Scientists from the South Ural State University have developed a lower limb prosthesis that can be easily modified for different purposes: for wearing at home, for walks and fast walking. The Chelyabinsk transformer is lighter, cheaper and stronger than existing imported analogues.
The cost of one imported ankle prosthesis can reach half a million rubles, and its repair, adjustment and other maintenance, which are possible only at the manufacturer's service center (today, political sanctions limit service altogether), cost tens of thousands. Considering that the design of a traditional prosthesis is non-separable, a person will need up to four orthopedic products depending on needs. At home and with minimal loads, the patient wears one prosthesis, for more intense loads he puts on another, when going for a quiet walk, he uses a third, and he will need a fourth for fast walking on the street. All versions of the "artificial leg" differ in rigidity, foot angle and shock absorption level, and therefore cannot replace each other.
The research team of the Departments of Technical Mechanics and Theory and Methods of Physical Culture and Sports of the South Ural State University proposed a domestic analogue of prostheses of famous foreign brands with significant advantages. As part of the state assignment "Development of scientific and technological foundations in the creation of new prosthetic limbs from composite materials", scientists for the first time developed a transformer prosthesis, the characteristics of which can be adjusted independently, changing only one element of the artificial foot. The new model of the medical device is collapsible: it provides for the replacement of the heel part of the prosthesis depending on the patient's needs. In terms of mechanical parameters, the prosthesis is completely identical to standard imported prostheses, but at the same time it is universal: it only requires a couple of additional removable elements (selected depending on the level of activity) instead of buying several expensive modules.
"When a person walks quickly, he has to take a wider step, but when the step becomes wider, the force of the impact on the foot increases and the patient immediately feels it on the prosthetic socket," explains Professor, Chief Researcher of the Department of Technical Mechanics at SUSU Sergey Sapozhnikov. - Painful sensations increase, which means that the force of the impact needs to be softened, the impact impulse needs to be stretched out over time. In order for a person not to feel pain from the prosthesis when walking quickly, the rigidity of the foot module needs to be made smoothly increasing. To do this, he just needs to screw on another heel component and he can hurry about his business. Upon returning, the patient can put on a "home" heel component to move comfortably around the apartment. Several of these " heels " can be made and attached to the main prosthesis, so that at home the person himself chooses what is comfortable for him to do his business in. He will no longer need to go to the service center when he wants to go for a walk. In addition to the “home” version, you can attach a rubber buffer to the bottom, which will also help you push off the surface more strongly when walking quickly due to the necessary increase in rigidity.”
To obtain maximum comfort from a transforming prosthesis, the patient can order the manufacture of replaceable components for individual biomechanical parameters. Such parameters are measured by biomechanics of the Department of Theory and Methodology of Physical Culture and Sports of SUSU using special Xsens equipment. Digital values are recorded on the computer screen, by which the specialist sees how the load is distributed on both legs and in what position the spine is at a normal walking pace. Based on the data obtained, the biomechanic can see the asymmetry of the body during movement and recommend devices that will help bring the body in space to a healthy symmetrical position.
"We receive information about the spatial and temporal parameters of movement, such as acceleration, speed, positions along the XYZ axes of each body segment and their changes during each motor cycle, " says Vitaly Epishev, associate professor of the Department of Theory and Methodology of Physical Culture and Sports at SUSU. "The kinematics database we created allows us to predict the required level of stiffness and shock-absorbing parameters of the prosthesis. As the user's level of motor activity changes and/or, for example, their weight changes, we can change an element of the prosthesis, thereby "adjusting" it to the changed biomechanics."
Among other things, the unique collapsible model will be lighter, more durable and several times cheaper than its predecessors due to the effective composite material. Chelyabinsk scientists made the artificial lower limb entirely from fiberglass, consisting of fiberglass and a binding polymer - epoxy resin. The structure of the fiberglass used is also unique: when making the composite, the developers arrange the fiberglass fibers in such a way that the finished material has the necessary strength and flexibility, like carbon fiber, from which most prostheses on the market are made. The presence of longitudinal cuts reduces the torsional rigidity of the prosthesis, allowing the sole to more effectively adapt to uneven surfaces and overcome obstacles (stones, small objects) when moving without losing balance. In addition, such a product is significantly more impact-resistant, unlike carbon fiber. And after replacing the metal tube simulating the shin bone with a fiberglass one, the entire structure becomes even lighter.
The foot module of the prosthesis consists of only two separate components - the heel and front plates, several millimeters thick, connected by a metal element. For comparison, only the front plate of a similarly rigid foreign prosthesis consists of many layers of carbon fiber (not counting the other auxiliary elements), which complicates and increases the cost of the entire structure.
In the university laboratory, the prosthesis successfully passed tests with loads of up to three hundred kilograms and demonstrated the required rigidity at all stages of loading. The universal prosthesis is awaiting final certification tests, patenting and trial operation on volunteer patients.
The transforming prosthesis was presented at the annual international industrial exhibition “INNOPROM” in Yekaterinburg.