These days, advances in prosthetic devices, bionic limbs and exoskeletons continue to advance and amaze. Not only are doctors and medical researchers able to restore mobility and sensation to patients suffering from missing limbs, they are now crossing a threshold where they are able to restore these abilities and faculties to patients suffering from partial or total paralysis.
This should come as no surprise, seeing as how the latest biomedical advances – which involve controlling robotic limbs with brain-computer interfacing – offer a very obvious solution for paralyzed individuals. In their case, no robotic limbs or bionic attachments are necessary to restore ambulatory motion since these were not lost. Instead, what is needed is to restore motor control to compensate for the severed nerves.
Thanks to researchers working at Case Western University in Ohio, a way forward is being proposed. Here, a biomedical team is gearing up to combine the Braingate cortical chip, developed at Brown University, with their own Functional Electric Stimulation (FES) platform. Through this combination, they hope to remove robots from the equation entirely and go right to the source.
It has long been known that electrical stimulation can directly control muscles, but attempts to do this in the past artificially has often been inaccurate (and therefore painful and potentially damaging) to the patient. Stimulating the nerves directly using precisely positioned arrays is a much better approach, something that another team at Case Western recently demonstrated thought their “nerve cuff electrode”.
This electrode is a direct stimulation device that is small enough to be placed around small segments of nerve. The Western team used the cuff to provide an interface for sending data from sensors in the hand back to the brain using sensory nerves in the arm. With FES, the same kind of cuff electrode can also be used to stimulate nerves going the other direction, in other words, to the muscles.
The difficulty in such a scheme, is that even if the motor nerves can be physically separated from the sensory nerves and traced to specific muscles, the exact stimulation sequences needed to make a proper movement are hard to find. To achieve this, another group at Case Western has developed a detailed simulation of how different muscles work together to control the arm and hand.
Their model consists of 138 muscle elements distributed over 29 muscles, which act on 11 joints. The operational procedure is for the patient to watch the image of the virtual arm while they naturally generate neural commands that the BrainGate chip picks up to move the arm. In practice, this means trying to make the virtual arm touch a red spot to make it turn green.
Currently in clinical trials, the Braingate2 chip is being developed with the hope of not only stimulating muscles, but generating the same kinds of feedback and interaction that real muscle movement creates. The eventual plan is that the patient and the control algorithm will learn together in tandem so that a training screen will not be needed at all and a patient will be able to move on their own without calibrating the device.
But at the same time, biotech enhancements that are restoring sensation to amputee victims are also improving apace. Consider the bionic hand developed by Silvestro Micerna of the École Polytechnique Fédérale de Lausanne in Switzerland. Unlike previous bionic hands, which rely on electrodes to receive nerve signals to control the hand’s movement, his device sends electronic signals back to simulate the feeling of touch.
Back in February of 2013, Micerna and his research team began testing their bionic hand, and began clinical trials on a volunteer just last month. Their volunteer, a man named Dennis Aabo Sørensen from Denmark, lost his arm in a car accident nine years ago, and has since become the first amputee to experience artificially-induced sensation in real-time.
In a laboratory setting wearing a blindfold and earplugs, Sørensen was able to detect how strongly he was grasping, as well as the shape and consistency of different objects he picked up with his prosthetic. Afterwards, Sørensen described the experience to reporters, saying:
The sensory feedback was incredible. I could feel things that I hadn’t been able to feel in over nine years. When I held an object, I could feel if it was soft or hard, round or square.
The next step will involve miniaturizing the sensory feedback electronics for a portable prosthetic, as well as fine-tuning the sensory technology for better touch resolution and increased awareness about the movement of fingers. They will also need to assess how long the electrodes can remain implanted and functional in the patient’s nervous system, though Micerna’s team is confident that they would last for many years.
Micerna and his team were also quick to point out that Sørensen’s psychological strength was a major asset in the clinical trial. Not only has he been forced to adapt to the loss of his arm nine years ago, he was also extremely willing to face the challenge of having experienced touch again, but for only a short period of time. But as he himself put it:
I was more than happy to volunteer for the clinical trial, not only for myself, but to help other amputees as well… There are two ways you can view this. You can sit in the corner and feel sorry for yourself. Or, you can get up and feel grateful for what you have.
The study was published in the February 5, 2014 edition of Science Translational Medicine, and represents a collaboration called Lifehand 2 between several European universities and hospitals. And although a commercially-available sensory-enhanced prosthetic may still be years away, the study provides the first step towards a fully-realizable bionic hand.
Yes, between implantable electronics that can read out brainwaves and nerve impulses, computers programs that are capable of making sense of it all, and robotic limbs that are integrated to these machines and our bodies, the future is looking very interesting indeed. In addition to restoring ambulatory motion and sensation, we could be looking at an age where there is no such thing as “permanent injury”.
And in the meantime, be sure to check out this video of Sørensen’s clinical trial with the EPFL’s bionic hand: