How safe are metal-on-metal hip implants?BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e1410 (Published 28 February 2012) Cite this as: BMJ 2012;344:e1410
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Measurement of Cobalt and Chromium in Whole Blood External Quality Assurance Specimens in the UK, April 2011 to March 2012
Chris F. Harrington and Andrew Taylor
TEQAS, Faculty of Health and Medical Science, University of Surrey, GU2 7XH, UK. firstname.lastname@example.org
In 2010 the MHRA issued a Medical Device Alert (MDA/2010/033) that recommended measurement of cobalt (Co) and chromium (Cr) in blood from patients experiencing discomfort or pain associated with metal-on-metal (MoM) hip prostheses. This followed concerns relating to possible adverse effects of metal released from the implants. The Alert suggested further investigations when concentrations greater than 7 ppb (µg L-1) were reported. A second Alert (MDA/2012/008) updated the advice and provided recommendations for the management of both symptomatic and asymptomatic patients classified into four groups based on the type of hip replacement. Accurate measurements of Co and Cr are imperative to the implementation of these Alerts and both documents stated that samples should be referred to laboratories participating in the Trace Elements Quality Assessment Scheme (TEQAS). The UK National External Quality Assessment Scheme for trace elements (TEQAS) is accredited by Clinical Pathology Accreditation (UK) Ltd and monitors the accuracy of laboratory measurements each month. We report here results obtained between April 2011 and March 2012 for Co and Cr in whole blood EQA specimens.
Each month two blood specimens, selected from six different pools (including an endogenous pool), were sent to scheme participants for analysis. Thus, within the year each of the pools were analysed on four different occasions. The pools were prepared by spiking equine blood with known amounts of the metals so that the concentrations matched those seen in samples from patients and so that recovery of the added Co and Cr could be calculated. Results obtained by the participants (up to 23 from the UK and overseas) were reported to the scheme organisers for analysis of the data. The mean recovery for the analysis of all 20 specimens for Co was 96.4% (SD 2.23, CV% 2.3) and for Cr was 96.1% (SD 3.19, CV% 3.3). The concentrations ranged from 10 to 60 µg L-1 for Co and 10 to 35 µg L-1 for Cr and the full set of data is shown in Tables 1 and 2. The excellent agreement between the amounts in the specimens (endogenous plus spike) and the mean values indicates that results reported are accurate. The agreement between the pools distributed on different occasions shows that results are also reproducible. These results should reassure surgeons and patients that the laboratories carrying out the measurement of Co and Cr are producing results that are fit for purpose.
Discussions among the trace element laboratories of the UK Supra-regional Assay Service (SAS) (www.sas-centre.org) of their experience receiving specimens from many hospitals, reveals that there are some patients where there is considerable disparity between the Co and Cr concentrations that are found in the blood specimens. Where both blood and serum samples are analysed, the metal concentrations usually follow the same pattern but variations are seen in certain cases. It would appear, therefore, that release of Co and Cr from implants is a complex process influenced by physiological, mechanical, prosthetic design and other factors.
Competing interests: No competing interests
The response from Depuy representatives Graham Isaac and Simon Sinclair sidesteps the substantive concerns described in the BMJ feature (1).
The main thrust of the article was the laxity of medical device regulation in Europe as a whole and some aspects of the US system (2). It described a system that allowed a whole class of implant– in this case large diameter metal on metal total hip replacement– to enter the global market without any clinical studies to assess their safety and effectiveness.
We do think it is necessarily alarming rather than “unnecessarily alarmist” that design changes to implants that were already known to release potentially toxic metal ions passed through the regulators without any need for clinical studies. These changes were the shortening of the taper (the part of the stem that meets the head) coupled with the use of large diameter heads and were an industry wide trend. These changes lead to a toggling effect that has been shown to damage the inside of the head causing the release of metal ions into the body.
