Does the Plaque Geometry Influence the Fatigue Performance of Nitinol Peripheral Stents? - A Finite Element Study

Fatigue resistance of Nitinol peripheral stents implanted into femoropopliteal arteries is a critical issue due to the particular biomechanical environment of this district. Hip and knee joint movements associated with patient’ daily activities expose the superficial femoral artery, and therefore the implanted stents, to large and cyclic deformations. These loadings may cause fatigue fracture of stents. The stress/strain field throughout the stent is likely affected by plaque features. In this study, finite element simulations of angioplasty, stenting and subsequent in vivo loading conditions (cyclic axial compression and bending) have been developed in different stenotic vessel models. A model of a stent, resembling the geometry of a commercial peripheral stent, has been reconstructed. A parametric model of stenotic artery has been developed, described by vessel inner diameter, obstruction ratio, length, plaque asymmetry and sharpness. In particular 4 configurations with one or two peaks, low or high sharpness and concentric or eccentric plaque have been considered. The results, analyzed in terms of amplitudes (ε1a) and mean values (ε1m) of the first principal strain through the stent, showed that the geometry affects remarkably the local stiffness and hence influences the stress distribution in the stent. Indeed, where the plaque is less stiff the stent is subjected to higher amplitude strain.

The abstract is submitted to the session "SMA modeling in medical industry: from raw material to final product design"