Embracing the Artificial Limb By Rachel Metz
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http://www.wired.com/news/medtech/0,1286,66633,00.html
02:00 AM Feb. 18, 2005 PT
If your vision of the future includes Robocop-like body appendages, several scientists hope to meet you there.
This isn't a silly cyborg fantasy, but what a group of scientists from Brown University, MIT and the Providence VA Medical Center in Providence, Rhode Island, see as the future of artificial limbs -- a project they have funded through the next five years via a $7.2 million research grant and an additional amount to build an advanced rehabilitation facility from the Department of Veterans Affairs.
The goal is to create artificial "biohybrid" limbs that merge man-made components with human tissue -- muscles, skeletal architecture and the neurological system --and work like fully functioning human appendages.
"Basically the challenge of developing a prosthesis is blending it or creating this intimacy between the artificial device and the human," said Hugh Herr, an MIT assistant professor in the school's health sciences and technology department and director of the biomechatronics group in its Media Lab.
Herr, himself an amputee, is working on the project by focusing on building "the next generation" of artificial knees and ankles. Other aspects of the biohybrid program will be generally applicable to both arms and legs, he said.
That such a futuristic program would be funded by the Department of Veterans Affairs is no surprise to some. In the last year, the VA alone fitted 6,000 new prosthetic limbs and performed adjustments and repairs on 40,000 of them, said Stephan Fihn, acting chief research officer for the Department of Veterans Affairs.
"In executive speak, it's a ... major line of business for us," he said.
While many of those fitted with new limbs are older veterans, there are also plenty of recently injured younger amputees who were wounded in conflicts in Afghanistan and the war in Iraq. The biohybrid work focuses on helping these types of people -- those with what Fihn calls "traumatic amputations."
More generally speaking, Herr estimated there are about 1 million amputees in the United States alone, and said about 150,000 leg prostheses are sold annually.
The idea for marrying an artificial limb to the human body sprang from the ideas of many different scientists, said Dr. Roy Aaron, an orthopedic professor at Brown Medical School and director of the project's Center for Restorative and Regenerative Medicine. Now, scientists from Brown, MIT and the Providence VA Medical Center are working to make this Inspector Gadget-like brainchild a reality.
There are some prostheses currently on the market -- the programmable C-Leg, for example -- that use computer chip technology, Fihn said. The C-Leg can be customized to work with a wearer's movement idiosyncrasies. Over time, it becomes "much more active than a passive appendage," Fihn said. But still, like uncomfortable wood and plastic limb replacements of the past, even this advanced model must be physically attached to the user.
For a biohybrid limb, doctors might insert a metallic rod into the residual bone of an amputee's limb and build the prosthesis around that platform, Fihn said.
Research will cover several different topics, including prosthetic limbs, tissue engineering, neuroscience, limb-lengthening techniques, ways of integrating prostheses with users by attaching them directly to amputees' bones, and the regeneration of skin, muscles and nerves.
Much of the general science necessary to create the final product is already in place, Aaron said, but some things, like neuroscience, will be used in new ways. So while recent reports showed the development of technology that allows users to move computer cursors with their minds, Aaron and his colleagues are wondering if they can use similar techniques to enable a person to move a robotic limb.
Another challenge that must be overcome is the risk of infection to the user.
"The problem, of course, is this is a foreign body that is simultaneously inside and outside the body," Fihn said.
Herr said he hopes to start testing biologically inspired leg devices -- prostheses that move like actual human legs but aren't biologically implanted -- in about a year.
"And the second step, pardon the pun, is linking that leg to the neural signals. And maybe a final step is attaching that limb directly to the skeleton," he said.
Lower-extremity amputees would qualify to test the prosthetics, Aaron said. He supposed wounded veterans would have first dibs, but said they would consider anybody who fit the criteria.
The final products of this research could help amputees both physically and psychologically. People tend not to be ashamed but "often celebrate the fact that they have an artificial limb, when it actually works," Herr said.
Those who've lost limbs currently view their prostheses as tools, not as parts of their own bodies, he said, adding that the group projects that when they can blend the two, amputees will "in a more profound way truly accept the artificial limb."