As pointed out in the article, even the National Joint Registry has described this class of implant as a “cause for concern” long before the feature appeared. Two weeks after the BMJ article appeared, The Lancet published findings of a high failure rate with these prostheses (3).
The article did not suggest, as you imply in the first paragraph of your letter, that the potential for reactions to wear debris from metal on metal hips was unknown. Indeed, we point to the fact that reactions to metal debris have been documented in the medical literature since the 1970s (4).
You also state that the FDA and the MHRA say that adverse effects are rare. We are unsure how anyone can say this with any authority given that no large scale epidemiological studies have been done on the latest generation of metal on metal hip prostheses.
You then go on to say that the article was misleading in implying that DePuy concealed information about raised metal ion levels in patients’ blood. We did not actually allege this in this article. What we did say is that the company has been aware of concerns over the carcinogenic potential of the metal ions for many years. Indeed, in your reply you acknowledge that when metal-on-metal hip implants were introduced, “it was recognized that one of the effects of having metal bearing surfaces would be that constituents of cobalt and chromium would be released locally and systemically”. You also state that patients with metal on metal hip implants—as well as other types— have “raised levels of ions”.
If this is the case, it begs the question why no clinical studies were carried out before the metal-on -metal Pinnacle hip system (called ULTAMET in your letter) was put onto the market. It also is of concern that even though DePuy knew metal ions would be released locally and systemically, they did not try to establish what levels would be considered safe for patients before rushing to market or modifying the design of the implants. As pointed out in the feature, certain valencies of these ions were either known to be carcinogenic (hexavalent chromium) or to possibly have carcinogenic potential (trivalent chromium and cobalt) long before changes to the design of the prostheses in question.
Given this, one would have thought DePuy would carefully follow up a cohort of patients once the implant was on the market measuring ion data and monitoring both local and systemic effects. Before the BMJ article went to press, we asked Depuy specifically—as we did with several other companies— if it had conducted any post-marketing surveillance of the Pinnacle hip prostheses and if it had published the results. DePuy did not respond to the question. A lack of such detailed follow up might be one reason why the reported incidence of such adverse effects in the literature is low.
If, as you appear to concede, metal ions are of concern - that constituents of cobalt and chromium would be released - why does the supporting paper that you cite as evidence of effectiveness and safety of the metal on metal Pinnacle not include metal ion data (5)? Internal DePuy documents obtained by the BMJ suggest investigators were discouraged from publishing ion data. Two of the three authors of the paper earned large sums of money from their relationships with DePuy. Lead author, William Barrett is a DePuy consultant who earned over US$1.6 million in royalties and consultancy payments between 2010 and 2011 and Kirk Kindsfater is a DePuy consultant who had earned close to quarter of a million dollars in the same time period. The third author, James Lesko, is from DePuy. In small print on the paper, it says that conflicts of interest can be found on a different page.
Is it any wonder the regulators have little evidence to draw upon to make their decisions about the effects of metal ions? This lack of data reflects a trend across the literature. Despite the metal on metal Pinnacle having been implanted into between 300 000- 500 000 people worldwide, there are only data for metal ions in under 150 patients with this prosthesis in the literature to date (6,7, 8)If the literature cannot be relied upon to provide rigorous evidence, there is an urgent need for robust regulation in the future featuring both premarket trials and rigorous post-marketing studies.
You say that the BMJ article “focuses” on the potential cancer risk from metal on metal implants. This was not the focus of the article but one aspect of it, and the article clearly stated that there was no evidence of a link. We simply highlighted how little was known about the long term effects of the metal ions, because of a lack of rigorous follow up.
Will companies only do what’s in the best interest of patients and the public if they are mandated to–and penalised if they don’t comply?
You say that the article raised “considerable alarm” about the levels of metal ions associated with the Pinnacle and imply that we failed to quote the proper figures from the literature. In fact the article clearly described the range of 5-20% from the three referenced studies (6, 9, 10).
