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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

Test 1 condition on eight-ring stent: mean and amplitude strain values in the link and in the V-strut are plotted on the constant-life diagram. Red and violet dots (a) include pairs of mean and amplitude values of all the finite elements belonging to the two most stressed zones (b).
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jfb-06-00299-f014: Test 1 condition on eight-ring stent: mean and amplitude strain values in the link and in the V-strut are plotted on the constant-life diagram. Red and violet dots (a) include pairs of mean and amplitude values of all the finite elements belonging to the two most stressed zones (b).

Mentions: For each FE analysis, the values (, ), related to the elements belonging to the two highly stressed zones were plotted on the constant-life diagram and compared with the material fatigue limit at 107 cycles in order to find the most critical point for fatigue failure in terms of distance from the limit curve. Figure 14 shows how the criterion indicates the V-strut as the most critical area for fatigue failure in test 1 condition for eight-ring stent. Even if the amplitude strain in the two highly stressed zones (red and violet dots) is the same, the distance from the material fatigue limit is greater for the V-strut, due to its low mean strain value.


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)

Test 1 condition on eight-ring stent: mean and amplitude strain values in the link and in the V-strut are plotted on the constant-life diagram. Red and violet dots (a) include pairs of mean and amplitude values of all the finite elements belonging to the two most stressed zones (b).
© Copyright Policy
Related In: Results  -  Collection

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

jfb-06-00299-f014: Test 1 condition on eight-ring stent: mean and amplitude strain values in the link and in the V-strut are plotted on the constant-life diagram. Red and violet dots (a) include pairs of mean and amplitude values of all the finite elements belonging to the two most stressed zones (b).
Mentions: For each FE analysis, the values (, ), related to the elements belonging to the two highly stressed zones were plotted on the constant-life diagram and compared with the material fatigue limit at 107 cycles in order to find the most critical point for fatigue failure in terms of distance from the limit curve. Figure 14 shows how the criterion indicates the V-strut as the most critical area for fatigue failure in test 1 condition for eight-ring stent. Even if the amplitude strain in the two highly stressed zones (red and violet dots) is the same, the distance from the material fatigue limit is greater for the V-strut, due to its low mean strain value.

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