The Future at Your Fingertips

Prosthetic arms play an important role in improving the lives of individuals who have experienced limb loss, offering them increased functionality and independence. These devices are designed to compensate for the loss of an arm and assist amputees in performing daily tasks that would otherwise be challenging or impossible. However, it is important to recognize that prosthetic arms come with their own set of challenges.

One common issue that amputees face with prosthetic arms is the discomfort caused by the compression of the residual limb. Residual limb compression is necessary to ensure a secure and stable fit of the prosthetic device, and to provide an interface with the residual muscles to control it. However, the pressure exerted by the prosthetic socket can lead to discomfort, skin irritation, and even sores if not properly managed.

Residual muscles do allow for some control of the prosthesis, but the number of available muscles and their functionality depend on the level of amputation. For individuals with amputations above the elbow, there will be only a few remaining muscles, and they only offer very limited control, especially when it comes to manipulating the hand. This limitation can make it challenging for amputees to perform any delicate or precise movements that require fine motor skills.

An effort spearheaded by researchers at Chalmers University of Technology in Sweden may soon give new hope to those that have experienced the loss of a limb. They have developed a new type of prosthetic arm that is tightly integrated with the user’s skeletal and muscular structure to provide natural control of the prosthetic arm. The physiological signals captured are interpreted by an artificial intelligence algorithm that controls even individual finger movements with just a thought.

Rather than the traditional socket-based attachment, the arm leverages a titanium implant that is securely anchored to the residual bone. Not only is this method of attachment very strong, but it also does away with the discomfort of a pressure fit socket.

Focusing on above-elbow amputations where sufficient musculature for fine control of the prosthesis is lacking, a cutting-edge surgical procedure was also developed. During this procedure, peripheral nerves were split and rerouted to remnant muscles and muscle grafts. In this way, the number of potential control signals was increased. An electrode was implanted into each of these muscles, such that the signals sent to them by the amputee’s brain could be measured.

Decoding these signals can still be a significant challenge in its own right, especially since nerve connections were reconfigured, so the researchers turned to artificial intelligence to interpret them. By simply providing the algorithm with example data from the user of the arm attempting to perform different actions, it was able to learn what various patterns of muscular activity mean. These intentions were then successfully mapped to actions on the arm, such that the user would only need to think of moving a finger in a normal fashion, and the corresponding change in the prosthesis would occur.

In the video above, a subject with an above-elbow amputation that underwent the surgical procedure demonstrates the arm. It can be seen that the individual has regained full control of all five fingers using this system. Perhaps one day these methods will provide even greater control. Maybe similar techniques will also prove to be capable of adding additional functionalities to leg prostheses as well.