It is also worth noting that the conclusion of one of these cited papers led the authors to stop using the Pinnacle implant. Importantly these authors are not likely to have been hostile to DePuy. At least one of them is a DePuy consultant who earned about US$400,000 from DePuy in the previous two years.
Depuy’s internal documents also show that in 2009, another DePuy consultant—who earned US$2.5 million in the previous two years in royalty and consultancy payments— emailed DePuy with his concerns about the metal on metal Pinnacle. “In previous discussions that I have had with DePuy regarding my reservations with metal on metal I have not had a receptive ear,” he wrote.
Interestingly, there is nothing in the published literature highlighting these concerns. Nor has there been anything in the published literature following the concerns of another surgeon who wrote to the company to say that he did not feel that “DePuy is doing enough to understand the extent of the Pinnacle metal on metal disease. I believe it borders on unethical to continue to market the product until the issues are elucidated. These products are harming patients.” This surgeon earned around US$70,000 from DePuy between 2010 and 2011.
The metal on metal Pinnacle is still on the market—although one of the stems used with it has been removed because of concerns over the taper. As you point out, Japanese surgeons spotted the problem. You do not say that this was in 2009 and that it took DePuy over two years to advise doctors in Japan not to use these stems.
The fact that these stems were ‘9/10’ rather than ‘12/14’ in the context of this article is not relevant to the point being made (although DePuy declined to answer our question about this taper prior to publication of the BMJ article). We included the concerns from the Japanese surgeons because the patterns of failure they had spotted were the same as those being reported by Virginia, USA and North Tees, UK since 2010.
You say that the BMJ was wrong in claiming that the design changes to the stem took place around 2004. You say the changes started in 2001 and were applied to other stems. According to the FDA website, the Corail stem—the one most commonly used in the Pinnacle hip system—was cleared for use in 2004. It is this that is referred to in the BMJ article. That we cannot say for certain when these design changes took placeis an indictment of the lack of transparency surrounding device regulation and the fact that individual components’ of a hip system can be cleared separately with no clinical testing.
Why DePuy—or indeed other companies—weren’t more cautious in adopting new designs that affect where the head and stem meet is perplexing. Josh Jacobs, now president of the American Academy of Orthopedic Surgery, wrote in the Journal of Bone and Joint Surgery America (the main US orthopaedic journal) in 1998 :
“The predominant source of the disseminated chromium-degradation products is probably the modular head-neck junction and may be a function of the geometry of the coupling.” This head-neck coupling is an important source of metal release that can lead to increased concentrations of chromium in the serum, he added saying: “This is a particularly timely concern because of recent clinical trends, including the reintroduction of metal-on-metal bearing surfaces.” (11)
You say that our article failed to explain the clinical need for the reintroduction of metal on metal implants. This is not the case. The article clearly states:
“The conventional total hip replacement consists of a metal head with a polyethylene cup. But these joints don’t last forever. Over time the plastic cup wears away against the hard metal head. Younger, more active people are especially likely to require early revision surgery to replace the worn out joint.” It also notes that the introduction was gradual, but eventually the commercial need to constantly innovate trumped patient safety.
Lastly, you cite the aforementioned paper by DePuy consultants (5)— published shortly after the BMJ feature came out—as evidence that the five year survival rate of the metal on metal Pinnacle is 97%, in keeping with NICE benchmarks. However, this paper is flawed.
It reports a pooled analysis of four previously unpublished studies. Over half (59.9%) of people included were taken from a non randomised, non controlled study. Only 59% of the total hip implants in this study had a femoral stem with a shortened taper and only 779 (72%) hips had greater than 2 year follow up—even though research suggests that tapers take a mean of four years to fail. Moreover, radiographic evaluation of cup placement—which should be standard for papers reporting research in orthopaedics– was only obtained on 420 (54%) of the 779 patients evaluated. The authors then use all 1076 hips to conduct survival analysis at five years.
