Saliva swab could reveal viability of hip replacements

Hip and other joint replacements are a common occurrence as we age, but the procedure doesn’t always work. Now, scientists believe a saliva swab could give valuable insight into whether or not the surgery will be effective in advance.

Around 15 per cent of Brits carry characteristics in their genes that mean their immune systems reject implants. They attack the tissue surrounding the new joint, which leads to pain and swelling, rendering the implant unusable.

Researchers at Newcastle University have identified DNA signals in saliva and blood samples that could predict an adverse reaction to a joint replacement. This builds on evidence already established from previous studies that approximately a fifth of individuals have a bad reaction to implants made from cobalt chrome.

Up until now, experts hadn’t known why, making it impossible to predict which patients would be affected by the issue post-surgery. Armed with the discovery, the scientists have developed a test to identify individuals with the gene and it has an accuracy rate of around 90 per cent.

Saliva swabs and blood tests were carried out on 600 people having surgery to replace joints in the last ten years. The data was then computer analysed and the results showed a correlation between complications and those with specific genes.

Joint-replacement surgery is necessary for around ten per cent of the population, due to either arthritis or wear and tear associated with ageing. Successful replacements can last between 15 and 25 years, giving the recipients more mobility and in some cases increased independence.

For patients whose first cobalt chrome implant is rejected, the reality is usually going under the knife a second time. An alternative joint made out of different materials will often be fitted within months of the original surgery.

ExplantLab is an organisation that looks into the relationship between genetics and the performance of medical devices. It was involved in the study with Newcastle University to look into why some implants fail.

Dr David Langton, director of ExplantLab, said: “There has been little research into why joint replacements don't work for some patients. If a joint fails, it needs to be replaced, and this carries a much greater risk of blood loss, infection and even death.

“Our findings are a big step towards offering patients more choice about what type of joint implant they decide on, and helping them to make informed decisions about the risks involved.”

According to the NHS, the majority of hip replacements are performed on people between the ages of 60 and 80. They are usually only recommended when treatments such as physiotherapy or steroid injections have not been successful.