Polyethylene wear rates with Zirconia and cobalt chrome heads in the ABG hip

We report a radiological analysis of 281 primary cementless ABG total hip arthroplasties performed between 1991 and 1994, with a mean follow-up of 78 months. We compare the polyethylene wear in hips with Zirconia ceramic heads manufactured prior to the introduction of hot isostatic pressing and hips with cobalt chrome heads. The mean linear wear rate was 0.19 mm/yr with 28mm Zirconia heads (n=203), 0.20 mm/yr with 32mm Zirconia heads (n=47) and 0.14mm/yr with 28mm cobalt chrome heads (n=31). We matched each of the 31 patients with 28mm cobalt chrome heads with a patient from the 28mm Zirconia group for gender and age. The mean linear wear rates in these two groups were 0.14mm/yr and 0.19mm/yr respectively (p<0.05). There were 19 revisions for osteolysis in 250 hips with Zirconia heads (7.6%) and no revisions in 31 hips with metal heads. We advocate regular review of patients with Zirconia on polyethylene bearing surfaces due to the high linear wear rates and associated osteolysis.