Modélisation et simulation du comportement d'une tige fémorale poreuse

Abstract

Current femoral stems used in arthroplasty procedures are very stiff which can create a mechanical incompatibility with the bone surrounding them. This incompatibility can cause stress shielding which can significantly reduce the life expectancy of the implants. One approach which can be used to reduce stress shielding consists in fabricating the stems from porous materials which are more flexible. The current work describes the modelling and simulation of a femoral stem with a porous region. First, an algorithm was developed in the Matlab environment in order to model the geometry of a lattice material with a diamond unit cell. The algorithm was used to model and export the STL file of three lattice materials with a constant cell size of 0.83 mm and varying densities of 20%, 42% and 60%. Finite element analyses performed using solid and beam elements as well as tests performed on additively manufactured samples were used to characterise the modelled materials. The stiffness of the 20% dense lattice material was evaluated at 1.61 GPa whereas the stiffnesses for the 42% and 60% dense materials were evaluated at 7.58 GPa and 20.27 Gpa, respectively. A femoral stem with a porous region made up of the 42% dense lattice material was designed. A finite element model of the stem was developed and the macroscale stiffness of the porous zone was set using the characterization results from the test samples. The porous stem as well as a fully dense stem were then additively manufactured and tested through compression testing. Displacements on the surface of the stems were measured via a digital image correlation system and compared with finite element modelling results through a validation analysis. This analysis confirmed that there is good agreement between the measured and finite element displacements. Finally, the porous stem designed for the study was shown to be approximately 30% more flexible than the fully dense stem.

Date	27 Sept 2016
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Patrick Terriault (Supervisor)