Researchers say that 32-year-old, Zac Vawter, successfully
controlled movements of a motorized artificial leg using only
his own thoughts. Video: Rehab Institute of Chicago.   Aided by
sensors receiving impulses from nerves and muscles that once
carried signals to his missing knee and ankle, the patient was
able to climb and descend stairs and walk up and down inclines
much as he could with a natural leg, based on directions that
came from his brain. Importantly, he was able to flex the
device's ankle, enabling a near-normal gait, something not
possible with current prosthetics.   Zac Vawter walked down
stairs with his bionic leg. Andrew A. Nelles for The Wall Street
Journal    For Mr. Vawter, Dr. Hargrove said, "it's all
intuitive. He can walk up or descend stairs in stride."  Dr.
Hargrove is lead author of a report on the technology, published
Wednesday by the New England Journal of Medicine.  More than a
million Americans are living with amputations, including some
1,600 soldiers who returned from wars in