|Not all prosthetics are compatible with people, and some individuals opt not to use them at all as they can sometimes be bulky or difficult to use / Photo by By SeventyFour via Shutterstock|
Losing a body part can be a devastating blow to anyone. Fortunately, as modern medicine and technology progress, people could be outfitted with custom prosthetics that could imitate their lost limbs. Just recently, the development of this technology has reached far greater heights.
Uses and Limitations
Prosthetics have been helpful to thousands of amputees for allowing them to be able to recover some of the abilities that their lost limbs performed. However, given the complexity of our limbs and the way they’re controlled by our neural systems through a complex network of nerves and muscles, it is difficult to completely replicate the movements that a normal functioning limb is capable of.
Not all prosthetics are compatible with people, and some individuals opt not to use them at all as they can sometimes be bulky or difficult to use, with about 20% of amputees rejecting their use. However, there have been huge advancements in both surgical techniques and technology that have been getting closer to achieving the results that everyone hopes to see.
Knowing the Prosthesis’ Position
MIT was able to develop a new surgical procedure that allows prosthetics to act more naturally. By using feedback from the remaining nerves and muscle grafts, the prosthetics will be able to tell its position in space without its owner having to rely on visual cues and also be able to feel the amount of pressure being applied to them. Before this method was devised, there was no dependable neural method for allowing an amputee to feel such things with their prosthetics.
Most amputees must visually follow their prosthetic limbs with their eyes in order to determine where it is in space and to make sure it's on the right track. This is because there is an absence of limb control through agonist-antagonist pair muscles, wherein as one muscle contracts, the other stretches or relaxes. The pair sends back signals to the brain at the same time to form a complete sensory picture that allows us to know intuitively where our limbs are even when we’re not looking at them, as explained by Technology Review.com.
By grafting new muscles to the places where the old ones were and attaching the still viable nerve endings to them, an amputee can sense their artificial limb as they normally would their old limb by sending brain signals to it and then receiving the corresponding signals back.
The University of Chicago, according to its own website, has formed a research team that has the ultimate goal of creating a prosthesis with the functionality and dexterity of a normal hand. Using their background experience with somatosensory and motor neuroscience, as well as a grant from the National Institutes of Health reaching about $3.4 million, they hope to create prosthetics that can be controlled with the human mind and receive better sensory input.
The system will incorporate robotic neuroprosthetics that works by implanting a number of electrodes, which serves as connections from the artificial limb to the brain that sends neural signals. These electrodes will detect the neural activity, say, of the person thinking about moving their robotic limb. Prosthetic hands will also be outfitted with complex sensors that will give the person a sophisticated mimic of the sense of touch. While they will also attempt to tackle to problem of moving a prosthetic limb through free space with better dexterity, their main concern will be solving the challenge of controlling a limb once it comes into contact with an object, and adjusting and calibrating the prosthetic in the right ways for it to manipulate the object properly.
There are a great many challenges that must be faced by researchers attempting to perfect prosthetic technology. Attempting to precisely mimic the motor-neural connection is one of them. Given that there can be anywhere from 12 to 15 thousand nerve fibers in a single-limb system, it is impossible to individually stimulate every single one of these in order to replicate perfect movements. Electrodes are only able to simulate hundreds of them at once, which makes the movements less accurate. Scientists thus use models to find out how certain groups of fibers respond when stimulated at once.
|The University of Chicago has formed a research team that has the ultimate goal of creating a prosthesis with the functionality and dexterity of a normal hand / Photo by By Zoriana Zaitseva via Shutterstock|
Another problem is the longevity of the brain-computer interface. In order to get the most accurate impulses, electrode arrays often need to be implanted into the brain. These neural implants will naturally be rejected by the brain, and it will fight off the foreign device. The implants therefore usually don’t last long—about a few years on average. It would be impractical to have a craniotomy done every few years to implant new ones, as explained by MedicalDevice-Network.com. Thus, scientists must find a way to make sure that these neural systems last a lifetime.
Finally, there’s the problem of the brain itself. The functions of the parts of our brain and how they all interconnect are still a complicated science that has not been perfected.
With several teams working toward the same goal, we may very well see realistic-looking and fully functional prosthetic limbs for amputees in the not-so-distant future.