One Step Closer To The Bionic Leg

In a breakthrough for prosthetics, a Chicago team has developed a robotic leg that is wired directly to the patient’s brain, allowing him to control the mechanism with his thoughts alone:

To accomplish this, surgeons redirected the nerves that previously controlled some of the man’s lower-leg muscles so that they would cause muscles in his thigh to contract in a technique called targeted muscle reinnervation. They then used sensors embedded in the robotic leg to measure the electrical pulses created by both the reinnervated muscle contractions and the existing thigh muscles. When the surgeons combined this information with additional data from the sensors, the man was able to use the leg more accurately than when attempting to control the leg with its sensors alone, the scientists report. They hope that other people with missing limbs will be able to use the technology within the next three to five years.

Derek Mead looks ahead to the next likely innovation:

Integrating a prosthetic directly into a patient’s nervous system would seem to be the answer. Rather than learning how to use one’s robo hand, it could be controlled just as directly as your flesh-and-bone models. The concept has been proven before; research earlier this year showed that a paralyzed person could control robot limbs with her thoughts, but actually deploying it in a prosthetic—especially one as challenging as a lower leg—is even harder. So far, the proof of concept appears to be working (walking?) well, and [lead researcher Levi] Hargrove’s team hopes to have it ready for broader use within a few years.

Update from a reader:

I’m a biomedical engineer who does this type of work every day. I don’t mean to throw cold water on the RIC prosthetic, but targeted reinnervation has been a tested and proven method for controlling prosthetics for almost a decade now. That’s not to say doing it in the leg isn’t an amazing piece of biomedical engineering, and I applaud everything Dr. Kuiken has done, from Jesse’s Arm to this leg work.

But the second problem with this bit of media over-hype is to say the prosthetic is “wired directly” to the brain. That is not the case. It is connected to already existing nerves in the leg (or for arm prosthetics, they connect it to arm nerves they surgically relocate to the pectoral muscle). To say that his prosthetic is “wired directly” to the brain would be like saying my smartphone is directly connected to, without mentioning that the Internet is involved. Directly interpreting brain neural output and using that to accurately control prosthetics is still far, far in the future.