Far from providing convincing evidence about the effectiveness of the implant, it only provides convincing evidence about the need for independent evaluation of medical implants.
All in all, we feel that this article was not “unnecessarily alarmist”, but it provided a necessarily alarming portrait of the state of medical device regulation today.
1. Isaac, G and Sinclair, S. Response to feature ‘How safe are metal on metal hip implants?’
2. Cohen, D. How safe are metal on metal hip implants? BMJ 2012;344:e1410
3. Smith AJ, Dieppe P, Vernon K, Porter M, Blom AW; National Joint Registry of England and Wales. Failure rates of stemmed metal-on-metal hip replacements: analysis of data from the National Joint Registry of England and Wales. Lancet. 2012 Mar 31;379(9822):1199-204.
4. Jones DA, Lucas HK, O’Driscoll M, Price CH, Wibberley B. Cobalt toxicity after McKee hip arthroplasty. J Bone Joint Surg Br 1975;57:289-96
5. Barrett WP, Kindsfater KA, Lesko JP, Large-Diameter Modular Metal-on-Metal Total Hip Arthroplasty: Incidence of Revision for Adverse Reaction to Metallic Debris. J Arthroplasty. Mar 14 2012 (Epub ahead of print]
6. Antoniou J, Zukor DJ, Mwale F, Minarik W, Petit A, Huk OL. Metal ion levels in the blood of patients after hip resurfacing: a comparison between twenty-eight and thirty-six-millimeter-head metal-on-metal prostheses J Bone Joint Surg Am 2008;90(suppl3):142-8.
7. Engh CA Jr, MacDonald SJ, Sritulanondha S, Thompson A, Naudie D, Engh CA. 2008 John Charnley award: metal ion levels after metal-on-metal total hip arthroplasty: a randomized trial. Clin Orthop Relat Res. 2009 Jan;467(1):101-11. Epub 2008 Oct 15.
8. Bernstein, M, et al. Femoral Head Size Does Not Affect Ion Values in Metal-on-Metal Total Hips Clin Orthop Relat Res (2011) 469:1642–1650
9. Takamua KM, Langton D, Ghandi JN, Nargol A, Joyce T, Lord J, et al. The main issue of large diameter MoM total hip arthroplasty: the taper junction. Presentation at American Academy of Orthopedic Surgeons annual meeting, San Francisco, 9 Feb 2012.
10. Fricka K, Engh CA, Hamilton WG, Ho H. Survivorship and revision analysis among primary metal on metal total hip arthroplasty using 36 mm diameter heads. Presentation at American Academy of Orthopedic Surgeons annual meeting, San Francisco, 9 Feb 2012.
11. Jacobs JJ, Skipor AK, Patterson LM, Hallab NJ, Paprosky WG, Black J, Galante JO. Metal release in patients who have had a primary total hip arthroplasty. A prospective, controlled, longitudinal study. J Bone Joint Surg Am. 1998 Oct;80(10):1447-58.
Competing interests: No competing interests
While we respect the BMJ’s right to rigorously investigate issues, this article is unnecessarily alarmist and in a number of instances factually incorrect. We submit this letter to highlight some of the factual errors and omissions regarding metal-on-metal hip implants generally, and, in particular, DePuy’s ULTAMET® metal-on-metal implant, which is one of the available options used with the Pinnacle® Acetabular Cup System.
Adverse Reactions to Metal Debris and Ions:
It is well documented that all hip implants, no matter what materials are used, experience wear over time and generate wear debris. Indeed, it was the widely published concerns that wear debris from metal-on-polyethylene hip replacements used in the 1990’s caused bone damage to a significant number of patients that re-kindled the orthopaedic community’s interest in developing a new generation of metal-on-metal implants. Contrary to the suggestion in the article, the potential for reactions to wear debris from metal-on-metal hip implants has been known and studied for over two decades, and the reported incidence of such adverse reactions is very low. According to the U.S. Food and Drug Administration, “Based on the limited number of case reports in published literature, the true incidence or prevalence of adverse systemic effects from MoM hip implants is not known at this time, but is believed to be rare.” Similarly, the MHRA, in releasing updated guidelines last month for monitoring patients with metal-on-metal hip implants, stated: “The majority of patients implanted with MoM hip replacements have well functioning hips and are thought to be at a low risk of developing serious problems.”
