Elevated metal ion levels have been associated with the presence of adverse local tissue reactions in patients with metal-on-polyethylene (MoP) total hip arthroplasty (THA) secondary to corrosion at head-neck taper junction. Patients are frequently concerned with their elevated systemic metal ion levels. This study investigated the rate of decline of serum cobalt and chromium ion levels after revision surgery.
A total of 39 patients with MoP THA were revised because of the presence of symptomatic adverse local tissue reactions on magnetic resonance imaging with elevated serum metal ion levels. The time between initial implantation of MoP THA (index surgery) and revision surgery was considered the duration of metal exposure. The prerevision measure of ion level was considered the intensity of exposure. Prerevision median serum Co and Cr levels, as well as revision serum Co/Cr ratio, were reported.
The median serum levels of cobalt and cobalt-to-chromium ratio significantly decreased from prerevision levels of 8.2 μg/L (0.2-56.1 μg/L) and 5.6 μg/L (0.1-53.3 μg/L) to 3.1 μg/L (0.2-14 μg/L) and 1.7 μg/L (0.4-3.8 μg/L) at postrevision (P < .01), respectively. The rate of decline of Co was 0.45% per day during the first month. For chromium, the rate of decline was slower with 0.08% per day during the first month.
At 3 months after revision surgery, cobalt and chromium ion levels declined by 34% and 8% of prerevision level, respectively. This study provides evidence-based practical information for surgeons to provide MoP THA patients when considering revision surgery for head-neck taper corrosion.