Power Prosthetics Propel Service Members to Better Lives

By Terri Moon Cronk

American Forces Press Service

BETHESDA, Md., April 27, 2012 – Marine Corps Cpl. Garrett Carnes was on a clearing mission in Afghanistan‘s southern Helmand province in February when he stepped on a pressure plate that exploded and cost him both legs.

Two months later, the former squad leader was fitted with prosthetic legs -- one with the X2 microprocessor power knee, and the new combination of a bionic foot and ankle at Walter Reed National Military Medical Center here.

Carnes, 22, called his first steps “motivating.” The gift of being able to walk so soon exceeded his expectations. “Mentally, it feels good to get back on my feet,” he said, taking steps on a slightly elevated ramp with parallel bars to grasp. “It’s a little awkward, like a baby who’s learning to walk.”

Such steps are taken every day at Walter Reed’s prosthetics gait lab, where rapidly changing technology is giving active-duty service members the chance to walk again and, in some cases, return to duty, said Dr. Charles Scoville, chief of amputee services in the orthopedics and rehabilitation department.

First considered impossible to design, the X2 and higher grade X3 knees have provided a new way of life for above-the-knee amputees, Scoville said. New microprocessors have five sensors, compared with the original C-Leg, which had two.

Now, a combination of gyroscopes, accelerators and hydraulics provide the knee with greater stability, mobility and versatility by recognizing actions, officials said. The multiple sensors can determine when the wearer wants to sit down or go up and down ramps and stairs, all without presetting the limb with a remote device, as required by the former technology.

The first prosthetic limbs, Scoville said, had mechanical knees that were neither limber nor conducive to the warfighter. The wearer had to swing the leg outward and project himself forward to walk.

The Biom ankle -- a combination foot and ankle prosthetic that works with the X2 or X3 knee and is specifically designed for returning warfighters -- is the newest device that enables flexibility.

Scoville describes the knee and ankle/foot combination as more intuitive than older versions.

“It does the work for you,” he said. By replacing the once-rigid prostheses, the new, lighter and user-friendly limbs allow enough flexibility to stand on one leg, and step or walk backward without falling, he said.

Army Staff Sgt. Billy Costello demonstrated his knee, foot and ankle flexibility by sitting on the floor and stretching to pull his foot toward him. He also lost a leg by stepping on an improvised explosive device while on a clearance mission.

“We had just taken out 19 IEDs,” he said. “I found one more the hard way.”

Costello was another patient who progressed faster than his doctors expected. Soon to be discharged, he is an intern at the FBI Academy in Quantico, Va. and plans to enter the National Guard when he returns to North Carolina.

“I still want to support the guys,” he said, adding that he would deploy if his medical condition allows it, but quickly added he doesn’t want to be a “liability” to his unit.

“The vast majority of patients won’t return to active duty,” Scoville said. “Our goal is to bring them to their highest level of function.”

Scoville said 1,453 troops with severe limb loss have been fitted with prostheses since December 2001 and of those, some 300 service members returned to duty, with 53 redeploying to Iraq and Afghanistan.

“We view patients as tactical athletes,” Scoville said. “They don’t have an off-season and they don’t know when their next game will be."

Marine Corps Cpl. Rory Hammill plans to resume his active lifestyle once he’s discharged from active-duty. Before an accident in Marja, Afghanistan claimed one of his legs, he was a runner, snowboarder and surfer, all of which he hopes to resume he said, close to the level of ability he once had.

These service members are just a few of the 200-250 patients who are fitted with prosthetic limbs each month at Walter Reed, said David Laufer, chief of orthotics and prosthetics services. By contrast, he added, the civilian sector produces about the same number per year. In addition to limbs, the lab also creates hands that can move fingers, with such dexterity that they can operate a computer mouse and perform other daily tasks. Designing and developing hands is the lab’s niche, Laufer said, noting that work is ongoing to enable hands to act intuitively like ankles, feet and knees.

Far fewer hands are made in the lab than legs. “The standard of care is shifting,” Scofield said. “It’s made a significant impact on the wounded warriors who live with these advances. We want people to know we’re restoring their lives.”