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Metal-on-metal hip implants

2012/13 MHRA Medical Device Alerts

The remainder of the information on this page was created in response to the Medical Device Alert issued by the Medicines and Health Regulatory Agency on Tuesday 28 February 2012.

Frequently asked questions

What are metal-on-metal implants?  In metal-on-metal devices, both the ball and socket components are made of metal (metal bearing surfaces). These metal implants have been used in total hip replacement surgeries and hip resurfacing procedures. Metal bearings can allow for the use or larger femoral head sizes which more closely resemble the natural hip ball and socket (these are often called large head metal-on-metal).

Why are there concerns about metal-on-metal hip implants?  In 2010 the National Joint Registry (NJR) data identified higher than expected revision rates for the metal-on-metal implants. (A revision is an operation to remove or replace one of more components of a joint prosthesis and all types of devices have incidences of revision). Studies have shown concerns for patient outcomes, relating to pain and function, and the possibility of metal debris damage to surrounding soft tissues. Attention has focused on whether these problems could be associated with the use of larger femoral head sizes and particular designs. For example, the ASR implants which were withdrawn by the manufacturer (DePuy) in 2010 following the publication of NJR statistics (see timeline).

What is the NJR's role in identifying failing devices? It is a key aim of the NJR to identify any brand of prosthesis showing high failure rates and allow prompt removal from the market.

To do this, the NJR seeks patient consent to monitor any replacement hip, knee, ankle, elbow or shoulder joint procedure. Data including the procedure type and the brand of prostheses is recorded for initial implant procedures and for any revisions of the device.

Fundamental to identifying failing devices is the close monitoring of patient time incidence rates (an incident is defined as a revision procedure where an implant has had to be replaced and patient time is defined as the number of years an implant has been in a patient). The NJR monitors the number of revisions per 100 patient years.

Information about implant performance is reported every six months to the NJR's Implant Performance Group. If the results of the monitoring show that an individual implant's performance lies outside of what would normally be expected, the Implant Outlier Group notify the Medicines and Healthcare Products Regulatory Agency (MHRA) that it may be an outlier.

The MHRA then undertakes an investigation in conjunction with the device manufacturer. The NJR will provide any additional data necessary to support that investigation.

I'm a patient, can I find out more about my implant from the NJR including what size it is? Yes, if you gave consent to the NJR to hold your personal information alongside your operation information, you can request a copy by contacting us.  This can be done by downloading a Patient operation request form and submitting it by email or by post to the NJR Centre (information on the form).

These requests may take between 2-4 weeks to process, as appropriate checks need to be carried out before disclosing patient personal information. Additionally or alternatively, patients may it find it a greater convenience to phone their hospital or surgeon directly where they can also seek out medical advice as appropriate.

I'm a patient with a metal-on-metal implant and I am concerned, where should I go for help? If you have a concern about your implant for whatever reason, please contact your GP, surgeon or the hospital where your operation took place. They will be able to advise on appropriate follow-up procedures.

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