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NJR research confirms high failure rates for stemmed metal-on-metal total hip replacements

13 March 2012

A study commissioned by the National Joint Registry, published in renowned medical journal The Lancet today, confirms stemmed metal-on-metal total hip replacements are failing at much higher rates than other types. The authors of the study conclude "metal-on-metal stemmed articulations give poor implant survival compared with other options and should not be implanted.".

The study was carried out by the NJR statistical support, analysis and research team led by Professor of Orthopaedic Surgery Ashley Blom at the University of Bristol.

Analysis of data from the NJR reveals that the survivorship (expected life) of stemmed metal-on-metal total hip replacements is particularly poor for women and also younger patients, in contrast to other bearing surfaces.

The data included more than 400,000 hip replacements (of which 31,171 are stemmed metal-on-metal) between 2003 and 2011 that were tracked for up to seven years after surgery.

Stemmed metal-on-metal failed much more quickly than other types of bearing surface, with a 5-year revision rate of 6.2%. Failure was related to head size, with larger heads failing earlier, corresponding to a 2% increase in the risk of failure for each 1mm increase in head size. By contrast, ceramic-on-ceramic implants did better with larger head sizes.

In women, failure rates for stemmed MOM implants were up to four-times higher than those of other bearing surfaces, and were also higher compared with men even with the same head size.

National Joint Registry Lead Elaine Young said:

"This is further testament to the power of the registry in identifying crucial information. With over one million records at seven years of data, the registry is maturing as a data source that can show outcomes based on the entire population receiving treatment, rather than small sample sizes. The diversity of surgeons, patients and implants included means that the results have good generalisability and external validity. This is a critical point - research like this gives surgeons focused data to inform choices about implant type and gives patients greater detail to help inform choices about their treatment."

  • The National Joint Registry (NJR) of England and Wales was established in 2002. Its purpose is to define, improve and maintain the quality of care of individuals receiving hip, knee and ankle joint replacement surgery across the NHS and independent healthcare sector. Data collection began in April 2003 and the registry now holds over 1 million records and more records about certain procedure types than any other registry in the world. As a result of the increasing volume and quality of data it is possible to make accurate analysis available to all stakeholders and contribute significantly to good practice and patient safety.

  • The Lancet is one of the world's leading medical journals - it publishes medical news, original research, and reviews on all aspects of clinical medicine and International Health. Established for more than 180 years, the journal is independent, without affiliation to a medical or scientific organisation and is an independent and authoritative voice in global medicine.

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