Finite element analysis and stent design: Reduction of dogboning

Issue title: Papers from the Regensburg Applied Biomechanics Symposium, June 2005

Guest editors: Joachim Hammerx and Michael Nerlichy

Article type: Research Article

Authors: De Beule, M.^{a; *} | Van Impe, R.^a | Verhegghe, B.^b | Segers, P.^c | Verdonck, P.^c

Affiliations: [a] Laboratory for Research on Structural Models, Faculty of Engineering, Department of Structural Engineering, Ghent University, Technologiepark-Zwijnaarde 904, B-9052 Zwijnaarde, Belgium | [b] Department of Mechanical Construction and Production, Faculty of Engineering, Department of Structural Engineering, Ghent University, B-9000 Gent, Belgium | [c] Cardiovascular Mechanics and Biofluid Dynamics Research Unit, Faculty of Engineering, Department of Civil Engineering, Ghent University, B-9000 Gent, Belgium | [x] Mechanical Engineering Faculty, Laboratory for Materials Technology, University of Applied Science, Regensburg, Germany | [y] University Clinic, Department of Traumatology, Regensburg, Germany

Correspondence: [*] Corresponding author. Tel.: +32 9 264 54 69; Fax: +32 9 264 58 38; E-mail: [email protected].

Abstract: In Western countries, cardiovascular disease is the most common cause of death, often related to atherosclerosis. This paper offers a brief introduction into some aspects of this disease and its treatment, where the use of stents is gaining increasing importance. Stents are supporting – mostly metal – tubular mesh structures which are opened in an obstructed artery in order to reopen it, and to offer radial strength to prevent elastic recoil of the dilated vessel. In addition to a variety of experimental tests to study the behavior of (new) stent designs, advanced numerical models (e.g. Finite Element Models) may offer interesting insights in the mechanical behavior of stents and will undoubtedly influence the design of future generation stents. A brief literature review on numerical studies dealing with the mechanical behavior of stents is presented. Subsequently, the finite element method is exploited to investigate and compare different designs of a “first generation” Palmaz Schatz stent in order to reduce the dogboning (i.e. ends of stent open first during expansion) to a minimum. Our computational models (Abaqus [1]) are described in terms of geometry, constitutive material models, numerical aspects and output quantities. Altering the original symmetric stent design to asymmetric designs decreased the dogboning from 27.24% to less than 10% for the vast majority of the studied asymmetric designs. For one particular configuration, the dogboning effect vanished completely. For this reason, taking asymmetry into account in the design of stents seems very promising, at least from the perspective of dogboning. However, as the dogboning only takes into account the radii (R) at the central and distal part of the stent, nothing can be concluded concerning the uniformity of the complete stent expansion. The mean value (Rm) and the root mean square (RRMS) of radii (differences) of the stent at the end of the loading phase (P=0.7 N/mm2) are much better parameters to give a clear indication of the uniformity of the expanded stent's shape. Although the model is suitable to study basic aspects of stent deployment, further research is necessary, especially accounting for newer generation stent geometries and more realistic balloon-stent interaction.

DOI: 10.3233/THC-2006-144-506

Journal: Technology and Health Care, vol. 14, no. 4-5, pp. 233-241, 2006