Diamond-like carbon coatings enhance the hardness and resilience of bearing surfaces for use in joint arthroplasty.
The purpose of this study was to evaluate the potential of a hard diamond-like carbon (DLC) coating to enhance the hardness and resilience of a bearing surface in joint replacement. The greater hardness of a magnesium-stabilized zirconium (Mg-PSZ) substrate was expected to provide a harder coating-substrate composite microhardness than the cobalt-chromium alloy (CoCr) also used in arthroplasty. Three femoral heads of each type (CoCr, Mg-PSZ, DLC-CoCr and DLC-Mg-PSZ) were examined. Baseline (non-coated) and composite coating/substrate hardness was measured by Vickers microhardness tests, while nanoindentation tests measured the hardness and elastic modulus of the DLC coating independent of the Mg-PSZ and CoCr substrates. Non-coated Mg-PSZ heads were considerably harder than non-coated CoCr heads, while DLC coating greatly increased the microhardness of the CoCr and Mg-PSZ substrates. On the nanoscale the non-coated heads were much harder than on the microscale, with CoCr exhibiting twice as much plastic deformation as Mg-PSZ. The mechanical properties of the DLC coatings were not significantly different for both the CoCr and Mg-PSZ substrates, producing similar moduli of resilience and plastic resistance ratios. DLC coatings greatly increased hardness on both the micro and nano levels and significantly improved resilience and resistance to plastic deformation compared with non-coated heads. Because Mg-PSZ allows less plastic deformation than CoCr and provides a greater composite microhardness, DLC-Mg-PSZ will likely be more durable for use as a bearing surface in vivo.
Roy
M E
ME
Missouri Bone and Joint Research Foundation, 1000 Des Peres Road, Suite 150, St. Louis, MO 63131, USA. mroy@mobojo.org
Whiteside
L A
LA
Xu
J
J
Katerberg
B J
BJ
D001178:Arthroplasty / Q000379:methods*; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D018130:Diamond / Q000494:pharmacology*; D006244:Hardness / Q000187:drug effects; D007596:Joints / Q000601:surgery*; D008422:Materials Testing; D036103:Nanotechnology; D013499:Surface Properties / Q000187:drug effects
D020099:Coated Materials, Biocompatible; D018130:Diamond