TRIBOLOGICAL AND MATERERIAL ANALYSES OF RETRIEVED ALUMINA AND ZIRCONIA CERAMIC HEADS CORRELATED WITH POLYETHYLENE WEAR AFTER TOTAL HIP REPLACEMENT

Abstract

The purpose of this study was to examine surface characteristics of 30 alumina and 24 zirconia ceramic femoral heads and to identify phase transformation in zirconia heads. We also studied penetration rate of alumina and zirconia heads into UHMWPE liner. The alumina heads had been implanted for a mean of 11.3 years (8.1 to 16.2) and zirconia heads for a mean of 9.8 years (7.5 to 15).

The mean surface roughness values of explanted alumina heads (Ra 40.12 nm and Rpm 578.34 nm) were similar to those for the explanted zirconia heads (Ra 36.12 nm and Rpm 607.34 nm). The mean value of monoclinic phase of two control non-implanted zirconia heads was 1% (0.8–1.5) and 1.2% (0.9–1.3), respectively. The mean value of monoclinic phase of 24 explanted zirconia heads was 7.3% (1% to 26%).

In the alumina head group, mean linear penetration rate of UHMWPE liner was 0.10 mm/yr (0.09 to 0.12) in hips with low Ra and Rpm values (13.22 nm and 85.91 nm, respectively). The mean linear penetration rate of UHMWPE liner was 0.13 mm/yr (0.17 to 0.23) in the hips with high Ra and Rpm values (198.72 nm and 1329 nm, respectively). This differences was significant (P=0.041)

In the zirconia head group, the mean linear penetration rate of UHMWPE liner was 0.09 mm/yr (0.07 to 0.14) in hips with low Ra and Rpm values (12.78 nm and 92.99 nm, respectively). The mean linear penetration rate of UHMWPE liner was 0.12 mm/yr (0.08 to 0.22) in hips with high Ra and Rpm values (199.21 nm and 1381 nm, respectively). This difference was significant (P=0.039).

The explanted zirconia heads which had a minimal phase transformation had similar surface roughness and a similar penetration rate of UHMWPE liner as the explanted alumina head.