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Why we don’t recommend resurfacing any more

Medical Device Alert: All metal-on-metal (MoM) hip replacements (MDA/2010/033) Issued: 22 April 2010 at 14:00

DEVICE

All metal-on-metal (MoM) hip replacements.

PROBLEM

The MHRA has received reports of revisions of MoM hip replacements involving soft tissue reactions. These reactions may be associated with unexplained hip pain.

The majority of patients implanted with MoM hip replacements have well functioning hips and are thought to be at a low risk of developing serious problems.

A small number of patients implanted with these hips may, however, develop progressive soft tissue reactions to the wear debris associated with MoM articulations. The debris can cause soft tissue necrosis and adversely affect the results of revision surgery. Early revision of poorly performing MoM hip replacements should give a better revision outcome.

Following extensive consultation with orthopaedic experts and using information from the National Joint Registry for England and Wales, the MHRA is issuing this interim advice to healthcare professionals involved in the management of patients implanted with MoM hip replacements.

The MHRA is continuing to monitor the situation in consultation with orthopaedic experts and may issue further advice.

MDA-2010-069 Final

ACTION

Put systems in place for the follow-up of patients implanted with MoM hip replacements including, where appropriate, blood metal ion measurements and cross sectional imaging.

For patients implanted with MoM hip replacements:
  • follow up patients at least annually for five years postoperatively and more frequently in the presence of symptoms. Beyond five years, follow up in accordance with locally agreed protocols
  • investigate patients with painful MoM hip replacements. Specific tests should include evaluation of cobalt and chromium ion levels in the patient’s blood and cross sectional imaging including MRI or ultrasound scan
  • consider measuring cobalt and chromium ion levels in the blood and/or cross sectional imaging for the following patient groups:
  • patients with radiological features associated with adverse outcomes including component position
  • patients with small component size (hip resurfacing arthroplasty only)
  • cases where the patient or surgeon is concerned about the MoM hip replacement
  • cohorts of patients where there is concern about higher than expected rates of failure
  • if either cobalt or chromium ion levels are elevated above seven parts per billion (ppb), then a second test should be performed three months after the first in order to identify patients who require closer surveillance, which may include cross sectional imaging
  • if imaging reveals soft tissue reactions, fluid collections or tissue masses then consider revision surgery.

British Orthopedist Association – Metal on Metal Hip Replacement and Hip Resurfacing Arthroplasty:  What does the MHRA Device Alert mean?

You will be aware that the MHRA (Medicines and Healthcare products Regulatory Agency) has been investigating the incidence of adverse events associated with metal on metal (MOM) hips.  An Expert Advisory Group was set up to investigate the incidence of problems and to establish guidelines that would help and advise surgeons and patients.  The clinicians on the group are all members of the Hip Society and include John Skinner, Martyn Porter, Keith Tucker, Paul Gregg and Peter Kay.  The NJR, BOA and MHRA were all represented and Jan van er Meulen acted as statistical adviser.  The NJR was used to find cases of revision of MOM and HRA.  A report has now been submitted to the MHRA and the MHRA has released a Medical Device Alert for all MOM bearings.

The key points are that excellent results are reported with MOM hip resurfacing arthroplasty (HRA) and THR from many centres.  It is accepted that MOM bearings have a higher incidence of painful joints.  There are a small but significant number of patients who develop pain and significant tissue damage.

It is felt that pain with MOM bearings should be investigated as we are still uncertain which patients are likely to progress or develop serious soft tissue reactions. These reactions (variously referred to as ALVAL, Pseudo tumour, effusions, bursae, tissue necrosis and ARMD (adverse reaction to metal debris)) are rare and probably have an incidence of somewhere between 1 and 9 per thousand devices implanted. It is possible that the incidence is higher in some areas and more frequent with some devices than others. The MRHA feel that there is insufficient evidence to highlight one particular device at this stage and it is fair to say that adverse reactions have been reported with all MOM devices.

The advice on a practical level is straight forward and probably just represents best practice for patients by their surgeons. It is likely that there will be media interest as the MHRA is briefing the press and that there will be a high level of enquiry by patients to trusts, hospitals and surgeons.

