Parametric Design of Hip Implant With Gradient Porous Structure

Abstract

Patients who has been implanted with hip implant usually undergo revision surgery. The reason is that high stiff implants would cause non-physiological distribution loadings, which is also known as stress shielding, and finally lead to bone loss and aseptic loosening. Titanium implants are widely used in human bone tissues; however, the subsequent elastic modulus mismatch problem has become increasingly serious, and can lead to stress-shielding effects. This study aimed to develop a parametric design methodology of porous titanium alloy hip implant with gradient elastic modulus, and mitigate the stress-shielding effect. Four independent adjustable dimensions of the porous structure were parametrically designed, and the Kriging algorithm was used to establish the mapping relationship between the four adjustable dimensions and the porosity, surface-to-volume ratio, and elastic modulus. Moreover, the equivalent stress on the surface of the femur was optimized by response surface methodology, and the optimal gradient elastic modulus of the implant was obtained. Finally, through the Kriging approximation model and optimization results of the finite element method, the dimensions of each segment of the porous structure that could effectively mitigate the stress-shielding effect were determined. Experimental results demonstrated that the parameterized design method of the porous implant with gradient elastic modulus proposed in this study increased the strain value on the femoral surface by 17.1% on average. Consequently, the stress-shielding effect of the femoral tissue induced by the titanium alloy implant was effectively mitigated.

A novel hybrid design and modelling of a customised graded Ti-6Al-4V porous hip implant to reduce stress-shielding: An experimental and numerical analysis

“…Porous stem had a total SSI percentage reduction of 70% when compared to the solid stem dataset (SSI of 32% and 10% for solid and porous stem respectively). This value is significantly greater than the value of total SSI percentage reduction in previous studies ranging from 17% to 57% ( He et al, 2018 ; Mehboob et al, 2020b ; Gao et al, 2022 ).…”

Additively manufactured controlled porous orthopedic joint replacement designs to reduce bone stress shielding: a systematic review

“…Computational models offer a cost-effective approach for trialing numerous designs and loading conditions; however, to provide physiologically valid predictions, model outputs must agree with experimental data. Seven studies followed this approach where model predictions were compared to physical tests of the matching implant under identical loading conditions [ 15 , 25 , 29 , 37 , 42 , 58 , 66 ]. For the remaining 35 studies, model outputs were not compared to in vitro models, which raises questions regarding the validity of the models.…”

“…A similar approach was applied in a study presenting a hip stem design based on optimized stress shielding and compliance [65]. Gao et al (2022) designed a femoral stem consisting of eight porous segments maximizing the stress transferred to the surrounding bone [66]. In contrast to other studies, Sun et al (2018) started the optimization process from a fully porous, low-stiffness implant and iteratively increased the stiffness of each mesh element until the global safety was reached [67].…”

Advancement in total hip implant: a comprehensive review of mechanics and performance parameters across diverse novelties

“…4 illustrates the unit cell and array structure of CAD and implicit-based porous unit cells utilized in the context of a hip implant stem application. 34,45,51,52,[73][74][75][76][77] To generate the image and topology based Gyroid and Schwarz Diamond porous and lattice structure, the formula stated in en ( 6) and ( 7) were followed by recent research. 42,65,78 f Gðx;y;zÞ ¼ sin…”