Numerical Analysis of the Effect of Material and Dimensions on the Mechanical Behaviour of Total Hip Prosthesis

Abstract

The objective of this work is to analyze by numerical simulation based on the finite element method, the in-vitro mechanical behavior of a total hip prosthesisfor four different femoral head diameters: 22.2; 28.0; 32.0 and 36.0 mm, with a constant thickness of 50.0 mm of acetabular cup and for three different pairs of biomaterials (head-cup): 316L/UHMWPE; 316L/PP virgin and 316L/PP extruded. In this context, the extruded polypropylene acetabularcupsare machined from a solid-state extruded polypropylene (PP) block using the Equal Channel Angular Extrusion(ECAE) process.Thus, this analysis will determine the stresses generated by the body to choose a mechanical behavior of prosthesis and a couple of materials that offer better bio-functionality. It will also highlight the effects of the internal diameter of the cup and the nature of the biomaterials used for the functioning and reliability of the prosthesis studied.The obtained results allowed us to evaluate the distribution of stresses and deformations by comparing the amplitude and location of the hot spot of the analyzed cases. These results demonstrate that the couple material 316L/UHMWPE, for the 36.0 mmfemoral head, indicates a better stress-strain distribution at the acetabularcup in comparison to those presented by the other two pairs of materials and extruded for the other three diameters. This can be attributed to the fact of the increase in the ductility of the material and in internal diameter that will tend to increase the surface contact and consequently decrease the pressures exerted between the head and the cup, thus it delays the appearance of wear and increasing the life of the acetabularcup.