The history of medicine is filled with tales of bold surgeons replacing human body parts with artificial ones and of even bolder patients living with them.

Artificial hearts are already beating tentatively in a few brave people, and biomedical engineers are constantly improving artificial limbs. Dozens of high-tech projects are under way that draw on the latest computer technology, synthetic materials and miniaturization methods.

But the history of bionic efforts goes back for thousands of years:

The Rig-Veda, a sacred poem of ancient India written some time between 3500 and 1800 B.C., recounts the story of Queen Vishpla, a warrior who lost her leg in battle and was fitted with an iron prosthesis so she could return to violent conflict.

Much, much later, in 218 B.C., Marcus Sergius, a Roman general, lost his right hand in battle during the Second Punic war. Surgeons fitted him with an iron hand, historians say, and thus equipped he led his Legion against the Carthaginians. He carried his own shield to victory with iron fingers curled.

Today, the science of prosthetics -- part medicine and part engineering -- has made the fitting of elaborately functioning prosthetic limbs and joints commonplace.

Orthopedic surgeons routinely replace malfunctioning hips and knees when those joints wear out or succumb to disease. Surgery to fit artificial shoulders, slowly developed during the past 30 years, is no longer rare. And in Scotland surgeons recently teamed with engineers to equip a woman amputee with a "bionic arm, " complete with a hand, elbow and fingers whose movements the patient controls remotely by electronic signals she generates by twitching her chest and back muscles

The vision of totally "bionic humans" remains the province of fantasy, from Dr. Frankenstein's lovelorn murderous monster and the Tin Woodman's quest for a heart, to television's "Six Million Dollar Man."

Yet scientific progress in the realm of artificial internal organs is advancing fast, and many versions are in early experimental stages. Some are here already, some still only the dream of basic researchers.

Here's a rundown:


At least three new implanted heart devices are now undergoing clinical trials. Manufacturers are seeking federal approval for permanently implanted pumps for patients who are ineligible for transplants, rather than as merely temporary "bridges" for heart-failure patients awaiting donated organs.

For cardiac patients whose own hearts often beat irregularly or squirm and quiver out of synch there are implantable pacemakers and "defibrillators" -- including combination cardioverters like the one that surgeons implanted just beneath Vice President Dick Cheney's collarbone last June after he suffered a series of heart attacks.

Implanted cardiac defibrillators like Cheney's are expensive -- as much as $60,000 each, including surgery costs -- and their service life is only four to five years. A recent study indicated that more than 200,000 new heart attack patients a year could benefit from the devices, but that would add $12 billion a year to the nation's health care bill. So defibrillators are unlikely for every heart attack patient with a faulty cardiac rhythm until the devices are simpler and a lot cheaper.

More than 1,500 "left ventricular assist" devices have been implanted as temporary pumps to bridge the gap while heart-failure patients await the rare luck of finding a transplant donor.

The cumbersome Jarvik-7 device, which was meant to be a truly artificial and permanent heart replacement, was tried 20 years ago but is now used only as a bridge for patients awaiting transplant.

Then, last July, came the self-contained Abiocor heart, meant as a permanent replacement. Of the first four patients who lived more than 60 days after their titanium-and-plastic hearts were implanted, only two were still alive this month. Surgeons at five American hospitals are still seeking terminally ill patients to test the experimental device.

Says Dr. Norman Shumway, the pioneering Stanford University cardiac surgeon who first developed the heart transplant technique more than 40 years ago: "An artificial heart is a tremendously difficult problem because the human body is living tissue. It's always going to be opposed to plastic materials and metal materials or anything else that isn't tissue. The so-called artificial hearts are clinical experiments, and money is what's driving the effort."

Because the heart's ventricles are the workhorse pumps of the cardiovascular system, several makers of the left ventricular assist devices are now enrolling patients in clinical trials, testing the systems to see if they can remain permanently implanted in heart patients who are considered ineligible for transplants.

While not truly artificial hearts, the competing systems are made by Oakland-based WorldHeart, Pleasanton-based Thoratec and Arrow International, based in Reading, Pa., and some patients are walking around today with their implanted heart pumps operating continuously for as long as four years.


