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Source & full article here: Arthroprosthetic Cobaltism — OrthopaedicPrinciples.com.

Cobalt poisoning by hip replacement: Arthroprosthetic-Cobaltism

Stephen Tower, MD, University of Alaska, Alaska, USA

  • Cobalt, in excess, has the potential to block oxidative metabolism at the mitochondrial level.
  • The peripheral and central nervous systems, the heart, and the thyroid gland are variably compromised whether the means of cobalt exposure is iatrogenic (use of cobalt chloride as a hematemic), industrial (exhalation or ingestion of cobalt powders or ores), from the ingestion of cobalt laced beer (beer drinkers cardiomyopathy), or arthroprosthetic (wear of chrome-cobalt articular surfaces or corrosion and fretting of modular chrome-cobalt femoral necks and heads).
  • The toxicity of cobalt has been known since 1948.(1 2)
  • The first case report of arthroprosthetic-cobaltism was in Italian in 2001. The mechanism was wear or a revision chrome-cobalt femoral head by ceramic bits from the primary fractured ceramic component embedded in the revision plastic socket liner.
  • The degree of hypercobaltemia was unreported; symptoms of peripheral neuropathy were first noted 9 months after the first revision operation. Diagnosis was serendipitous.
  • A metal laden pericardial effusion was found on CT scan, prompting a radiograph of the asymptomatic hip revealing an aspherical femoral head. Resection arthroplasty was not performed until 16 months after the first revision operation, by then the patient’s pathology had progressed to severe motor and sensory neuropathy, pericardial tamponade, and hypothyroidism(.3)
  • Reports of 8 additional extreme cases of cobaltism from the ceramic-on-metal wear have followed. Blood cobalt levels in mcg/L ([BCo]) have ranged from 400 to 1000, latency to symptoms ranged from 3-48 months, and latency to diagnosis or revision surgery from 9 to 72 months.
  • All patients had neurologic pathology, most were hypothyroid, and all but three were noted to have cardiomyopathies. One patient died of heart failure, those patients followed > 6 months post second revision improved as their [BCo] declined.
  • The typical presentation of cobaltism was fatigue and anorexia, followed by numbness and weakness, hypothyroidism, deafness and blindness, and finally and sometimes fatally, heart failure or arrhythmias. Hypothyroidism was diagnosed in most cases before the diagnosis of cobaltism was made and some clinical improvement noted with onset of thyroid replacement therapy. None of the patients had notable sentinel hip symptoms before onset of overt systemic pathology.(4-11)

Additional Comments directly from Dr Tower:

As the new publication in OP notes we are now noting what appears to be cardiac and neurologic cobaltism in patients with MoP or even MoC hips if they employ taper junctions between CoCr and Ti components, in some patients even with single digit blood cobalt levels! It appears that if the Co is generated by Mechanically Assisted Crevice Corrosion that the material produced is more toxic mcg for mcg than that produce by articular surface wear. This is concerning because it is likely that about 90% of the hips done in the US over the past decade have likely employed a modular CoCr head. The Stryker Rejuvenate hip was certainly the canary in the cage for this mechanism of hypercobaltemia, pseudotumors, and potentially cobaltism.
We have redone about 15 Rejuvenate hips with hypercobaltemia ([BCo] > 1 mcg/L) for pseudotumors and several appear to have had cardiac and neurologic issue with [BCo] ranging from 4 to double digit. I also am seeing other commonly used hips that are out 5-10 years that are developing apparent taper corrosion problems with hypercobaltemia (range 1-4) pseudotumors, and in one case maybe a catastrophic cardio-vascular complication (aortic dissection). We now have 3 Alaskan patients that have developed lymphoma while implanted with a MoM hip (2 Duroms) and one Rejuvenate. All were hypercobaltemic. Latency from hip implantation to diagnosis was 3-7 years and in 2 case the diagnosis was incidental to revision surgery (one Durom) or the work-up suggested for patients with Rejuvenate hips (lymphadenopathy was noted on MS MRI).
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