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General Orthopaedics

Oxidized Zirconium Femoral Heads - a Multicentre Randomised Control Wear Analysis Study

International Society for Technology in Arthroplasty (ISTA) 2012 Annual Congress



Abstract

Introduction

In Total Hip Arthroplasty (THA), polyethylene wear reduction is key to implant longevity. Oxidized Zirconium (OxZi) unites properties of a ceramic bearing surface and metal head, producing less wear in comparison to standard Cobalt-Chromium (CoCr) when articulating with Cross-linked polyethylene (XLPE) in vitro. This study investigates in vivo polyethylene (PE) wear, outcomes and complications for these two bearing couples in patients at 5 year follow-up

Methods

400 patients undergoing THA across four institutions were prospectively randomised into three groups. Group I received a cobalt-chrome (CoCr) femoral head/ cross-linked polyethylene (XLPE) liner; Group II received an OxZi femoral head/ ultrahigh molecular weight polyethylene (UHMWPE) liner; Group III received an OxZi femoral head/XLPE liner. All bearing heads were 32 mm. Linear wear rate was calculated with Martell computer software. Functional outcome and complications were recorded.

Results

At median follow-up of 3.7 years, implant survivorship was 98% across all groups with no difference in SF-36, WOMAC, pain score or complications (p > 0.05). After the first 12 months of creep, rate of linear wear over 3 years was 0.07 mm for Group I, 0.16 mm for Group II, and 0.03 mm/year for Group III. A significant difference was detected when using UHMWPE (p = 0.012) but not when using XLPE (P = 0.75).

Conclusion

At midterm follow-up, an XLPE acetabular liner is more important in reducing wear than the femoral head bearing. There is a trend towards lower wear when coupling OxZi rather than CoCr with XLPE; further long-term analysis is recommended to observe this pattern.