Prosthetic arms that look and function seemingly much like the real things have come of age in the last decade, but while they seem amazing to an outsider, these arms are very much limited by their interface with the rest of the body. Now a couple studies out of the U.S. and Sweden published in Science Translational Medicine are heralding a new generation of advanced prostheses that integrate much closer and respond more naturally to the user’s body thanks to direct-to-bone coupling and two-way implanted electrodes.
In the Swedish study, a man at Chalmers University received an osseointegrated (fused to bone) prosthetic, a technology developed at Sahlgrenska University Hospital some years ago. Previously, though, to make the hand contract external electrodes placed on the stump were used to read the intention of the user. While effective during demonstration, there are problems that make long term use of external electrodes frustrating when putting on a prosthetic and thereafter during use. Besides relaying signals from the nerves to the prosthesis, the device is able to send signals the other way, which was shown to develop into a sense of touch.
The other study was performed at Case Western Reserve and Louis Stokes Cleveland VA Medical Center where two people were fitted with peripheral nerve interfaces in their arms. These were used to send electrical signals to the nerves in an attempt to mimic the sensation of touch. Incredibly, they were able to achieve just that and by manipulating the signal in different ways they managed to induce different sensations within the phantom fingers of these people. This wasn’t just a short term capability, but remained effective for more than a year with both patients.
Here’s a couple videos of the Swedish amputee using his new arm:
And here’s the U.S. patient who has a sense of touch through his robotic hand:
Perspective article: Bionic Limbs: Clinical Reality and Academic Promises…