Researchers at the Chalmers University of Technology have developed a new artificial joint that can restore joint movements to those who have a demented forearm.
In the new system, the implant is placed in both the skin and the radius – in the two forearms in the bones – with an artificial joint that acts as an interface between the two implants and the prosthetic arm. The entire device provides more naturalistic movements with intuitive natural control and sensory feedback.
"Our new device offers a more natural range of motion, reducing the need for compensating shoulder or torso movements that could significantly improve the daily lives of many forearm amputees," biomedical engineer Irene Bonie, who worked on the project as an international student attending Chalmers, said in a statement.
One of the most difficult things that is lacking in hands is the inability to rotate the wrists' routine tasks, for example, by turning the door handle or simply turning the object, for example, a piece of paper.
"A person with amputation of the forearm can use a motorized wrist that is controlled by electrical signals from other muscles," says Max Ortiz Catalan, Associate Professor at Chalmers Electricity Department. "However, these same signals are also used to control the prosthetic arm.
"It creates a very cumbersome and unnatural control system in which patients can simultaneously activate either a prosthetic arm or a hand, and they need to change back and forth," he added. "In addition, patients do not have sensory feedback, so they do not have any feeling about the condition or movement of the hand."
Patients who have lost both hands and wrists often maintain enough muscle to allow them to rotate the radius above the cherry. The traditional palm prosthesis, which is attached to the body by compressing the knee, closes the bones and prevents any possible hand turning.
"Depending on the level of amputation, you could still have most of the biological actuators and sensors left behind," said Ortiz Catalan. "They let you feel, for example, when you turn on the key to start a car.
"You do not promote the wheel to see how far you rotate, you just feel", he added. "Our new innovation means that you do not sacrifice this useful movement because of the poor technological solution, such as the prosthetic hand. You can continue to do it naturally."
Artificial joint work with an osseointegrated implant system developed by Integrum AB, a Swedish company that has collaborated with Chalmers in the project.
The study was published in 2007 IEEE Transactions on Neural Systems & Rehabilitation Engineering.