Each year in the United States 150,000 people will have a limb amputated. It can be particularly devastating to lose a hand, due to the incredible amount of sensory information received from them. Bionic prosthetics are a hot area of research right now as these devices seek to replicate the function of the hand as much as possible. A new prototype arm prosthetic is not only able to help hold things but is actually able to transmit sensory data to the user in real time.  The creation of the device was a large international collaboration led by Silvestro Micera and the results were published in Science Translational Medicine.

Dennis Aabo Sørenson from Denmark lost the lower portion of his left arm nine years ago during an accident involving fireworks on New Year’s Eve. Now 36 years old, Sørenson gained a renewed sense of touch in a clinical trial, thanks to a new bionic prosthetic. At the onset of a trial, doctors were initially worried that his nerves would not work since they had been out of use for nearly a decade. Fortunately, preliminary testing showed that they were still functional and sensitive.

The prosthetic device, called LifeHand 2, builds off of the first generation LifeHand device which was the first thought-controlled bionic prosthetic to have rudimentary touch feedback and was successfully tested in 2009. This next-generation device is covered in sensors that interpret information based on the movement of the artificial tendons. The sensors are connected to four electrodes that actually tap in to Sørenson’s nervous system at the base of his natural arm. Complex computer algorithms were developed to translate the rough electrical signals into a more refined impulses that could be processed by the human brain without overloading it with sensory input. 

Surgery was performed in January 2013 in Rome as a host of neurologists and surgeons oversaw the implantation of the electrodes. Over the course of nearly three weeks, tests were performed on the electrodes to ensure that they were functioning and communicating with Sørenson’s brain properly. This also allowed the team to discover what changes, if any, would occur once scar tissue began to form around the implants. There was no change in function as the scarring set in, much to the delight of the researchers.

For the next week, Sørenson was connected to the hand for extensive testing. The greatest success came when he was blindfolded with headphones in and was asked to identify objects just through touch. He described the sensory feedback as “incredible” and was able to identify the shape and hardness of the item -- something he had not been able to do in many years. 

Unfortunately, due to regulations for clinical trials, Sørenson was only able to have the electrodes implanted for one month. The researchers feel confident that the electrodes could have remained in place for a number of years without adverse effects. Sørenson’s normal prosthetic reacts to muscle movement in his upper arm and can grip objects. However, it does not have sensory feedback which makes pressure control difficult at times. Amputees endure a large amount of psychological trauma at the loss of limb, function, and sensory input, and the research team realizes he will have to go through that loss all over again after the brief resurgence of a sense of touch. However, he reports that he was happy to help in the technological advance not just for his sake, but for all amputees who will benefit as a result of the study.

Due to the nature of the LifeHand 2 bionic prosthetic, it will still be a number of years before it will be approved for commercial use. In the meantime, researchers will continue to advance the technology, making smaller versions of the sensors that are more finely tuned and adding greater dexterity in the fingers.

Check out this video of the the LifeHand 2 in action: