Development of a porous metallic femoral stem: Design, manufacturing, simulation and mechanical testing

Abstract

This paper focuses on the development of a porous metallic biomimetic femoral stem designed to reduce stress shielding and to provide firm implant fixation through bone ingrowth. The design of this stem starts with the creation of the diagram allowing the establishment of a relationship between the bone ingrowth requirements and the metal additive manufacturing technology limitations. This diagram is then used to determine the optimum porosity (33%) that should compose the porous part of the stem. Afterward, selective laser melting is used to manufacture the porous stem altogether with its fully dense replica. Finite element analysis and numerical homogenization methods are then employed to predict the mechanical behavior of the stem. Both stems are finally tested following the ISO 7206-4 (2010) requirements under static loading conditions. The digital image correlation technique is employed to obtain the displacement and strain fields during the tests, and to validate the finite element model. While the finite element model of the dense stem has been successfully validated, that of the porous stem has shown ~40% higher stiffness than that measured experimentally. It has been proven that this discrepancy is due to the difference between the experimentally-measured (42%) and the numerically-targeted (33%) porosities.