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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

Numerical (half) model of the simplified crimping simulation on one ring of peripheral stent. This is performed through a rigid contact, defined between the stent outer surface and the external cylinder one: starting from the fully-expanded configuration (a), the cylindrical rigid surface moves in negative radial direction until the stent reaches its final crimped shape (b).
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jfb-06-00299-f009: Numerical (half) model of the simplified crimping simulation on one ring of peripheral stent. This is performed through a rigid contact, defined between the stent outer surface and the external cylinder one: starting from the fully-expanded configuration (a), the cylindrical rigid surface moves in negative radial direction until the stent reaches its final crimped shape (b).

Mentions: To validate the numerical model, crimping tests and simulations were performed as described in Section 2.3. In particular, four specimens composed of eight rings each were tested, starting from a fully expanded diameter of 8 mm up to a diameter of 3 mm. In the FE analysis only a repetitive unit was considered, taking advantage of the Maris Plus™ repetitive axial pattern (Figure 9). The whole hoop force was then calculated by multiplying the numerical force obtained on the reduced model for a number of times (8) allowing the reproduction of the whole device tested.


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)

Numerical (half) model of the simplified crimping simulation on one ring of peripheral stent. This is performed through a rigid contact, defined between the stent outer surface and the external cylinder one: starting from the fully-expanded configuration (a), the cylindrical rigid surface moves in negative radial direction until the stent reaches its final crimped shape (b).
© Copyright Policy
Related In: Results  -  Collection

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

jfb-06-00299-f009: Numerical (half) model of the simplified crimping simulation on one ring of peripheral stent. This is performed through a rigid contact, defined between the stent outer surface and the external cylinder one: starting from the fully-expanded configuration (a), the cylindrical rigid surface moves in negative radial direction until the stent reaches its final crimped shape (b).
Mentions: To validate the numerical model, crimping tests and simulations were performed as described in Section 2.3. In particular, four specimens composed of eight rings each were tested, starting from a fully expanded diameter of 8 mm up to a diameter of 3 mm. In the FE analysis only a repetitive unit was considered, taking advantage of the Maris Plus™ repetitive axial pattern (Figure 9). The whole hoop force was then calculated by multiplying the numerical force obtained on the reduced model for a number of times (8) allowing the reproduction of the whole device tested.

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