Polyethylene Wear Against Alumina and Zirconia Heads in Cemented Total Hip Arthroplasty

We compared the polyethylene wear of acetabular sockets articulated with 22.225-mm alumina heads with the polyethylene wear of those articulated with 22.225-mm zirconia heads in cemented total hip arthroplasty during a mean follow-up period of 5.4 years. Using a computer-aided technique, we measured polyethylene wear radiologically in 46 hips with alumina heads and 58 hips with zirconia heads. The preoperative diagnosis in all cases was osteoarthritis. The mean linear wear rate and mean volumetric wear rate of polyethylene sockets against zirconia heads were 0.133 mm/y and 39.8 mm3/y, respectively, significantly greater (P < .01) than the wear rates against alumina heads (0.078 mm/y and 24.2 mm3/y, respectively). Age at operation, patient body weight as well as height, thickness of polyethylene, and socket abduction angle did not influence the wear rates. We speculate that the excessive polyethylene wear was caused by phase transformation of zirconia, leading to an increase of surface roughness.