STRENGTH, ELASTICITY, AND PLASTICITY OF EXPANDABLE METAL STENTS - IN-VITRO STUDIES WITH 3 TYPES OF STRESS

PURPOSE: Five types of expandable metal stents (Palmaz, Strecker, Gian turco, Cragg, and Wallstent) were subjected to standardized tests to o btain objective, comparable data of their mechanical characteristics. MATERLALS AND METHODS: The stents were subjected to area loads, point loads, and circular loads; the resistance of the stents to a continual ly increasing deformation was measured. Elasticity and deformation cha racteristics of the stents were also noted. Another experiment simulat ed the situation of the stent in an implanted state. The stents were c overed with a thin self-adhesive foil to simulate optimal wall contact by limiting the mobility of the mesh struts. RESULTS: For all types o f stress, the Palmaz stent showed the highest resistance but was compl etely inelastic. The Strecker stent and the Wallstent showed higher re sistance when coated in foil (simulating good wall. contact). The Gian turco stent showed the lowest resistances but was completely elastic. A point load on a Wallstent caused concentric constriction over a long er distance. CONCLUSIONS: Palmaz stents are appropriate for insertion into highly resistant obstructions. Strecker stents and Wallstents req uire good wall contact to achieve adequate strength. Because of their unique deformation characteristics, Wallstents may not function well i f implanted into eccentric stenoses of tough consistency. The Gianturc o stent showed the lowest resistances.