Abstract
Introduction
Although good mid-term results have been reported with some metal on metal hip replacements, reported complications due to metal on metal (MOM) related reactions are a cause for concern. We have assessed the early clinical outcome and results of routine metal artefact reduction MRI findings in a consecutive series of patients with a modern large head metal on metal hip replacement.
Methods
62 ASR XL Corail total hip replacements (THR) and 17 ASR resurfacings were performed at our hospital between 2005 and 2008. All patients were reviewed and assessed with an Oxford hip score (OHS), a plain radiograph and a MRI imaging was obtained on 76 (96%) hips. Implant position was assessed using Wrightington cup orientation software.
Results
At a mean follow-up of 32 months, 8 ASR XL Corail THRs had been revised. 6 revisions were performed for MRI-confirmed MOM-related pathology. Histology confirmed a MOM reaction in all 6 cases. Of the 76 hips that were MRI scanned, 27 (36%) had typical features of a MOM reaction. These were classified as mild in 5 (7%), moderate in 18 (24%) and severe in 4 (5%). 78 patients completed an OHS and the mean score was 21. The mean OHS was 37 pre-operatively in those that had been revised, 19 in patients with abnormal MRI findings and 23 in those with a normal MRI. 10 patients with abnormal MRIs had a near perfect OHS (15 or less)
Conclusion
The ASR XL Corail THR has an unacceptably high early failure rate. MRI detected metal debris related soft tissue related reactions were very common and often asymptomatic. We recommend that patients with this implant should be closely followed up and undergo routine metal artefact reduction MRI screening.
