The ethylene oxide sterilised Opera acetabular component demonstrates high rates of loosening and revision compared to the gamma irradiated Ogee cup: a cohort study demonstrating potential shortcomings of revision-based registry data

Aims: To evaluate the long-term clinical outcomes of 2 cemented ultra-high molecular weight polyethylene (UHMWPE) acetabular components, with the main difference between the 2 components being their method of sterilisation. Patients and methods: Data was collected prospectively on 352 consecutive total hip replacements, performed between March 2000 and July 2004, at a single centre. A posterior approach was used with a cemented C-Stem femoral component (DePuy, Warsaw, IN, USA) in all cases and either the Ogee (DePuy, Warsaw, IN, USA) or the Opera (Smith & Nephew, Memphis, TN, USA) acetabular implant. Patients were reviewed clinically and radiologically with a median 12-year follow-up (6-16 years). Results: The risk of experiencing loosening was 90% lower for the Gamma irradiated implant (GII) group compared to the ethylene oxide sterilised implant (EOSI) group, which was statistically significant (p = 0.003), (HR 0.10; 95% CI, 0.02-0.45). The incidence of cup revision was also lower in the GII group (p = 0.029), but after adjustment for age, gender and BMI was not statistically significant (p = 0.104). 15-year survivorship with failure/loosening as an endpoint was 70.1% for the EOS implant and 92.9% for the GII (OR 4.99; CI 95%, 1.75-14.2) and with revision as an endpoint was 81.4% for the EOSI and 92.9% for the GII (OR 2.60; CI 95%, 0.87-7.75) Conclusions: We report increased rates of loosening, revision and failure for the EOSI compared to the GII at long-term follow-up. This may have been attributable to the different sterilisation methods used.