New safety concerns over knee replacements

The long-term safety and effectiveness of millions of knee replacement implants is unknown, highlighting inherent problems in the regulation and monitoring of medical devices, according to a leading surgeon.

Andrew Carr, professor of orthopaedic surgery at the University of Oxford, warned that surgeons are being hindered by a lack of reliable information as the demand for knee implants grows.

There are more than 15 companies producing dozens of slightly different knee implants that UK surgeons can pick from depending on patient characteristics and surgical preference. Unlike medicines, companies are not required to clinically test medical devices in patients – they must only prove that a knee, hip or breast implant is safe and durable outside the body in order to gain the required kitemark.

Writing in The Lancet, Professor Carr points out that an aging population and increase in obesity rates means the dramatic rise in knee implants looks set to continue. "Widespread surveillance of existing implants is urgently needed alongside the carefully monitored introduction of new implant designs as part of well-conducted large-scale randomised trials," he wrote.

There were 76,780 knee replacements in 2010, a 30 per cent increase in five years, according to the National Joint Registry, which monitors the failure rate of implants by analysing data submitted from surgeons. However, the information on the registry is organised into groups of similar components per brand, making it difficult to monitor individual products.

A small variation can lead to significant improvements or problems in safety and effectiveness, say experts.

Jill Paterson, from Leigh Day solicitors, is currently representing 25 Australian patients involving one knee implant which failed quickly leading to pain and inflammation. “While we don't want to stifle innovation, it is too easy to put something out in the market without testing it properly. The hip and PIP disasters are making people look at this again.”

Carr's warning comes a week after 50,000 patients were told they would need annual blood tests to monitor for toxic effects of metal hip replacements - previously declared safe and effective by manufacturers and regulators. Lawyers acting for almost 2,000 PIP breast implant patients, implanted with non-medical silicon enhancements, will this Friday seek court approval for a type of group action.

Dr Susanne Ludgate, clinical director of the MHRA, said: “The National Joint Registry (NJR) is a key source of information on the long-term safety and performance of knee joint replacements and is the largest such registry in the world. The NJR assists surgeons in making choices and regulators in monitoring performance.

“Since April 2003 all knee joint replacement operations in England and Wales have been recorded in the NJR. In 2010 81,979 knee joint replacements took place in England and Wales.

"Knee replacements transform the lives of many patients who in the past were subject to increasingly severe pain and progressive lack of mobility.”