Abstract
Introduction
In the early 2000s hip resurfacing became an established bone conserving hip arthroplasty option particularly for the fit and active patient cohort. The performance of second-generation metal-on-metal bearings had led to the reintroduction of hip resurfacing. The Birmingham Hip resurfacing (BHR) was introduced in 1997. This was followed by a number of different designs of the hip resurfacing. The Durom hip resurfacing was introduced in 2001. These two designs had different metallurgical properties, design parameters particularly clearance and different implantation techniques. Data from joint registries show that both prosthesis perform well.
Objectives
Our objective was to perform a retrospective survival analysis comparing the Birmingham to the Durom hip resurfacing and analyse the mode of failures of the cases revised.
Methods
Data was collected prospectively but analysed retrospectively. The two cohorts comprised patients treated by two senior surgeons at different units. The follow up range was 1 to 14 years with a mean of 10 years. The end-point was revision for any cause. However this was further substratified.
Results
The outcome of all patients was known. The two cohorts exhibited no significant difference in demographics. No failures in either cohort were attributed to adverse reaction to metal debris. Revision for any cause was analysed by plotting Kaplan-Meier Survival curves. The Durom cohort (n=273) had 5 deaths and 9 revisions. The Birmingham cohort (n=567) had 5 deaths and 22 revisions. The Kaplan-Meier survival curves for the two resurfacing designs were different. The Durom cohort demonstrated a concave curve with more early failures. This was contrary to the BHR's convex curve with higher incidence of late failures. We analysed the data by substratifying into failure of femoral or acetabular component and neck fractures.
Conclusions
The Kaplan-Meier survival analysis demonstrates that the Durom hip resurfacings had a higher rate of early failure. However extrapolation of the curves suggests that the Durom may have a superior long term survival compared to the BHR. We postulate that this may be due to the femoral implantation technique with less late failures in Duroms and an apparent acceleration of failures in BHR cohort around the ten year stage. Joint registry data also reflect this pattern.
