New Prosthesis Could Help Keep Troops in the Fight

Army Spc. Charles Parker looks on as Sven Zarling, from Otto Bock International, demonstrates the capabilities of a prototype of a prosthesis designed to give above-the-knee amputee servicemembers mobility they need to remain on active duty if they choose. The prosthesis uses a microprocessor to control the knee’s hydraulic functions and can anticipate the wearer’s actions and make changes in real time. Photo by Fred W. Baker III   (Click photo for screen-resolution image);high-resolution image available.

A preview of the new technology yesterday at Walter Reed Army Medical Center drew key staff and several servicemember amputees. The open forum allowed users to see improvements in prototype form and ask developers questions or offer suggestions.

In 2006, Otto Bock HealthCare, a global provider of prosthetic components that started out providing devices for German World War I veterans in 1919, began developing a prosthetic knee system that is an upgrade to its already popular C-Leg. It was awarded a three-year $1 million contract to develop a leg that will allow more servicemembers to stay on active duty if they choose to.

The prosthesis is for above-the-knee amputees and uses a microprocessor to control the knee’s hydraulic functions and anticipate the wearer’s actions and make changes in real time.

This will give servicemembers greater flexibility to change speeds or directions without sacrificing stability.

The project began in 2006, and developers are through the prototype development. Barring any technical problems, the new prosthesis should be available to servicemembers in 2009.

Mobility will be improved, allowing more movement without the user having to concentrate on the knee, said Hans-Willem van Vliet, the program manager.

The new system will have more sensors, a faster hard drive, more memory, and will provide smooth transitions between movements such as level-ground walking, climbing stairs, and running.

It also will allow servicemembers the ability to turn around while walking and walk backward in one fluid movement, something that is not possible with the current C-Leg. It will adapt automatically between walking speeds and gaits, Vliet said.

He emphasized that engineers have not simply improved the C-Leg, but have completely rebuilt the technology on the inside.

Engineers also are working to stretch battery life to 50 hours on one charge. This will give servicemembers on long road marches the duration they need to reach a power supply for recharging.

Requirements also call for making the system salt-water resistant, a difficulty with the onboard computer systems. They also are planning a remote control, about the size of a car-lock remote, that will allow the user to switch among as many as 10 modes with the click of a button.

The current C-Leg allows servicemembers two operating modes: one for walking and one for bicycling or another activity. To switch between modes, the wearer has to swing the leg forward in a jerky fashion. In some instances the user may not be able to switch modes because of limited movement. Reprogramming a mode requires a visit to a technician.

Air Force Lt. Col. Andrew Lourake, a pilot at Andrews Air Force Base, Md., is the first above-the-knee amputee to return to active duty as a pilot. He was fitted with a C-Leg five years ago. Lourake said he could not do his job without the C-Leg because it allows him to switch between walking and flying modes. Still, he said, he is impressed with the new design and plans to be one of the first to own one, even if he has to pay for it out of his own pocket. The current C-Leg costs about $30,000. The new system is expected to cost about the same.

“I’m excited. It has a lot of the stuff that I asked for a couple of years ago. It’s huge in functionality and active living,” Lourake said.

Right now, he has to reprogram his second mode from flying mode to bicycling or running. With the new leg, he won’t have to make as many visits to his prosthetic technician.

“I’ll have everything right in the leg, and I’ll never have to touch the computer again,” he said.