Study of Contact Parameters in Metal-On-Plastic Hip Endoprosthesis with the Analytical-Numerical Method of Contact Mechanics
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National Aviation University Ukraine, Aerospace Faculty, Kosmonavta Komarova 1, Kyiv, Ukraine
Faculty of Mechanical Engineering, Lublin University of Technology, ul. Nadbystrzycka 36, 20-618 Lublin, Poland
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Jarosław Zubrzycki   

Faculty of Mechanical Engineering, Lublin University of Technology, ul. Nadbystrzycka 36, 20-618 Lublin, Poland
Adv. Sci. Technol. Res. J. 2023; 17(3):145-153
The purpose is to analyze the influence of the elastic characteristics of the materials of the tribological pair: acetabular–femoral head on the maximum pressures in the hip joint endoprosthesis. Based on the proprietary calculation method of hip joint endoprostheses, an analysis of the impact of UHMW-PE elasticity characteristics (Young's modulus and Poisson's ratio) on the contact parameters was carried out: maximum contact pressure, and contact angle. The study determined the value of contact pressures depending on the changes in the elastic characteristics of UHMW-PE and changes in the geometry of the tribological pair (variable radii of the Grade2TDN head and the UHMW-PE acetabulum). It was found that increasing Young's modulus of UHMWPE increases its stiffness, which causes a noticeable increase in contact pressures in the endoprosthesis. The quantitative and qualitative regularities of this impact were determined. The developed method allows for earlier estimation of contact pressures depending on the external load (patient's body weight), and geometric parameters of the artificial hip joint (diameter of the endoprosthesis head and the acetabulum). This allows you to make a personalized endoprosthesis resistant to damage. It is very important in modern medicine because life expectancy in developed countries is longer and the durability of endoprostheses should be 10–12 years. Hospital statistics show that the need for total hip replacement concerns even younger people. Implantation of a hip joint prosthesis is an invasive and costly procedure, hence the need to produce prostheses with a long service life (over 15-20 years) before re-arthroplasty. The obtained test results showed that the use of an endoprosthesis cup made of UMHW-PE with higher stiffness (high E1 value and low ν value) results in an increase in maximum contact pressures p(0). Increasing the Poisson's ratio in the tested range causes an increase in the contact pressure p(0) even 1.1 times. Increasing the diameter of the head of the D2 endoprosthesis decreases the contact pressure by an average of 2.32 times. On the other hand, a change in the radial clearance  in the tribological pair of the hip endoprosthesis from 0.1 mm to 0.2 mm causes an increase in contact pressures by an average of 1.35 times.
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