Following another media flare-up in the ongoing metal-on-metal discussion, NHS has followed UK competent authority the MHRA into releasing a positioning document of its own. The article can be found here.
In this new piece, the NHS acknowledges that the problems are not behind us and deals with the claims that they may be more widespread than originally thought. It goes on to provide guidance for patients and feedback from esteemed clinician organisations to clarify the state of play.
Firstly it is acknowledged that Metal-on-Metal (MoM) hips do suffer a higher number of problems and that they have been implanted in approximately 30,000 people in UK, representing 10% of hip operations between 2006 and 2009, and 50% of all hip replacements in people younger than 50 years.
Problems are reportedly associated with loosening of the joint, fracture and particularly wear particles from the bearing surfaces, although the document goes on to refute the use of the word “poisoned” which has appeared in much of the media, claiming instead that the cobalt and chromium levels, while an indication of wear are unlikely to result in anything other than local soft tissue damage.
Presenters at last year’s British Hip Society (BHS) meeting reported that a high proportion of MoM devices from other manufacturers may also be showing similar results to the withdrawn DePuy device. They found that, overall, the MoM devices showed a higher than anticipated early failure rate. 49% of people who had been fitted with the DePuy device needed it to be replaced by six years and between 12 and 15% who had other metal-on-metal hip replacements needed these to be replaced by five years.
Although MHRA has not yet issued specific guidance, BHS and British Orthopaedic Association (BOA) advice remains as follows:
• Everyone with a hip replacement that has been withdrawn should be informed and told that they will be under close clinical follow-up.
• Some form of follow-up should be carried out at least annually and patients should be given contact information so that they can be reviewed quickly if they have pain or lose function in their hip.
• Patients should be followed for the life of the implant until more data are available.
If someone with a withdrawn MoM hip replacement experiences no pain or loss of function, no further investigations are required apart from standard follow-up.
• If a person with a withdrawn MoM hip replacement reports that they are in pain, the cause of the pain should be further investigated. Blood cobalt and chromium levels should be measured to indicate how much the device has worn, but there is no evidence that the implant must be replaced above a certain metal concentration.
• Treatment decisions should be confirmed with a second experienced “revision” surgeon.
Finally the guidance concludes that people who have had a hip replacement, who are concerned, should contact their orthopaedic surgeon or GP. Furthermore patients should be given records of the type of hip replacement they had and receive any necessary follow-up.