Two million people in the United States are living with amputations. For many of them, prosthetic devices offer greater mobility.

Now, researchers are testing a new generation of prosthetics that are like nothing you’ve seen.

Not much slows down Zac Vawter, not even an amputated leg.

"I lost my leg in a motorcycle accident," said Vawter, who received a prosthetic that helps him get around, but has its limitations. "If I were to sit down and leave the knee locked, it would stay locked."

But a thought-controlled myoelectric leg does what Vawter's prosthetic can't. Before Vawter could use it, orthopedic surgeon Doug Smith took nerves from his lower leg and redirected them to his hamstring muscle.

"Instead of firing when you think about bending your knee, it would fire when you think about raising your ankle," said Smith, orthopedic surgeon, Harborview/UW Medicine.

When Vawter wants to move the leg, the brain signal travels down his spinal cord, through the nerves; electrodes in the prosthetic pick up signals from the muscles. 

"You can have a prosthetic device that actually works according to your thought," Smith said.

The device is still being studied, so Vawter can't take it home, but he looks forward to the day he can.

"Stairs with that leg, the 'bionic leg,' is really phenomenal," Vawter said.

Until now, only thought-controlled arms were available. Although the cost of the "bionic leg" hasn't been determined, researchers said a version could be available for consumer use within three to five years.

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