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Computational Modeling to Predict Fatigue Behavior of NiTi Stents: What Do We Need?

Dordoni E, Petrini L, Wu W, Migliavacca F, Dubini G, Pennati G - J Funct Biomater (2015)

Bottom Line: However, their effectiveness is still debated in the clinical field.However, confidence in numerical methods is only possible after verification and validation of the models used.For the case of NiTi stents, mechanical properties are strongly dependent on the device dimensions and the whole treatments undergone during manufacturing process.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Milan 20133, Italy. elena.dordoni@hotmail.it.

ABSTRACT
NiTi (nickel-titanium) stents are nowadays commonly used for the percutaneous treatment of peripheral arterial disease. However, their effectiveness is still debated in the clinical field. In fact a peculiar cyclic biomechanical environment is created before and after stent implantation, with the risk of device fatigue failure. An accurate study of the device fatigue behavior is of primary importance to ensure a successful stenting procedure. Regulatory authorities recognize the possibility of performing computational analyses instead of experimental tests for the assessment of medical devices. However, confidence in numerical methods is only possible after verification and validation of the models used. For the case of NiTi stents, mechanical properties are strongly dependent on the device dimensions and the whole treatments undergone during manufacturing process. Hence, special attention should be paid to the accuracy of the description of the device geometry and the material properties implementation into the numerical code, as well as to the definition of the fatigue limit. In this paper, a path for setting up an effective numerical model for NiTi stent fatigue assessment is proposed and the results of its application in a specific case study are illustrated.

No MeSH data available.


Related in: MedlinePlus

Contour map of mean and amplitude strain values due to the cyclic loading condition defined for test 1 on an eight-ring stent; in the red boxes, magnifications are shown of the most stressed areas.
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jfb-06-00299-f013: Contour map of mean and amplitude strain values due to the cyclic loading condition defined for test 1 on an eight-ring stent; in the red boxes, magnifications are shown of the most stressed areas.

Mentions: FE simulations reproducing the same experimental conditions were performed. The previously described numerical stent model (geometry and material parameters) was used. Displacement boundary conditions were applied by means of Multi-points Constraints Elements (MPC184), connecting an external master node to the nodes of each stent end; displacements in axial direction were imposed to one master node, while the other was kept fixed. Each FE analysis allowed us to determine the highly stressed zone of the stent in terms of mean and amplitude values of the first principal strain. For example, the mean and amplitude strain distributions for test 1 condition and eight-ring stent are shown in Figure 13: the most stressed zones are always located in two areas, identified as the link and the V-strut directly connected to the link.


Computational Modeling to Predict Fatigue Behavior of NiTi Stents: What Do We Need?

Dordoni E, Petrini L, Wu W, Migliavacca F, Dubini G, Pennati G - J Funct Biomater (2015)

Contour map of mean and amplitude strain values due to the cyclic loading condition defined for test 1 on an eight-ring stent; in the red boxes, magnifications are shown of the most stressed areas.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493513&req=5

jfb-06-00299-f013: Contour map of mean and amplitude strain values due to the cyclic loading condition defined for test 1 on an eight-ring stent; in the red boxes, magnifications are shown of the most stressed areas.
Mentions: FE simulations reproducing the same experimental conditions were performed. The previously described numerical stent model (geometry and material parameters) was used. Displacement boundary conditions were applied by means of Multi-points Constraints Elements (MPC184), connecting an external master node to the nodes of each stent end; displacements in axial direction were imposed to one master node, while the other was kept fixed. Each FE analysis allowed us to determine the highly stressed zone of the stent in terms of mean and amplitude values of the first principal strain. For example, the mean and amplitude strain distributions for test 1 condition and eight-ring stent are shown in Figure 13: the most stressed zones are always located in two areas, identified as the link and the V-strut directly connected to the link.

Bottom Line: However, their effectiveness is still debated in the clinical field.However, confidence in numerical methods is only possible after verification and validation of the models used.For the case of NiTi stents, mechanical properties are strongly dependent on the device dimensions and the whole treatments undergone during manufacturing process.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering 'Giulio Natta', Politecnico di Milano, Milan 20133, Italy. elena.dordoni@hotmail.it.

ABSTRACT
NiTi (nickel-titanium) stents are nowadays commonly used for the percutaneous treatment of peripheral arterial disease. However, their effectiveness is still debated in the clinical field. In fact a peculiar cyclic biomechanical environment is created before and after stent implantation, with the risk of device fatigue failure. An accurate study of the device fatigue behavior is of primary importance to ensure a successful stenting procedure. Regulatory authorities recognize the possibility of performing computational analyses instead of experimental tests for the assessment of medical devices. However, confidence in numerical methods is only possible after verification and validation of the models used. For the case of NiTi stents, mechanical properties are strongly dependent on the device dimensions and the whole treatments undergone during manufacturing process. Hence, special attention should be paid to the accuracy of the description of the device geometry and the material properties implementation into the numerical code, as well as to the definition of the fatigue limit. In this paper, a path for setting up an effective numerical model for NiTi stent fatigue assessment is proposed and the results of its application in a specific case study are illustrated.

No MeSH data available.


Related in: MedlinePlus