As part of follow-up studies on metal-on-metal hips, including metal-on-metal hip resurfacing, surgeons are monitoring the blood metal levels of patients. I recently posted the following to the Surfacehippy group in response to a query about what the acceptable levels of metals in patients’ blood. Some minor editing and enhancement has been added.
Regarding metal levels, there are two levels that are considered, one is with respect to getting signals that the device has excess wear for which the primary concern is for the neighboring tissue and a second, which could be considerably higher, where the levels could affect your overall heath.
It is a bit dicey to Google this because there are lawyer’s web sites and news releases out there which seem to be trumping up the metals risks, in a sort of fear-mongering to get clients or at least initial contact with patients who might eventually become clients. I recommend anyone doing research online to confine your searching to PubMed or other bibliography of published research.
There is a range of numbers out there for the level that might be associated with earlier signs of excess wear, usually edge wear, with some suggesting levels as low as 5 mcg/L (or ppb) while a more common number seems to be 7-10 as a range which would motivate doctors to do more testing, be more watchful for other symptoms of loosening, ill-health, etc. It should be noted that a patient might briefly see metal levels of 10 or greater during the early run-in wear (first year or two, depending on activity level), so time since the surgery is another factor that should be considered. 20 mcg/L seems to be a threshold for serious consideration of immediate revision (Tower, 2010).
The level that would cause significant health problems is also rather murky. It seems to be patient dependent as some patients may have, or even develop, allergic type reactions to the metals or otherwise may be more sensitive for one reason or another. Cobalt seems to be the main culprit in causing ill health effects that can include tinnitus, hearing loss, rashes (e.g. underarm), peripheral neuropathy and cardiac dysfunction.
The following URL is a report of two cases that has some details of patients who experienced ill health effects due to metals from a metal-on-metal hip. http://www.epi.alaska.gov/bulletins/docs/b2010_14.pdf
One had blood cobalt of 122 mcg/L at 3.5 years post-op and the second had 23 mcg/L. Even in such cases it is worth noting that blood levels of metals drops after revision and the ill health effects seem to be reversible, there was a recently published paper that documented the rapid decline in metals in a number of cases. This is not too surprising as it has been demonstrated that the kidneys in particular are very efficient at processing cobalt.
In the UK there had been cobalt added to beer at one point to enhance the head and cobalt had been used to treat some blood conditions in the past such as sickle-cell anemia, some ill-health effects observed included hypothyroidism, thyroid hyperplasia (enlargement forming neck goiter), and cardiomyopathy, particularly in the heavy beer drinkers which may be have exacerbated by deficiencies in dietary protein, zinc and magnesium.
There was a recent published report of a death due to cobalt poisoning in a hip patient. The victim did not have a metal-on-metal hip but had a metal-on-polyethylene device which was a revision to a ceramic-on-ceramic device that had failed. It turned out that remaining ceramic debris from the original device had caused so much wear to the metal head it rapidly elevated the patient’s cobalt levels leading to fatal cardiomyopathy. His cobalt levels measured 6321 mcg/L, yes, more than six thousand. mcg/L (Zyweil et al., 2013).
I have been long meaning to update my “Proposed Metal Defense Protocol” document to include some of these recent findings to add to some of the background material on chromium and cobalt, just too busy at the day job to do a good job at it, though I have been trying to keep up with published research. Nevertheless you might find it helpful; it is in the documents section of the group, in the Supplements folder: http://groups.yahoo.com/group/surfacehippy/files/Supplements
Tower S., Alaska Med. 2010 Sep;52:28-32. Arthroprosthetic cobaltism: identification of the at-risk patient.
Zywiel MG, Brandt JM, Overgaard CB, Cheung AC, Turgeon TR, Syed KA., Bone Joint J., 2013 Jan;95-B(1):31-7. doi: 10.1302/0301-620X.95B1.30060. Fatal cardiomyopathy after revision total hip replacement for fracture of a ceramic liner.