For amputees, the loss of a limb doesn’t necessarily mean a complete loss of limb function. Some prosthetic limbs can even give amputees advantages in everything from athletic abilities to everyday dexterity. But one hard fact has always remained, even as technologies have improved: An amputee can’t actually feel any sensations coming from a prosthetic limb. That may not be true for much longer.
This week, a team of researchers at European universities published a study that profiles the case of Dennis Aabo Sørensen, the first-ever amputee who can get real-time feeling from a prosthetic hand, which is hooked up surgically with electrodes implanted in the remaining nerves of his upper arm.
The study, published in Science Translational Medicine, discusses how EPFL’s Silvestro Micera worked with a team to develop a sensor-laden artificial hand that detects touch by measuring the tension from artificial, finger-controlling tendons and then translating the data into an electrical current. That current isn’t strong enough for the nervous system to understand, however, so the researchers went a step further, sending the electrical signal directly through the wires implanted in Sørensen’s nerves. Once they did that, Sørensen’s hand could both send and receive information to and from his nervous system.
Sørensen, a 36-year-old amputee who lost the use of his left hand nine years ago during a fireworks accident, received his surgically-implanted hand system in January 2013. It was a big step up from his former prosthetic hand, which could only detect muscle movement (squeeze and it closes, relax and it opens). He discusses his experience with the new hand in a statement: “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.”
While researchers were initially concerned that Sørensen’s nerves would be less sensitive than normal because they hadn’t been used in many years, they quickly realized their worries were unfounded. The amputee’s sense of touch was still intact.
Unfortunately for Sørensen, the hand was removed after a month because of safety restrictions. But Micera and his team have high hopes for the technology in the future. As they remind us in their study, this experiment was conducted on just one person. Many more amputees will have to use the hand before it can be proven effective and safe. And before the technology and procedure can become widespread, all the sensory feedback equipment needs to be fine-tuned and miniaturized.