Papers filed at the High Court, as reported by The Telegraph, reveal that DePuy, one of the largest manufacturers of medical devices in the world, was aware of manufacturing problems in its hip replacement systems. 

DePuy manufactured the Pinnacle and ASR metal-on-metal hip replacements, of which over 23,000 have been fitted since 2003. The ‘Pinnacle’ was discontinued in 2013, but DePuy admitted it became aware of problems with the size of the metal-on-metal liner – the Ultamet – in 2008. The company has refused to address when the problem causing the issue was rectified. 

It is significant that DePuy is only now admitting the “error in the measuring techniques” of its metal-on-metal hip systems, which was caused by one of the polishing machines heating the components so that they expanded. The components were then measured when they were hot but were a different size at room temperature. 

Metal-on-metal hips have far higher wear rates than other hip implants, which means they may need to be replaced earlier than more traditional metal-on-plastic components. There is also a real concern that, as the metal components wear, the metal ions can enter a patient’s bloodstream and cause a condition known as metallosis. The problem was previously thought to be caused by the materials used to manufacture the components, and by the hips’ design and, although this may still be the case, DePuy’s recent admittance of a manufacturing fault may have compounded the issue. 

Professor Timothy Briggs, consultant orthopaedic surgeon, said that a “mismatch in size” could cause debris to break off the implant components and enter the bloodstream. Even a very small difference in size will change the wear characteristics and “may well generate more metal ions”. 

Arran Macleod, associate in the Penningtons Manches clinical negligence team specialising in product liability claims, said: “There is already concern about the design of metal-on-metal hip components and whether it has caused many of the patients’ problems. Although this is arguably still the case, incorrectly sized components placed together will increase the rate of wear of the components and increase the patients’ vulnerability to metallosis. 

“As DePuy hasn’t admitted when the manufacturing problems were rectified, thousands of patients could potentially have been fitted with components the company knew were faulty. There are time limits for bringing a product liability claim against a manufacturer, but we would be happy to speak with anyone who has been fitted with a DePuy Pinnacle or ASR metal-on-metal hip and has experienced increased pain and discomfort, to discuss their available options.”