Summer 1997 Mission


Mission

Rehabilitation engineers
work to perfect
artificial limbs

Lifelike prostheses even respond
to thought commands

By Mike Lawrence

The world of rehabilitation engineering has come a long way since pirate Long John Silver's wooden leg. Additions to the human body are doing everything but grow themselves and scientists, including those at the Health Science Center, are even working on that.

While researchers work to perfect the regrowth of tissue in the body and get nerves to communicate with computer chips, caregivers can already offer patients energy-storing artificial feet and ankles with a spring in their step like healthy feet. . . a myoelectric hand that can grasp a pencil when the wearer gives a thought command. . . use of lasers to help computers design limbs and facial parts that match the wearer's contours perfectly. . . and new materials that are lighter weight, more lifelike and stronger, some even bulletproof.

A patient with a prosthetic arm or hand today may have a computer chip in operation similar to the ones that keep your car's engine operating correctly. Additions to the body fit better, do more and don't wear out as fast as the old wood, metal and leather appliances of just 20 years ago.

And the patients just keep coming. In addition to war injuries from the latest military hot spots, congenital abnormalities are still appearing, accidents still occur and diseases, especially diabetes in South Texas, still cause loss of limbs and parts of limbs.

"When I came here as a prosthetist 15 years ago, I think the department wondered if it could keep me busy," recalled Virgil W. Faulkner, associate professor of rehabilitation medicine. "But we've seen a several hundred percent increase in patients. They come from all over South Texas and Mexico."

Health Science Center researchers are now among the world's leaders in several aspects of rehabilitation medicine including:

  • CAD CAM—computer-assisted design, computer-assisted manufacture—of prostheses;
  • Laser imaging to define wounds and abnormalities to then be fitted with prostheses; and
  • Development of new materials, including plastics incorporating carbon fibers that are much stronger than previous plastics.
  • "Surgical techniques that save more of an injured limb have improved our ability to help patients as well," added Faulkner. "For example, a below-the-knee amputation, with modern rehabilitation, can result in only a 10 to 20 percent loss of original function, which is much better than in previous years."

    Improvements in microsurgery also preserve muscles and nerves that can be used with the newer prostheses. Some patients can be fitted with a myoelectric prosthesis, for example, that will allow them to send a mind command to flex a particular muscle, which will in turn send a signal to move an arm or a hand. Electrodes, located inside the arm socket, can pick up a muscle's electric signal and amplify it so that it is strong enough to turn on a switch that lets electricity from a battery operate the artificial hand.

    CAD CAM technology was originally developed in England, but Health Science Center researchers are at the forefront of its use for producing human prostheses. About half of the patients seen by Health Science Center rehabilitation engineers are helped by CAD CAM technology.

    A spin-off of the CAD CAM work is the use of lasers to measure wounds faster and with more accuracy than was previously possible. Two similar sets of equipment in the Health Science Center's rehabilitation computer lab and at the county hospital district's University Health Center Downtown can rotate a ruby diode laser around a patient's entire limb in just six seconds. During that time, the laser reads the contours of the limb and transmits the information to a computer which can then reproduce it graphically and tell another machine to carve the shape of a prosthesis that will be a perfect fit.

    "You can also evaluate the healing process of a wound with this technology because the laser can detect very minute changes in the surface that your eye might not identify," said Nicolas E. Walsh, MD, professor and chairman of rehabilitation medicine.

    In the late 1980s, Health Science Center researchers helped to open up the field of lighter-weight, stronger biomaterials with their study of nylon, polyester, acrylic and carbon fibers. A study conducted on campus was one of the first to show the advantages of certain materials, particularly carbon fibers, which are now routinely woven into a laminate used for fabrication of prostheses.

    "Although limbs have come a long way, we can still improve them with additional capability, and we're working to accomplish that," said Dr. Walsh. With efforts to reduce basic problems such as friction between the prosthesis and the body; development of energy-storing parts that will receive an impact and rebound; and use of titanium implants, which were pioneered in dentistry and will grow directly to bone, providing a stronger prosthesis, the world of rehabilitation medicine is offering patients new limbs that are not only lifelike, but perhaps will be an improvement on what nature originally provided.

    What disability? Active patient wears out prosthesis


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