Metal Ion Levels:
The article states that DePuy had been aware since 2008 of raised metal ion levels in people with ULTAMET metal-on-metal implants and implies that DePuy concealed this information. This assertion is misleading as it has long been known that patients with metal-on-metal hip implants – and also occasionally hip implants with other bearing surfaces – have “raised levels of ions.” In fact, an article published by Antoniou et al. in a widely read orthpaedic journal and referred to in your article cited seven references on this subject, which date back as far as 1996. When metal-on-metal hip implants were introduced, it was recognized that one of the effects of having metal bearing surfaces would be that constituents of cobalt and chromium would be released locally and systemically. However, data for prior generations of metal implants did not indicate clinical problems from these releases in well functioning implants, some of which had been in place more than 15 years.
The article expresses considerable alarm about the levels of metal ions associated with the ULTAMET metal-on-metal implant, appearing to claim that 20% of patients with ‘DePuy’s flagship Pinnacle hip system’ had blood metal ions above the 7 parts per billion (ppb) level in the MHRA guidance. The three studies cited for this proposition do not support this. The one peer-reviewed publication amongst them found that 5% of patients with ULTAMET implants had levels above 7ppb, with mean cobalt levels at or below 2.3 ppb at all time points measured.
In addition, the article does not establish that the level of metal ion release has clinical significance. Indeed, the U.S. FDA recently stated that there is insufficient evidence to correlate the presence of localized lesions, clinical outcomes, and/or the need for revision with specific metal ion levels for individual patients.
Although the article focuses on the potential risk of cancer from metal-on-metal implants, the connection between metal-on-metal devices and any form of cancer remains unproven, as the article itself concedes. The British Orthopaedic Association/British Hip Society, in response to the media attention generated by the article’s reference to cancer risks, stated that “Currently there is no verified evidence that having a metal on metal hip replacement increases cancer risk.” The BOA/BHS went on to warn that “It would be unwise to suggest removing these joint replacements and taking additional risks of surgery just on the possible cancer risk.” The BOA/BHS statement also noted that while the media reports mentioned one study that found abnormalities in bladder cells of patients with metal-on-metal hip implant, those same reports failed to mention a larger, longer term study that did not show any increased risk of bladder cancer in metal-on-metal hip implant patients. Furthermore an article in the current volume of BMJ comprising 40,576 patients with metal-on-metal hip implants showed that “…there was no evidence that metal on metal bearing surfaces were associated with an increased risk of any cancer diagnosis in the seven years after surgery”.
Observations of taper corrosion have been reported over the years in modular total hip replacement systems, regardless of what bearing surface is used. The clinical significance of these observations has not been established. Contrary to the assertion in the article, DePuy’s most commonly used tapers (‘12/14’) have employed the same angles and surface finishes since they were first introduced. The article also mistakenly asserts that current taper lengths were first introduced in 2004. In fact, the current taper length was first used in 2001. Since 2001, DePuy has gradually adopted this taper length on other stems.
The company investigates any specific complaints it receives related to taper corrosion. For example, as noted in the article, DePuy received complaints about taper corrosion from some surgeons in Japan. However, the article fails to mention that the stems at issue used a particular taper first introduced in the mid 1980’s, which is referred to as a ‘9/10’ taper, and that those stems, when used with metal-on-metal implants, were only available in Japan. The article also omits that in connection with its investigation, DePuy communicated with doctors in Japan in June 2011 and advised them not to use those particular stems in combination with certain metal-on-metal implants.
