Abstract
Solid metallic hip implants have much higher stiffness than the femur bone, causing stress-shielding and subsequent implant loosening. The development of low-stiff implants using metallic porous structures has been reported in the literature. Ti6Al4V alloy is a commonly used biomaterial for hip implants. In this work, Body-Center-Cubic (BCC), Cubic, and Spherical porous structures of four different porosities (82%, 76%, 70%, and 67%) were investigated to establish the range of ideal porosities of Ti6Al4V porous structures that can match the stiffness of the femur bone. The effective mechanical properties have been determined through Finite Element Analysis (FEA) under uniaxial compressive displacement of 0.32 mm. FEA predictions were validated with the analytical calculations obtained using Gibson and Ashby method. The effective mechanical properties of 82%, 76%, 70%, and 67% porous BCC and Cubic structures were found to match the mechanical properties of cortical bone closely. They were also well comparable to the Gibson-Ashby method-based calculations. BCC and Cubic porous structures with 67–82% porosity can mimic the stiffness of the femur bone and are suitable for low-stiff hip implant applications.
Highlights
Ti6Al4V alloy is a commonly used biomaterial for loadbearing orthopedic implants [1]
Results show that the effective elastic modulus and yield strength of BCC, Cubic, and Spherical porous structures decrease with increasing pore size and porosity and decreasing strut size (Fig. 8a,b)
The effective elastic moduli of the Cubic and Spherical porous structures were found to range from 18.52 GPa to 29.03 GPa and from 13.94 GPa to 27.66 GPa, respectively, when the porosity was varied from 82% to 67% (Tab. 2)
Summary
Ti6Al4V alloy is a commonly used biomaterial for loadbearing orthopedic implants [1]. Solid Ti6Al4V has an elastic modulus around 110 GPa, much higher than those of the natural bones [2]. The difference of elastic modulus between a solid Ti6Al4V implant and the adjacent bone causes stress-shielding, leading to implant loosening [3]. To avoid the risk of implant loosening, the implants should ideally be developed with comparable mechanical properties to those of natural bones. Metallic porous implants and porous structures have been investigated in the literature to reduce the problems associated with stiffness mismatch of the implants and optimize porous structure designs [4–11]. The mechanical properties of porous structures and their biological behavior, such as cell attachment and tissue growth, depend on the structural parameters of the porous structure, including the unit cell type, porosity, and pore size [12].
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