Prosthetic limbs get smarter with microprocessors

Donald Crosby, injured by a gunshot wound during combat in the Vietnam War, has worn a prosthetic leg since 1971, so he can attest to how much better prostheses are now compared with then.

“The very first knee unit I had was nothing more than a door hinge with a screw to give it some friction,” he said. “That’s how far the field has come.”

The prosthesis he got fitted with last week at McGuire Veterans Affairs Medical Center was nothing like the first one and was a significant improvement over even his previous one.

It took him only minutes to realize just how much better it was. He stepped into a swimming pool at McGuire, not having to worry that the tiny microprocessor inside the prosthetic knee, controlling its movement, would stop working.

“I swim about once a week,” he said. “I am going to show up to my water aerobics class and swim class and see how many eyeballs pop and mouths drop,” he said. Normally he would take the prosthesis off before getting in water.

Crosby, 66, who lives near Charlottesville, is one of the first veterans locally to get the new waterproof Ottobock X3 microprocessor-controlled knee developed by the German firm named for the prosthetist Otto Bock, who started the company in 1919.

The X3 knee is an upgrade from a previous version, the X2, and was developed in collaboration with the Military Amputee Research Program to be more rugged, have a longer battery life and a more intuitive feel.

It used to be that an amputation would likely end a service member’s career. That is not necessarily the case anymore, but those men and women who remain on duty need prostheses that allow them to perform to military standards.

More than 1,700 service members have lost limbs as a result of the wars in Iraq and Afghanistan, conflicts in which roadside bombs and improvised explosive devices cause devastating blast injuries.

The X3 microprocessor, a tiny battery-powered computer, “can read what you are doing with the leg,” explained John R. Fox, chief of the Orthotic and Prosthetic Lab at McGuire hospital. “Whether you are swinging it forward or if you’re going to fall, so to speak. It’s got safety features built into it. … Somebody said it reads 5,000 motions per second.”

It can also tell when there is a change in terrain, and the wearer can go from a walk to a run in seconds. It can be programmed using Bluetooth. Users have a remote to switch modes from walking to riding a bike, for instance.

“Whereas the first one, in order to program it, someone had to walk alongside me with wires connected to it,” Crosby said.

“If (people) see me walking on a level surface, they would not notice any difference” in his gait, Crosby said. “Technology … has made walking faster, made it more smooth, built in some safety features. If I should stub my toe, for example, it gives you that split-second that you can catch yourself and you’re not falling flat on your face. I can’t tell you how many times I have done that.”

There are other microprocessor knees, but they are not waterproof, Fox said. And there are other prosthetic knees that are waterproof, but they don’t have the microprocessor controls, he added.

“Most amputees don’t wear their limb into the water. And it’s difficult to be in the pool without a limb on because you are on one foot. But to have a prosthesis and stand there in the water is a pretty remarkable thing to a lower-limb amputee,” Fox said.

Crosby, a finance and budget manager for facilities planning and construction at the University of Virginia, said the longer battery life is also a big plus. His previous knee had to be recharged every night.

“This one has a battery life of five days, so I can forget it for a day now, or if I do forget it for a day I don’t have to worry (that) … I’m leaving work at 4 o’clock and it just went into safety mode because the battery died,” Crosby said.

Fox said the knee can cost $60,000 to $80,000, the higher end the cost at retail, and adding a prosthetic foot and other components can bring the total cost to more than $100,000.

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