New hope is on the horizon for amputees, with a mind-controlled robotic arm that was developed by Chalmers University of Technology researcher Max Ortiz Catalan in Sweden. The first implantation of the limb has already been carried out by a surgical team led by Dr. Rickard Brånemark at Sahlgrenska University Hospital in Goteborg, Sweden. Initial results have been “excellent.”
Since the 1960s, not much has changed in the world of prostheses. The electrical impulses in the muscles can control special limbs to a certain extent, but the technology really hasn’t evolved since it first came about in the 60s. Even the high- end, high-tech models are difficult to control.
The basic model prosthetic is a socket prostheses that is attached to the body using a tightly fitted socket attached over the end of the limb. Many find these to be uncomfortable, and only about 50% of amputees will use them.
The new mind-controlled limb, however, is using the world-famous Brånemark titanium implant, or OPRA Implant System, which actually anchors the prosthesis directly into the bone through a process known as osseointegration.
“Osseointegration is vital to our success. We are now using the technology to gain permanent access to the electrodes that we will attach directly to nerves and muscles,” says researcher Catalan, who is an industrial doctoral student at Chalmers.
“Our technology helps amputees to control an artificial limb, in much the same way as their own biological hand or arm, via the person’s own nerves and remaining muscles. This is a huge benefit for both the individual and to society,” he added. “All movements must by pre-programmed. It’s like having a Ferrari without a steering wheel. Therefore, we have developed a new bidirectional interface with the human body, together with a natural and intuitive control system.”
When prosthetics use electrical signals to control movement, the electrodes are placed over the skin. The signals change when the skin moves, and they are affected by sweat, which complicates the control of the limb.
In this project, researchers are implanting the electrodes directly onto the nerves and remaining muscle. They expect the signals to be significantly more stable, since the electrode will be directly touching the source. The electrical impulses from the nerves in the arm will be captured by a neural interface, which will send them to the prostheses through the titanium implant. Complex algorithms will decode the signals, allowing the patient to control the prosthesis with only thought.
“Many of the patients that we work with have been amputees for more than 10 years, and have almost never thought about moving their missing hand during this time,” explains Catalan. “When they arrived here, they got to test our virtual-reality environment or our more advanced prostheses in order to evaluate the decoding algorithms. We placed electrodes on their amputation stumps, and after a few minutes, they were able to control the artificial limbs in ways that they didn’t know they could, most of the times. This made the patients very excited and enthusiastic.”
“By testing the method on a few patients, we can show that the technology works and then hopefully get more grants to continue clinical studies and develop the technology further. This technology can then become a reality for lots of people. We want to leave the lab and become part of the patients’ everyday life. If the first operations this winter are successful, we will be the first research group in the world to make ‘thought-controlled prostheses’ a reality for patients to use in their daily activities, and not only inside research labs.”
The first test patient has stated said that the arm works with “almost no effort,” that more movements can be made than the patient’s previous robotic hand, and that several movements can be made simultaneously. More research and testing needs to be done before this thought-controlled prosthetic device can be made widely available, but early results are very encouraging!