Endoprostheses are small struts placed by intravascular way to restore the
vascular lumen and flow conditions. The purpose of this work is to provide
models for evaluation and characterisation of some mechanical properties of
a balloon-expandable stent by using the finite element method. Here we pre
sent the results for a metallic tubular peripheral prosthesis: the P308 Pal
maz stent. We focus on the mechanisms linked to the structure expansion and
its long-term behaviour. Several models are constructed in order to determ
ine the stent shape after dilation and to assess the stress and strain fiel
ds in its wall due to this transformation. They inform us about the shorten
ing percentage on expansion, degrees of radial and longitudinal recoil, and
weaknesses of the structure. Various methods, differing in their levels of
complexity, are then attempted to exhibit the predominant factors responsi
ble for the crushing of a stent under external pressure. Moreover, the sens
itivity of this critical pressure to geometric imperfections is studied. La
stly, since this kind of material is implanted for a lifetime, we test the
stent with regard to fatigue life. Beyond safety considerations, this type
of characterisation provides mechanical properties that are often difficult
to obtain by experiments. If it was available for various stents, such inf
ormation could be used to choose the appropriate prosthesis fbr specific ap
plications. Moreover, confronted with observations from practitioners, they
might lead to a better understanding of the failure or success of a partic
ular design and to work on the product optimisation. (C) 2000 Elsevier Scie
nce Ltd. All rights reserved.