Abstract
Purpose: We analysed prospectively our experience with the zincrone-polyethylene bearing for total hip arthroplasty for implantations performed between 1987 and 1997. This bearing is designed to reduce in vivo wear due to the excellent biological qualities of this ceramic.
Material and methods: Total hip arthroplasty was performed on 867 hips over the ten year period (1987–1997) in patients followed for mean seven years. All had titanium or stainless steel stems with a cemented or press fit cup (inner diameter 26-mm or 28-mm). We used Y-TZP zircone, a polycrystalline tetragonal-phase zircone stabilised by adjunction of ytterium (Prozyr). Mean patient age was 58 years (17–87). Mean body weight was 70 kg (40–125) and mean height was 167 cm (140–196). The sex-ratio was 1.3.
Results: Overall survival determined with the Kaplan-Meier method was 60% at 13 years (95%CI=55–65%). Revisions (all causes including infection) were performed on 118 hips. To our knowledge, for the entire cohort, one patient presented a zircone head fracture. Radiographic analysis showed a particular type of fracture related to isolated acetabular loosening. Comparative analysis of this type of loosening for 785 heads (26-mm) and 92 heads (28-mm) was not significant (log rank test). Taking surgical revision as the endpoint for isolated acetabular failure, implant survival at 13.5 years was 74% (95%CI=68–80), confirming the particular mode of failure with this bearing.
Discussion: This prospective analysis showed the absence of superiority of the zircone head in vivo for reduction of wear in comparison with metal heads in young subjects. The purely epidemiological data reveal formal evidence of the deleterious nature of zircone in contradiction with the expected beneficial tribiological effect. We have no physicochemical explanation for these failures. The pathology findings were non-specific, but the failure was real.
Conclusion: Considering these findings, we have abandoned use of this ceramic since 1997.
Correspondence should be addressed to SOFCOT, 56 rue Boissonade, 75014 Paris, France.
