The wear of a polyethylene socket articulating with a zirconia ceramic femoral head in canine total hip arthroplasty

Wear of yttria-zirconia (zirconia) in the femoral head was investigated in mature mongrel dogs weighing 10 to 13 kg, Two dogs, which were used as a co ntrol group, were sacrificed 18 months after implantation of the uncemented modular hip system with an alumina ceramic (alumina) femoral head. A zirco nia femoral head was implanted in five dogs: one was sacrificed 12 months a fter implantation, two at 18 months, and two at 24 months. In each femoral head and polyethylene (PE) socket, the surface was observed by means of sca nning electron microscopy (SEM); the mean articulation surface roughness on the femoral head and PE socket and the thickness of the PE socket were mea sured, Wear was not seen on the surface of either the zirconia or the alumi na heads, In both groups, minute white spots on the smooth surface of the P E socket were visible by SEM. In the alumina and zirconia groups the mean r oughness was 0.1 mu m. The mean thickness of the PE socket was reduced by 0 .2 mm in the alumina group. In the zirconia group it was reduced by 0.2 to 0.3 mm, However, the mechanical strength of zirconia is known to be greater than that of alumina and it may be possible to reduce the diameter of the femoral head, The smaller zirconia head may contribute to the reduction of the wear of the PE socket in an uncemented modular total hip system. (C) 19 99 John Wiley & Sons, Inc.