Abstract
Objectives: Implantation of bare metal stents has therapeutic limitations, such as the permanent nature and the thrombogenicity. This has lead to the development of bioabsorbable polymer stents. With regard to the material, the stent design is a highly important factor for mechanical performance. Hence, in this study we examined the influence of the stent design on the mechanical properties of the entire stent. Materials/Methods: Three different designs were created as two dimensional stent outer shells with the CAD software Pro/Engineer Wildfire 3.0, Parametric Technology Corporation, Needham, USA. The stent outer shell was the basis for the three dimensional modeling with the preprocessor Patran, MSC Software Corporation, Santa Ana, CA, USA. For the nonlinear finite-element-analysis stent expansion, recoil and the pressure of the vessel were defined in separate load cases. Abaqus, Dassault Systemes, Providence, RI, USA, was used as processor and postprocessor. Three designs with the most promising results in terms of mechanical properties were used for manufacturing prototypes were investigated regarding recoil and radial strength. Stents were with from polymer tubes of a poly-(L-lactid) based polymer blend with an inner diameter of 1.4 mm and a wall thickness of 0.15 mm, for prototype manufacturing. Results: In the finite-element-analysis the recoil of Design A, B and C was 2.18%, 4.26%, and 2.82% and the collapse pressure was 0.81 bar, 0.66 bar, and 0.52 bar, respectively. In vitro testing yielded recoil values for Design A, B and C of: 2.09±0.11%, 2.14±0.25%, and 2.15±0.21%. The collapse pressure was 0.40±0.03 bar, 0.34±0.06 bar, and 0.44±0.04 bar, respectively. Conclusion: The differences of the results may be found in the elasto-plastic defined material properties. In next steps the finite-element-model will be further improved as a tool to reduce the need for experimental investigations during the development of polymer stents.
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Schultze, C., Grabow, N., Martin, H., Schmitz, KP. (2009). Finite-element-analysis and in vitro study of bioabsorbable polymer stent designs. In: Vander Sloten, J., Verdonck, P., Nyssen, M., Haueisen, J. (eds) 4th European Conference of the International Federation for Medical and Biological Engineering. IFMBE Proceedings, vol 22. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-89208-3_520
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DOI: https://doi.org/10.1007/978-3-540-89208-3_520
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