Abstract
Objective: Metal-on-metal bearings are in widespread use for total hip replacement (THR); however, possible complications resulting from the dissemination of metal particles and ions throughout the body are a cause for concern. Recent studies have shown an increase in metal-related problems, including adverse local tissue reactions and the formation of pseudotumors. We investigated the serum levels of cobalt and chromium ions in patients with large-diameter metal-on-metal THR.
Methods: The purpose of this study was to compare the amounts of metal (cobalt and chromium) ions released from two different types of prostheses (components made of wrought or cast alloy). Serum metal ion levels were determined and compared in 45 patients who had undergone unilateral metal-on-metal THR. In addition, magnetic resonance imaging of the hip was performed in 89 patients with wrought components and 108 patients with cast components.
Results: Multivariate analysis showed significantly higher cobalt levels at 3 months and 1 year postoperatively in patients with components made of cast alloy compared with those made of wrought alloy. Six patients with wrought components (7%) and 10 patients with cast components (9%) were diagnosed with a pseudotumor. The prevalence of pseudotumors was not significantly different between the groups. Seven patients with cast components (6%) required revision, and this figure was significantly higher than that for patients with wrought components (0%).
Conclusion: The present study showed that patients with metal-on-metal components made of cast alloy demonstrated higher serum metal ion levels and a higher prevalence of metal-related problems than those with components made of wrought alloy.
