This is unlikely as we have very selectively undertaken hip resurfacing using the implant with the best track record (The Birmingham Hip Resurfacing or BHR) and have not electively performed any primary metal on metal hip replacements. We have instead favoured ceramic, oxidized zirconium and polyethylene bearings.

The term “metal-on-metal” refers to hip devices where both the ball and socket joint are made of a metal alloy (commonly Cobalt-Chrome). This bearing surface was considered superior in comparison to alternatives, mainly due to the metals durability allowing the implants to last longer. In addition the ball part of the device is larger making the joint more stable and less likely to dislocate.

However, despite these advantages, recent information has raised some concern with relation to the use of certain metal-on-metal hip devices. These concerns are centered on adverse reactions occurring in the body to excess metal wear particles. This has led to the recall of the Depuy ASR/ASR XL hip implants.

As with any hip device, when the two bearing surfaces of the ball and socket rub against each other gradual wear of these surfaces occur. This wear releases metal debris (ions and particles) which are normally broken down by the body’s immune system, absorbed into the blood stream and filtered by the kidneys and released in the urine. However, in the case of certain metal-on-metal devices, excess wear occurs which can go onto cause both local and generalized / systemic reactions in some patients. These may present with symptoms such as pain and swelling around the hip joint and subsequent loosening of the implants. This process may be referred to as Metalosis, Adverse Reaction to Metal Debris (ARMDs) or Pseudotumours.

As a result, since 2010 the UK Medicines and Healthcare Regulatory Agency (MHRA) has issued a number of safety alerts advising that all patients who have received metal-on-metal hip implants are followed up. The follow-up process may vary from a simple questionnaire to more extensive investigations which include blood tests for raised metal ions/ Xrays and MRI scans. Where implant failure is identified, the treatment option of choice is a revision hip replacement to an alternative bearing surface.

Despite these concerns, there is still strong evidence in the literature to suggest that the overall incidence of this adverse metal reaction is low and that the vast majority of patients have not had any problems with their metal-on-metal hip implants.

Metal-on-metal hip resurfacing still remains a viable option in certain groups of individuals such as young fit active patients with large femoral heads and strong bone.

Frequently asked questions?

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

The hospital at which the surgery was performed will have an accurate record of your operation and what implant was used. Most hospitals are in the process of following up their metal-on-metal patients and therefore may have already tried to contact you. If however, you have any concerns you may contact the surgeons secretary who performed the operation directly, or go via your GP.

Do these concerns relate to all metal-on-metal hip replacement devices?

Yes – although there is evidence in literature that certain implant designs such as the Depuy ASR/ASR XL implants were more susceptible to failure than others. In addition to this, relatively speaking, more problems have been associated with large head metal-on-metal total hip replacements as compared with metal-on-metal hip resurfacings.

What worrying symptoms should I look out for?

The most common symptom is onset of pain around the hip and groin. This may or may not be associated with swelling. It is important to note however, that these symptoms are not specific to an adverse metal reaction and therefore, further investigations may be required to diagnose the cause. Some patients have complained of generalized symptoms including lethargy and depression but the link to metal on metal implants has not been proven.

What follow-up should I be receiving after my metal-on-metal hip replacement?

Most hospitals have already implemented a follow-up protocol of their metal-on-metal hip patients. The follow-up process varies depending on the hip implant design and your symptoms. Where patients are well this may entail a simple review in clinic. If, however, any specific concerns are raised then further investigation in the form of blood tests and Xrays may be required. This may be further followed up with MRI scans.

Certain metal-on-metal implants such as the ASR/ASR XL implants and large head total hip replacements are recommended to be followed up on an annual basis for the lifetime of the implant.

What will happen if there is evidence of failure of my hip replacement?

The surgeon will discuss the cause of the wear and damage. If there is evidence of an adverse reaction to the metal and excess wear then ultimately revision surgery of the hip will be required to an alternative bearing surface.

Is the metal-on-metal bearing still being used?

Yes – although there has been a decline in the use of the bearing surface, there is still strong evidence in literature that certain implant designs (hip resurfacing in appropriate patients) in certain groups of individuals perform very well. Your consultant surgeon will be best able to advise you on this.

What are the long term risks related to metal-on-metal hip replacements?

The long term implications of metal-on-metal wear debris is unclear. There is published literature correlating raised metal ions with increased risk of genetic complication in animal studies. However, to date there has been no evidence of this in humans. In particular there is no evidence to suggest that raised metal ions following metal-on-metal hip replacements are associated with an increased risk of cancer.

Where can I get more information on the subject?

Probably the best source of information will be the consultant surgeon who has performed the hip replacement. In addition, the internet has a wide range of available resources to include patient forums.

Alternatively official websites that will provide up to date information include:-

http://www.mhra.gov.uk
http://www.boa.ac.uk