The new magnetic hip that can last a lifetime By THEA JOURDAN
29th January 2008
At the moment, wear and tear means conventional hip replacements may last only around ten years.
But the MagneHip, the brainchild of British orthopaedic surgeons Paul Lee and Michael Clarke, contains a magnet which helps the prosthetic last at least three times as long.
It is undergoing laboratory testing and should start clinical trials on NHS patients within three years.
Hip replacement operations are common among the over-50s due to natural erosion of the joints. Around 65,000 hip replacements are performed each year in Britain.
A significant number of patients need to undergo second or even third surgeries – known as revisions – because plastic and metal prosthetic joints can wear out after a decade and need to be replaced.
Revision hip surgery is more time-consuming than first-time replacements. The outcome is often less satisfactory because the bones have been weakened by the first surgery and provide a less secure base for the prosthetics.
Patients tend to be older with more health problems, too.
Complete pain relief is less common than in first-time hip replacements and complication rates are twice as high.
Many elderly patients cannot undergo the surgery at all because they are too frail, so have to cope with years of pain and poor mobility.
The MagneHip, which was recently named the Best Joint Replacement Idea at the 2007 Bone And Joint Innovation Awards, has the ability to deal with wear and tear.
As hip replacements move with the body, tiny bits of metal are worn off and become stuck in the joint. This causes the artificial hip to loosen, eventually leading to the need for a replacement.
The MagneHip has a built-in magnet and reservoir to trap debris before it becomes stuck in the joint. The design was inspired by motor vehicle engine lubrication systems, which also use magnets to filter debris.
The MagneHip does eventually wear down, but much more slowly than the conventional hip replacement because it is made entirely from hard-wearing chromium cobalt alloy.
“A colleague and I worked on the idea for five years before we came up with a design that solves the problem,” says Paul Lee, who has built a working prototype.
“It is all based on the workings of a car engine, which uses the same sort of system to make it last longer.”
Patients who have the magnetic hip implanted will not find themselves attracting metal objects.
“You won’t feel yourself drawn to lamp posts or attracting iron nails,” says Mr Lee, who is based at Leicester’s University Hospitals. “The magnet has a powerful pull, but it has a limited range of only about 2cm.
“It is a standard permanent magnet which has a lifetime of 1,000 years and so does not need replacing.’
Arthritis Care’s Jane Spence welcomes the innovation.
“Hip surgery can bring dramatic improvement in mobility and quality of life,’ she says.
“For thousands of the nine million Britons with arthritis, it can mean a return to work and an active social life, instead of isolation and disability.
“Breakthroughs in the field are exciting, and Arthritis Care welcomes any genuine advances in the search for ever more practical and effective treatments.
“We will be keenly interested in the results of the clinical trials.”
Meanwhile in the U.S., patients may soon get a replacement made from diamonds. Diamicron is developing a diamond-coated hip implant system which could last a lifetime.