Iceland based Össur makes some of the slickest bionic limb attachments you can buy. The company’s lower leg prosthetics have the ability to sense the phase of the gait and smoothly power the artificial ankle joint to the appropriate angle for different points in the stride. While that’s pretty handy for making predictable movements on predictable terrain, what would be even better is if the prosthetic could be automatically positioned at any time in response to residual muscle commands still naturally generated by the wearer.
On Wednesday, the Össur team announced that they have in fact already achieved just that with the willing cooperation of two amputees. The team is calling their results nothing less than “subconscious thought control,” and nobody seems to be contesting that claim. At the the heart of the new prosthetic is their standard Proprio foot, only now instead of taking commands from a suite of inertial or other position sensors, it smoothly responds to myoelectric sensors embedded in the wearers intact calf muscle.
The 3mm x 5mm sensors were not directly developed by Össur — instead, they were supplied by the US-based Alfred Mann Foundation. They are inductively energized by a power system embedded in the overlying socket that receives the ankle prosthetic. After a 15-minute surgery to implant the sensors, and a few minutes to play around with moving the joint, the users found they could precisely position the joint as if it were their own natural foot.
To say that they are doing this just by thinking is in a strict sense true, but it is not quite the same principle as a direct brain-controlled interface (BCI). For one thing, it is much more accurate and reliable. The device is so fast that it reads natural commands sent from the motorneurons to the muscle and initiates actuation of the foot faster, and then the commands actually contract the user’s own calf muscle. However, although the process is fairly described as automatic, the user still has to make the actual motive effort. That is a little different than just making the purely mental effort of imagining a moving foot, or whispering an intention of movement in one’s inner voice.
One bonus of the concept is that the user’s own muscle, while not bearing true loads in any practical sense, is still exercised toward a productive end. Not only does that help maintain the muscle, but we might presume that the ‘feels’ accompanying the movement would be convincing and satisfying. In perusing the Össur build-a-body website, it looks like they have many other kinds of amenities an amputee might want to add to their shopping cart. Nothing yet as far as true osseointegrated limbs are available, but there are fancy vacuum systems which compensate for fluctuations in limb volume to maintain a snug fit. Depending on how and where the vacuum is applied, it might also serve to keep the limb engorged with blood to maintain it dimension.
Össur also has various joint locks, clutches, and attachment sockets which can even add functionality lacking in the real thing. There still doesn’t seem to be much info out there as far as how capable the actuators in the joints are. In other words, how much power might potentially be available in the basic design to do more than just passive positioning. It looks like they have hydraulic capability in some of their ankles, but we might have to wait a bit to learn everything they have in store.
Learn more here http://www.ossur.com/about-ossur/news-from-ossur/1396-ossur-introduces-first-mind-controlled-bionic-prosthetic-lower-limbs-for-amputees