Page 440

drome and measured symptoms of pain. The participants abandoned the use of these alternative keyboards despite a “positive” effect. One might be led to believe by the NRC-IOM report that this study prevented carpal tunnel syndrome or provided evidence of a worthwhile intervention. I don't think so. Another study was misrepresented as demonstrating an association between computer keyboard use and slowed median nerve velocity. Not mentioned in discussing that study was that there were no abnormal median nerve velocities and there were no clinical carpal tunnel syndromes. Carpal tunnel syndrome is wrongly presented as being associated with computer keyboard use. Despite the panel's recognition of the lack of scientific evidence to link carpal tunnel syndrome to keyboard use, the report does not acknowledge this fact.

In order to determine the association between risk factors (exposures) and a disease (outcome variable), both the risk factors and the disease should be well defined. When a fall on the outstretched hand results in a fracture at the wrist, the relationship between the trauma and the injury is clear. This is often not the case for work-related musculoskeletal disorders. Some conditions, like carpal tunnel syndrome, have a pathogenesis that can be defined and measured objectively with electrodiagnostic studies. The majority of work-related musculoskeletal disorders of the upper extremity fall into a more amorphous category, such as hand pain when there is no objective way to define the condition or measure its severity and there is no clear anatomical basis for the symptoms.

Carpal tunnel's clinical picture of pain and paresthesias on the palmar-radial aspect of the hand, often worse at night, is readily recognized. Carpal tunnel syndrome is a condition of middle-aged people and is more common in females. In the first population-based study, the mean age at diagnosis was 50 years for men and 51 years for women; women accounted for 78.5 percent of the cases.62 Most middle-aged people work, so more often than not, carpal tunnel syndrome occurs in working people. The role that work-related activities play in its pathogenesis is controversial. On the basis of six cases, no controls, and a definition of occupation that included housewives, Brain in 1947 was the first to implicate occupation as a causal factor in the disorder.11 A high prevalence of work-related musculoskeletal disorders, including carpal tunnel syndrome, has been reported in professions requiring high-force wrist motions, such as assembly line workers, meatpackers, and material handlers. Much of the recent focus, however, has been on keyboard operators, whose activities, while extremely repetitive, do not require high force. It is not universally accepted that job-related factors are important determinants for predicting the appearance of carpal tunnel syndrome.25,68 In the general population, its prevalence is the same whether people perform repetitive activities or not.6 A recent study reported that its prevalence for repetitive



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement