Characterisation of the performance of an absorbable magnesium stent by experimental and numerical analysis
Galvin, Emmet
(2014)
Characterisation of the performance of an absorbable magnesium stent by experimental and numerical analysis.
PhD thesis, Dublin City University.
Magnesium stents are a promising candidate in the emerging field of bioabsorbable stents and could obviate many of the limitations of current permanent stent platforms such as stent thrombosis and in-stent restenosis. In this study, viable magnesium stents were manufactured from WE43 magnesium alloy precursor tubes
by a combination of laser cutting and chemical and plasma-based surface treatments. The mechanical and corrosion performance of the stent was elucidated
via experiments. It was shown that the plastic strain that is induced in the stent struts during the deployment procedure has a critical influence in directing both the
kinetics and the nature of subsequent corrosion processes in the alloy. The deployment and scaffolding characteristics of the stent were determined and
contrasted with those of a commercial stainless steel stent. The magnesium stent was shown to support significantly higher levels of cyclic strain amplitude which plays a crucial role in reducing in-stent restenosis. This study provided new insights into the performance of a current magnesium stent design and material and demonstrated the influence of deployment induced corrosion on the long-term scaffolding ability of the stent. A finite element based phenomenological corrosion model was developed and calibrated based on the results of the corrosion experiments. A plastic strain parameter was introduced in the modelling framework
to account for the effects of plastic strain on corrosion behaviour. The model was found to be capable of predicting the experimentally observed mass loss profile and the temporal corrosion-induced reduction in the radial stiffness of the stent.