title: Evaluation of impingement behaviour in lumbar spinal disc arthroplasty.
abstract: BACKGROUND
  The objective of our in vitro study was to introduce a test method to evaluate impingement in lumbar spinal disc arthroplasty in terms of wear, contact pattern, metal ion concentration and particle release.
  
  
  METHODS
  Impingement wear simulation was performed on a 6-station spinal wear simulator (Endolab, Germany) on a lumbar spinal disc system (activ L Aesculap AG, Germany) using four different protocols specific to impingement in flexion, in extension, in lateral bending and in combined flexion bending. Impingement contact stress is intentionally created by applying an angular displacement of +2° in addition to the intended range of motion in the impingement direction, whereas a bending moment of 8 Nm remains constant during the impingement phase (plateau).
  
  
  RESULTS
  An average volumetric wear rate of 0.67 mm(3)/million cycles was measured by impingement under flexion, of 0.21 mm(3)/million cycles under extension, of 0.06 mm(3)/million cycles under lateral bending and of 1.44 mm(3)/million cycles under combined flexion bending. The particle size distribution of the cobalt-chromium wear particles released by impingement in flexion (anterior), extension (posterior), lateral bending (lateral) and combined flexion bending (antero-lateral) revealed that most of the detected cobalt-chromium particles were in a size range between 0.2 and 2 µm.
  
  
  CONCLUSIONS
  The impingement wear simulation introduced here proved to be suitable to predict in vivo impingement behaviour in regard to contact pattern seen on retrieved devices of the activ L lumbar disc arthroplasty design in a pre-clinical test.
authors.affiliation: Aesculap AG Research and Development, Am Aesculap-Platz, 78532, Tuttlingen, Germany, thomas.grupp@aesculap.de.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grupp
authors.forename: James J
authors.initials: JJ
authors.lastname: Yue
authors.forename: Rolando
authors.initials: R
authors.lastname: Garcia
authors.forename: Christian
authors.initials: C
authors.lastname: Kaddick
authors.forename: Bernhard
authors.initials: B
authors.lastname: Fritz
authors.forename: Christoph
authors.initials: C
authors.lastname: Schilling
authors.forename: Jens
authors.initials: J
authors.lastname: Schwiesau
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Blömer
mesh_terms: D002858:Chromium Alloys; D005858:Germany; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D007595:Joint Prosthesis; D008159:Lumbar Vertebrae / Q000601:surgery*; D008422:Materials Testing; D008953:Models, Anatomic; D010316:Particle Size; D016059:Range of Motion, Articular; D059145:Total Disc Replacement
chemical_list: D002858:Chromium Alloys