Abstract
Background:
Potential systemic toxicity of metal ions from metal-on-metal hip arthroplasties (MoMHA) is concerning. High blood cobalt (Co) levels have been associated with neurological, cardiac and thyroid dysfunctions.
Questions/purposes:
The aim of this research was to investigate the prevalence of systemic Co toxicity in a MoMHA population, to identify confounding factors, and to indicate a Co level above which there is a high risk for systemic toxicity.
Patients and Methods:
We conducted a cross-sectional study of patients with a MoMHA, using questionnaires validated to detect cobaltism in cobalt industry workers. We retrospectively identified 161 patients with Co levels >4 μg/L and 337 patients with Co levels <4 μg/L and collected 385 completed questionnaires. There were 207 men and 178 women with a mean age of 60 years (24–86). Mean follow-up was 5.7 years (1 to 13). Co levels were subdivided into <4 μg/L, 4–10 μg/L, 10–20 μg/L and >20 μg/L groups.
Results:
There were significant correlations (p ≤ 0.003) between increasing Co levels and prevalence of sleeping disorders, cognitive problems, equilibrium disturbances, neuropathic symptoms, fatigue, somatic disorders and mood changes. More frequent and severe symptoms were found with Co > 20 μg/L (p = 0.017). Several years post-revision, some patients still complained of chronic symptoms possibly associated with longer exposure. Female gender and age ≤50 years were confounding factors.
Conclusions:
We demonstrated a correlation between increasing Co levels and toxicity symptoms (p ≤ 0.003). As in the published case reports of MoMHA related cobaltism, the highest incidence of symptoms was found with Co > 20 μg/L. Patients with repeated Co measurements >20 μg/L are at risk for systemic toxicity.
