Keep On Typing

Computer programmers, office
workers, college students and Internet addicts everywhere can now breathe a
sigh of relief: there is better evidence that genetics rather than hand use
is the cause of carpal tunnel syndrome (CTS). A new study presented today
at the 74th Annual Meeting of the American Academy of Orthopaedic Surgeons
indicates that the causal link between CTS and repetitive use of the hands
is much weaker than has been assumed.


"The idea that CTS is related specifically to typing or overuse of the
hands in general is pervasive in modern society," said David Ring, MD,
senior author of the study. Ring is an assistant professor of orthopaedic
surgery and a hand and upper extremity surgeon at Massachusetts General
Hospital in Boston. "It is commonly accepted as true, but according to the
scientific evidence, the link between hand use and carpal tunnel syndrome
is overstated and may be inaccurate. In contrast, there is strong evidence
for an inherent, genetic risk for CTS. CTS sufferers are most likely
innocent bystanders and should not be blamed for their illness."



Patients with CTS experience hand numbness, and eventually develop
weakness and atrophy of some of the small hand muscles that control the
thumb. "Another common misconception," said Ring, "is that patients with
carpal tunnel syndrome present with complaints of activity-related wrist
pain. In fact, the hallmark of CTS is numbness that wakes you at night or
is present when you wake in the morning. The numbness can be so intense
that it's painful, but pain without numbness is not characteristic of CTS."



Carpal tunnel syndrome remains poorly understood. Pressure in the
carpal tunnel (a tunnel formed by the small wrist [carpal] bones and the
transverse carpal ligament) is involved in the pathophysiology, and release
of the pressure by dividing the transverse carpal ligament stops the
process. The cause of the increased pressure, however, remains unknown in
the vast majority of patients.



Researchers evaluated data for the cause of CTS by a quantitative
scale, based on the Bradford Hill criteria (widely accepted by the
scientific establishment), which determines a causal relationship. Average
scores for biological factors (genetics, race, age, etc.) were double those
of occupational factors (occupation, repetitive hand use, vibration, etc.).
In addition, the average strength of causal association (odds ratio) was
about three times as strong for biological factors as it was for
occupational factors.



"This application of stringent science to theories of causation may
affect claims of disability, workers compensation and personal injury,"
noted Ring. "It should also influence the information that physicians are
providing their patients about carpal tunnel syndrome. Physicians have the
power to increase or decrease illness and disability with their words. In
my opinion, we should provide patients with the most optimistic, positive,
practical and enabling illness concepts that are consistent with the best
available scientific data."


American Academy of Orthopaedic Surgeons

aaos