Creation and finite-element analysis of multi-lattice structure design in hip stem implant to reduce the stress-shielding effect

Abstract

The term stress-shielding is frequently used to mention the reduction in mechanical stimulus in the surrounding bone due to the presence of a biomaterial inert implant whose mechanical properties are superior to bone. As the natural consequence of this, mineral loss occurs in the bone over time and creating subsequent weakness. One of the methods to reduce stress-shielding problem is to develop hip-stem implant designs that will transfer the load more to the bone. Therefore, in this study, multi-lattice designs were developed to reduce the stress-shielding effect in hip implant applications. For this, the proximal part of the hip implant stems has been divided into three parts. Simple cubic, body centered cubic, and face centered cubic lattice structures were created on the upper parts. Inner vertical and inner vertical + inner horizontal beams were added to the lattice structure of the upper part for middle and lower parts, respectively. Due to the multi-lattice designs, the maximum von Mises stress values on the hip implant stem were reduced from 289 to 189 MPa, as well as a weight reduction of up to 25.89%. Stress-shielding signals were obtained by determining the change in strain energy per unit bone mass caused by the presence of the femoral hip implant stem and its ratio to intact bone. In the case of using hip-stems having multi-lattice designs, there is a significant increase (max. 150.47%) in stress-shielding signals from different zones of the femur.

Titanium Lattice Structures Produced via Additive Manufacturing for a Bone Scaffold: A Review

“…Gok [ 136 ] developed a multi-lattice design by dividing the proximal zone of a hip implant stem into three parts. Due to the multi-lattice design, a weight reduction of 25.89% was obtained and the maximum von Mises stresses in the stem were reduced from 289 to 189 MPa.…”

Optimisation of Selective Laser Melted Ti6Al4V Functionally Graded Lattice Structures Accounting for Structural Safety

“…The design of lattice metamaterials is often inspired by naturally lightweight hierarchical structures including bamboo stems [2,3] and human proximal femurs [4,5]. Recently, lattice metamaterials have attracted increasing attention in engineering sectors (e.g., the turbine blades design presented by Alkebsi et al [6]) and medical applications (e.g., the hip implant structural designs presented by Gok [7]). This is owing to the advanced properties of lattice metamaterials, such as the high stiffness-to-weight ratio, high strength-to-weight ratio, excellent heat transfer capability, and outstanding energy absorption capability [8,9].…”

In-situ modulating laminated microstructure of α+β+TiC in titanium composites by laser powder bed fusion of Mo2C/Ti powder mixture towards biomedical applications

“…The improved YS and UCS benefit patients clinically by enhancing the ability of biomaterials against premature shape change and final fracture. Compared to the case modulated using VED of 100.5 J/mm 3 , although sacrificing material strength slightly, the elastic modulus of the in-situ Ti-7.5Mo-2.4TiC composites modulated using VED of 82.3 J/mm 3 is successfully lowered to around 90 GPa, which is much lower than that of commercially available CP Ti and Ti-6Al-4V, contributing to an alleviated stress shielding effect; nevertheless, its material strength is still much higher than the UCS (170 [60] ~200 MPa [61]) of the human femur bone -the bone having the greatest capability of undertaking compressive loads in humans, suggesting the obtained composites are strong enough for clinic use. More importantly, compared to our previous work, the in-situ Ti-7.5Mo-2.4TiC composites modulated using VED of 82.3 J/mm 3 achieve a significantly improved ductility, producing a more than three times higher elongation value (16.4 ± 1.4% in this study vs 5.4% in our previous study [21]).…”