Mechanical properties of metallic stents: How do these properties influence the choice of stent for specific lesions?

Purpose. To assess selected balloon-expandable and self-expanding stents fo r radial force, flexibility, radio-opacity, and trackability, and to relate these physical characteristics to potential indications for placement. Methods: Force-strain curves were plotted for each stent and the force requ ired to produce 50% luminal narrowing was recorded. The ability of the sten t to show elastic recoil following deformation was also noted. Flexibility was measured by bending the stents against a force transducer and recording the force required per degree of flexion. Radio-opacity was measured by co mparing each stent against a standard aluminum step wedge. Trackability was measured by testing the ability of the stent on its delivery system to tra ck over angles of 90 degrees and 60 degrees. Results: The balloon-expandable stents showed greater radial strength and r adio-opacity but, apart from the AVE Iliac Bridge stent, showed poorer flex ibility and trackability. The self-expanding stents showed less radial forc e but were able to re-expand following deformity. They were generally more flexible and had better trackability but lower radio-opacity. Conclusion: There is no stent which exhibits all the ideal properties requi red and therefore the interventionist will need to keep a range of stents a vailable if all lesions are to be addressed.