Limits...
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

Development of the geometric model for finite element (FE) analyses of a commercial stent: (a) the 2D sketch of the repetitive unit is first (b) extruded in the radial direction and then (c) rotated by 120° to build the 3D geometry of the stent repetitive unit; then the unit is copied in (d) circumferential and (e) axial directions, obtaining the whole stent.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4493513&req=5

jfb-06-00299-f005: Development of the geometric model for finite element (FE) analyses of a commercial stent: (a) the 2D sketch of the repetitive unit is first (b) extruded in the radial direction and then (c) rotated by 120° to build the 3D geometry of the stent repetitive unit; then the unit is copied in (d) circumferential and (e) axial directions, obtaining the whole stent.

Mentions: To create the geometrical model of Maris Plus™ stent, the CAD software ProENGINEER Wildfire 4.0™ was used, after the acquisition of physical model dimensions. In order to fasten the creation of the model, the symmetries of the stents were acknowledged and a repetitive unit was identified, consisting of one third of three V-strut crowns. The starting point was the 2D sketch of the repetitive unit (Figure 5a): it was first extruded in the radial direction with an offset equal to the stent thickness (0.2 mm) (Figure 5b), and then rotated by 120° in order to achieve the 3D geometry of the stent repetitive unit (Figure 5c). Once we obtained the repetitive unit, the whole stent was generated by replicating the desired number of such units in the circumferential (Figure 5d) and axial directions (Figure 5e).


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)

Development of the geometric model for finite element (FE) analyses of a commercial stent: (a) the 2D sketch of the repetitive unit is first (b) extruded in the radial direction and then (c) rotated by 120° to build the 3D geometry of the stent repetitive unit; then the unit is copied in (d) circumferential and (e) axial directions, obtaining the whole stent.
© Copyright Policy
Related In: Results  -  Collection

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

jfb-06-00299-f005: Development of the geometric model for finite element (FE) analyses of a commercial stent: (a) the 2D sketch of the repetitive unit is first (b) extruded in the radial direction and then (c) rotated by 120° to build the 3D geometry of the stent repetitive unit; then the unit is copied in (d) circumferential and (e) axial directions, obtaining the whole stent.
Mentions: To create the geometrical model of Maris Plus™ stent, the CAD software ProENGINEER Wildfire 4.0™ was used, after the acquisition of physical model dimensions. In order to fasten the creation of the model, the symmetries of the stents were acknowledged and a repetitive unit was identified, consisting of one third of three V-strut crowns. The starting point was the 2D sketch of the repetitive unit (Figure 5a): it was first extruded in the radial direction with an offset equal to the stent thickness (0.2 mm) (Figure 5b), and then rotated by 120° in order to achieve the 3D geometry of the stent repetitive unit (Figure 5c). Once we obtained the repetitive unit, the whole stent was generated by replicating the desired number of such units in the circumferential (Figure 5d) and axial directions (Figure 5e).

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