Chicago researchers helping develop technology that could transform prostheses
September 25, 2013|By Juan Perez Jr., Chicago Tribune reporter
Zac Vawter's right leg weighs about 10 pounds, slightly less than his left. But it works normally; he doesn't have to do much more than think to rotate his ankle, walk or climb stairs.
Rather than tissue and bone, the 32-year-old amputee's right leg is a prosthesis made of aluminum, two motors, sensors and a powerful computer system.
Zac Vawter wears a thought-controlled bionic leg at the Rehabilitation Institute of Chicago. (Phil Velasquez, Chicago Tribune)
Vawter is wearing millions of dollars worth of emerging technology that could transform the lives of wounded veterans, accident victims and the elderly. Vawter's bionic leg can essentially read his mind.
A group of Chicago researchers is using about $8 million of the Army's money to expand the experimental field of mind-controlled prostheses, with hopes of bringing the technology to military and consumer markets in the next five years.
The Rehabilitation Institute of Chicago unveiled the latest prototype bionic device this week, in conjunction with its report on robotic leg control to be published Thursday in the New England Journal of Medicine.
The study published in the journal is a progress report on a project with a long history and years of work remaining, but it also can be seen as affirmation of progress.
"We're laying the foundation for the advances that are to come," said Levi Hargrove, head of the center's lab for neurally engineered prostheses and orthotics.
Col. John Scherer sees the technology's potential. From Fort Detrick, Md., he directs Army research intended to restore as much function as possible to veterans with traumatic injuries involving limited mobility, or vision and hearing loss.
There are more than 1,600 amputees from the Iraq and Afghanistan wars, Scherer said. About 80 percent of that population has lower-extremity amputations, he said.
Though prosthetic technology has improved since 2001, the existing technology isn't necessarily designed for a young, active population, Scherer said.
"We're trying to say, 'Hey, we have a population that needs advancements as well,'" he said. "So we're obviously funding projects in those areas to make those advancements so our injured service members can resume the life that they want to live."
Transforming Vawter into a version of the Six Million Dollar Man relied on a rather straightforward concept.
In 2009, Vawter sped a Suzuki motorcycle too quickly through a curve on a rural Washington road. The resulting crash forced doctors to amputate the lower part of his right leg.
During surgery, doctors rewired Vawter's severed nerves into surviving leg muscles, laying the groundwork for advanced prostheses. Within months, Vawter could flex his upper leg when prompted to try to plant or rotate his missing foot.
His brain was sending clear electrical signals to a body part that didn't exist. Vawter began working with the rehabilitation center in December 2010.
Researchers measured his brain signals while he tried to flex and extend the missing knee and ankle. The center's team also developed elaborate software — using tens of thousands of lines of code — to translate the neural signals into specific leg motions.
"It's a fascinating world," Vawter, a software engineer, said while testing the prosthesis inside a 14th-floor laboratory at the rehabilitation institute.
"It's neat to see the way that they're using software, algorithms and machine learning to make this work," the Washington state resident said.
The prosthesis's knee and ankle joints are powered by two small motors. Thirteen mechanical sensors are embedded along the prosthesis, including an accelerometer, gyroscope and sensors to determine how much weight Vawter puts on the leg or how fast he's moving.
Small metal electrodes attach to Vawter's remaining leg to catch his neural signals.
In the lab this week, Vawter sat and thought about bending his knee. A monitor showed a spike in neural activity. The prosthesis's motors whirred. Vawter's knee bent.
When he decided to stand he rose easily from his seat. That's when the leg's gadgets kicked in to predict and account for his movements.
"Ready to go," he said.
Vawter used an earlier prototype of the leg to climb 103 stories of the Willis Tower last year. The latest version has dramatic software improvements that allow him complete independence and a seamless range of motion directed by his thoughts.
The prosthesis used at Willis Tower last year only had modes for walking and stair climbing and required engineers to monitor the device, Hargrove said.
"This is a huge breakthrough," he said. "There isn't anything stopping him from doing that other than maybe security at the front desk."
Researchers will continue to refine the mechanics to reduce the potential for fall-inducing errors. It'll be up to the marketplace to improve the technology further and attach a price tag to it. The team, though, is thrilled with the progress.
"I never, ever thought we would accomplish so much in five years. Never," Hargrove said in the lab. "I'm glad we have."