Bionic ears, or cochlear implants, have a long history, too.

The first primitive versions were implanted in 1957, and thousands of hearing-impaired people are now using far more sophisticated versions.

A new high-resolution device has already been tested in profoundly deaf patients at UC San Francisco's Cochlear Implant Center, where scientists have been researching the surgically implanted systems for nearly 40 years.

The normal cochlea, a snail-shaped organ of the inner ear, is lined with thousands of tiny hair cells that vibrate in a fluid under the impulse of incoming sounds. Damage to the hair cells can impair hearing severely, and the more damage, the more profound is the deafness

At UCSF, Dr. Anil Lalwani and his colleagues have been testing a new implant called the Clarion CII Bionic Ear, which picks up sounds at a wide range of frequencies and sends the high-resolution signals to the brain.

One of many such devices, the Clarion's external sound processor converts incoming sounds to digital code, then transmits the code by radio to the "bionic ear," implanted beneath the skin at the side of the head. From there a thin internal electrode winds through the cochlea past the damaged hair cells, and sends the coded signals directly to the acoustic nerve at a million impulses a second.

According to Jan Larky, the audiologist on Lalwani's team, a national test of Clarion's new coding system has shown that a large majority of patients prefer it to older systems for clarity in hearing speech, music and even the distortions in telephone voices.


No scientist has yet created a bionic eye for the totally blind, but at Stanford University Medical Center Dr. Harvey A. Fishman, an ophthalmologist and physical chemist, is in the early research stages.

He is working with chemical engineer David Bloom to try to help people whose central vision is blinded by the disease called macular degeneration.

The team is developing a silicon computer chip loaded with specialized cells from the optic nerve that would act as an artificial implanted retina to receive and transmit visual signals to the brain.

In Fishman's experiments, he hopes to use a digital camera to pick up images of the outside world and send them to the optic nerve via the silicon chip.

"The big question," says Fishman, "is whether we can re-stimulate the nerves in the retina this way. It sounds simple, but it's complex as hell because it involves putting microscopic biological circuitry onto a chip, and that presents a huge biocompatibility problem."


Scientists at the UC Davis Transplant Institute are researching a variety of "bioartificial" devices combining human tissue cells and plastics to attack problems of organ rejection after transplants and diseases such as diabetes and hepatitis.

In one partnership with biomedical engineers at the Lawrence Livermore National Laboratory, Dr. Mark Zern and his colleagues are focusing on hepatitis, using techniques of genetic engineering to keep human liver cells dividing again and again.

These "immortalized" cells, as they are known, would then be housed in what the team calls a bioreactor -- plastic foam where the liver cells would multiply and be picked up by blood circulating through the reactor to fill all the complex functions of a normal healthy liver.

Anthony Makarewicz, a Livermore biomedical engineer, is experimenting with various types of specialized plastic foams, seeking the ideal material for a bioreactor in which the team could grow up to 100 billion liver cells.

"At least 100,000 people die of liver failure every year," Maklarewicz says, " and we can see where a bioartificial liver could save at least 20,000 of those patients."


People are still people and machines are still machines, but with more and more human functions being performed by implanted devices and prostheses, the era of the "Bionic Human" seems to be approaching. Research is under way on many fronts, but not even computer scientists are trying to create a true bionic brain with bionic emotions. This human figure shows some of what's here now, what's improving, and of what may be coming. .


-- Retinal cell chip research under way . .


1957 Cochlear implant developed

1980 Successful cochlear implant

-- Implant sound codes improving .


1969 Temporary artificial heart

1982 Jarvik-7 artificial heart implanted

2001 Abiocor, a permanent artificial heart, implanted

-- Permanent left ventricular assist system in trials .


218 B.C. Prosthetic hand with flexible fingers

1998 Human hand transplant

-- First attempt at arm with hard fingers electronically controlled .


1963 First successful liver transplant

-- Bioartificial liver using immortalized liver cells undergoing research .


1937 Modern artificial leg premieres

-- Artificial knees improving

-- Microprocessor-controlled artificial leg under development .


1905 First attempt at hip replacement

-- Steel and polymer hip joints improving

Source: Chronicle research