Outcomes of a metal-on-metal total hip replacement system.
Matharu GS., Theivendran K., Pynsent PB., Jeys L., Pearson AM., Dunlop DJ.
INTRODUCTION: High short-term failure rates have been reported for a variety of metal-on-metal (MoM) total hip replacements (THRs) owing to adverse reactions to metal debris (ARMD). This has led to the withdrawal of certain poorly performing THRs. This study analysed the outcomes of a MoM THR system. METHODS: Between 2004 and 2010, 578 uncemented MoM THRs (511 patients, mean age: 60.0 years) were implanted at one specialist centre. The THR system used consisted of the Corail(®) stem, Pinnacle(®) cup, Ultamet(®) liner and Articul/eze(®) femoral head (all DePuy, Leeds, UK). All patients were recalled for clinical review with imaging performed as necessary. RESULTS: The mean follow-up duration was 5.0 years (range: 1.0-9.1 years). Overall, 39 hips (6.7%) in 38 patients (all 36 mm femoral head size) underwent revision at a mean time of 3.5 years (range: 0.01-8.3 years) from the index THR with 30 revisions (77%) performed in women. The cumulative eight-year survival rate for all THRs was 88.9% (95% confidence interval [CI]: 78.5-93.4%), with no difference (p=0.053) between male (95.2%, 95% CI: 84.2-98.7%) and female patients (85.3%, 95% CI: 70.2-92.1%) at eight years. Seventeen revisions (44%) were performed for ARMD. There was no significant difference in absolute postoperative Oxford hip scores between men and women (p=0.608). The mean acetabular inclination in unrevised THRs was 44.0°. Forty-seven non-revised THRs (8.7%) had blood metal ion concentrations above recommended thresholds (seven had periprosthetic effusions). CONCLUSIONS: Although this MoM THR system has not failed as dramatically as other similar designs, we recommend against continued use and advise regular clinical surveillance to identify ARMD early.