Prostheses, which are needed not only to restore the appearance of a lost limb, but also its functions, are of two types: traction and bionic . Traction or active prostheses are controlled by rods (special threads) inside the prosthesis. They are completely controlled by the efforts of the person himself without any electronics due to flexion and extension of the preserved joint. Bionic prostheses are robotic . These are some of the most modern and advanced prostheses available today. They are called prostheses with an external energy source. Control in bionic prostheses is carried out by signals arising from muscle contraction, which are read by EMG sensors or muscle activity sensors.
The prosthesis consists of a hand with an electromechanical drive, a cultivation sleeve, a hand rotation mechanism, EMG sensors, a battery, a charger, electric cables and, at the user's request, a cosmetic shell.
A bionic prosthesis is designed as anthropomorphically as possible to a human hand, so you need to know its weight and size: the width of the hand and the length of the fingers. They are selected based on the age of the user. Further, after production, EMG sensors are also individually located, which read muscle activity and transmit a control signal to the prosthesis controller.
The prosthesis is held on the arm with the help of a culturing sleeve that connects the prosthesis and the arm. The sleeve fits snugly to the arm and is located inside the prosthesis, the existing part of the limb is inserted into it. The sleeve is also made individually for each user.
The prosthesis is controlled with the help of muscle activity sensors, which are built into the socket. They read the electrical potential from the muscles as they contract. The information from the sensors is transmitted to the microprocessor of the hand and, through computer algorithms, is converted into motor commands, and the prosthesis performs a certain gesture or grip.
Today, all bionic prostheses are controlled by muscle impulses that arise when a phantom gesture is “presented” in the head and the muscles of the hand try to perform this gesture. In the future, of course, we will be able to read this representation directly from the motor cortex of the brain, but before that, there are still 15-20 years of development in the field of neurointerfaces.
With a modern prosthesis, a person can do almost any kind of self-care, everyday life and lead an active lifestyle - tying shoelaces, dressing, cooking, riding a bicycle. For example, Motorica's latest model, Manifesto's prosthetic arm, can perform 14 different types of grips, which are set via a mobile application. Whereas the previous model, Indy, only performs one type of grip. In addition to restoring lost functions, the prosthesis expands the basic ones. For example, with a prosthesis, you can pay for purchases using the NFC module or monitor the body's indicators on the built-in smart watch.
There are two main directions of development of prostheses in terms of technology: improvement of the human-machine interface, which controls prostheses to achieve fine motor skills and control of individual fingers, as well as technology for sensing prostheses. This is necessary so that a person can feel what object and how he takes it.
Now a very small percentage of people without limbs use a prosthesis. The reasons are different, but one of them is not always a simple system for processing the necessary documents. It is important to make this system as transparent and simple as possible for all people with disabilities. When all people without arms or legs start using prostheses, the process of making prostheses will move to another level. It will become more affordable and cheaper.