Bionic LimbsTEST_DO NOT USE

A motorcycle crash took Mark Marich's leg in an instant. It took him 30 years and 10 replacement legs to regain a comfortable footing.

Today, he strides with the slightest of limps through prosthetics clinics in East Greenwich and Providence, where he helps fit other amputees with artificial arms and legs. He coaches his 12-year-old's Little League team. With his 190-pound frame, he can rocket a golf ball 240 yards.

An unexpected glimpse of his sleek, silvery right leg imparts a chill. His knee bulges not with arthritis, but with a computer microprocessor. It looks like something looted from a "Star Wars" battle droid.

It's called a C-leg. The "C" stands for the computer that watches his step. "I don't have to think about walking," he says. "That's the key."

He walks comfortably up hills and across changing terrains. He descends stairs with alternating feet. With a nightly battery recharge, Marich is gliding through life in khaki, carbon fiber and titanium.

Only about 300 C-legs are worn in this country. But soon there will be many more futuristic arms and legs.

Thanks to booms in computing, electronics and materials engineering, the last several years have delivered the biggest burst of prosthetics progress ever, say researchers and builders. They predict even faster improvements in the next decade, propelled by advances in mating smarter electronic parts with engineered human tissue.

The science of prosthetics, not some alien intelligence, is putting the first cyborgs on Earth.

Often motivated by the ravages of war, humans have been replacing limbs for more than 2,000 years. Romans crafted simple prostheses of wood, metal and leather.

But the technology slumbered through most of the 20th century, even as the human imagination invented cybernetic heroes like the "Six Million Dollar Man" and "Robocop." Villains with hooks and peg legs fell out of fashion, but an artificial knee created 40 years ago by aerospace engineer Hans Mauch still walks the earth. Building a missile, Mauch once said, was sheer simplicity compared to copying the complexity of a human limb.

"I think many people had some extraordinary ideas decades ago, but the technologies were not up to implementing them," says Hunter Peckam, a biomedical engineer for the U.S. Department of Veterans Affairs. "The technology is increasingly up to the job."

Prosthetic limbs are constructed from super-strong, lightweight compounds developed for fighter jets. They carry miniature circuits perfected for cellular telephones and batteries refined for laptop computers.

Artificial arms can be anchored right into the bone of amputees. Replacement hands can automatically tighten on a slipping glass. An amputee has played piano with a computer-controlled hand.

Researchers are looking beyond. They are studying ways of restoring the lost sense of touch, position and other sensations. They are testing systems to convert human nerve and brain signals into electronic cmmands for prosthetic limbs. Laboratories have begun growing skin and bone that might one day flesh out a prosthesis.

"There's more research going on the last five years than there has been in the last 20," says David Gow, a prosthetics designer at Princess Margaret Rose Orthopedic Hospital in Edinburgh, Scotland. "We've got intelligent kettles and intelligent fridges, but we don't have intelligent limbs."

The science of prosthetics was just growing out of infancy in 1969. That summer, Marich, riding a borrowed motorcycle, swerved when a driver pulled out in front of him. Marich lost control and crashed head-on into another car.

He was filled with an awful anguish when he left the hospital. What would the future hold for a maimed 17-year-old? How would his friends look upon him? "I was a young, active, do-anything-do-all kind of a kid. What am I going to be able to do?" he remembers wondering.

His first artificial leg was made of wood, with a hand-carved socket to carry his weight. It was heavy and made no adjustments for changes in his step or walking surface. A moment's distraction could send him sprawling.

Over the years, with prosthetic limbs available through his work as a prosthetist, he changed his own leg as better ones reached the market. Finally, Otto Bock, the company that makes C-legs, enlisted him in 1999 to test its new prosthesis.

At first, it was like a Maserati driven by someone used to an old Chevy. Marich's trainers told him to relax. "Stop thinking about what you're doing," they said. "Just walk!"

The C-leg carries sensors in its ankle and knee that relay force and position readings to its computer 50 times a second. The computer analyzes the signals and controls motors that hydraulically adjust the bending of the knee for smoother movement.

