Abstract
Background and purpose The outcome of modern resurfacing remains to be determined. The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) started collection of data on hip resurfacing at a time when modern resurfacing was started in Australia. The rate of resurfacing has been higher in Australia than in many other countries. As a result, the AOANJRR has one of the largest series of resurfacing procedures. This study was undertaken to determine the results of this series and the risk factors associated with revision.Patients and methods Data from the AOANJRR were used to analyze the survivorship of 12,093 primary resurfacing hip replacements reported to the Joint Replacement Registry between September 1999 and December 2008. This was compared to the results of primary conventional total hip replacement reported during the same period. The Kaplan-Meier method and proportional hazards models were used to determine risk factors such as age, sex, femoral component size, primary diagnosis, and implant design.Results Female patients had a higher revision rate than males; however, after adjusting for head size, the revision rates were similar. Prostheses with head sizes of less than 50 mm had a higher revision rate than those with head sizes of 50 mm or more. At 8 years, the cumulative per cent revision of hip resurfacing was 5.3 (4.6–6.2), as compared to 4.0 (3.8–4.2) for total hip replacement. However, in osteoarthritis patients aged less than 55 years with head sizes of 50 mm or more, the 7-year cumulative per cent revision for hip resurfacing was 3.0 (2.2–4.2). Also, hips with dysplasia and some implant designs had an increased risk of revision.Interpretation Risk factors for revision of resurfacing were older patients, smaller femoral head size, patients with developmental dysplasia, and certain implant designs. These results highlight the importance of patient and prosthesis selection in optimizing the outcome of hip resurfacing.
Highlights
Background and purposeThe outcome of modern resurfacing remains to be determined
The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) started collection of data on hip resurfacing at a time when modern resurfacing was started in Australia
In osteoarthritis patients aged less than 55 years with head sizes of 50 mm or more, the 7-year cumulative per cent revision for hip resurfacing was 3.0 (2.2–4.2)
Summary
The AOANJRR started collection of data in September 1999. The present analysis includes all primary conventional and resurfacing total hip replacements recorded by the Registry. The cumulative per cent revision (CPR) of primary total hip replacements was estimated at each of the first 8 years using the Kaplan-Meier method. Hazard ratios (HRs) from Cox proportional hazards models, adjusting for age and sex where appropriate, were used to compare revision rates. Time points were iteratively chosen until the assumption of proportionality was met; the hazard ratios were calculated for each selected time period. Analyses comparing outcomes of age, sex, and head size for resurfacing hip procedures, and conventional total versus resurfacing hip procedures, were performed on patients with primary diagnosis of osteoarthritis (OA) excluding revisions for infection
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