Coventina's Column

Abstract

Another month, another medical implant panic. Scarcely had the public calmed down after the poly implant prothese breast implants furore than another news story emerges of foreign bodies inserted therapeutically into people’s bodies causing iatrogenic harm. This time it is metal-onmetal hip implants (i.e. those in which both the head and the lining of the cup are made from a cobalt–chromium alloy). An excellent article on the subject summarizes the problem (BMJ 2012;344:e1410). These hip implants, which have been used on many millions of patients worldwide, not only have a higher failure rate (11.8% for re-surfacing and 13.6% for total hip replacement in metal on metal hips compared with 3.3% and 4.9% in hips made of other materials), but they release metal ions. These can destroy bone and muscle, leading to worse disability than that caused by the disease for which they were implanted. Even more seriously, the leak of chromium and cobalt ions into the blood and lymph may lead to cancer – these ions were found to be carcinogenic in lab animals as far back as the 1980s. They were also linked to cardiomyopathy in 1966. The internal memos show the manufacturers of the metal-on-metal implants were aware of the fears of carcinogenicity in humans in 2005, but as so often happens in big business, commercial concerns took precedence over health concerns. Three members of the Medicines and Healthcare products Regulatory Agency (MHRA)’s appointed investigations group had serious conflicts of interest and were linked to a major manufacturer of the implants. Key expert advise was ignored, and even when the group recommended that risks of genotoxicity should be discussed with all the patients before they consented to a metal on metal hip in 2007, this was not communicated to the surgeons. This major regulatory breakdown led to continued widespread use of these implants until 2011, when concerns were again raised. This is the kind of fiasco one might expect in a non-democratic country where corruption is rife and freedom of information is not a right; that this occurred in the West beggars belief and makes a travesty of our values. The individuals who placed people with blatant financial interests on the MHRA group and the companies that ignored expert evidence and advise should be subjected to a full investigation and disciplined. Drug and medical device companies wield vast power. This should never again be allowed to encroach upon the field of regulation, which should be 100% free of conflicts of interest.