4.5 out of 5 stars
Systemic toxicity related to metal hip prostheses. Bradberry SM et al. Clin Toxicol 2014;52:837-847.
As TPR has reported before, cobalt poisoning can cause hypothyroidism, cardiomyopathy, and neurotoxicity. Neurological manifestations include:
- optic nerve damage and retinopathy with reduced visual acuity
- bilateral nerve deafness and tinnitus
- polyneuropathy (sensory and motor)
- cognitive impairment and memory loss
A number of papers and case reports have described clinical cobalt toxicity related to metal-on-metal hip prostheses or revision of a failed ceramic prosthesis with metal parts. Although these cases are somewhat rare, missing the association can be catastrophic. Recently, a report in theNew England Journal of Medicine described a 59-year-old woman with bilateral metal-on-metal hip prostheses who received a heart transplant for severe progressive cardiomyopathy. She also developed hypothyroidism, initially attributed to previous treatment with amiodarone. Cobalt toxicity was not diagnosed until months after transplant surgery.
This superb paper describes and critically reviews that 18 cases in the medical literature of systemic toxicity in patients with metal hip prostheses. The authors — using somewhat vague criteria — determined that i 10 of these cases the systemic manifestations were probably related to cobalt exposure.
Some key take-home points from the paper.
- metal ions released from hip prostheses impair osteocyte function and may contribute to implant failure
- cobalt decreases uptake of iodine by the thyroid, leading to hypothyroidism and goiter
- patients with hip implants at highest risk for cobalt toxicity are those whose failed ceramic prostheses have been revised using cobalt-containing metal parts
- there is scant evidence supporting treating these patients with chelation
This is important reading. You’re not likely to see a case of this, but if you do you don’t want to miss the diagnosis. Bottom line: think cobalt toxicity if you see a patient with a metal hip and hypothyroidism, heart failure, and/or neurologic deficits.