Modeling of Coated Biodegradable Stents

A bioresorbable stent supports the stenosed blood vessel during the healing period after coronary angioplasty and then gradually disappears. Unlike permanent stents, the biodegradable stent forms no obstacle for future interventions. Moreover, the degradable stent material presents an ideal vehicle for local drug delivery. Long term side effects inherent to drug eluting stents such as in-stent restenosis and late stent thrombosis might be avoided [1]. To date, several bioresorbable stents are being developed or are currently being tested in clinical trials. Two classes of biomaterials are being used in biodegradable stent technology: biodegradable polymers and bioerodible metal alloys. Polymers can be tailored to have a well-defined degradational behaviour but have relatively poor mechanical properties. Biocorrodible metals such as magnesium alloys have good mechanical characteristics but display a more complex an less predictive degradational behaviour. A biocorrodible metallic stent coated with a biodegradable polymer might be able to combine the benefits of both metallic and polymeric biodegradable stents. Finite element modelling can play an important role in the study of nevel stent designs. To correctly simulate the behaviour of degradable stents a material model must be developed that incorporates the effect of degradation on all material characteristics. In case of a coated biocorrodible magnesium stent this includes corrosion modelling, the effect of the coating and the influence of mechanical loading on the corrosion rate.