The Cutting Edge: COMPUTING / TECHNOLOGY / INNOVATION : A New Generation of High-Tech Prosthetics Offers Hope to Amputees : Research: Latest artificial limbs allow for greater mobility and comfort and restore some sense of feel.

When doctors amputated Reba Ruiz’s right leg two years ago, she feared a dramatic halt to her busy life.

But thanks to a state-of-the-art artificial limb, the 68-year-old Torrance computer consultant and business manager for the Mutual Amputee Aid Foundation jogs, goes horseback riding and keeps up with her seven grandchildren.

“There’s nothing I can’t do,” says Ruiz, one of thousands of amputees around the world who stand to benefit from a series of dramatic developments in artificial limb technology.

This new generation of prosthetics offers a wider, more natural range of mobility, restores some sense of feel and prevents the deterioration of tissue that often occurs in the remaining part of an amputated limb. Now some researchers even hope they may eventually find the secret to limb regeneration in humans.

All of this comes as a big change in what has long been a relatively low-tech field.

“Historically, everything in the field of prosthetics--fitting, design and manufacturing--was done by hand,” says Virgil Faulkner, associate professor of rehabilitation medicine at the University of Texas Health Science Center in San Antonio. The result was prostheses that were awkward, heavy and imprecise.

But Ruiz’s new leg, developed by John Sabolich, national prosthetics director of Novacare Inc. in King of Prussia, Pa., is a sign of what’s to come. Embedded in the leg are pressure and temperature sensors, which transfer pressure pulses or hot and cold sensations to the surviving nerve endings in the limb. These nerve endings relay the impulses to the brain, which interprets them as heat, cold or pressure.

Sabolich’s system seems to so closely approximate the sensations felt by real limbs that it sometimes “fools” the brain into experiencing phenomena it can no longer experience.

“If a foot is missing and has been for a number of years, many times people start to feel as if their foot is there again,” Sabolich says. “People tell me, ‘John, I feel my heel pressing into the ground,’ ‘I feel my toes wiggling.’ What I think is happening is that the brain has always been connected mentally and neurologically to the floor. With an artificial limb, the brain is cut off from the ground and doesn’t like it and responds with phantom pain. Reconnecting the brain with the floor again through this biofeedback system, the brain is able to fill in the missing information.”

The Sabolich system has other advantages. Because the fit of a traditional prosthesis is imprecise--basically a fabricated cup into which the remaining limb is stuffed--the muscles and other tissues of the amputated arm or leg atrophy. This shrinkage in turn necessitates a new fitting of the prosthesis.

But Sabolich has developed a contoured socket that prevents atrophy. The amputee actually builds up tissue mass because the muscles have a place to contract into.

“There’s a place on the socket for every group of muscles, tendons and bones to fit in,” Sabolich explains. “When you put on your leg, it’s more like slipping your hand into a glove than jamming it into a Styrofoam cup.”

The contoured fit also gives amputees a more natural sense of balance.

“The first leg I had 15 years ago weighed seven pounds,” says Chuck Tiemann of Blackwell, Okla., who lost his left arm and right leg in a work accident in 1980 and now wears two Sabolich limbs. “The [leg] I have now weighs just two pounds, and it fits like a glove. I don’t have leg adhesions or blisters. I live a very good, active life. It’s not the sense I had before the amputation, but it’s sure better than no sense at all.”

More improvements are on the way. Faulkner and his colleagues at the University of Texas have developed a tridimensional imaging device using video cameras and laser beams that makes possible an even more precise fit of prostheses.

Other scientists are fine-tuning amputees’ control over their range of movement.

Bob Radocy, president of Boulder, Colo.-based TRS Inc., a company that designs and manufactures prosthetic devices--and an amputee himself--has worked with University of Colorado engineers to develop a device that replicates the hand’s forefinger-and-thumb grasping skills.

“A person wearing our device can grasp as hard as they could with their normal hand,” Radocy says. “Yet it’s so sensitive, they can pick up an egg.”

A button on the device allows amputees to change the force of their grip--ranging from one to 15 pounds--by a simple touch. Traditional gripping devices require amputees to manually increase or decrease the number of elastic bands in a prosthesis in order to adjust strength.

Researchers at the University of New Brunswick in Fredericton, Canada, are developing a prosthetic elbow that will allow amputees the kind of joint rotation that most people can take for granted.

“If you try to imagine brushing your teeth [without the ability to rotate your elbow], you can appreciate the importance of this possibility,” says Edmund Biden, director of the Institute of Biomedical Engineering at the University of New Brunswick.

Other researchers are working on the seemingly impossible: human nerve and limb regeneration. So far, experiments have been successfully performed only on laboratory animals, but the results suggest promising possibilities for humans.

Robert Valentini, assistant professor of bio-materials and orthopedics at Rhode Island Hospital, works with biodegradable polymers--made of synthetic materials or naturally occurring substances such as collagen--that act literally as bridges between the ends of severed nerves.

“If you put your arm through broken glass and sever your nerve, it is possible to insert a synthetic bridge in the gap that prevents scar tissue from growing between the ends of the cut and guides the outgrowing nerve to reach its appropriate structure,” Valentini says.

The guide can then be used to add substances that promote cellular growth, accelerating the process of regeneration. Valentini has regenerated and closed nerve gaps in mice, rabbits and a monkey.

At the University of Dayton in Ohio, Panagiotis Tsonis, a molecular biologist, has been studying spontaneous limb regeneration in salamanders for clues about how the process might be replicated in humans. Tsonis believes his inquiry into the salamander genes responsible for regeneration will help humans because “the salamander’s limb is basically a miniature of our limbs. It’s exactly the same structure. We have the same bones, the same muscles, everything.”

In the meantime, the more modest prosthetic gains still make an immense difference to many.

“The first time I touched my wife with the sense of feel was exciting,” says Tiemann, the double amputee in Oklahoma. “I felt like my fingers were tingling, like a pleasant vibration. And I can feel the warmth of my kids. It’s fantastic. If you told me years ago about this, I wouldn’t have believed it.”