What metal ion levels are considered high and to be of concern for a patient to seek out treatment by Mr. McMinn

People report being told by their surgeons that they have “elevated levels of cobalt” ranging from single digit numbers (one person reported 9.2 for example) up to numbers as large as 2400+. What is the point at which one should have serious concern? If one person is living a normal life with 2400+, is it really significant if you have a level of 10 or 20? Or does the cobalt affect people in different ways?

What is considered to be toxic level of Cobalt in blood, some say 5.0 – others 7.0?

There is a lot of confusion in this area because of the different measurement techniques and specimens used, and the units in which they are expressed. Different cut-off levels have been advocated by different authors varying from 2 to 25 parts per billion, ppb (34 to 424 nanomoles-per-litre, nmol/L) of cobalt, none of which is based on any valid test of systemic toxicity.

Provided the correct specimen is used and analyzed by the correct method (refer to Q1), metal ion levels provide a reasonable measure of bearing wear. In most cases it can be said that a patient with high metal ion levels is more likely to have an adverse reaction than someone with regular levels.

The MHRA (medicines and healthcare products regulatory agency) the statutory body that regulates resurfacing devices in the UK advocates the figure of 119 nmol/L cobalt (or 7 parts per billion, ppb) for resurfacings. This was not arrived at, by performing the kind of pharmacokinetic tests that are carried out for drug toxicity. It was based on the distribution and variations of cobalt levels in patients with well-functioning metal-on-metal (MoM) resurfacing. Levels above this do not indicate systemic toxicity. They have used it more as a rough guide to identify potential cases for local debris related reactions only.

It is suggested that it is reasonable to reassure patients with less than 7ppb that they had a well functioning MOM hip and monitor those with greater than 7ppb. It does not mean that this level causes systemic toxicity. It only implies that among patients who develop a local reaction the blood levels are often greater than 7ppb.