title: Wire-based ureteral stents: impact on tensile strength and compression.
abstract: OBJECTIVE
  To evaluate the performance of coil-based ureteral stents in terms of tensile strength and the radial compression force.
  
  
  METHODS
  Three Cook Resonance (RES) metallic coil stents and three coil-reinforced Applied Medical Silhouette (SIL) ureteral stents were tested. An MTS MicroBionix Testing System using Testworks II software, vibration isolation table, and 5-N load cell were used to measure tensile and compressive strength. Stents were placed in hydraulic grips spaced 24 cm apart and stretched at a rate of 5 mm/s for 1 second under uniaxial tension. Extrinsic compression was exerted in 0.2-mm increments to maximum compression. The Young's modulus, E, was calculated for each trial using the engineering stress. Comparisons were made with the Cook C-flex, which in previous studies was shown to be stiffer and more resistant to compression than other traditional polymer stents.
  
  
  RESULTS
  The RES and SIL stents demonstrated tensile strengths of 936 +/- 485 kPa and 770 +/- 82 kPa, respectively (P = 0.02). The elastic modulus required to cause extrinsic compression was lower for the RES (63,248 +/- 3218 Pa) than for the SIL (105,664 +/- 11,529 Pa) (P <0.001). Both stents were more resistant to stent compression than previously tested stents without coil-reinforcement, the strongest of which was the Cook C-Flex (E = 30,355 +/- 910 Pa; P <0.001).
  
  
  CONCLUSIONS
  Both the Cook Resonance and Applied Medical Silhouette stents are more resistant to extrinsic stent compression than ureteral stents that are not coil-reinforced. The Cook Resonance has a higher tensile strength, whereas the Applied Medical Silhouette is more resistant to extrinsic compression.
authors.affiliation: Department of Urologic Surgery, University of Minnesota, Minneapolis, Minnesota 55455-0392, USA.
authors.forename: Renato N
authors.initials: RN
authors.lastname: Pedro
authors.forename: Kari
authors.initials: K
authors.lastname: Hendlin
authors.forename: Carly
authors.initials: C
authors.lastname: Kriedberg
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
mesh_terms: D019245:Compressive Strength; D008422:Materials Testing; D008670:Metals; D015607:Stents; D013718:Tensile Strength; D014513:Ureter
chemical_list: D008670:Metals