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New Prosthesis Allows Amputees to Feel Again

Could you taste without a tongue? Smell without a nose? Feel without any hands?

The answer may soon be yes. Scientists in Europe have just created a prosthetic limb that allows amputees to feel again.

Prosthetics have come a long way. The earliest written record of prosthetics being used dates back to well over 2000 years ago when a prisoner without a leg used a wooden stump. In the 1500s, Ambroise Pare, a French surgeon, changed the field of medicine by introducing amputations as a means of treatment. Shortly thereafter, Dr. Pare began creating prosthetics for those patients. Today, the field of prosthetics is much evolved and has revolutionized amputees’ quality of life. Whether you’re an athlete or a stay-at-home parent, different prosthetics exist to accommodate various lifestyles. The latest focus in the industry is towards robotic prosthetics. One prototype that has caught the attention of the medical community is one that allows amputees to regain the sensation of feeling.

Led by neural engineer Silvestro Micera, a research team has developed a bionic hand that actually lets amputees experience sensation. Using microelectric implants and sensors, a person is now able to touch an object and identify it based on both shape and rigidity.

Let’s quickly recap how sense works in the human body. When you reach out and touch something, you stimulate mechanoreceptors in the superficial and deep layers of the skin. These receptors have nerve fibers that eventually track up along the spinal cord and then to the brain. Thus, sensation is recognized. This prosthetic works in a similar way. The prosthetic contains artificial tendons, the positions of which are detected by attached sensors. The patterns associated with these changes in position are then translated using an algorithm into an electrical signal that the nervous system can interpret. Finally, these electrical signals are sent to electrodes, which were previously surgically implanted into the amputee’s ulnar and median nerves, that then make their way to the central nervous system.

A one-month long clinical trial with this new prosthetic limb was experimented on Dennis Aabo Sorsensen — a Danish man who lost his left hand nearly a decade ago due to a firework accident. To ensure that the prosthetic limb was the only source of sensation, Dennis was blindfolded and wore earplugs. What were the results? Dennis was able to feel the difference between cotton, plastic and wood. “Suddenly, I could tell if it was a hard object…the response, the feedback, from the arm to my nerves and to my brain, they came very strong.” Not only was Dennis able to sense different materials, but he could also distinguish between the shape and the hardness of objects. Perhaps what is most impressive is the almost instantaneous reaction that occurred from feeling the object to the brain receiving and interpreting the sensory information.

So how safe is this prosthetic and when will it be available on the market? Micera states that it will take a few years of additional research before the limb is optimal for public use. Unlike other prosthetics, this requires the surgical implantation of electrodes into amputees’ nerves. As these electrodes are placed directly into the nerves, there is a risk of permanent nerve injury in the long-term. After the clinical trials were over, Dennis had his electrodes removed.

What’s next in the field of prosthetics? When it comes to human senses, there is far more than just the sensation of fine touch – we can also sense temperature and crude touch. Scientists believe that the technology behind this robotic prosthetic may pave the way towards more advanced artificial limbs that can detect even more. Only time will tell.

“I would love to have the new prosthesis because it is so amazing to feel something that you haven’t been able to feel for so many years,” says Dennis.

Ghady Rahhal Ghady Rahhal (4 Posts)

Contributing Writer

Medical College of Wisconsin

Ghady Rahhal graduated from SUNY with a bachelors in Molecular Biology and minors in chemistry and philosophy. Shorty thereafter, Ghady moved to Boston and worked as a Network & Clinical Analyst for a healthcare company that focused on community-based care. Prior to attending college, Ghady lived in Lebanon which has given him an appreciation for Global Health - a field which he continues to be active in today. Currently, Ghady is a medical student at the Medical College of Wisconsin.