At around $40,000, a fully outfitted C-leg can cost twice as much as an older prosthesis. The company lent Marich his. Health insurers sometimes challenge coverage for such advanced prosthetics.

But these artificial limbs can repay their cost, and more, in human productivity. On a recent day, Marich, now 49, lowered himself nimbly beside an examining table and tilted forward on a stool. He gave no sign of wearing a prosthetic leg.

He began wrapping plaster-soaked bandages around what was left of an amputee's left leg. The hardened plaster would shape the contours of a mold for a body-hugging, custom-fit socket. Since Marich's accident, plastics have added strength and comfort to prosthetic sockets.

Marich also rolled a new silicone liner, a more recent development, onto the patient's leg. The liner forms a suction seal to hold the prosthetic on without straps or belts.

At some clinics, lasers scan amputated limbs to generate a three-dimensional image. A socket or mold can be fabricated from the digital picture. "I can regenerate a mold by clicking a button. You can never create the same thing twice with your hand," says Paul E. Prusakowski, president oO&P Clinical Technologies of Gainesville, Fla.

As an amputee, Marich puts something else at the top of his wish list: a prosthetic limb attached to his skeleton, just like his original leg. His wish is granted to amputees in Gothenburg, Sweden.

Three decades ago, Dr. Per-Ingvar Branemark discovered that when titanium anchors are dropped into holes drilled in bone, the bone grows around the metal and holds it fast. Prosthetic devices can be clamped to the anchors.

Dentists first implanted the metal in gums to fasten false teeth. Dozens of amputees have undergone the operation, known as osseointegration, in the past 10 years, largely in Sweden. Their artificial arms and legs are held by titanium implants in their shoulders, thighs or other bones.

"You get rid of all the disadvantages with the socket: skin sores, retention problems," says Branemark's son, Rickard, an osseointegration surgeon like his father.

He says an amputee can better control the prosthesis, and it feels more a part of the body. One man even reported that his phantom leg — the mental picture that amputees keep of their lost limb — had withered but was starting to grow out again with the titanium attachment.

Unexpectedly, amputees also report feeling a contrast in surfaces, like the difference between grass or concrete, through their anchored prostheses and bones, Branemark says.

Some researchers have experimented with sensor-carrying prosthetic limbs that send pressure and other sensations directly to an amputee's skin. One experimenter is teaching amputees to recognize the changing sounds from different surfaces brushed over by gloves with tiny built-in microphones. Such gloves could cover prosthetic hands.

Many researchers say amputees must eventually be able to feel what they are touching, how hard they are gripping, and where they are reaching. "Without feedback, they cannot get better function," says Miguel Nicolelis, a Duke University neurobiologist.

Some sensations, though, must await better control of motion. After all, who cares about feeling the piano keys if you can't play?

Jay Schiller taps with one hand on a computer keyboard that controls a robotic arm.

Its eight needle-like injectors drop minute samples of a chemical into a row of test wells. The arm whirs to the next row and delivers more helpings.

Schiller, 30, a chemist at a drug-testing company in Princeton, N.J., can manage the robot ably with one hand. He has practiced many tasks this way since age 18.

In 1988, he was a University of Delaware student playing the saxophone in the marching band. One day at a train station, he brushed against an exposed wire. A high-voltage charge shot across his body, knocking him senseless and searing a hand and foot so badly that both were amputated.

His first prosthetic hand was a two-pronged hook that just opened and closed. "It was not something I was looking forward to wearing," he says. "It was kind of unsightly, especally for an 18-year-old."

He eventually switched to an artificial arm controlled by the muscles in his own forearm. Sensors inside the socket read faint electrical impulses produced when his muscles contract. The signals tell a motor inside his artificial hand when to open and close.

The technology, known as myoelectric, is now about 30 years old. It has replaced many body-powered prosthetic hands, which are operated by jerking a cable through a harness wrapped around an amputee's shoulders and chest.

Beneath a silicone cover resembling a hand, though, his hook has changed little. It works fine, with its simple opening and closing motion, for grasping light objects and tools. But he can't even think about playing the saxophone with it.

