Robotics...

What is this Mind-Controlled Prosthetic Arm?

 

For the first time, robotic prostheses controlled via implanted neuromuscular interfaces have become a clinical reality. This technique is called osseointegration and works by connecting the prosthesis directly to the bone, nerves and muscles and it gives patients new opportunities in their daily life and activities.

 

Rickard Branemark led a surgical implantation and collaborated closely with Mark Ortiz Catalan and Professor Bo Hakansson at Chalmers Uni of Technology on this development.

 

“Going beyond the lab to allow the patient to face real-world challenges is the main contribution of this work,” says Max Ortiz Catalan, research scientist at Chambers Uni of Technology. “We have use osseointegration to create a long-term stable fusion between man and machine, where we have integrated them at different levels. 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 inion between the body and the machine; between biology and mechatronics.”

 

In January 2013 a Swedish arm amputee was the first person in the world to obtain a prosthesis with a straight connection to bone, nerves and muscles. The patient has been given a control system that is directly connected to his own. He has a physically challenging job as a truck driver in northern Sweden, and since the surgery he has found that he can cope with all the situations he faces; everything from clamping his trailer load and operation machinery, to unpacking eggs and tying his children’s skates, with no influence of the environmental surroundings.

 

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,” says Max. “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.”

 

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. Because the implant is a bidirectional interface, it can also be used to send signals in the opposite direction – from the prosthetic arm to the brain. This is the researchers’ next step, to clinically implement their findings on sensory feedback.

 

In separate research, doctors have been able to recreate the sensations of different objects in a prosthetic hand. Igor Spetic, of Madison, Ohio, was able to identity a cotton wool ball for the first time while blindfolded after it was passed over the back of his prosthetic. “I knew immediately it was cotton,” he said.

 

The system, which is limited to the lab at this point, uses electrical simulation to give the sense of feeling. Their goal is not just to re-establish function, but to build a reconnection to the world.

 

Keith Vonderhuevel, of Sidney, Ohio, who lost his hand in 2005 had the system implanted as well. “The sense of touch actually gets better,” he said. “One time it felt like water running across the back of my hand.”

 

“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 not in place,” says Max 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 prosthesis that provides such information, but we are working towards changing that in the very short term.”

 

 

 

How Does This Technology Work?

(Only if you’re ready to be bombarded with sciency stuff)

 

This technology is based on the OPRA treatment, where a titanium implant is surgically inserted into the bone and becomes fixated to it by a process known as osseointegration (Osseo = bone). A component is then attached to the titanium implant to serve as a metallic bone extension, where the prosthesis is then fixated.

 

Electrodes are implanted in nerves and muscles as the interfaces to this biological control system. These electrodes record signals which are transmitted via the osseointegrated implant to the prostheses, where the signals are finally decoded and translated into motions.