title: A rolling-gliding wear simulator for the investigation of tribological material pairings for application in total knee arthroplasty.
abstract: BACKGROUND
  Material wear testing is an important technique in the development and evaluation of materials for use in implant for total knee arthroplasty. Since a knee joint induces a complex rolling-gliding movement, standardised material wear testing devices such as Pin-on-Disc or Ring-on-Disc testers are suitable to only a limited extent because they generate pure gliding motion only.
  
  
  METHODS
  A rolling-gliding wear simulator was thus designed, constructed and implemented, which simulates and reproduces the rolling-gliding movement and loading of the knee joint on specimens of simplified geometry. The technical concept was to run a base-plate, representing the tibia plateau, against a pivoted cylindrical counter-body, representing one femur condyle under an axial load. A rolling movement occurs as a result of the friction and pure gliding is induced by limiting the rotation of the cylindrical counter-body. The set up also enables simplified specimens handling and removal for gravimetrical wear measurements. Long-term wear tests and gravimetrical wear measurements were carried out on the well known material pairings: cobalt chrome-polyethylene, ceramic-polyethylene and ceramic-ceramic, over three million motion cycles to allow material comparisons to be made.
  
  
  RESULTS
  The observed differences in wear rates between cobalt-chrome on polyethylene and ceramic on polyethylene pairings were similar to the differences of published data for existing material-pairings. Test results on ceramic-ceramic pairings of different frontal-plane geometry and surface roughness displayed low wear rates and no fracture failures.
  
  
  CONCLUSIONS
  The presented set up is able to simulate the rolling-gliding movement of the knee joint, is easy to use, and requires a minimum of user intervention or monitoring. It is suitable for long-term testing, and therefore a useful tool for the investigation of new and promising materials which are of interest for application in knee joint replacement implants.
authors.affiliation: Department of Orthopaedic, Laboratory of Biomaterials and Biomechanics, Medical School Hannover, Germany.
authors.forename: Berna I
authors.initials: BI
authors.lastname: Richter
authors.forename: Sven
authors.initials: S
authors.lastname: Ostermeier
authors.forename: Anke
authors.initials: A
authors.lastname: Turger
authors.forename: Berend
authors.initials: B
authors.lastname: Denkena
authors.forename: Christof
authors.initials: C
authors.lastname: Hurschler
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D002516:Ceramics; D003035:Cobalt; D005269:Femur; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods; D008954:Models, Biological; D009038:Motion; D020959:Polyethylene; D013499:Surface Properties; D013977:Tibia
chemical_list: D003035:Cobalt; D020959:Polyethylene