How many people have lost a leg and then controlled a robotic replacement leg with their mind?

According to Nature.com, a man who lost his leg in a motorcycle wreck in 2009 is the first person to control a robotic replacement leg with his mind. The technology uses muscle signals to amplify messages sent by the brain in conjunction with a process called targeted muscle reinnervation. Scientists said they hope that other people with missing limbs will be able to use the technology within the next three to five years.