Lynda Williams: Another disastrous medical experiment

No NZ agencies have done anything about ensuring that medical devices used in New Zealand are fit for purpose, have undergone clinical trials and are safe. Photo / File

Recent events have highlighted the fact that neither the Ministry of Health nor any other government agency has done anything about ensuring that medical devices used in New Zealand are fit for purpose, have undergone clinical trials and are safe. This despite the fact that several major scandals have made the headlines both here and internationally over the past six months.

Through the media New Zealanders have been made aware of the fact that medical devices such as breast implants, the gynaecological mesh, and hip joint replacements can avoid having to undergo clinical trials before they are marketed and sold as the best thing since sliced bread.

The latest medical device to dominate headlines around the world are two models of metal-on-metal hip joint replacements. The first of these was the DePuy hip implant; the second is the Mitch THR hip implant. The Ministry of Health and Medsafe remained quiet until confronted by several major exposes in the NZ Herald in 2011 that led to light bulbs going on in the heads of a number of New Zealanders who had had a hip replacement. But nothing appeared on the Medsafe website.

As New Zealand patients struggled to get information an article appeared in the February 2012 issue of the British Medical Journal by investigations editor Deborah Cohen. It began: Hundreds of thousands of patients around the world may have been exposed to toxic substances after being implanted with poorly regulated and potentially dangerous hip devices, a BMJ/BBC Newsnight investigation reveals this week. Despite the fact that these risks have been known and well documented for decades, patients have been kept in the dark about their participation in what has effectively been a large uncontrolled experiment.

The metal-on-metal hip replacement implants arrived on the scene in 1997. The head at the top and the lining of the cup it fits into are made of cobalt-chromium alloy rather than ceramic or polyethylene. Of course they were marketed as the latest advance in hip replacement and were specifically targeted at younger patients who needed a hip replacement that would last their life-time.

As the BMJ paper points out, multiple studies and research organisations have warned about the carcinogenic potential of metal-on-metal hips. That cobalt and chromium ions lead to genotoxic changes, (changes that are damaging to DNA and therefore capable of causing mutations or cancer), both in laboratory settings and in animals was described in scientific journals over 30 years ago.

It comes as no surprise to learn that the manufacturers were aware of the potential for genotoxicity. A DePuy internal memo from July 2005 says: In addition to inducing potential changes in immune function, there has been concern for some time that wear debris may be carcinogenic. The mechanism is not known and only 24 local malignancies have been reported in patients with joint replacements. Also worrying is the possibility of distant effects. One study suggested a threefold risk of lymphoma and leukaemia 10 years after joint replacement. The metal to metal total hip appears to be quite promising and in the laboratory the data is (sic) definitely in its favour. However, the ultimate test is the long term human experience.

Rather than advising regulators and patients of their concerns, companies tweaked the design of these devices.

The experiment continued, but only outside the USA. While the DePuy ASR products were approved by the Australian Therapeutic Goods Administration in October 2003, they were not cleared by the US Food and Drug Administration until January 2008. However, the failure rates for total hip replacements were soon found to be higher than they should be, and concerns began to be raised. In December 2009 DePuy withdrew the ASR products from both the Australian and New Zealand markets.

In August 2010 DePuy contacted Medsafe proposing to distribute a recall notice to all ASR trained surgeons in New Zealand. Medsafe did not list the recall on its website, and nor did it provide any information to patients about the problems associated with metal-on-metal hip replacements. When the Herald asked the Minister of Health about Medsafe's failure to list the ASR recall on its website when other recalls were listed, Tony Ryall replied As part of the new joint agreement with Australia, which comes into effect July 1, I would expect such recalls to be listed on the joint website. The fact that it hasn't reflects Medsafe's past practice and this will be changing.

The rebuke from the Minister was clearly enough to make Medsafe spring into immediate action. A comprehensive timeline of events and documents leading up to the recall of ASR hip replacements is now on their website. It tells a by now very familiar and extremely depressing story.

When problems began to surface with ASR hip joints and various committees in the UK met to discuss the issues, the concerns were not made public and no alert was put out to surgeons or patients. Another disturbing aspect to this was mentioned in the BMJ article which referred to the fact that there were special risks for women of child-bearing age due to the fact that metal ions had been detected in umbilical cord and placental blood.

Neither the European nor the American regulators picked up the high levels of metal ions produced by the modified hip replacement devices when they came onto the market, as there was no requirement for any post-approval studies that would follow-up patients implanted with devices capable of producing toxic debris.

The BMJ paper ended with the following conclusion: After a series of failures, device regulation is in need of radical change. For its part, the FDA has decided to place all hip implants into a high risk category fast track entry will be forbidden".

In Europe there is little doubt the current system is not fit for purpose and talks are underway about how to improve it. As Professor Freemantle asks: Why is it that people are afforded different levels of protection depending on whether they have a heart attack, diabetes, or a hip replacement in their old age? The methods of device regulation seem to be more from the 1950s than the 21st century.

Professor Freemantle's question is a very good question indeed. Because New Zealanders who have had hip replacements are unaware that they have been part of yet another disastrous experiment, it is a question that needs an answer from both the Minister of Health and the Health & Disability Commissioner.