title: A comparison of the physical properties of four new generation flexible ureteroscopes: (de)flection, flow properties, torsion stiffness, and optical characteristics.
abstract: OBJECTIVE
  Several kinds of flexible ureteroscopes are in use for the removal of kidney stones. This study evaluated and compared the characteristics of four new-generation flexible ureteroscopes.
  
  
  METHODS
  The flexible ureteroscopes studied were: the ACMI Dur-8 Elite, the Storz Flex-X2 the Olympus XURF-P5, and the Wolf 7325.076. Measured properties included (de)flection, instrument insertion, flow properties, torsion stiffness, and optical characteristics. Active tip deflection and irrigation flow rates with and without various endoscopic tools were assessed.
  
  
  RESULTS
  All ureteroscopes score better on (de)flection with an empty working channel, compared with a channel when tools are inserted (differences minimum 0.3 degrees--maximum 80.6 degrees). The Olympus XURF-P5 is the only ureteroscope with passive (de)flection capability, whereas the ACMI DUR-8 Elite is the only ureteroscope that has a secondary active (de)flection capability. The Storz Flex-X2 and the Wolf 7325.076 ureteroscopes show nearly identical best deflection capabilities with and without tools inserted in the working channel. The longest (Olympus XURF-P5, 70 cm) and shortest (ACMI DUR-8 Elite, 64 cm) ureteroscopes have, respectively, the lowest and highest flow rates. Best optical quality is offered by the Olympus XURF-P5 and Wolf 7325.076 ureteroscopes, which have low optical distortion (-9.7; -7.7%), high resolving power (17.95; 16.00 line pairs per millimeter), and a large field of view (62.9; 63.2 degrees). The Storz Flex-X2 and Wolf 7325.076 ureteroscopes have lowest torsion stiffness.
  
  
  CONCLUSIONS
  The ex vivo evaluation of the deflection capabilities, passage of instruments, flow properties, torsion stiffness, and optical characteristics yielded quantitative measures of the in vivo performance capabilities of four new-generation flexible ureteroscopes. New ureteroscopes should be subjected to this or similar evaluation and comparison. Only in this way can the urologist make an informed and objective decision regarding appropriate instrument choice.
authors.affiliation: Department of Urology, Catharina Hospital, and Eindhoven University of Technology, Eindhoven, The Netherlands. Marcpaffen@yahoo.com
authors.forename: Marc L J E
authors.initials: ML
authors.lastname: Paffen
authors.forename: Joris G
authors.initials: JG
authors.lastname: Keizer
authors.forename: Grischa V
authors.initials: GV
authors.lastname: de Winter
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Arends
authors.forename: Ad J M
authors.initials: AJ
authors.lastname: Hendrikx
mesh_terms: D055620:Optical Phenomena; D018583:Pliability; D012212:Rheology; D054159:Torsion, Mechanical; D020709:Ureteroscopes