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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

Example of detection of mean axial force drops at different number of cycles, corresponding to fracture of wires. Each line represents one loop of acquired data, made at 8000 cycles.
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jfb-06-00299-f004: Example of detection of mean axial force drops at different number of cycles, corresponding to fracture of wires. Each line represents one loop of acquired data, made at 8000 cycles.

Mentions: During the fatigue tests, a peak-to-valley acquisition was used: for each loading cycle, the maximum and minimum values of the axial force were acquired and stored in a data file in order to evaluate its trend for the whole testing duration as a function of number of cycles. Since a wire fracture determines a decrease in the specimen resistant section, the force signal acquired shows an evident drop, greater than the minimum force resolution of the testing machine. Therefore, this method allowed the detection of the exact number of cycles for each wire fracture (Figure 4). This information is useful for defining material limit curves for a number of cycles lower than 107.


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)

Example of detection of mean axial force drops at different number of cycles, corresponding to fracture of wires. Each line represents one loop of acquired data, made at 8000 cycles.
© Copyright Policy
Related In: Results  -  Collection

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

jfb-06-00299-f004: Example of detection of mean axial force drops at different number of cycles, corresponding to fracture of wires. Each line represents one loop of acquired data, made at 8000 cycles.
Mentions: During the fatigue tests, a peak-to-valley acquisition was used: for each loading cycle, the maximum and minimum values of the axial force were acquired and stored in a data file in order to evaluate its trend for the whole testing duration as a function of number of cycles. Since a wire fracture determines a decrease in the specimen resistant section, the force signal acquired shows an evident drop, greater than the minimum force resolution of the testing machine. Therefore, this method allowed the detection of the exact number of cycles for each wire fracture (Figure 4). This information is useful for defining material limit curves for a number of cycles lower than 107.

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