title: Oxidized zirconium versus cobalt-chromium in TKA: profilometry of retrieved femoral components.
abstract: BACKGROUND
  Oxidized zirconium (OxZr) was introduced as an alternative bearing for femoral components in total knee arthroplasty (TKA) in an attempt to reduce wear compared with conventional cobalt-chromium (CoCr) alloys.
  
  
  OBJECTIVE
  The aim of this study was to compare matched pairs of retrieved OxZr and CoCr components using surface profilometry; specifically, we sought to compare the surface roughness of (1) retrieved OxZr TKA components with retrieved CoCr components; (2) the medial versus the lateral femoral condyles of retrieved components; and (3) unimplanted OxZr TKA components with unimplanted CoCr components.
  
  
  METHODS
  Ten retrieved posterior-stabilized Genesis II TKA with OxZr femoral components were identified and matched to retrieved CoCr femoral components by duration of implantation, patient age, and body mass index. A noncontact white light interferometer was used to evaluate surface roughness. One pristine, unimplanted component of each design was analyzed as a control.
  
  
  RESULTS
  The retrieved components showed significantly (p < 0.0001) lower roughness for the OxZr components than the CoCr components. CoCr retrievals showed a significantly greater average surface roughness on the medial condyle. No difference was found between the condyles of the OxZr components. The pristine CoCr implant had a significantly lower surface roughness than the pristine OxZr component.
  
  
  CONCLUSIONS
  CoCr roughens significantly more in situ compared with OxZr components.
  
  
  CONCLUSIONS
  Bearing surfaces are typically damaged in vivo. The extent of damage is variable between patients and implants; however, rougher surfaces should be associated with more wear. Whether the differences observed in our study prove meaningful requires long-term clinical data.
authors.affiliation: Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Heyse
authors.forename: Marcella E
authors.initials: ME
authors.lastname: Elpers
authors.forename: Danyal H
authors.initials: DH
authors.lastname: Nawabi
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Wright
authors.forename: Steven B
authors.initials: SB
authors.lastname: Haas
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D002858:Chromium Alloys; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D015040:Zirconium
chemical_list: D002858:Chromium Alloys; D015040:Zirconium