Mechanical Interaction between Overlapping Stents and Peripheral Arteries - Numerical Model

The Superficial Femoral Artery (SFA) is the longest section of the femoropopliteal artery and can reach a length of 28-32 cm. Multiple stenoses can occur along its length. In such cases, two or three overlapping stents are inserted into the artery. Stent overlapping significantly increases the risk of stent fracture. Following restenosis, the procedure can lead to intermittent claudication, limb ischemia and in some cases eventually amputation. The study motivation is to evaluate the outcomes of deploying overlapping stents in terms of stresses exerted on the artery and implants and establish the fact that overlapping stents must not be designed as solitary stents. This study evaluates the stresses overlapping stents exert on the artery and on each other using a numerical (finite element) model. The model formulated comprises the stents and a two layers artery, each layer presenting hyper-elastic mechanical material properties. Results demonstrate significant increase in radial and circumferential stresses exerted on the artery at regions of overlapping stents compared with those of single stents (~50%). With similar results relating to the implant stresses. Therefore, procedures involving overlapping stents must employ uniquely designed implants of axially variable radial stiffness, not as performed today.