Artificial Joint Restores Natural Wrist Movements to Amputees

A new study describes how an artificial joint reestablishes important wrist-like movements to forearm amputees, which could dramatically improve their quality of life.

Developed by researchers at Integrum (Mölndal, Sweden), Chalmers University of Technology (Göteborg, Sweden), and The BioRobotics Institute of Scuola Superiore Sant’Anna (Pontedera, Italy), the wrist prosthesis is based on an osseointegrated implant system placed into the two bones of the forearm--the ulna and radius--with an intermediate artificial joint that restores the functionality of the original distal-radioulnar joint, acting as an interface between the two osseous implants and the prosthetic hand.

By enabling the radius and the ulna to move with respect to each other, the natural range of wrist rotation is preserved, improving performance of activities of daily living and reducing compensatory movements that potentially lead to secondary health problems over time. The wrist device was fitted to an osseointegrated transradial amputee and its functionality assessed by a battery of tests, revealing that it can successfully restore natural forearm rotation, resulting in more naturalistic movements with intuitive natural control and sensory feedback. The study was published on November 13, 2018, in IEEE Transactions on Neural Systems & Rehabilitation Engineering.

“Depending on the level of amputation, you could still have most of the biological actuators and sensors left for wrist rotation. These allow you to feel, for example, when you are turning a key to start a car,” said senior author Max Ortiz Catalan, PhD, of Chalmers University of Technology. “You don't look behind the wheel to see how far to turn -- you just feel it. Our new innovation means you don't have to sacrifice this useful movement because of a poor technological solution, such as a socket prosthesis. You can continue to do it in a natural way.”

One of the major obstacles to an amputee in regaining a high level of function is the inability to rotate the wrist in order to perform pronation and supination movements. This twisting motion is used every day, whether to turn a door handle, use a screwdriver, start a car or simply to turn over a piece of paper. Current prosthetic technologies offer only limited relief to this problem.

Related Links:
Integrum
Chalmers University of Technology
The BioRobotics Institute of Scuola Superiore Sant’Anna