As the advice stands it does not constitute a formal recall of all patients. It means that all patients should probably be contacted by letter and told of the Alert. Patients can be reassured that in the absence of pain or symptoms, the serious soft tissue reactions/tissue necrosis are rare.

If patients are anxious then they may be offered a blood test to measure cobalt and chromium levels. The main purpose of this is that low levels are reassuring and strongly predict not having an adverse outcome or soft tissue reaction. Slightly elevated levels or very high levels are less certainly understood but probably correlate with high wear at the bearing. Ultimately in the presence of pain, high cup inclination angle and elevated metal ions then revision should be considered. It can be argued that in the presence of pain and high inclination angles revision should be considered anyway.

It is likely that cobalt and chromium levels may be useful for screening but they are not well understood at present. High levels may start as low as 7 ppb for either metal. High levels have a higher correlation with revision, pain and soft tissue reactions, but the correlation is not absolute in the short term. It may be longer that follow up will clarify this.

The alert mandates follow up at least annually, for the first five years and then as per locally agreed protocol thereafter. It may be that life-long review is appropriate for some components. Not all patients will require in person follow up. It may be that postal questionnaire or phone call is all that is required in asymptomatic stable joints and those with proven provenance. Patients should be warned to contact the surgeon/hospital if symptoms change or function or hip scores deteriorate.

All revisions should be documented in the NJR and several centres are happy to analyse the implant for cause of failure.

It should be noted that there are several causes of failure including impingement, psoas/adductor tendonitis, failure of fixation of components, femoral neck fracture or resorption/AVN, neurological, referred pain from spine, sacrum or adnexae, hernia. These are not generally associated with the soft tissue reactions that have triggered the MHRA intervention.

It seems that we as the orthopaedic profession will be called on to reassure, investigate and manage patients through this difficult time. We believe that there remains uncertainty as to the incidence of this problem and that although fluid collections around these implants may be common, severe reactions are thankfully rare. If they occur, the surgery may be complex as the soft tissue damage reported can be severe.

Pain in patients with MOM bearings should be investigated and if it is associated with features such as high component inclination angles, high metal ion levels and soft tissue reactions, then this should be taken seriously. It does seem to be a progressive condition and early revision in selected cases may be sensible.

It will be a long time before we know whether this is an overreaction but we all agree that patient safety is paramount. In the current climate of uncertainty the advice to follow up our patients seems sensible and may even facilitate good practice with PCT/insurance company support.

Measuring cobalt and chromium ions

Chromium and cobalt and other metals present in surgical implants are usually measured by inductively coupled plasma mass spectrometry (ICPMS) using either quadruple (QICPMS) or high resolution mass spectrometry (HR-ICPMS). Both are capable of accurate analysis, but only HR-ICPMS instruments will allow the measurement of some other metal ions such as titanium and nickel. Electro thermal atomisation atomic absorption spectrometry may also be used, but is less common now in the leading trace element analysis laboratories.

Blood samples for trace element analysis must be collected in trace element free tubes. Tubes are available with either EDTA anticoagulant for the analysis of whole blood samples or with no additive for the analysis of serum samples. There is a small difference in results obtained from whole blood and serum, but both can be used to assess release of laboratory without the need for separation of serum, a step which may allow potential for sample contamination. Some laboratories may advise against the use of stainless steel needles for sample collection, but the amount of contamination introduced via this route is usually low relative to the amount of chromium and cobalt released from high wear joints.

Synovial fluid samples should be collected into the same blood collection tubes or into sterile plastic ‘universal’ containers. Urine samples should be random collections voided directly into a plastic universal container, although in rare circumstances a timed 24-hour collection may be appropriate. In this case the laboratory should be contacted for advice before sample collection is commenced. In all circumstances glass and metal-containing containers must be avoided.

Trace element assays are available from the Supra-Regional Trace Element laboratories. In all cases the samples must be referred to the analytical laboratory via the local clinical biochemistry laboratory. Most laboratories will be unable to accept referrals from individual surgeons. All laboratories use QICPMS. HR-ICPMS is also available at London (Imperial College).

