A Multi-Dimensional Non-Uniform Corrosion Model for Bioabsorbable Metallic Vascular Stents

Bioabsorbable metallic vascular stents (BMVSs) are an innovative technological advancement in the medical engineering field of vascular implants. BMVSs have great potential to revolutionize vascular intervention, but the lack of understanding of the construction material’s natural corrosion within the body inhibits their use in clinical medicine. In this study, a corrosion function concept for in vivo implants was created to develop a multi-dimensional non-uniform corrosion model with a larger goal of simulating the mechanical integrity of BMVSs. This novel corrosion model simulates the corrosion rate and its effects on magnesium (Mg) alloy AZ31B and is based on continuum damage mechanics. The model was calibrated and validated by three experiments on the degradation of Mg alloy specimens. These experiments focused on multi-dimensional corrosion, mass loss rate, and mechanical integrity during the corrosion process. Lastly, in order to verify the applicability of the novel model, the resulting corrosion behaviors and mechanical characteristics of the BMVSs were implemented into a finite element framework to produce a complex, over-arching simulation of the BMVS’s in vivo degradation. The results of the experiments and simulations showed a proportional link between the corrosion of BMVSs and the number of exposed surfaces. A non-linear decline in mechanical integrity with increasing mass loss was also discovered through experimentation and modeling. Furthermore, the model and simulation can provide some details about changes in morphology and mechanics in BMVS corrosion. This work gives new insights into accurately modeling for BMVS degradation and can be used to optimize product development of BMVSs.