London research to lead to longer-lasting shoulder replacements
Researchers at Imperial College are aiming to find out why shoulder replacements – the most common form of joint replacement surgery after hips and knees – fail and become loose.
Around ten per cent of the 5,000 shoulder replacements performed in the UK fail completely, and many more don't work properly, because of loosening. Shoulder replacement surgery is most commonly performed to reduce pain and restore some mobility in patients with severe osteoarthritis. It is also carried out on rheumatoid arthritis patients, and on patients who have been in accidents.
Now a team of bioengineers and surgeons at Imperial College, London, have been awarded a three year £58,000 grant from the Arthritis Research Campaign to investigate the reasons for this, which they hope will lead to improved implant designs and better surgical techniques.
"The main reason why shoulder replacements fail is because the artificial joint becomes loose from the shoulder blade socket, known as the glenoid, because the socket is very small and therefore fixation is not very good," explained Dr Ulrich Hansen, team leader and lecturer in orthopaedic biomechanics in Imperial's mechanical engineering department.
"Loosening of the glenoid will mean patients will be in some pain, and their movements will be limited, and other than having the replacement revised, patients just have to put up with it. We're going to use lab tests and computer techniques to evaluate design features, in particular the thickness of the cement used to hold the joint in place. Then hopefully we will be able to do something about it."
Another member of the research team, orthopaedic surgeon Andrew Wallace at St Mary's Hospital in Paddington, said they wanted to help design a prosthesis that would last a lifetime, rather than having to revise them after ten to 15 years.
"The best results we have are in older osteoarthritis patients when you get a replacement survival rate of about 90 cent over 15 years, but that's because these patients are older and not as active," explained Mr Wallace. "The worst results are in younger people who've had an injury or trauma. Once you get rid of their pain and restore movement, they naturally want to do more, so the joint gets more wear and you get problems with loosening in up to 30 per cent of cases."