"I guess I never realized how much I loved doing it until I couldn't do it anymore," he says. It hurt to abandon hope. But he feared disappointment even more.

Other arm amputees had told William Craelius they wanted their fingers back, too.

A biomedical engineer at Rutgers University, in Piscataway, N.J., Craelius knew that many amputees and even people missing hands since birth retained the forearm tendons and muscles normally used to move fingers. Their brain-to-arm nerve circuitry was often intact for each finger.

Could they move prosthetic fingers as they would move real ones? "It was such a simple idea that most people didn't think it was worth anything," Craelius remembers.

He began work in 1997. He stuck pressure sensors inside a socket, put it on some amputees, and asked them to move the fingers of a virtual hand on a computer screen. The sensors signaled the muscle movements to a computer controller, which was taught to identify the pattern for each finger movement. Some test subjects had trouble, but others moved the virtual fingers easily.

Now Craelius needed a prosthetic hand. A tinkerer, he packed an old hand with model airplane motors and rigged them with line and fishing tackle — like tendons — to five robotic fingers. Then, he wired the computer controller and its custom software to the motors in the hand. He placed the pressure sensors in a socket and put the homemade hand at the end.

Amputees were soon picking up a ball, pencil and champagne glass with the bionic hand. But Craelius, who hopes to perfect and market the system, had bigger ideas. He thought of Jay Schiller.

Answering an ad for test subjects, Schiller had signed onto the project. Craelius knew the chemist once played saxophone and studied some piano as a child.

Schiller had been adept at moving the virtual fingers. But he had never tried the prosthetic hand. Could he play piano with it?

The sensors were wired to his forearm. The prosthetic hand was connected to the computer controller and placed on a stand above a piano keyboard, but left detached from Schiller's arm. It was like Terminator Meets Amadeus.

Schiller thought of a comforting song from his childhood. To the buzz of motor, the disembodied hand slowly pecked out "Mary Had a Little Lamb" with three fingers. It wasn't great music, but it was a telling moment in the history of prosthetics.

"It was absolutely amazing," says Schiller. "I didn't think that would be possible."

Some researchers are placing sensors under the skin in search of more natural command of movement.

Ronald Riso, at Denmark's Aalborg University, is experimenting with half-inch, electrode-laced silicone tubes that can be implanted around nerve fibers inside an amputee's remaining arm. The electrodes could pick up signals from the amputee's nerves to command the motors of artificial limbs.

Other researchers are going straight to the brain. Several paralyzed patients have had electrodes implanted in their brain's motor cortex, which normally controls hand movements. Their brain signals are fed to a virtual computer keyboard that patients learn to command simply by thinking of the key strokes.

One mute stroke patient of Dr. Roy Bakay at Rush-Presbyterian-St. Luke's Medical Center, in Chicago, has been writing simple messages with his thoughts for four years. Such systems could eventually work for amputees too, researchers say.

Others want to dispense with motors. They are working on bionic muscles made of metal-laced plastics. These synthetic ribbons twitch under a slight electrical current, like a biological muscle contracting when a nerve fires.

Some surgeons are replacing flesh with flesh. About a dozen hand transplantations have now been carried out with hands from dead donors. Surgeons have reattached cut nerves, blood vessels and muscles, and amputees have regained some motion.

But transplant patients need immunity-weakening drugs to avoid rejection of foreign tissue, and the supply of donated hands is limited.

So tissue engineers are busy growing human skin cells on synthetic scaffoldings, hoping one day to cover man-made limbs with laboratory-cultured skin. Other labs are growing bone, blood vessels and other human tissue from undifferentiated cells collected in the body.

Some researchers are even speculating that one day an amputee's own cells might be biochemically cued to replay the elaborate pattern of nerve, muscular, blood vessel and other development to grow a whole limb.

Some foresee a convergence of electronic and cellular research in the nearer future. "You could imagine creating a prosthetic limb that would be part-man, part-machine," says cell researcher George Daley, at Harvard Medical School.

Schiller says he's encouraged by the pace of change. He even picked up his old saxophone recently and wondered how it would feel to play again. He's not so afraid to dream anymore.

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