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Answers to commonly asked questions from patients with metal-on-metal hip replacements / resurfacings

John Skinner1 and Alister Hart2 , Consultant Orthopaedic Surgeons and Directors of the London Implant Retrieval Centre Source: Click here

1Royal National Orthopaedic Hospital, Stanmore UK 2Charing Cross Hospital, London UK

Contents

  1.  What are the concerns about metal-on-metal hips; should I be worried? Does this apply to hip-resurfacing and total hip replacement?
  2. What is the difference?
  3. What make of metal-on- metal hip has been recalled? How do I know if I have a metal-on-metal hip?
  4. How do I find out what material my hip is made of?
  5. If I have a metal on metal hip, should I contact my GP or orthopaedic surgeon?
  6. Should I be receiving regular check-ups? What should these checks involve?
  7. What will happen if there is any damage to the hip? Who regulates the use of hip devices?
  8. How would I find out when a type of hip has been recalled?
  9. Do I need to report any side-effects to the MHRA as well as my doctor?
  10. Should I get legal advice if I have a hip that has been recalled?
  11. Are there any long-term risks associated with the procedure, in addition to the recent
  12. recall?
  13. Is metal-on-metal still being used?
  14. What are the advantages of it?
  15. How do surgeons decide what type and material of hip replacement to use?
  16. How can I find out what type and material of hip replacement would be best for me? How do I make sure I have a good, experienced surgeon?
  17. Where can I get more information?
  18. Why was research not carried out before the hips were offered to patients?

What are the concerns about metal-on-metal hips; should I be worried?

When they work well, metal on metal hip resurfacing and total hip replacements give years of trouble free use with very low levels of wear. However all artificial hips will wear producing small amounts of debris. With all materials there is a body response to this debris which can cause lysis (erosion) of bone, loosening of the implants. With metal on metal hips this debris is in the form of particles or ions of cobalt and chromium that the metal is made of.

In most people the metal ions are absorbed into the blood stream and are generally filtered by the kidneys and passed out in the urine. The concentration of cobalt and chromium in the blood can give some information as to how the hip is wearing.

These are low levels measured in parts per billion (ppb).   However the concentration of metal ions in the fluid around the hip joint can be much higher. It is these high local concentrations of metal ions that cause damage to the tissues either by local toxicity or by the bodies response as it tries to get rid of them.

While all hip debris causes some local response, metal debris in some susceptible individuals can cause extensive tissue damage and in some cases death of tissue cells, including muscle, tendon, nerve and bone. Thankfully this extreme response is rare but this is why any symptoms are taken very seriously. We want to prevent minor tissue reactions developing into major problems.

 In 2010, the UK Medicines and Healthcare Regulatory Agency issued three safety alerts, one for all metal on metal hips and two for ASR hips. The Australian and UK National Joint Registries also reported high failure rates for ASR Hip replacements and all large diameter metal on metal bearing total hip replacements. Depuy International then recalled all the ASR hip resurfacings and ASR XL total Hip Replacements. The MHRA has advised that all MOM hips are followed up for 5 years and all ASR / ASR XL hips be followed up for the life of the implant. Approximately 100,000 of the ASR hips have been implanted worldwide since 2004 and approximately 10,000 in the UK.

The cause of failure is still not fully explained but usually presents as pain in the first instance. The most accepted explanation so far is that high wear of the hip results in metal debris that irritates the lining and muscles surrounding the hip.

Does this apply to hip-resurfacing and total hip replacement?

Yes it applies to both types of metal-on-metal hip, however recent evidence suggests that the problem may be greater for large diameter metal on metal total hip replacement.

What is the difference?

A hip resurfacing retains the ball part of the ball and socket hip joint and puts a metal cap over the surface of it. There is also a metal cup on the pelvis side. In a total hip replacement, the ball on top of the thigh bone is removed and a stem is fixed into the shaft of the thigh bone using either bone cement or uncemented technology. A ball is then fixed onto a spigot on this stem. Both types have a metal ball rubbing against a metal cup, although with total hip replacement non- metal on metal bearings can be used.

What make of metal-on- metal hip has been recalled?

The Depuy International ASR hip resurfacing and the ASR XL total hip replacement.

How do I know if I have a metal-on-metal hip?

If you have had a Hip Resurfacing operation then it is a metal on metal bearing hip. They all are. Most total hip replacements are not metal on metal bearings and use other materials including ceramic and high density polyethylene. Your hospital will always have a record of your operation and what implants were used. You can contact the hospital directly if your operation was done recently and you are still under the care of the surgeon. Most hospitals will have tried to contact you already if you have a metal on metal hip. Otherwise contact your GP and they can help put you back in contact.

If you signed a consent form for details of your operation to be sent to the National

Joint Register you can contact them directly and they can tell you details of your implant. Tel: 0845-3459991 or Email: health_servicedesk@northgate-is.com

How do I find out what material my hip is made of?

As above

If I have a metal on metal hip, should I contact my GP or orthopaedic surgeon?

