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Monday, July 23, 2007

Iraq veteran demonstrates motorized artificial foot

By Felicia Mello, Globe Correspondent

After losing a foot and part of a leg to a landmine during the invasion of Iraq, Garth Stewart is determined to keep active. The 24-year-old retired Army specialist makes time for jujitsu and boxing in between history classes at Columbia University in New York. Still, sometimes the artificial limb he uses can't keep up with his busy schedule.

"Your hip ends up doing so much work because it has to draw the foot forward," he said. "At the end of the day you have soreness in your back."

Hoping to help Stewart and others who have lost limbs walk more normally, a team of researchers from MIT, Brown University and the Providence Veterans Affairs Medical Center today unveiled the first motor-powered prosthetic foot. The computer-controlled appendage can relax or stiffen in response to changing terrain, propelling the wearer forward more quickly and reducing fatigue.

"The ankle kind of has a mind of its own," Stewart said in a telephone interview, after demonstrating the device in front of an audience of reporters and fellow amputees at the medical center. "At first I felt like it was fighting me, but once I got accustomed to the rhythm, it felt like having my leg back."

The US Department of Veterans Affairs, which spent $7.2 million to develop the prosthesis, has poured resources into creating better aids for the large number of wartime amputees returning from Iraq and Afghanistan. Six percent of soldiers wounded in the Iraq conflict have required amputation of a limb, compared with 3 percent in previous wars, according to a 2004 US Senate report.

"One of the things that's different about this war is that soldiers are surviving injuries that formerly would have been fatal, due to advances in field medicine and also the fact that soldiers are protected with Kevlar body armor," said Robert Swift, associate chief of staff for research at the medical center. "However, what's not protected is their limbs."

Seventy percent of leg amputees suffer from back problems caused in part by traditional prostheses, said Hugh Herr, a Massachusetts Institute of Technology professor and a double amputee who helped develop the device and tested it on himself.

Herr said in an interview that he and his colleagues "stole ideas from nature" to create the prosthesis, which is heavier than a conventional artificial foot but requires less energy to walk. It uses a motor instead of muscle and springs to replace the stringy tendons that connect muscle to bone.

The researchers plan to begin clinical trials on the prosthesis in March.

Herr said he and his team are also working on developing artificial limbs that would be controlled directly by the brain rather than by a computer, by taking advantage of the 'phantom limb' phenomenon in which an amputee's brain tries to move an appendage that is no longer there.

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