Bionic cross-country leg

Artificial leg taught to obey the brain

Kirill Stasevich, CompulentaExisting prosthetic legs are not too perfect.

It is clear that completely mechanical devices cannot respond to a person's thoughts; in order to move such a prosthesis, it is necessary to use the preserved muscles and bones. Well, developments equipped with their own motor are quite difficult to manage and sometimes force people to make unnecessary hypertrophied movements.

With regard to the management of artificial arms and legs, scientists have long been trying to make prostheses as similar as possible to real limbs. Roughly speaking, the task is to teach the prosthesis to understand the neural signals that the brain sends to the arm or leg. And it is complicated by the fact that the nerves transmitting these signals lead to those muscles that are lost during amputation along with the limb.

In 2006, Todd Kuyken and his colleagues from the Rehabilitation Center in Chicago (USA) proposed redirecting the branches of the control nerves that led to the lost limbs to the place lying above the amputation. At first, it was possible to "innervate" the prosthesis of the shoulder part of the arm; in a new article published in the New England Journal of Medicine, researchers describe a similar operation performed for a prosthetic leg. A certain Zack Wouter participated in the medical experiment, who lost his right leg below the knee as a result of an accident. Scientists redirected two branches of the sciatic nerve, which usually go to the muscles of the foot, lower leg and calves, to the femoral areas: now the signals, usually going to the ankles, got to the muscles lying directly above the knee.

Here, in the surviving part of the leg, electrodes were placed that recorded electrical signals from the contracting muscles. That is, the signals that used to go to the shin were obviously received at the wrong address, but then they were "removed" from the muscles by special sensors and transferred to the prosthesis. A special program deciphered the electromyographic data and, with the help of all the same sensors (among which were accelerometers and gyroscopes), controlled the movement.

A man with an artificial leg on a treadmill (photo by Rehabilitation Institute of Chicago).

The result was more than impressive: a person could, for example, climb stairs, alternating between real and artificial legs, which is impossible to do with other prostheses (they have to be lifted to each new step after a healthy leg). Now the owner of such a prosthesis could walk up the stairs without stopping and even, moreover, could move an artificial leg while sitting, which again cannot be done with prostheses that do not know how to "listen" to nerve and muscle signals.

It should be emphasized that this is still not exactly mind reading: the device understood the electromechanical activity of the muscles, but not at all the desire of a person to move his leg.

If the artificial leg used only mechanical sensors, the accuracy of the commands was about 87%. If those that read neural signals were also connected to mechanical sensors, the share of errors in foot control fell to 1.8%.

The authors of the development say that their goal is to get rid of even such an error, because any "misunderstanding" of the electromechanical signal by the prosthesis can lead to fatal consequences.

Prepared based on the materials of LiveScience (New Prosthetic: Man Controls Bionic Leg with Thoughts).

Portal "Eternal youth" http://vechnayamolodost.ru27.09.2013