title: Comparison of carotid stents: an in-vitro experiment focusing on stent design.
abstract: OBJECTIVE
  To examine and compare different carotid stent designs with regard to flexibility, adaptability (adjustability), conformability (compliance) to the vessel, and scaffolding to reduce plaque prolapse and embolization.
  
  
  METHODS
  Six stents of different design were compared (Precise, Acculink, Protégé, Xact, Wallstent, and Cristallo Ideale). Optical microscopy was used to determine exact dimensions and scaffolding of each stent. Radial force was tested using a parallel plate setup, and flexibility (torsion and bending) was measured in water at body temperature. Particle penetration simulation was performed using plastic spheres from 1.5- to 6.0-mm outer diameter.
  
  
  RESULTS
  Stent dimensions met the manufacturers' data; none of the products showed any failure during the test program. Cell sizes in the middle part of the stents ranged from 1.36 mm(2) (Wallstent) to 15.10 mm(2) (Acculink). Bending forces at 20 degrees /30 degrees ranged from 0.063 N / 0.074 N (Cristallo Ideale) to 0.890 N / 0.616 N (Xact); forces to achieve torsion at 10 degrees /15 degrees ranged from 0.032 N / 0.043 N (Acculink) to 0.905 N / 1.071 N (Xact). According to the parallel plate method, mean lowest force was measured for Xact (0.765 N), while the Wallstent had the highest force (2.136 N). Mean radial force measurements were lowest for Cristallo Ideale (9.06 N at mid part) and highest for Protégé (24.09 N). The Cristallo Ideale stent at mid part resisted penetration by all but the smallest plastic spheres (1.5-mm spheres penetrated only at 0.65 N); the Precise and Protégé stent had the highest variation in sphere penetration (1.5- to 4.0-mm spheres). Only the Acculink let 6-mm spheres penetrate.
  
  
  CONCLUSIONS
  Despite comparable stent sizes, these carotid stents showed differences in behavior due to stent design. The open-cell design displayed the greatest flexibility and adaptability to the vessel but easily allowed particle penetration due to the open structure. Closed-cell designs had low flexibility and thus low adaptability to the vessel but high resistance to particle penetration due to the closed-cell design and high scaffolding. The hybrid stent design (Cristallo Ideale) was able to combine both the flexibility of an open-cell structure and the resistance to particle penetration of closed-cell structures.
authors.affiliation: Department of Diagnostic and Interventional Radiology / Neuroradiology, Academic Hospitals Flensburg, Germany. muehue@diakol.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Müller-Hülsbeck
authors.forename: Philipp J
authors.initials: PJ
authors.lastname: Schäfer
authors.forename: Nikolas
authors.initials: N
authors.lastname: Charalambous
authors.forename: Silvio R
authors.initials: SR
authors.lastname: Schaffner
authors.forename: Martin
authors.initials: M
authors.lastname: Heller
authors.forename: Thomas
authors.initials: T
authors.lastname: Jahnke
mesh_terms: D017130:Angioplasty / Q000295:instrumentation*; D002339:Carotid Arteries / Q000601:surgery*; D004617:Embolism / Q000209:etiology / Q000517:prevention & control; D008422:Materials Testing; D018583:Pliability; D011474:Prosthesis Design; D011475:Prosthesis Failure; D015607:Stents; D054159:Torsion, Mechanical