Germany-based Otto Bock Healthcare has announced that its prototype prosthetic arm which can be controlled by thought is ready to hit the market. The device has been in testing on Christian Kandlbauer -- who doesn't have any arms and has a conventional prosthetic on his right side -- for the past four years. He's the first person in Europe to have a mind-controlled prosthesis installed, but the research is complete and the finished product should soon be available to the public. The arm makes use of targeted muscle reinnervation (TMR), which uses nerves that controlled the lost arm to control the prosthesis. Dr. Hubert Egger, Otto Bock's project manager for mind-controlled prosthetics, explains that the residual nerves are transferred to the chest in a six-hour operation and enable the prosthetic control. "The next step is to add a sense of touch." Dr. Egger explains that the idea for mind-controlled prosthetics came from one of Otto Bock's research partners in the US. Otto Bock being a privately owned, independent family business, there was time and money to start up a long-term project with the ultimate objective of creating a state-of-the-art prosthetic that could mimic nature. "Nature is wonderful and we will never be that good; but we want to try to make prosthetics that come pretty close," says Dr. Egger. Fate gave Otto Bock a partner in the project when Christian Kandlbauer, young man from Styria, lost both his arms in a terrible accident in 2005. As Otto Bock worked closely together with the General Hospital in the Austriancapital, they were asked to look at what the best prosthetic solution would be for him. "He lost his left shoulder joint which made him a suitable candidate for the procedure," Dr. Egger explains. "We told him what his options were: he could have a cosmetic prosthesis that would be of no practical use to him at all, or he could take part in a research project which, if successful, would be of great benefit to his quality of life in the long term. He had to think about this of course, but in the end we convinced him that there was no risk involved whatsoever. " Christian Kandlbauer had to have surgery first to transfer residual nerves to new target chest wall muscles. He had four nerves removed from his left arm network and redirected to his left chest muscles. Before his accident, these muscles were responsible for moving his left arm, but following the transfer they could act as natural amplifiers for signals from the four redirected nerves. "Every time you move your arm your brain transmits electrical signals that propagate along the motor nerve fibers in your spinal cord to the arm muscles," Dr. Egger explains. "What we did to mimic that natural process is use Christian's residual nerves and connect them to the chest wall muscles. They act now as biological amplifier for the signals coming from the brain." The prosthesisitself contains a powerful minicomputer that performs 500 million calculations per second to analyse the signals and determine the movement the amputee is imagining. At almost the same time, control signals are calculated for the motors, triggering the movement in the prosthesis in less than 80 milliseconds. Following surgery, Christian followed an intensive therapy programme that basically taught him to let his mind steer his prosthetic arm. Dr. Egger and his research partners meanwhile kept on working on improving the arm. "Initially Christian couldn't take the prosthesis home as technicians were needed to help him take it off and put it on. We also had to reduce the weight; the prosthesis initially weighed in at six kilograms which was too heavy as the weight of the two prostheses, left and right, has to be balanced. We brought that down to 2.5 kilograms and by January 2009 we had the take-home prosthesis ready." Christian Kandlbauer has since been able to wear the prosthesis for everyday use; he can independently drive his car and go to work. He is obviously delighted; with a myo-controlled arm on the right side and a cosmetic arm on the left he would be dependent on other people for pretty much everything and would not be able to lead a normal life. Now, he pretty much can. Dr. Egger points out that Christian's prosthesis has three active joints, which is enough for him to perform most common tasks. Interesting is that on the Otto Bock website, Christian Kandlbauer is quoted as saying that the arm "feels like it is part of the body – in contrast to his right- arm myo-controlled prosthesis that is. This is important, confirms Dr. Egger. "What happens when you have had a limb amputated is that you still have a memory of that limb. This is what we researchers call phantom-limb. To use the mind-controlled prosthesis you need to exercise that memory to get you brain to send signals representing the movement of the phantom limb." It's fascinating subject matter that promises to get even more fascinating: the people of Otto Bock are currently working on adding more active joints to the prosthetic, the ultimate objective being the addition of a sense of touch. This sounds almost too futuristic to be true but it can be done, Dr. Egger assures us. "It already works in a lab environment. I don't want to get people's hopes up as we don't know yet how it would work in everyday life but I think it will become a reality in about five years time. The quality of life a sense of touch adds is enormous for a patient." He adds that they're also researching mindcontrolling prosthetics for the lower limbs, in other words, the legs. "That will require a different procedure. When you are walking you don't consciously think about moving your legs. Forinstance, you can walk and talk at the same time. That means movement of lower limbs while walking is more automatically than movement of upper limbs for instance while grasping an object with your hand. You actually need to see the object. The automatic course of locomotion enables the use of artificial sensors, like force and angle sensors, for lower limb prostheses control. Another major innovation in this field, the c-leg, operates on the basis of artificial sensors exclusively without direct reference to the nervous system. There are more than 35.000 users on the market worldwide. Involving mind control in lower limb prosthesis will require a different procedure. Dr. Egger says mind-controlled prostheses are available now. But it is not possible to tax costs at that time. In fact, a determining factor for costs is the medical status of the patient which has to be discussed very detailed prior. top - home