Introduction of the current generation of metal-on-metal implants:
The article suggests that the current generation of metal-on-metal hip implants was introduced despite known risks and without a clear clinical need. This is not true. Early failures in the first generation of metal-on-metal implants, largely attributed to limitations in the manufacturing process, led to the widespread adoption of polyethylene as the bearing of choice. However a subsequent review of these early metal-on-metal implants showed that many of them exhibited long-term success with much lower wear than polyethylene systems. As a result, when concerns emerged over the damage caused by polyethylene debris, and since manufacturing techniques had advanced, the orthopaedic community had renewed interest in metal-on-metal bearings once again. The other alternatives at this stage were newer polyethylenes that did not yet have long term clinical track records, and ceramics which had also experienced early failures in prior generations. An additional benefit of metal-on-metal implants was that they allowed for larger femoral heads to be used which provide greater stability and lower risk of dislocation. Viewed in context, the re-introduction of metal-on-metal hip implants was a well-considered response to the patient safety concerns being voiced about traditional polyethylene bearing technology.
Revision rate data:
DePuy continues to monitor on a monthly basis data about the ULTAMET metal-on-metal implants from a variety of sources, including published and unpublished data from national joint registries, published literature, company-sponsored clinical trials and internal complaint data. The ULTAMET metal-on-metal implant is performing in a manner consistent with or better than other metal-on-metal products and consistent with benchmarks set by the UK National Institute of Health and Clinical Excellence (NICE). Further, DePuy has conducted four separate studies that include patients with ULTAMET metal-on-metal implants with a head size equal to or greater than 36mm. The pooled results from those studies comprising 1076 hips (779 with a greater than 2 year follow-up), which show a 5 year survival rate of 97%, are consistent with the data from the national joint registries. A femoral stem with a shortened taper was used in 59% of these cases.
* * *
As shown with the examples above, the article fails to provide a balanced presentation of the facts surrounding metal-on-metal implants in general, and DePuy’s ULTAMET metal-on-metal implants in particular. Given the serious nature of the issues raised by the article, and the potential, as noted by the BOA/BHS in their statement, that patients may be scared into having unnecessary surgical procedures, a more balanced presentation would have been appropriate and more in keeping with the BMJ’s stated aim of ‘helping doctors make better decisions’.
Competing interests: Employees of DePuy Orthopaedics Inc
Your article on safety of metal on metal implants has caused concern and confusion amongst my patients who have been provided with a Pinnacle cup implant using polyethylene or ceramic bearings.
Your article implies that the Pinnacle cup system is generally using metal on metal bearings, which is not the case.
I contacted DePuy who stated that about 500 000 Pinnacle cups have been implanted outside USA of which 16 % used a metal bearing. This data shows that 84% of Pinnacle cups have been fitted with polyethylene or ceramic bearings (see chart attached with permission from DePuy).
I should be grateful if in the future your publications avoid creating unnecessary concern by offering correct data.
Competing interests: No competing interests
The European Commission recently asked the EU Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) to conduct an in depth investigation on the potential health risks of faulty PIP silicone breast implants. Following the safety concerns voiced in your article BEUC invited the European Commission to ask the opinion of the scientific committee also in relation to the metal on metal hip implants.
The breast and the hip implants cases clearly showed that the current rules governing medical devices are inadequate and that the whole system needs to be reviewed.
The EU and the Member States should take a bold action in order to increase patient safety and restore consumer confidence. The pre-market and the post-market regulatory framework must be strengthened to ensure that medical devices are safe and effective.
In a letter we addressed to the EU Health Commissioner in January we encouraged the Commission to assess the possibility of requiring a form of marketing authorization similar to that foreseen for medicines for high risk devices. It is difficult for consumers to understand why a device implanted in their body doesn’t go through the same thorough assessment as the pills they take for example against high blood pressure. Yet, if there is a problem with a medicine they can stop taking it immediately while if there is a problem with a device they have to go for an invasive and risky surgery to have it removed.
