Oxidised zirconium femoral heads do not reduce polyethylene wear in cemented total hip arthroplasty at five years

A RANDOMISED, CLINICAL STUDY OF 120 HIPS USING RADIOSTEREOMETRIC ANALYSIS
Aseptic loosening caused by periprosthetic osteolysis is the main factor limiting the long-term survival of total hip arthroplasty. The wear particles (debris) generated by the artificial joint are the key element in the multifactorial pathogenesis of osteolysis. The industry's efforts to advance total hip arthroplasty have therefore focused on improving the characteristics of the bearing surfaces, so as to slow down wear.
A study recently published in The Bone and Joint Journal, carried out in Norway, reports the five-year results of a randomised, controlled trial in which radiostereometric analysis was used in order to assess the effect of an oxidised zirconium surface on polyethylene in vivo.
In all, data were used from 120 patients, 85 women and 35 men with a mean age of 70 years, who were listed for primary total hip arthroplasty and randomised into four study groups. The patients were blinded to the study, and either conventional polyethylene or highly cross-linked polyethylene of identical design was used in them. On the femoral side, a 28 mm femoral head was used in the patients, which was either cobalt-chromium or oxidised zirconium.
Wear of the bearing surfaces was measured by radiostereometric examination at five years, while the clinical outcome was measured using the Harris Hip Score.
There was no difference in polyethylene wear between the two femoral head materials with either type of acetabular cup. On comparing the two types of polyethylene, however, there was a statistically significant difference in favour of the highly cross-linked polyethylene, irrespective of the type of head used. The authors concluded that there is no advantage whatever to oxidised zirconium over the chromium-cobalt head, as regards polyethylene wear and at five years of follow-up. These findings do not support the laboratory results, which have in the past shown a reduced rate of wear with oxidised zirconium femoral heads. They do, however, strengthen the evidence for the better durability of highly cross-linked polyethylene.
Source: BJJ, November 2015