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Metal-on-metal hip implants

Portfolio politics

Louise Newson

Monday, 05 March 2012

LN_Blog_March052012.jpgThe Medicines and Healthcare Products regulatory Agency (MHRA) has recently announced that around 49,000 UK patients with metal-on-metal hip implants with a femoral diameter of 36mm or more will need follow-up tests for the rest of their lives.

These follow up tests are annual blood tests to check metal ion concentrations in their blood. In addition, patients with certain symptoms which include pain or limping should also undergo an annual MRI scans. There does not actually seem to be a safe level for metal ions which has been determined for patients with hip implants.

This follows an investigation by the BMJ which revealed that metal ions can leak into the body thereby causing problems. Metal-on-metal hip components are constructed form a cobalt-chromium alloy. Levels of these ions seem to persist in patients whose implants suffer wear and tear.

So does all this matter? These ions can seep into local tissue causing reactions that destroy muscle and bone and can lead to long-term disability. In addition, these ions can also leach into the blood stream.

Although several cohort studies have found no increased risk of cancer after total hip replacement, one recent retrospective study of causes of death found patients with metal-on-metal hips had higher cancer mortality than patients with metal-on-polyethylene during the first twenty years after implant surgery.

What I find most worrying is that there has been documented concern regarding these implants for several years. Multiple studies and research organisations have warned about the carcinogenic potential of metal-on-metal implants. Even the manufacturers have been aware of the potential for genotoxicity for many years. Despite these concerns, marketing for metal-on-metal hip implants has continued.

Understandably, many patients (and doctors) are now very confused and worried about their hip implants. The procedure for regulatory approval of new devices surely needs to be scrutinized and reviewed. In addition, it has been recommended by experts that there needs to be an independent system for post-marketing analysis for implantable medical devices that is robust. This seems very sensible indeed!

Author's Image

Louise Newson

Louise is a part-time GP in Solihull, as well as a writer for numerous medical publications, including www.patient.info. She is an Editor and Reviewer for e-learning courses for the RCGP. She is an Editor for Geriatric Medicine journal and the British Journal of Family Medicine. Louise has contributed to various healthcare articles in many different newspapers and magazines and is the spokesperson for The Information Standard. She has also done television and radio work. Louise is a medical consultant for Maverick TV and has participated regularly in ‘Embarrassing Bodies Live from the Clinic’. Louise has three young children and is married to a consultant urological surgeon. Although her spare time is limited she enjoys practising ashtanga yoga regularly and loves road cycling – she has raised over £2K for a local charity, Molly Olly Wishes by competing in a 120km cycle ride!
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