Researchers Develop Promising Technique to Aid Amputees' Movement of Artificial Limbs

By Jessica Berman

Washington
11 February 2009

Researchers have developed a promising technique to help double arm amputees move their artificial limbs using a procedure that harnesses the remaining nerves that would otherwise be lost due to their injuries.  

Arm amputees commonly use devices attached to their shoulders to transfer movement to cables that operate artificial arms or wrists.

But these conventional prosthetic limbs operate only one motion at a time and are imprecise and artificial arms that operate using brain signals are still in the developmental stage.

Now, researchers at the Rehabilitation Institute of Chicago are working on a third option that holds promise for double arm amputees. The technique is called targeted muscle reinnervation, or TMR. It preserves the remaining nerves of arm amputees that might otherwise be lost in the injury.

TMR surgically transfers the nerves to the wall of the chest or the non-functioning muscles in the upper arm above the injury.

The idea is to stimulate the remaining arm nerves to generate electrical signals to operate prosthetic devices.

Researchers conducted a study involving five volunteers who had lost their arms, but had the TMR procedure. The participants were asked to perform 10 different tasks, including flexing and rotating their wrists, moving their elbows and grasping, using a virtual prosthetic arm.

Double amputee Jess Sullivan was one of the volunteers.

"It's amazing when you are sitting there and you close your hand and the computer, the virtual screen closes, and you can make it move fast or slow," he said. "I mean you control the whole thing. It's exciting."

Researcher Todd Kuiken says investigators used advanced computer algorithms to help patients control their own movements.

"Now when the patient thinks, 'Close hand,' for example, a little piece of muscle on their biceps or their chest contracts to tell their prosthetic hand to close," he said.

Researchers, led by Dr. Kuiken, found that all of the patients were able to adequately operate arm prosthetics with TMR, with three patients using advanced prosthetics.

"I hope that people with amputations realize that people are working on improving the technology and that there are technologies coming down the pike that will help them," he said. "Whether it's this technology or other similar technologies, a lot of people are working to minimize the impact of disability and apply technologies to help people with disabilities."

Todd Kuiken and his colleagues report their work in this week's issue of The Journal of the American Medical Association.