title: Comparison of mechanical deformation properties of metallic stents with use of stress-strain analysis.
abstract: OBJECTIVE
  Elastic and plastic deformation properties of the Wallstent, Palmaz stent, and Strecker stent were evaluated quantitatively with an in vitro model simulating forces exerted by an eccentric lesion.
  
  
  METHODS
  A miniaturized compression testing device was constructed. Stress-strain graphs were obtained for each stent, and the elastic moduli and yield points were calculated.
  
  
  RESULTS
  There is a 21-fold range in the elastic modulus among the Wallstent, Palmaz stent, and Strecker stents. The Palmaz stent was the only device to exhibit permanent plastic deformation. The 10-mm Palmaz stent will undergo 15% focal eccentric narrowing at 0.75 atm of pressure; the "standard braid" and "less shortening braid" 10-mm Wallstents at 0.55 and 0.25 atm, respectively; and the 10-mm tantalum Strecker stent at 0.08 atm. Overlapping of stents doubles the stiffness of the Wallstent and the Strecker stent and doubles the yield point of the Palmaz stent. The 4-9 mm Palmaz stent is 30% more resistant to deformation than the larger 8-12-mm version when expanded to identical 8-mm diameters.
  
  
  CONCLUSIONS
  The "standard braid" version of the 10-mm Wallstent provides 2.3-fold additional strength for resistant stenoses compared with the "less shortening braid." Overlapping or nesting of stents may permit full expansion should there be incomplete expansion or recoil of a single stent. The 4-9-mm Palmaz stent is preferable from the standpoint of allowing the use of a smaller (7-F instead of 9-F) introducer sheath and also for providing superior resistance to deformation. A purely elastic stent such as the Wallstent is preferable in locations where permanent plastic deformation may occur, such as the thoracic outlet.
authors.affiliation: Department of Radiology, Georgetown University Hospital, Washington, DC 20007.
authors.forename: S V
authors.initials: SV
authors.lastname: Lossef
authors.forename: R J
authors.initials: RJ
authors.lastname: Lutz
authors.forename: J
authors.initials: J
authors.lastname: Mundorf
authors.forename: K H
authors.initials: KH
authors.lastname: Barth
mesh_terms: D000497:Alloys; D004548:Elasticity; D004867:Equipment Design; D006801:Humans; D008961:Models, Structural; D015607:Stents; D013314:Stress, Mechanical; D013635:Tantalum
chemical_list: D000497:Alloys; C013616:nitinol; D013635:Tantalum