Most hospitals that have put in a number of metal on metal bearing hips will have a system to advise patients. Try contacting them directly. If not your GP can help you and refer you back to your orthopaedic surgeon.

Should I be receiving regular check-ups?

The advice from the MHRA is that all patients with MOM hips should be followed up for 5 years and that all ASR or ASR XL hips that have been withdrawn, should be followed up for the life of the implant. There is probably no need for other metal on metal hips to be formally followed up, but if you develop pain or start to limp you should tell your doctor who will arrange for referral or investigations.

What should these checks involve?

These can take many forms and if there is no problem then a telephone conversation or questionnaire annually may be all that is required. If you have pain, or it is an ASR component, or you have some x-ray findings, then a more detailed assessment will be performed. This may include physical examination, blood tests to measure blood metal – Cobalt and Chromium ion concentrations and possibly ultrasound or MRI examinations. If you develop pain or a limp it is important to tell the doctors looking after you.

What will happen if there is any damage to the hip?

Not all pains and problems are due to adverse reactions to metal. Other causes of pain that can affect all types of hip replacement include loosening, wear and infection. If there is damage to the hip then you will require revision surgery where the metal on metal bearings will be removed and new bearings in the form of a new socket and ball will be inserted. It will also need a femoral stem to fix the ball onto (total hip replacement). If you already have a stem in place and it is well fixed and not damaged, then this can often be saved. Your surgeon will discuss this.

Who regulates the use of hip devices?

A national regulator called the Medicines and Healthcare Products Regulatory Agency (MHRA) oversees the process of classifying a medical device in the UK

How would I find out when a type of hip has been recalled?

Medical Device Alerts are the MHRA‘s way of communicating safety information. They also have an excellent website where you can check if you are concerned (http://www.mhra.gov.uk).

Do I need to report any side-effects to the MHRA as well as my doctor?

Anyone can submit a problem with a medical device to the MHRA. This includes clinicians, healthcare workers, carers, patients and members of the public. You don’t have to tell the MHRA, but manufacturers do have to inform them when they know of failures that have been revised. This, along with NJR data ensures that the MHRA can keep abreast of problems.

Should I get legal advice if I have a hip that has been recalled?

First see your doctor to determine if there is a clinical problem. Your health must come first if there are problems. With the ASR and ASR XL devices, in most cases, the manufacturers are paying for all investigations and treatment to put things right. However the ASR / ASR XL hips are the subject of legal proceedings worldwide and you should get legal advice to see if you are entitled to compensation.

Are there any long-term risks associated with the procedure, in addition to the recent recall?

There is little research on the long term effects of these hips on either the tissues around the hip or on tissues elsewhere in the body.

There are concerns regarding the high levels of heavy metals (cobalt and chromium) in the blood however there are very few reports of actual clinical problems.

Is metal-on-metal still being used?

Yes. It is the only way of performing a resurfacing operation where the thigh bone is simply capped. There does seem to be clinical evidence that in younger males (under 55 years) or men who are very active, then some metal on metal hip resurfacing replacements seem to show as good or slightly better results than total hip replacement. However, the use of metal on metal bearing hips has reduced very sharply in the last 2 years.

What are the advantages of it?

It allows hip resurfacing and can allow much larger diameter heads to be used, in total hip replacement. The larger the femoral head then the greater the stability of the hip replacement and dislocation is a recognised complication of all artificial hip joint replacements. Larger heads can also permit a greater range of movement of the hip. Finally when designed and made well, working well, positioned well and lubricated well by joint fluid, metal on metal bearings show some of the lowest wear rates of any materials used in hip replacement. This is what made them so popular. However if any of the factors are not right, then the wear can be extremely high and the wear debris of cobalt and chromium can be very troublesome.

How do surgeons decide what type and material of hip replacement to use?

Most surgeons find two types of hip replacement that they are happy with. Firstly one for young and active patients and secondly one for the much commoner group of older patients. There are many good hip replacements that have good follow up and excellent results published in the medical literature.

How can I find out what type and material of hip replacement would be best for me?

Research is constantly being performed trying to answer this question. All materials have advantages and disadvantages. However most modern materials are showing excellent results and it is likely that more than one type may be equally effective for you. Skin patch testing is not reliable.

How do I make sure I have a good, experienced surgeon?

Your GP will have had other patients having hip surgery in your area so will have a very good idea who to recommend. If you have friends, family or other patients who have had hip surgery they can also give you a ‘customer view.’ Recommendation is the best way.

Where can I get more information?

Your doctor and particularly your surgeon will be able to discuss all matters related to your hip and hip surgery with you.  The internet has lots of information and the websites of the British Hip Society and the British Orthopaedic Association are useful.

Why was research not carried out before the hips were offered to patients?

A lot of research was carried out before these implants were offered to patients. The ASR ASR XL devices were tested extensively in laboratories and on hip simulator devices. In perfect laboratory conditions they had very low wear rates. In people the bodies biological response to metal wear products was not fully appreciated. It seems that some people may mount a particularly strong response in certain circumstances and this can damage the local tissues.

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