problems with MoM articulation

I got this the other day from the BOA - is the AAOS doing something similar?

Metal on metal articulation in hip surgery



Both the British Hip Society and British Orthopaedic Association feel that it is important to ensure that all surgeons either performing, assessing or revising metal on metal bearing hip resurfacing or replacement are fully aware of some of the current developments in this area.



The History



It is known that all forms of prosthetic hip replacement have design and material associated problems; no one has yet invented a hip that will last for ever in all cases. Tissue reactions of varying types have been documented around the majority, if not all forms of hip replacement and represent part of the risk that is accepted when hip surgery is performed. Undoubtedly there are excellent reported results for a number of metal on metal hip resurfacing/replacements world wide. However, following a number of publications/presentations about the local and potential systemic effects of metal on metal hip articulation, the BOA set up a committee 2 years ago to review the evidence and science to ensure that patients were not being put at risk. This committee, along with the Mutagenicity Committee reporting to the Medical Protection Agency and Medicines and Healthcare Related products Agency, noted that whilst there was experimental evidence that the wear products from some metal on metal articulations could cause genetic damage to cells, to date there had been no reported clinical cases indicating that whilst this was a potential problem it had not presented as a clinical problem. The guidance offered was that, as with all surgical procedures, all patients should have the possible risks and benefits explained and caution exercised in women of childbearing age. There were however a small number of reports of a local tissue reaction around metal on metal hip articulations the cause of which was unknown. It was noted that metal sensitivity, local concentrations of metal ions and implant design and surgical technique were possible factors. As you may be aware the BHS have already organised and run symposia on the potential problems of M/M at the BHS meeting in Leeds and at the BOA in Manchester



Subsequently in January 2008 MHRA contacted the British Hip Society and the BOA as the MHRA had received reports of soft tissue problems around hip replacements with metal bearings, including surface replacements. MHRA wished to discuss these findings with Steve Cannon (BOA President) and Keith Tucker (BHS President). It was thought appropriate to invite members of the Steering Committee from the NJR to contribute to the group.



Those attending were Susanne Ludgate (MHRA), Andy Crosbie (MHRA), Elsie Damien (MHRA), Steve Cannon (BOA),Bill Darling(Chair, NJR Steering Committee), Paul Gregg (Vice Chair, NJR Steering Committee), Martyn Porter BHS Past President and Member, NJR Steering Committee), Keith Tucker (BHS and member NJR Steering Committee). The meeting was held in the Robert Jones Board Room at the BOA offices in Lincoln’s Inn Field on 28 January.



All members present were aware of the small incidence of abnormal reaction to certain metal/metal implants. What was not known is:-



(a) The extent of the problem



(b) The nature of the problem, whether this is idiosyncratic to certain patients or whether it is a feature of poor surgery, poor design or poor implant manufacture.



It was suggested:



· The National Joint Registry to identify all metal on metal bearings and sub-group them to the different types, including codes, whether they were surface replacement or other M/M bearings.



· The NJR will be asked to tabulate all revisions of M/M bearing hips, including designs and details. There has been increasing concern about large metal on metal bearings with stems. This type of hip replacement has not been submitted to the Orthopaedic Data Evaluation Panel for review.



· Revision rates for M/M per unit/surgeon per year to be determined.



· Revision rate to be linked to number of operations performed by individual surgeons (is this a problem more common in inexperienced hands?)



Other possible suggestions were:



· To undertake an NJR Patient Reported Outcome Measures Study collecting data from patients. Patients would know whether they were having pain, etc.



· To approach the Histopathology Departments of the hospitals where the revision surgery was undertaken to obtain histological reports, etc. Steve Cannon made the point that many Trusts will not have a Histopathologist of sufficient experience to give a worthwhile report and he wondered whether surgeons would actually send specimens. The BHS Executive (meeting on 20 January) felt that most surgeons would take a specimen if they encountered abnormal looking tissues. (Steve Cannon confirmed that the RNOH retrieval centre would be pleased to receive histological slides from other Trusts for verification.)



Bill Darling (Chair, NJR Steering Committee), made it very clear that he was very much in favour of the NJR helping with this investigation and was pleased to add his support. He felt it was a very worthwhile use of NJR. It was also noted that we are unlikely to find out about metal on metal failure without the revision surgeons reporting to NJR. The NJR have agreed financial support for their part of the study.



It was suggested that John Skinner should head up a small group, to work out a way forward. It was agreed that this group should include John Skinner, Andy Crosbie (MHRA), the President of the British Hip Society and a representative from NJR. The group would have the power to co-opt as necessary.



On 20 February: Elaine Young, NJR Project Manager at the Department of Health, confirmed that there appeared to be merit in the proposed working group to be chaired by John Skinner but that further discussion would take place at the British Hip Society in Norwich on 28 February, where Andy Crosbie from the MHRA was present.



At that BHS meeting Andy Crosbie presented the view from the MRHA, indicating that a number of reports about tissue reactions around metal on metal bearings had been received. He reported the finding of the Mutagenicity Committee and the importance of informing patients about potential risks but asked BHS members to report all cases of revision and tissue reaction to the MRHA. John Skinner summed up the clinical evidence and proposed a mechanism for investigating the issues with implant retrieval, soft tissue analysis and metal iron concentration assay. Clare Marx then chaired a session about metal on metal resurfacing and in the period for discussion asked whether BHS members had encountered patients with metal on metal bearing who were complaining of pain; the majority of members present indicated they had (though it is recognised that patients can have pain following any type of hip replacement). The issue of metal on metal was subsequently discussed at the business meeting of the Hip Society and the merit of setting up of a working party to report to the MRHA under the chairmanship of John Skinner was confirmed.



The current Situation



The BHS and BOA propose that all cases of revision hip surgery for pain and soft tissue reaction around metal on metal hip resurfacing/replacement articulation are reported to the MHRA and that, in all cases of proposed revision, either the Stanmore Group or other groups with a histological and metal ion interest are contacted prior to revision so the appropriate specimens can be taken at the time of surgery. It is also imperative that all radiographs and any other imaging are collected and made available to the Working Party. The Stanmore retrieval centre is linked to UCL and Imperial College and has access to Harwell and the University of Cambridge (a very potent group!) ABHI have agreed to fund a lot of the research that will be undertaken; many of the implant companies will be contributing substantial amounts of money to the project and we are very grateful to them



The BOA and BHS ask all members to support the working party chaired by John Skinner and report all cases to the working party. This working party is entirely appropriate as it had arisen out of meeting at the BOA involving Susanne Ludgate MHRA Medical Director and subsequently supported by Elaine Young, DH NJR Project Manager. It is recognised that in isolation neither the BOA, BHS, MHRA nor NJR could provide the answers working alone but collaborating together through a working party they potentially could.



The safety of patients is paramount. We believe that this collaboration between the BHS, BOA MHRA and NJR is the responsible way forward. This will ensure that the balance between a surgical intervention that can confer massive benefits to patients and the possible risks is assessed scientifically so that our patients will have the opportunity receive the best possible care in the future.



The Inaugural MHRA/BOA/BHS Metal–on-Metal Hip Group Meeting took place on 23 April 2008 chaired by John Skinner in London. This is to be an expert advisory group working under the auspices of the MHRA. The initial programme of work will be to define a mechanism to identify and collect all available information so as to understand the extent and science behind the observations. Our aim will be to keep the membership of the BOA and BHS fully informed of any developments.