title: Performance assessment of femoral knee components made from cobalt-chromium alloy and oxidized zirconium.
abstract: BACKGROUND
  The surface characteristics of the femoral component affect polyethylene wear in modular total knee replacements. In the present retrieval study, the surface characteristics of cobalt-chromium (CoCr) alloy and oxidized zirconium (OxZr) femoral components were assessed and compared.
  
  
  METHODS
  Twenty-six retrieved CoCr alloy femoral components were matched with twenty-six retrieved OxZr femoral components for implantation period, body-mass index, patient gender, implant type, and polyethylene insert thickness. The surface damage on the retrieved femoral components was evaluated using a semi-quantitative assessment method, scanning electron microscopy, and contact profilometry.
  
  
  RESULTS
  The retrieved CoCr alloy femoral components showed less posterior surface gouging than OxZr femoral components; however, at a higher magnification, the grooving damage features on the retrieved CoCr alloy femoral components confirmed an abrasive wear mechanism. The surface roughness values Rp, Rpm, and Rpk for the retrieved CoCr alloy femoral components were found to be significantly higher than those of the retrieved OxZr femoral components (p≤0.031). The surface roughness values were higher on the medial condyles than on the lateral condyles of the retrieved CoCr alloy femoral components; such a difference was not observed on the retrieved OxZr femoral components.
  
  
  CONCLUSIONS
  The surface roughness of CoCr alloy femoral components increased while the surface roughness of the OxZr femoral components remained unchanged after in vivo service. Therefore, the OxZr femoral components' resistance to abrasive wear may enable lower polyethylene wear and ensure long-term durability in vivo.
  
  
  METHODS
  Level IV.
authors.affiliation: Concordia Joint Replacement Group, 1155 Concordia Avenue - Suite 310, Winnipeg, MB, Canada R2K 2M9. Electronic address: jbrandt@cjrg.ca.
authors.forename: J-M
authors.initials: JM
authors.lastname: Brandt
authors.forename: L
authors.initials: L
authors.lastname: Guenther
authors.forename: S
authors.initials: S
authors.lastname: O'Brien
authors.forename: A
authors.initials: A
authors.lastname: Vecherya
authors.forename: T R
authors.initials: TR
authors.lastname: Turgeon
authors.forename: E R
authors.initials: ER
authors.lastname: Bohm
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D002858:Chromium Alloys; D019245:Compressive Strength; D016208:Databases, Factual; D005260:Female; D005269:Femur; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008422:Materials Testing / Q000379:methods; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D020127:Recovery of Function; D012189:Retrospective Studies; D018570:Risk Assessment; D016896:Treatment Outcome; D015040:Zirconium
chemical_list: D002858:Chromium Alloys; D015040:Zirconium
keywords: Cobalt chromium alloy; Oxidized zirconium; Retrieval analysis; Surface roughness; Total knee replacement