Stress assessment of the hip joint endoprosthesis’s head and liner design in different sizes with a pyrocarbon friction pair

Background. Aseptic loosening of hip replacement components is a worldwide problem. To reduce the risk of developing this postoperative complication, work is underway to improve the materials of the friction pair, the wear products of which are the main cause of aseptic instability. The purpose of the study is to use the mathematical modeling of the mobility unit of a hip joint endoprosthesis with a friction pair made of monolithic pyrolytic carbon, evaluate the stresses in the structure and determine the dependence of the obtained indicators on the size of the components. Materials and methods. The assessment of stresses in the structures of a friction pair made of pyrocarbon was carried out on a mathematical model of the head and liner, with the loads described in GOST R ISO 14242-3– 2013. Two designs with a diameter of 28 mm and 38 mm were investigated. The variable parameters were the size of the gap between the mating parts of the head and the liner and the angle of application of the load to the liner. Results. The stresses in the structures did not exceed the strength of the materials. The margin of safety was 4.5 in the 28 mm design and 5.2 in the 38 mm design.