‘Bionic’ Artificial Limbs Offer a Step Toward Normalcy

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 just a slight limp through two Rhode Island prosthetics clinics, where he fits other amputees with artificial arms and legs. He coaches his 12-year-old’s Little League team. 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.”

With a nightly battery recharge, Marich is gliding through life in khaki, carbon fiber and titanium.

Thanks to breakthroughs 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.

The science of prosthetics was just growing out of infancy in 1969 when Marich swerved his borrowed motorcycle to avoid another vehicle that had pulled in front of him. He lost control and crashed head-on into a 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 view him? “I was a young, active, do-anything, do-all kind of a kid. What am I going to be able to do?” he wondered.

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

Over the years, with prosthetic limbs available through his work, he changed his own leg as better ones reached the market.

Marich, now 49, has benefited from plastics that add strength and comfort to sockets. More recently, silicone liners have been used to form a suction seal and hold on prosthetics without straps or belts.

At some clinics, lasers scan amputated limbs to generate a three-dimensional image. A mold or socket itself can be fabricated from the digital picture.

Otto Bock, the company that makes “C-legs,” enlisted Marich 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 the ankle and knee that relay force and position readings to its computer 50 times a second. The computer controls motors that hydraulically adjust the bending of the knee.

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.

Now Marich wants more--maybe a prosthetic limb attached to his skeleton, just as his lost leg was. 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.

Dozens of amputees have undergone the operation in the last 10 years, largely in Sweden. Their artificial arms and legs are clamped onto 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, who does the surgery too.

He says an amputee can better control the prosthesis, and it feels more like a part of the body. Unexpectedly, amputees sense a contrast in surfaces--such as grass vs. concrete--through their bones and anchored prostheses.

Other researchers have experimented with sensor-carrying prosthetic limbs that send pressure and other sensations directly to an amputee’s skin. But many amputees want better movement first.

Jay Schiller taps with the fingers of just one hand on a computer keyboard that controls a robotic arm. The arm has needle-like injectors that drop minute samples of a chemical into rows of test wells.

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, when he lost a hand and foot in an electrical accident.

His first prosthetic hand was a two-pronged hook that just opened and closed. He later switched to an artificial arm controlled by faint electrical signals from the muscles in his own forearm.

Beneath a silicone cover resembling a hand, though, Schiller’s hook has changed little. He can’t even think about playing the saxophone, as he once did in his college marching band.

“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.

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 retained the forearm tendons and muscles used to move fingers. 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,” he remembers.

Craelius began work in 1997. He stuck pressure sensors inside a socket and asked amputees 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.

A tinkerer, Craelius then built a prosthetic hand with individual finger movement. Test subjects without hands were soon picking up a ball, pencil and champagne glass.

But Craelius, who hopes to perfect and market the system, had bigger ideas. He thought of Jay Schiller, who had answered an ad for test subjects.

Could Schiller, who had studied piano as well as saxophone, play keyboard with the bionic hand on his first attempt to use 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 motors, 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 implanting electrode-laced silicone tubes around nerve fibers under the skin to pick up signals right from an amputee’s nervous system.

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 keystrokes.

Others are working on future bionic muscles: synthetic ribbons that twitch under a slight electrical current.

Some surgeons are transplanting hands directly from dead donors. They have reattached cut nerves, blood vessels and muscles, and amputees have regained some motion.

Meanwhile, tissue engineers are growing skin, bone and other tissue in the laboratory, hoping to flesh out man-made limbs with laboratory-cultured tissue. “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.