WebMD Health News
Louise Chang, MD
Feb. 16, 2007 -- Long hours surfing the Internet or typing won't wreck your
wrists, a new study shows.
Carpal tunnel syndrome, long associated with overuse of the hands and wrists
when surfing the Internet or typing, is linked more to genetics than repetitive
use, according to the study.
It was presented today at the 74th Annual Meeting of the American Academy of
Orthopaedic Surgeons in San Diego.
"The link between carpal tunnel syndrome and hand use is overstated and may
be inaccurate," says study researcher David Ring, MD. Ring is an assistant
professor of orthopaedic surgery at Harvard Medical School and a hand surgeon
at Massachusetts General Hospital, Boston.
"The scientific support for the concept [that carpal tunnel is caused by
overuse] is, on average, relatively weak," he says. "The major risk factor for
carpal tunnel is genetic."
Exactly what those genetic factors are is not known, he says, but they may
be related to the structure of the hand and wrists
In carpal tunnel syndrome, the median nerve, running from the arm into the
hand, becomes pressed or squeezed at the wrist.
This nerve controls sensations to the thumb's palm side and part of all the
fingers except the little finger.
When the median nerve is squeezed, there can be tingling, pain, weakness, or
numbness in the wrist and hand that radiates up the arm.
Treatment options include rest, immobilization of the wrist, and surgery to
reduce pressure on the nerve.
"A common perception is that carpal tunnel is related to hand use," Ring
That perception is more common among consumers, he says, but some doctors
also believe it.
Studies on whether carpal tunnel syndrome is associated with hand use have
Ring differentiates between carpal tunnel syndrome and repetitive strain
injury, which he prefers to call idiopathic (cause unknown) arm pain.
In this condition, he says, there is pain "but no evidence of injury. It
doesn't involve the carpal tunnel."
To clarify the debate, Ring and his colleagues looked at 117 studies on
carpal tunnel syndrome published in the medical literature.
They used scientific criteria that determines the strength of a
cause-and-effect relationship by giving it a score.
The researchers looked at biological factors -- such as genetics -- and
occupational factors -- such as a person's job or the amount of repetitive hand
After analyzing the studies, "The quality and strength of evidence
supporting genetic or inherent risk factors was felt to be moderate," Ring
"The quality and strength of evidence supporting occupational risk factors
was felt to be poor," he says.
Average scores for biological factors linked to carpal tunnel syndrome were
double those of occupational factors, such as occupation or repetitive hand
use, Ring reports.
"The link to genetics is strong and believable," Ring says. "If you are
diagnosed with carpal tunnel, you are an innocent bystander. You did nothing to
"This should give reassurance to those who use their hands a lot," he
SOURCES: David Ring, MD, assistant professor of orthopaedic surgery, Harvard
Medical School; hand and upper extremity surgeon, Massachusetts General
Hospital, Boston. 74th Annual Meeting of the American Academy of
Orthopaedic Surgeons, San Diego, Feb. 16, 2007.
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