All laboratories participate in the national QC programme TEQAS, run from the School of Molecular and Biomedical Sciences, University of Surrey. This includes assessment of chromium and cobalt. Most laboratories will also participate in other international EQA schemes.

http://www.mhra.gov.uk/Publications/Safetywarnings/MedicalDeviceAlerts/CON082089

Medical Device Alert: DePuy ASR acetabular cups used in hip resurfacing arthroplasty and total hip replacement (MDA/2010/044)

Issued: 25 May 2010 at 14:30
DEVICE

DePuy ASRTM acetabular cups used in hip resurfacing arthroplasty and total hip replacement.

DePuy ASRTM acetabular cups are used with:

• ASRTM surface replacement heads for hip resurfacing arthroplasty; or

• ASRTM XL femoral heads for total hip replacement.

PROBLEM

The MHRA has received reports of higher than anticipated rates of revision for ASRTM acetabular cups.

Subsequent to the publication of the MHRA’s Medical Device Alert MDA/2010/033 for metal-on-metal hip replacements on 22 April 2010, the National Joint Registry (NJR) of England and Wales informed the MHRA that ASRTM acetabular cups had been identified from registry data as having higher than anticipated rates of revision in hip resurfacing and total hip replacement procedures (see Appendix). The MHRA has also received similar reports from two of the 257 clinical centres in the UK that have implanted these devices.

DePuy produces two different instruction documents for this device: the instructions for use (IFU) supplied with the device, and the surgical technique manual. A cup inclination angle of 45º is recommended for reaming and implantation in all versions of the surgical technique manual. However, the original IFU did not contain reference to specific cup placement angles. Based on post-market experience, in October 2008, the manufacturer added to its IFU (Revision C) a recommended cup inclination angle of between 40º and 45º and distributed a document entitled ‘The importance of correct acetabular component positioning’ highlighting the importance of cup angles to implanting surgeons from February 2009.

All users were informed of correct cup angles in the manufacturer’s Field Safety Notice of 8 March 2010. The FSN did not recommend any additional follow-up for patients in the absence of symptoms. However, the performance of devices implanted outside the manufacturer’s currently recommended angle range (40º– 45º) is not known.

DePuy ASRTM acetabular cups have been in clinical use in the UK since 2003.

ACTION

Put systems in place for the follow-up of patients already implanted with ASRTM acetabular cups.Ensure that ASRTM acetabular cups are implanted in accordance with the manufacturer’s instructions for use as amended in 2008 (Revision C).

Follow up all patients implanted with ASRTM acetabular cups at least annually for five years postoperatively. Beyond five years, follow up in accordance with locally agreed protocols.

For patients already implanted with ASRTM acetabular cups who are symptomatic or implanted with cup angle greater than 45º and particularly where a small component has been implanted:

  • consider measuring cobalt and chromium ion levels in whole blood and/or performing cross sectional imaging including MRI or ultrasound scan
  • in line with MDA/2010/033, if metal ion levels in whole blood are elevated above 120 nmol/L (cobalt) or 135 nmol/L (chromium) [ie seven parts per billion (ppb) for either metal ion], a second test should be performed three months after the first in order to identify patients who require closer surveillance, which may include cross sectional imaging
  • if MRI or ultrasound scan reveals soft tissue reactions, fluid collections or tissue masses then consider revision surgery

For new patients ensure that ASRTM acetabular cups are implanted in accordance with the manufacturer’s most recent IFU (Revision C) and surgical technique (version 3) and in particular that the cup inclination angle is between 40º and 45º.

Note: Measurements of cobalt or chromium ions should be carried out:

National Joint Registry

The three year revision rates of the cemented cups varied from 0.4% for the Wroblewski Golf Ball and 0.6% for the Low Profile Muller to 2.2% for the Apollo. The statistical evidence that brand is associated with revision rates is very strong (p < 0.0001).

There was similar variation in the three year revision rates of the cementless cups, although the lowest was 1.1% for the Reflection. The highest revision rate was for the Exceed (2.8%) with similar revision rates for the CSF (2.7%) and EPF-Plus (2.6%). Statistical testing indicates that there is strong statistical evidence for an association between brand and revision rate (p = 0.005).

