title: Reduced wear of cross-linked UHMWPE using magnesia-stabilized zirconia femoral heads in a hip simulator.
abstract: BACKGROUND
  To reduce wear, the ideal bearing surface in joint arthroplasty should be smooth and hydrophilic. Ceramics generally offer better wettability than metals and can be polished to a smoother finish. However, clinical studies have found no reduction in liner wear when using yttria-stabilized zirconia (Y-TZP) instead of cobalt chromium alloy (CoCr) femoral heads.
  
  
  OBJECTIVE
  We (1) determined whether a hard, diamond-like carbon (DLC) coating would enhance the wettability of CoCr and magnesia-stabilized zirconia (Mg-PSZ) femoral heads without increasing roughness, and (2) compared their wear performance.
  
  
  METHODS
  In an observational study limited to CoCr and Mg-PSZ heads, we measured roughness and contact angle on as-received and DLC-coated heads. Eight heads then were subjected to 11 million cycles of wear in a hip simulator against cross-linked ultrahigh molecular weight polyethylene (XLPE) liners.
  
  
  RESULTS
  Mg-PSZ femoral heads were smoother and more hydrophilic than CoCr heads. Although DLC coatings did not reduce roughness, they reduced the contact angle of CoCr and Mg-PSZ substrates, which may provide enhanced lubrication in vivo. In hip simulator tests, liners bearing against CoCr heads wore at a greater rate compared with Mg-PSZ heads. The DLC coating on Mg-PSZ heads did not reduce wear further.
  
  
  CONCLUSIONS
  The wear rate of XLPE versus Mg-PSZ was seven times less than CoCr heads, probably owing to lower roughness and greater wettability of Mg-PSZ heads.
  
  
  CONCLUSIONS
  The use of Mg-PSZ femoral heads should lead to reduced wear in vivo compared with CoCr heads, but the clinical benefit of DLC-coated Mg-PSZ is unclear.
authors.affiliation: Missouri Bone & Joint Research Foundation, 1000 Des Peres Rd., Suite 150, St. Louis, MO 63131, USA. mroy@mobojo.org
authors.forename: Marcel E
authors.initials: ME
authors.lastname: Roy
authors.forename: Leo A
authors.initials: LA
authors.lastname: Whiteside
authors.forename: Mark E
authors.initials: ME
authors.lastname: Magill
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Katerberg
mesh_terms: D002244:Carbon; D002858:Chromium Alloys; D003432:Cross-Linking Reagents; D006244:Hardness; D006245:Hardness Tests; D006622:Hip Prosthesis; D006801:Humans; D008422:Materials Testing; D011095:Polyethylenes; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D017155:Wettability; D015040:Zirconium / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003432:Cross-Linking Reagents; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D002244:Carbon; D015040:Zirconium; C028541:zirconium oxide