Wounded Warrior first to use next-generation powered legs

By Craig ColemanApril 24, 2009

Wounded Warrior first to use next-generation powered legs
(Photo Credit: U.S. Army) VIEW ORIGINAL

WASHINGTON (Army News Service, April 24, 2009) -- Lt. Col. Greg Gadson, a bilateral above-the-knee amputee, stood in bright sunlight on the patio of Walter Reed's Bldg. 88, April 17.

A pack of reporters pointed mini-audio recorders, and a clutch of television cameramen rolled tape. The Wounded Warrior's prosthetic legs looked, with their composite construction and gray-on-silver design, like futuristic science fiction movie props.

Gadson is the first person to use the completed version of the Power Knee2, a next-generation powered prosthetic knee featuring new artificial intelligence and sensor technology that makes it possible for above-the-knee amputees to walk with increased confidence, safety and a more natural gait.

Earlier, Gadson walked on his new bionic legs from the Military Advanced Training Center to Bldg. 88 flanked by his doctor, Lt. Col. Paul F. Pasquina, chief of integrated orthopedics and rehabilitation at Walter Reed Army Medical Center and the National Naval Medical Center, and his prosthetist, Michael Corcoran.

The trip across the street went smoothly, Gadson used two canes for balance. But just one week earlier, his first training session with his new knees was more challenging. Gadson walked gingerly around the MATC indoor track that morning. The powerfully-built former West Point football star marched step after step, connected by a long cable to the overhead oval support system, a pulley and rail that keeps patients from falling to the ground while they practice walking.

He took one, two, three steps - then one of the knees buckled, and he was left swinging by the tether cable. Corcoran, the prosthetist, helped him stand again. Gadson lost his balance often, but each step was a small victory.

With each stumble, engineers from Ossur, the prosthesis' designer, tapped furiously at a laptop keyboard connected to the prosthetics by Bluetooth, making adjustments based on Gadson's gait.

Corcoran said that Gadson's willingness to fall was key to his ability to help the design team. He said people learning to walk on prosthesis who are afraid to fall won't push themselves.

"Basically, he's perched up on these prosthesis, and that's a long way off the ground," Corcoran said. "Imagine you're standing on a table and lose your balance. It's a similar feeling. For him to be able to pick himself up and carry on has got us to this point. It's a testament to [Lt.] Col. Gadson that we're here."

"He was a leader on the field at West Point, he was a leader to his battalion in combat, he's a leader in our rehabilitation environment," said Pasquina. "To be part of that for us as a medical team has been an honor."

Pasquina said the medical team tries to challenge the available technology in order to give the patient as much mobility and independence as possible. They simulate movements ordinarily made in the home, like climbing and descending stairs.

"Which unfortunately does mean you do need folks like [Lt.] Col. Gadson, who are willing to take some spills along the way," Pasquina said. "But you need leaders like him to bring this technology to market."

Pasquina noted the new knee is not a military application. "The intent is not to have better prosthetic knees for Soldiers, the intent is to have better prosthetic knees for the world's population."

Corcoran also said the knee wasn't designed for athletes, but for everyone. "If I lost a leg this is what I'd be looking for," he said.

Gadson's involvement in the project began when the designers asked him to walk on the original Power Knee, first produced in 2006. The developers took feedback from amputees on how to improve the technology. The new knee is smaller, lighter, quieter, and implements an advanced stumble recovery mode, improving its safety. Gadson traveled to Iceland, where the designer is based, to participate in the development.

"A lot of the complaints and feedback we were able to give them, they incorporated," Gadson said. "The engineers did a great job in responding to challenges and taking our feedback during development."

Gadson trained with the new knees four times in the seven days between his first experience with the final product and the news conference. In that time the improvement in his stability was evident. He was able to walk unaided. Corcoran explained that when an amputee steps and lands on the leg, the knee locks, and when they roll over the knee during the stride, it releases. This is done through sensors in the prosthesis.

"These legs really mimic your walk," Gadson said. "I'm trying to think back to what it used to be like to walk...the feeling of natural motion. When you are wearing a passive (unpowered) prosthetic, you have to kick that leg out and you're listening or feeling for a secure lockout before you put that foot down. This is much more natural. You know that whatever position the leg's in, whether it's in or locked out, it's going to be stable. That really gives you a more natural motion."

Gadson expects the power in the new knees, coupled with the extended range of the new batteries, to impact his quality of life.

"I can already see myself doing things that I never would do, like maybe I might go shopping in crowds. Your range and your overall stability is better." he said.

Partnering with industry and academia on new technologies to help individuals is exciting, Pasquina told reporters.

"And no folks are more worthy of this than our injured servicemembers," he said. "We're just honored to be at this place in our history where we can bring things such as this to help patients."

Gadson's next goal is to learn to walk on his new knees with one cane, then progress to wearing them full time, rather than the two to four hours he uses them today. He knows he will improve with experience. "It's going to come," he said. "But I'm really confident I'm going to get there and I'm really optimistic about what these legs can offer."

(Craig Coleman writes for the Stripe at Walter Reed Army Medical Center)

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VIDEO: "Power knee" prosthetic device