Six hip resurfacing brands were entered at least 500 times (Table 3.4). The lowest three year revision rate was seen for the BHR (3.3%) and the highest for the ASR (7.5%) and Converse (7.4%). There is very strong statistical evidence for an association between brand and revision rate (p < 0.0001).

Table: Revision at three years according to resurfacing cup brands for primary hip replacement procedures undertaken between 1st April 2003 and 30th November 2008, which were linked to a HES episode.

Revision rates according to bearing surface

Of the 157,232 first primary hip replacements, data on bearing surface were entered in the NJR for 120,987, excluding all resurfacing procedures and implants with large head sizes (>32mm). Table 3.5 presents the three year revision rates for the four most frequently entered articulation combinations.

The highest revision rate was seen in patients with a ceramic on ceramic surface (2.2%) and lowest in those with a metal on polyethylene surface (1.6%). However, multivariable analysis adjusting for age, sex, physical status and prosthesis type demonstrated that the statistical evidence for an effect of bearing surface on revision rate was weaker (p = 0.07).

Table: Revision at three years according to bearing surface for primary hip replacement procedures (excluding all resurfacing procedures) undertaken between 1st April 2003 and 30th November 2008, which were linked to a HES episode.

Table: Revision Rates of Primary Total Resurfacing Hip Replacement

Note: Two resurfacing hip procedures using only a Conserve resurfacing head and no acetabular component have been removed from the above table.

Table: Yearly Cumulative Percent Revision of Primary Total Resurfacing Hip Replacement

Note:  Two resurfacing hip procedures using only a Conserve resurfacing head and no acetabular component have been removed from the above table.

Associate Professor Michael J. Neil

Michael John Neil is a member of the Department of Orthopaedic Surgery at St. Vincent’s Healthcare Campus, Sydney, a tertiary referral institution and teaching hospital of the University of NSW, which encompasses St. Vincent’s Public and Private Hospitals, St.Vincent’s Clinic, The Garvan Institute of Medical Research and the Sacred Heart Hospice.

His clinical interest and expertise is in joint replacement surgery of the hip and knee.  Since his appointment to the staff in 1989, A/Prof. Neil has introduced a number of surgical procedures to St. Vincent’s which are now performed routinely in the treatment of hip and knee arthritis.  These include revision total hip and knee replacement using the S-ROM modular cementless prosthesis, structural allograft (bone donated from another person) reconstruction of the hip and knee during revision surgery, minimally invasive unicompartmental knee replacement using the Repicci technique, Birmingham hip resurfacing, patello-femoral replacement, core decompression of the femoral head for avascular necrosis and arthroscopic surgery of the hip.

A/Prof. Neil performs on average approximately 800 operative procedures per year of which 400 are joint replacement procedures.  These comprise of 150 total hip replacements, 100 total knee replacements,100 Repicci unicompartmental knee replacements and 50 revision (re-do) hip and knee replacements.  Operations are only performed on St Vincent’s Campus, either at St Vincent’s Private Hospital or the Day Surgery Unit, St Vincent’s Clinic.

A/Prof. Neil has presented and published widely on joint replacement surgery and is a frequently invited faculty member at scientific meetings in Australia and overseas.  In August 2006, he was appointed to the editorial board of the Journal of Arthroplasty, the representative journal for the American Association of Hip and Knee Surgeons.  He is also a member of the Delta Orthopaedic Group formed ten years ago for the purpose of orthopaedic education with the use of live operative demonstrations and lectures both in Australia and overseas.  He is Conjoint Associate Professor of Orthopaedic Surgery in the Faculty of Medicine at the University of New South Wales and has served as Chairman of the Southside Board of Studies of the Australian Orthopaedic Association, the body responsible for the selection and training of young orthopaedic surgeons.  A post-graduate fellowship programme in arthroplasty commenced under his supervision in 2003 and attracts applicants both from Australia and overseas for a minimum period of 6 months. He is intensely interested in orthopaedic education, training and research.

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