Numerical And Experimental Analysis Of The Change In The Mechanical Properties Induced By Different Material Internal Features

In orthopedic medical devices, differences in elasto-plastic behavior between bone and metallic materials could lead to mechanical issues at the bone-implant interface, such as stress shielding, bone fracture or implant failure. To reduce mismatching-related adverse events between bone and prosthetic mechanical properties, an in-body geometry optimization could be the right approach to reduce prosthetic stiffness. Therefore, this study aims to assess the elastic behavior of four different in-body gap prismatic geometries (quadratic, hexagonal, octagonal, and circular) and how much they reduce bulk stiffness. Uniaxial compression tests were performed on five cubes with a 20mm thickness, each containing a different set of internal prismatic gaps. For each design, the elastic response was calculated and compared with a full-volume cube, used as control. All cubes showed a stiffness reduction compared to the control, greater in cubes with quadratic (21%), octagonal (18%), and circular (17%) transversal sections, compared to the hexagonal one (6%). Moreover, finite element models were implemented and tested, showing coherent values obtained through the experimental tests. In addition, a bi-material approach was studied in silico and the results suggested that variable elastic behavior could be obtained by using composite material, providing lower mechanical properties than commonly used commercial prosthetic materials.