The risk based classification system should be improved especially for new and ‘border-line’ products and the jungle of aesthetic products and self-testing devices should be better regulated. More data on the safety, quality and efficacy should be required before a product is placed on the market.
For a stronger and more efficient surveillance system it is essential to build a central EU reporting system and to improve the traceability of products but also to better involve patients in the reporting of incidents.
It is necessary to enhance coordination and information exchange among the national competent authorities and to guarantee a consistent enforcement of the legislation.
Severe penalties and dissuasive sanctions should be imposed in case of non-compliance and an appropriate mechanism should be put in place to help consumers to seek redress and compensation when problems occur.
Finally, patients should be provided with better information on the benefits and the risks of medical devices and higher ethical and transparency standards should be respected by all actors involved in the sector.
Thanks again for your investigation. We hope the problems you highlighted will be addressed in the context of the forthcoming revision of the EU medical devices legislation and patient safety will be improved.
Competing interests: No competing interests
Letter to the editor
The article ‘Hip implants: how safe is metal on metal?’ by Deborah Cohen and the accompanying commentaries do not accurately describe the work of the MHRA, in collaboration with expert advisers and the orthopaedic associations, in providing objective advice to clinicians on this topic.
The MHRA was the first regulatory agency in the world to issue advice to clinicians about metal-on-metal implants. It is not the case that the MHRA issued “emergency guidance…in response to the BMJ’s investigation”. The Medical Device Alert (MDA) we issued on 28 February 2012 updated advice that was issued in April 2010 in the light of the continuing review of evidence by the expert group set up in 2008. The members of that group were nominated as representatives of their professional organisations by the British Orthopaedic Association, the British Hip Society and the National Joint Registry. All are leading international experts in their field. The suggestion that they were influenced by commercial interests is indefensible.
We recognise the central importance of post-market surveillance of implants, which is why the National Joint Registry was set up in 2003. It is now the largest joint registry in the world, providing detailed outcome data which drive clinical practice. The proportion of hip implant patients receiving large head metal-on-metal prostheses has dropped to two percent and appears to be still falling.
The regulation of medical devices differs from that of pharmaceuticals for good reasons. Long term performance of implants cannot be adequately studied in pre-market studies of feasible size. The causes of device failure are not analogous to adverse drug reactions and therefore the study designs used to estimate risk-benefit relationships must be different. Learning from the rigorous analysis of outcomes is not ‘regulatory failure’; it is evidence-based medicine.
Joint replacement surgery is now one of the most beneficial interventions of modern medicine as a result of incremental improvements in techniques and devices. The review in progress of the EU Medical Devices Directives provides the opportunity to further strengthen a system of regulation which is in principle appropriate to the nature of the challenges presented by this widely diverse range of products.
Professor Sir Kent Woods
Medicines and Healthcare products Regulatory Agency (MHRA)
151 Buckingham Palace Road
London SW1W 9SZ
Competing interests: Chief Executive Medicines and Healthcare products Regulatory Agency (MHRA)
This is a very worrying report for those, including myself, who had this type of large metal on metal hip replacement carried out in early 2010. Annual checks for increased ions in the blood are all very well, but in the intervening months surely an MRI scan should also be carried out in order to ensure that bone and muscle around the metal implant is not being eaten away, thus avoiding irreversible disability.
I cannot understand how these Hip Replacements where allowed to go on knowing that cancerous elements and irreversible damage could occur. Also, why were these implants still given to unsuspecting patients when scientists were scratching their heads pondering why shedding was taking place allowing surgeons to carry on performing the implants? This report has given thousands of people the worry of irreversible damage, i.e. disability or cancerous outcomes and there is nothing that can be done until the damage reveals itself. This is utterly unbelievable!!
