunnel Syndrome
A recent study on Carpel Tunnel Syndrome (CTS) conducted by the Mayo Clinic in Scottsdale, Arizona, concluded “the frequency of Carpal Tunnel Syndrome in computer users is similar to that in the general population.” These conclusions were reported in the mainstream press and appeared to be good news for those in opposition to the proposed OSHA ergonomic guidelines. A closer look at the study, however, indicates that it was in no way definitive.
The condition is characterized by pain, numbness and tingling of the palmer surface of the hand into the thumb, index finger, long finger and half the ring finger. With advancement of the condition there may be loss of sensation, muscle weakness or loss of coordination and finally atrophy of the muscle below the thumb. Because the condition involves compression of the median nerve, in advanced cases there may be demyelination (breakdown of the sheath covering the nerve) and fibrosis of the nerve.
Unfortunately, a closer look at the Mayo study indicates that it was in no way definitive. The study did not use a control group in order to simulate the general population. The study used self-selected subjects and did not systematically control for ergonomic variables such as workstation design and risk factors. In the study 27% of the 214 subjects reported CTS symptoms but only 10.5% showed positive findings on nerve condition studies. Does that necessarily mean the other 16.5% did not have CTS? The study tended to ignore this group. Does this also mean that CTS cannot be diagnosed solely with other routinely used motor and neurological tests? Even in severe cases, nerve conduction studies tend to demonstrate only an 85% to 90% sensitivity.
The incidence of occupationally caused CTS has been questioned for some time. In a review of the literature by Barton et al.(1992), it was determined that most cases of CTS were not caused by work. With there being many other causes for the condition certain jobs may precipitate or amplify the symptoms in persons so predisposed.
Admittedly, while there is a need to standardize the diagnostic criteria for musculoskeletal conditions researchers must accurately quantify occupational stressors before these conditions can be linked directly to ergonomic exposure.
1) Bridger, R.S., Introduction to Ergonomics. New York: McGraw-Hill,1995
2) Brier, Steven R, Primary Care Orthopedics. Mosby, Inc.,1999
3) Cailliet, Rene, Hand Pain and Impairment. Philadelphia: F.A.Davis Co.,1994
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