A patient has been using a prosthetic arm that's controlled by electrodes implanted in his nerves and muscles for over a year.
Image: Ortiz-Catalan et al., Sci. Trans. Med., 2014
A real-life patient now has a fully-implanted "mind-controlled" robotic prosthetic for the first time. A Swedish truck driver who had his arm amputated over a decade ago became the first to properly get the arm, which is surgically implanted so as to be controlled by his biological nerves and muscles.
That means that he can control the arm in a pretty natural way, with the nerves and muscles sending signals to the prosthetic in order to move it. It's like you'd move your own arm—you don't have to really think about it.
A paper published today in the journal Science Translational Medicine describes the procedure, which took place in January 2013.
While the idea of mind-controlled prosthetics has been around for a little while, and we've even seen prosthetic limbs controlled by the nerves before, the remarkable thing about this prosthetic is how deeply the neuromuscular interfaces are implanted.
The device is "osseointegrated," which means it's attached directly to the skeleton. The user doesn't have to wear it all the time, however, as only a titanium implant is actually integrated with the bone, and the arm attaches to that. An advantage to this is that it eliminates the cup-like socket used by conventional arm prostheses, which eliminates a lot of potential discomfort and allows for greater freedom of movement.
Researchers led by Max Ortiz Catalan at the Chalmers University of Technology in Sweden reported that, over the course of a year in use, their implanted electrodes offered greater control than the more conventional "surface electrodes," which are placed on the skin.
They wrote that the patient has been using the arm in his daily life ever since. "No complications were observed over one-year implantation, and all components will remain implanted indefinitely," they added.
There are several advantages to using the implanted control system over comparable surface electrodes. The latter work in much the same way, but they're prone to issues such as cross-talk, and can be affected by environmental factors like changes in temperature.
That unreliability is obviously irksome to the user, and the patient with the new arm reported a host of benefits. On a purely practical level, he told the researchers that the more refined control he had over the arm's grip allowed him to pick up small or fragile objects like eggs.
While the study only includes one patient, which means the researchers can't make too many bold claims about the extent of the system's capabilities just yet, it suggests the potential for prosthetics that are both stably attached to the body and easier to control than ever before.
So far we have shown that the patient has a long-term stable ability to perceive touch in different locations in the missing hand
If that weren't exciting enough, there's also the prospect of communication going the other way through the arm—from the prosthetic to the nerves, and on to the brain. According to the authors, "by incorporating signal feedthrough mechanisms into the osseointegrated implant system, long-term communication between the artificial limb and implanted neuromuscular interfaces is possible."
This would not only allow for more accurate control but also give the user sensory feedback; he or she could effectively "feel" with the prosthetic hand.
This is simply incredible.
In a statement, Ortiz Catalan said that this communication between prosthetic limbs and the body had been a "the missing link." The results on the sensory feedback aspect of the arm are only preliminary, but seem to be heading in a positive direction.
"So far we have shown that the patient has a long-term stable ability to perceive touch in different locations in the missing hand," he said. "Intuitive sensory feedback and control are crucial for interacting with the environment, for example to reliably hold an object despite disturbances or uncertainty."
It's still not as good as the real thing when it comes to human limbs, but it sounds like a pretty strong step closer. And when a prosthetic arm can truly rival its biological equivalent, it won't be much longer until it can surpass it.