MHRA Advice for Patients
Response to MHRA Alert
There have been reports in the print media in recent weeks about soft tissue problems developing in patients with metal-on-metal (MoM) hip resurfacings and hip replacements. In addition, the British Hip Society and the MHRA (Medicines and Healthcare products Regulatory Agency) have issued advice about these problems. You can view the advice from the MHRA by clicking here and you can view the advice from the British Hip Society by  clicking here.
The MHRA acknowledges that a 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. A small number of patients implanted with these hips may, however, develop progressive soft tissue reactions to the wear debris associated with MoM articulations.
These soft tissue problems have been given different names in different Centres. A renowned orthopaedic hospital in Oxford has chosen the name ‘pseudotumours’. Others call them Adverse Reactions to Metal Debris.
What are pseudotumours and what causes them?
The term pseudotumour refers to a problem whereby a patient with a hip resurfacing or a hip replacement begins to develop discomfort or pain or a swelling and collection of fluid in the region around the hip joint. The word ‘pseudotumour’ has caused consternation among patients who are worried if this is some kind of a hidden cancer or a pre-cancerous condition. These need to be put into perspective.
First, let us be clear that these reactions have nothing to do with cancer.
Second, there isn’t a single artificial hip system, whether metal, ceramic or plastic, that does not generate wear debris and pseudotumour-type reactions develop with all types of wear debris.
Third, no artificial hip device metal or ceramic or plastic lasts long unless it is placed in an optimal position.
Fourth, it is now becoming obvious that pseudotumours develop due to excessive wear of metal or plastic from the device. This can happen due to one of two reasons.
The first relates to the device itself. One Centre in the UK has reported a high incidence of pseudotumours in a particular resurfacing device (ASR Articular Surface Replacement) even when the operations have been performed well by a very experienced surgeon. BHRs performed by the same surgeon did not show a pseudotumour in a single case even though the BHRs have been in-situ for a longer period of time than the ASRs. The MHRA has issued another specific alert referring to the higher failure rates with the ASR devices. This can be viewedhere.
The second reason relates to device placement. Some patients operated in another Centre developed pseudotumours with several different types of resurfacings, irrespective of the type. The components that had been removed from these patients were tested in a highly sophisticated laboratory. The laboratory found that in every case with a pseudotumour, the wear pattern suggested edge-loading. Edge-loading of a MoM resurfacing or replacement occurs when the components are implanted in an unfavourable position and leads to a situation like running a car engine after draining out all the oil. The components here had worn excessively in an unnatural manner because of their placement. In components which did not show edge-loading i.e. those components which had been placed in the correct position to start with, no one had developed a pseudotumour. The operations in this particular Centre had been performed in many cases by trainees.
These problems are more common in young women for one of several reasons. One reason is that the size of components needed in women is smaller and therefore there is less margin for error in placement. Furthermore the underlying reason for the development of arthritis in young women is often a condition called ‘hip dysplasia’. In dysplasia the socket of the hip is not only shallow but the direction of both the socket and the ball can be abnormal. This three dimensional abnormality can sometimes lead to component malposition even in the best hands. In addition, women through the usage of costume jewellery etc are more likely to be pre-sensitised to metal (most often to nickel which is a trace constituent of the alloy used in metal components). This may lead the tissues in some women to react to the very low levels of nickel released from artificial devices. As a matter of precaution, patients with a suspected metal allergy are required to have a simple blood test prior to surgery.
From the above it is obvious that both a well-proven device and an experienced surgeon are the key factors for a successful resurfacing.
What symptoms do these patients develop?
Out of more than 3100 Birmingham Hip Resurfacings over the past 12 years, we had 10 patients (1 in 300) who developed a local adverse reaction like this. In most of these there was only a collection of fluid around the hip joint nearly 10 years or more after their original operation. They complained of groin pain or discomfort. A few developed swelling of the foot or ankle because of the collection of fluid above. In many cases there were subtle X-ray changes, although not in all. In addition, in a couple of cases there was osteolysis (bone resorption). Other Centres have reported muscle damage or pressure effects on the nerves or blood vessels from the fluid, fractures or dislocations.
What is the solution if a person develops a pseudotumour several years after a hip resurfacing?
If a person presents with a history suggestive of a pseudotumour, he/she needs to be examined by an orthopaedic surgeon and undergo X-rays, a special multi-slice CT scan and some blood tests in order to establish the diagnosis. The CT scan must be able to reduce artefact from the metal in order to provide any useful information. In some cases it may be necessary to exclude infection by aspiration of the hip joint. If it is indeed a pseudotumour then a revision operation to convert the resurfacing into a total hip replacement with a non-metal-metal bearing will have to be performed.
How do patients recover after revision of a resurfacing to a hip replacement for a pseudotumour?
The ten patients described above have recovered as if they were recovering from any other revision hip replacement. Their hips are functioning well. The worst affected of these patients underwent the revision operation in January 2010 and needed bone grafting of the socket. She has seen the sensational reports in the newspaper and questions “What is all the fuss about? I have had 10 good years of my life restored to me. I had then been in my early 50s and now I am in my 60s. I noticed hip discomfort a few months before the 10th anniversary of my operation and I had to undergo a revision operation to convert my hip resurfacing into a hip replacement and I am now getting back to normal again.” She adds, “Ten years ago, had I known that I would need a revision at this stage I would not have changed one thing. I would have gone ahead with the resurfacing operation”. Two months after her revision operation, she kindly agreed to be filmed and you can follow her account in the video below.
Joan Lindh Video
Further Information
Derek McMinn was recently interviewed by Vicky Marlow from the Surface Hippy website. In these video interviews, Mr McMinn discusses a range of topics on Hip Resurfacing including device designs, the importance of component positioning and the recent MHRA Alert for Metal-on-Metal bearings.
Please see the link below to access the videos, available in 3 parts.
For more information about the associated risks of metal-on-metal hip resurfacings and hip replacements, please see the documents below:
Advice from the British Hip Society [KB] (click to begin download)
'Metal-on-Metal: Questions & Answers' [196KB] (click to begin download)
'Pseudotumors following Total Hip and Knee Arthroplasty' [2MB] (click to begin download)
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