Competing interests: No competing interests
In the current era of commercialized medicine, molecular assessment of the safety of the therapy under question may be delayed and misleading in the absence of clinical trial, as in this case. As a consequence unsuspecting trusting patients may suffer irreparable damage at the hands of surgeons little informed by the manufacturers of devices. In this case, as claimed by Mr Nargol, the device is a foreign body and metal and has the potential to cause destruction of bone muscle and organic tissues, in spite of the good claims of the producer.
Hence, globally, wherever there are confirmed reports of patients sustaining injury, under regulation, there should be provision of adequate compensation for damage to patients from the manufacturer as an essential part of research aimed in the right direction.
Competing interests: No competing interests
Diagnosed with congenital acetabular dysplasia of the left hip at 25, I underwent three unsuccessful surgeries before finally having a hip resurfacing procedure in 2002.
I read the MHRA alert and Cohen's article from two perspectives. Firstly, that of a patient who is now unsure whether my metal on metal hip replacement is one of those covered by the alert. Secondly, as a human factors specialist whose expertise is to understand why incidents and errors occur.
From a human factors perspective I would make the following comments: Healthcare organisations have become very accomplished at demonstrating compliance with standards and regulation. But if the regulatory context has weaknesses in it, compliance does not always equal safety.
Going forward, learning about what went wrong needs to consider human factors issues. For example, Cohen's article describes unheeded warnings by senior managers and decision making traps like 'groupthink' and 'fixation' being at play as the evidence about the risks emerged.
Most importantly, investigating what has gone wrong needs to be carried out in the spirit of openness and learning, not blame. We also need to recognise that hindsight is a wonderful thing but that it sometimes makes past events more easily forseeable than it was to those involved in the decision making at the time.
From the perspective of a patient who has a metal-on-metal hip replacement but is unsure whether they are affected, I would make the following comments. The next few months present the best opportunity we will have to identify the true magnitude of the risk and the number of patients affected. It is therefore important that reporting arrangements back to the Central Alerting System collects robust data, not simply a statement assuring the Department of Health that each Trust is compliant with the MHRA alert.
Secondly, issuing patient information describing the process from hereon would be greatly appreciated. For example, I have been geographically mobile since 2002 and know that my operation took place before the National Joint Registry was fully operational. Whilst I have already contacted the PALS team at the hospital where my operation took place to advise them of my latest address, other patients may not think to do this. Patient information that provides reassurance and sets out the process from hereon is therefore really important.
My final point is that for many patients like myself, these devices have improved our quality of life enormously. Before the 2002 resurfacing procedure, I was very much as a bystander as life went on around me because I was in a great deal of pain. In contrast, I have spent the ten years since my operation pain-free and physically active. It is important that we do not forget the benefits the surgery has had for patients like myself.
Competing interests: Dr Carthey is a Human Factors Specialist who supports NHS organisations to embed human factors and improve patient safety.
In April 2004 as a Rheumatoid Arthritis patient at the Norfolk and Norwich University Hospital Trust, i was referred to Orthopeadic Surgery for a double Hip Replacement. Whilst aged only 31, my arthritis had rapidly progressed from painful hands in 1998, to the inability to walk at all by 2004.
Once on the ward my surgeon said that he was not going to replace my hips with metal on metal replacements as there had been talk in the profession about there being a possiblity of problems, as the wearing action may cause pieces of the metal to fragment and come off and go into the blood supply. I am indebted to my surgeon as without his foresight and care, i may well have been having issues and very real concerns at this time.
Subsequently, he replaced my hips with metal on ceramic sockets and i have been ok. I receive a review once every two years but know (as i was informed in post operative care) that i have their number and can call anytime and go in should i have any problems.
I was very interested to watch the Paxman interview on Newsnight and the questions asked of the head of the MHRA, who seemed suggest that questions arose in 2006. This obviously contradicts with my experiences. I would be interested to hear what further details may come from this information i am providing to you today.
Competing interests: No competing interests