While the growth of transplant technology has pushed back the boundaries of conventional medicine, other frontiers await exploration. The development of artificial body parts presents scientists with perhaps their greatest challenge: to duplicate, using human technology, the handiwork of nature. Although the field is still relatively new, some manmade compo-
nents—including synthetic blood vessels and heart valves—have been available for several years. Among the more recent accomplishments: Myoelectric arms: These lightweight, mostly plastic prostheses are designed for amputees or people born without limbs. Powered by small nickel-cadmium batteries, the artificial limb responds to minute electrical impulses
from the muscles in the wearer’s stump and can provide a gripping force sufficient to perform such tasks as holding a knife or riding a bicycle. The cost in Canada ranges from $6,000 for a prosthesis below the elbow to $10,000 for an above-elbow model.
Cochlear implants: Although they cannot reproduce the sensation of normal hearing, cochlear implants—or artificial inner ears—enable profoundly deaf patients to improve their understanding of speech. Unlike standard hearing aids, which amplify sound for the hard of hearing, the cochlear im-
plant actually takes the place of the cochlea, the seat of the hearing organ. The tiny wire device, implanted in the inner ear, uses a microphone and speech processor to translate sounds into electrical signals, which in turn stimulate the auditory nerves. The cost ranges from $8,000 for the American-made House/ 3M single-channel im-
plant to $20,000 for the sophisticated Australian Multi-Channel Hearing Prosthesis, which uses 22 separate electrodes. Artificial hearts: One of the most exciting advanees in so-called spare-parts medicine is the Jarvik heart, designed and produced by researchers at the University of Utah in Salt Lake City and named after chief developer Dr.
Robert Jarvik. Essentially air-driven pumps made of plastic and titanium, Jarvik hearts are used as a temporary bridge to keep patients alive while they await natural-heart transplants. Among the most expensive of bionic devices, the popular models—the Jarvik-7 and its smaller counterpart, the Jarvik-7-70— cost $25,000 to $30,000 apiece. But the investment has reaped some reward: of the five patients in Canadian hospitals who have received Jarvik hearts since 1986, three are still alive.
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