Mechanical Properties and in Vivo Assessment of Electron Beam Melted Porous Structures for Orthopedic Applications

Abstract

Electron beam melting (EBM) is an additive manufacturing technique with the ability to produce porous implants with desired properties for orthopedic applications. This paper systematically investigated the mechanical properties and in vivo performance of two commonly used stochastic porous structures (the Voronoi structure and the randomized structure) fabricated by the EBM process. The pore geometries of two porous structures were characterized through micro-computed tomography (μCT). In addition, clinically relevant mechanical performances were evaluated for both structures, including tensile testing, shear testing and abrasion resistance testing. In vivo assessment of the two porous structures was further conducted in a dog model for three different follow-up periods. It was found that the Voronoi structures showed a higher mechanical strength compared to the randomized structures, even though both structures exhibited similar pore geometries. Further analysis revealed that the non-uniform stress distribution caused by the sample size and boundary effects led to a decrease in strength in the randomized structures. The in vivo assessments revealed the Voronoi structure exhibited a higher bone ingrowth ratio compared to the randomized structure due to its radially oriented pore geometry and homogenous pore size distribution. This study suggested that the EBM Ti-6Al-4V Voronoi porous structure has favorable mechanical performance and good osseointegration properties for orthopedic implants.