Equipped with an electronic implant, this new prosthesis allows forearm amputees to perform wrist movements, which improves their manual dexterity and their quality of life.
Pick up an object, rotate it 180° to turn it over, then put it down. For forearm amputees who are missing a hand, these movements are probably the most difficult to perform. And for good reason: conventional prostheses rarely allow this type of movement, called pronation (palm down) and supination (palm up).
This lack of manual dexterity greatly affects the quality of life of people deprived of hands. For example, they are unable to turn a door handle or a knob on a stove, to use a screwdriver or simply to turn the page of a book.
A new technological feat could soon help these patients perform these delicate tasks and thus greatly improve their quality of life.
An osseointegrated prosthesis
In the review IEEE Transactions on Neuron Systems & Rehabilitation Engineeringa group of researchers from the Chalmers University of Technology in Sweden, explains that they have succeeded in developing a new artificial joint capable of restoring the complex movements of the wrist of people with forearm amputees.
“A forearm amputee can use a motorized wrist rotator controlled by electrical signals from the remaining muscles. However, these same signals are also used to control the prosthetic hand,” explains Max Ortiz Catalan, associate professor at the Department of Electrical Engineering at Chalmers. “This results in a very cumbersome and unnatural control scheme, where patients can only activate the prosthetic wrist or hand at a time and only have to switch one after the other. receive no sensory feedback, so they have no sensation of the position or movement of the hand.”
Unlike these conventional prostheses, the new joint works thanks to a surgically osseointegrated implant in each of the two bones of the forearm, the ulna and the radius. An artificial joint in the form of a wrist then acts as an interface between these two implants and the prosthetic hand. Thus assembled, this device allows much more natural movements, with intuitive control and sensory feedback, explains Max Ortiz Catalan. “This allows the user’s remaining skeletal structure and musculature to be utilized in the same way as that of an able-bodied person.”
Much better manual dexterity
“Depending on the level of amputation, it’s possible that most biological actuators and sensors are left for wrist rotation. They allow you to feel, for example, when you turn a key to start a car. You don’t don’t look back at the wheel to see how far to turn – you feel it.Our new innovation means you don’t have to sacrifice that useful movement because of a poor technological solution, such as a socket prosthesis. to do it in a natural way”, explains Max Ortiz Catalan.
According to Jason Minnenaar, one of the biomedical engineers who worked on this prosthesis project with biological sensor, the patient equipped with the artificial joint and evaluated on his manual dexterity obtained much better results than those benefiting from a prosthesis. conventional. “Our new device provides a much more natural range of motion, minimizing the need for compensatory shoulder or torso movements, which could significantly improve the daily lives of many forearm amputees,” says Irene Boni, P.Eng. biomedical.
.
