title: Improved wear performance with crosslinked UHMWPE and zirconia implants in knee simulation.
abstract: BACKGROUND
  Suggestions for improved wear performance of total knee replacements have included replacement of standard CoCr femoral components with ceramic and replacement of 3.5-Mrad ultra-high molecular weight polyethylene (UHMWPE) inserts with 5- or 7-Mrad UHMWPE inserts. The ceramic materials used clinically have included alumina, zirconia ceramic and oxidized zirconium.
  
  
  METHODS
  We compared both CoCr and zirconia versions of the Bi-Surface knee replacement in a 6-station knee simulator using alpha calf serum for lubrication (20 mg protein per mL) to evaluate the relative bearing performance.
  
  
  RESULTS
  We studied the 4-way knee simulation of implant materials: zirconia ceramic, CoCr, 3.5-Mrad UHMWPE, and 7-Mrad UHMWPE. With CoCr femoral components, the 7-Mrad UHMWPE resulted in a 5- to 8-fold reduction in wear compared to the 3.5-Mrad insert. With the 3.5-Mrad insert, the zirconia bearing provided approximately 4-fold wear reduction compared to CoCr. These wear rates with standard UHMWPE were similar to published wear studies on entire knees. With the exception of the CoCr/7-Mrad and ZrO2/3.5-Mrad combinations, the wear differences were statistically significant.
  
  
  CONCLUSIONS
  The ZrO2/7-Mrad UHMWPE combination gave the best performance, with no measurable wear over the 5.5 million cycle test duration.
authors.affiliation: Department of Orthopedics, Loma Linda University Medical Center. Loma Linda, CA, USA.
authors.forename: Riichiro
authors.initials: R
authors.lastname: Tsukamoto
authors.forename: Sam
authors.initials: S
authors.lastname: Chen
authors.forename: Taiyo
authors.initials: T
authors.lastname: Asano
authors.forename: Mikio
authors.initials: M
authors.lastname: Ogino
authors.forename: Hiromu
authors.initials: H
authors.lastname: Shoji
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Ian C
authors.initials: IC
authors.lastname: Clarke
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D006801:Humans; D007720:Knee Prosthesis; D008422:Materials Testing; D008954:Models, Biological; D011095:Polyethylenes; D011474:Prosthesis Design / Q000295:instrumentation*; D013499:Surface Properties; D016474:Weight-Bearing; D015040:Zirconium
chemical_list: D011095:Polyethylenes; D015040:Zirconium