title: Do oxidized zirconium femoral heads reduce polyethylene wear in cemented THAs? A blinded randomized clinical trial.
abstract: BACKGROUND
  Charnley low-friction torque total hip arthroplasty (THA) remains the gold standard in THA. The main cause for failure is wear of the socket. Highly crosslinked polyethylene (HXLPE) has been associated with reduced wear rates. Also, oxidized zirconium has shown in vitro reduced wear rates. However, to our knowledge, there are no data comparing oxidized zirconium femoral heads with metal heads against HXLPE or ultrahigh-molecular-weight polyethylene (UHMWPE) when 22.25-mm bearings were used, which was the same size that performed so well in Charnley-type THAs.
  
  
  OBJECTIVE
  We hypothesized that after a minimal 4-year followup (1) use of HXLPE would result in lower radiographic wear than UHMWPE when articulating with a stainless steel head or with an oxidized zirconium head; (2) use of oxidized zirconium would result in lower radiographic wear than stainless steel when articulating with UHMWPE and HXLPE; and (3) there would be no difference in terms of Merle d'Aubigné scores between the bearing couple combinations.
  
  
  METHODS
  One hundred patients were randomized to receive cemented THA with either oxidized zirconium or a stainless steel femoral head. UHMWPE was used in the first 50 patients, whereas HXLPE was used in the next 50 patients. There were 25 patients in each of the four bearing couple combinations. All other parameters were identical in both groups. Complete followup was available in 86 of these patients. Femoral head penetration was measured using a validated computer-assisted method dedicated to all-polyethylene sockets. Clinical results were compared between the groups using the Merle d'Aubigné score.
  
  
  RESULTS
  In the UHMWPE series, the median steady-state penetration rate from 1 year onward was 0.03 mm/year (range, 0.003-0.25 mm/year) in the oxidized zirconium group versus 0.11 mm/year (range, 0.03-0.29 mm/year) in the metal group (difference of medians 0.08, p < 0.001). In the HXLPE series, the median steady-state penetration rate from 1 year onward was 0.02 mm/year (range, -0.32 to 0.07 mm/year) in the oxidized zirconium group versus 0.05 mm/year (range, -0.39 to 0.11 mm/year) in the metal group (difference of medians 0.03, p < 0.001). The Merle d'Aubigné scores were no different between the groups with a median of 18 in each of the groups (range, 16-18).
  
  
  CONCLUSIONS
  This study demonstrated femoral head penetration was reduced by oxidized zirconium when compared with metal on both UHMWPE and HXLPE. However, apart the metal-UHMWE group, all other groups had a steady-state penetration rate well below the osteolysis threshold with a low difference between groups that might not be clinically important at this point. Longer-term followup is needed to warrant whether wear reduction will generate less occurrence of osteolysis and aseptic loosening.
  
  
  METHODS
  Level II, therapeutic study.
authors.affiliation: Department of Orthopaedic and Reconstructive Surgery, Clinical Orthopaedic Research Center, Centre Hospitalo-Universitaire Cochin-Port Royal, 27 Rue du Faubourg St Jacques, 75014, Paris, France.
authors.forename: Amine
authors.initials: A
authors.lastname: Zaoui
authors.affiliation: Department of Orthopaedic and Reconstructive Surgery, Clinical Orthopaedic Research Center, Centre Hospitalo-Universitaire Cochin-Port Royal, 27 Rue du Faubourg St Jacques, 75014, Paris, France.
authors.forename: Samer El
authors.initials: SE
authors.lastname: Hage
authors.affiliation: Department of Orthopaedic and Reconstructive Surgery, Clinical Orthopaedic Research Center, Centre Hospitalo-Universitaire Cochin-Port Royal, 27 Rue du Faubourg St Jacques, 75014, Paris, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Langlois
authors.affiliation: Department of Orthopaedic and Reconstructive Surgery, Clinical Orthopaedic Research Center, Centre Hospitalo-Universitaire Cochin-Port Royal, 27 Rue du Faubourg St Jacques, 75014, Paris, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Scemama
authors.affiliation: Department of Orthopaedic and Reconstructive Surgery, Clinical Orthopaedic Research Center, Centre Hospitalo-Universitaire Cochin-Port Royal, 27 Rue du Faubourg St Jacques, 75014, Paris, France.
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Courpied
authors.affiliation: Department of Orthopaedic and Reconstructive Surgery, Clinical Orthopaedic Research Center, Centre Hospitalo-Universitaire Cochin-Port Royal, 27 Rue du Faubourg St Jacques, 75014, Paris, France. moussah@club-internet.fr.
authors.forename: Moussa
authors.initials: M
authors.lastname: Hamadouche
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001843:Bone Cements / Q000627:therapeutic use*; D003432:Cross-Linking Reagents / Q000737:chemistry; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D010014:Osteolysis / Q000209:etiology / Q000517:prevention & control; D010084:Oxidation-Reduction; D010297:Paris; D011095:Polyethylenes / Q000737:chemistry*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D013193:Stainless Steel; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult; D015040:Zirconium / Q000737:chemistry*
chemical_list: D001843:Bone Cements; D003432:Cross-Linking Reagents; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D013193:Stainless Steel; D015040:Zirconium