Abstract:
Conventional solid orthopedic implants face various mechanical and biological issues when
they are implanted in the human body. The most important mechanical problem being faced
due to use of these implants is stress shielding effect which is caused by mismatch of
mechanical properties, Young’s modulus and yield strength, between the implant and host
bone. Porous orthopedic implants designed with lattice structures can overcome this problem
as their mechanical properties can be tailored to match with host bone. For this purpose, it is
important to understand the effects of topological parameters of lattice structure on its
mechanical properties. In this work, eighteen lattice structures have been systematically
modelled keeping in view the predefined porosity range for lattice structures intended to be
used in orthopedic implants. Finite element analyses (FEA) have been carried out on these
lattice structures modelled with IsoTruss, Diamond and Fluorite unit cell types, 0.200mm,
0.225mm and 0.250mm strut thicknesses, and 3.375mm3 and 1 mm3 of unit cell volumes where
each lattice structure contains either value of these topological parameters. Young’s modulus
and yield strength of each lattice structure under uniaxial compression loading are determined
from the results of FEA. The material of lattice structures used in this work is 316L stainless
steel. Sixteen lattice structures have been found within the predefined porosity range. Out of
eighteen lattice structures, Young’s moduli and yield strengths of only nine lattice structures
have been laid within the range of these properties for either trabecular or cortical bones. The
trends of these properties to the change in topological parameters have been observed. The
sensitivity of these properties to the change in topological parameters for various categories of
lattice structures and the efficiency of each lattice structure to use its material content for
increasing the mechanical properties have also been determined. Furthermore, all lattice
structures having similar type of unit cell have been found in conformity with Ashby Gibson
model.
