Développement d'une tige fémorale biomimétique intégrant une structure cellulaire poreuse

Abstract

The stiffness mismatch existing between the bones and the monolithic metallic implants that are used for the orthopaedic prostheses leads to the stress shielding phenomenon and, in the long-term, to the implant failures which prohibit their uses for young and active patients. To this matter, the addition of metallic ordered porous structures to the implants is considered reducing the stiffness of the cement less femoral stems used in the total hip arthroplasties. In the current document, two scientific articles are introduced to expose the design and assessment of a femoral stem integrating an ordered porous structure. The first article exposes the design concerns and the methodologies for the embodiment of the stem using the additive manufacturing process of the laser-powder bed fusion. The diamond lattice porous structure is selected and integrated to the stem with a porosity of 58% and a pore size of 800 μm. Using the Ti-6Al-4V alloy, these design parameters lead to the apparent mechanical properties of the porous structure of 8.4 GPa and 91 MPa for the modulus of elasticity (E*) and the yield strength (SY*), respectively. These values are contained within the combined intervals of the corresponding properties for the cortical and trabecular bones. Static mechanical tests adapted from the ISO 7206-4 standard serve to validate the numerical model of the stem and evaluate its increase of flexibility when compared to its fully dense replica. The measurements, obtained using a digital image correlation system, allow, on the one hand, the validation of the numerical model of the stem, and on the other hand, to observe a flexibility increase of 31% of the dense stem. The second article concerns the post-operative bone resorption assessment resulting from the evolution of the equivalent strains at the outer surface of the femur. This is made possible by using a numerical model of a synthetic femur implanted, which is setup similarly to the mechanical test of the first article. The digital image correlation system is also used in this case to validate the numerical model. Finally, the porous stem shows a surface ratio of bone resorption lower (18.4%) to that of its dense version (22.8%).

Date	13 Jun 2018
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Vladimir Brailovski (Supervisor) & Patrick Terriault (Co-supervisor)