Mind-controlled prostheses no longer science fiction

A SWEDISH arm amputee fitted robotic prostheses has been documented to control the implants with his mind and perform tasks  that come with being a truck driver and father. In January 2013, he was the first person in the world to receive a prosthesis with a direct connection to bone, nerves and muscles. The novel osseointegrated (bone-anchored) implant system allows him to control the robotic prostheses via implanted neuromuscular interfaces. Both this achievement and its long-term stability is described in a study*  published in the Science Translational Medicine journal.

“Going beyond the lab to allow the patient to face real-world challenges is the main contribution of this work,” said Max Ortiz-Catalan, lead author and research scientist at Chalmers University of Technology.

A Swedish truck driver, the first patient treated with the osseointegrated implant system for neural control, with Max Ortiz Catalan (left) and Rickard Br?nemark

The mind-controlled prosthesis was not the patient’s first. After his amputation over 10 years ago, he was fitted with one controlled via electrodes placed over the skin. Such a control system, however, can be unreliable and have limited functionality, and patients commonly reject them as a result.

In contrast, the new osseointegration technique creates a long-term stable fusion between man and machine and  integrated at different levels. Osseointegration technology in limb prostheses was pioneered by associate professor Rickard Br?nemark and his colleagues at Sahlgrenska University Hospital, which allowed direct skeletal attachment.

Professor Br?nemark led the surgical implantation and collaborated closely with Mr. Ortiz-Catalan and Professor Bo H?kansson at Chalmers on this project.

“The artificial arm is directly attached to the skeleton, thus providing mechanical stability. Then the human’s biological control system, that is nerves and muscles, is also interfaced to the machine’s control system via neuromuscular electrodes. This creates an intimate union between the body and the machine; between biology and mechatronics,” Mr. Ortiz-Catalan explained.

Today, with the novel control system that is directly connected to his own, the patient has found that he can cope with all the situations he faces; everything from clamping his trailer load and operating machinery to unpacking eggs and tying his children’s skates.

The osseointegrated implant system gives the patient new opportunities in his activities as a truck driver and his daily life at home

The patient is also one of the first in the world to take part in an effort to achieve long-term sensation via the prosthesis, which owing to the implant’s  bidirectional interface can also be used to send signals in the opposite direction – from the prosthetic arm to the brain. The next step for the researchers is to clinically implement their findings on sensory feedback.

“Reliable communication between the prosthesis and the body has been the missing link for the clinical implementation of neural control and sensory feedback, and this is now in place,” said Ortiz-Catalan. “So far we have shown that the patient has a long-term stable ability to perceive touch in different locations in the missing hand. Intuitive sensory feedback and control are crucial for interacting with the environment, for example to reliably hold an object despite disturbances or uncertainty. Today, no patient walks around with a prosthesis that provides such information, but we are working towards changing that in the very short term.”

And, of course, the researchers plan to treat more patients with the novel technology later this year. “We see this technology as an important step towards more natural control of artificial limbs,” he said. “It is the missing link for allowing sophisticated neural interfaces to control sophisticated prostheses. So far, this has only been possible in short experiments within controlled environments.”

* M. Ortiz-Catalan, B. H?kansson, and R. Br?nemark. “An osseointegrated human-machine gateway for long-term sensory feedback and motor control of artificial limbs” Science Translational Medicine