METAL ON METAL HIP IMPLANTS ALERT

METAL ON METAL HIP IMPLANTS ALERT

Misdiagnosis: lymphoma, breast cancer, sarcomas and melanoma
In April 2010, the UK drug and medical device watchdog, the MHRA issued a Medical Device Alert covering all Metal on Metal hip implants and replacements.
The Alert does includes but is not limited to the controversial DePuy artificial hip and hip resurfacing products. It covers all products of similar design where the ball and socket components of either a total hip replacement or a hip resurfacing system are made of metal.
The Alert was issued by the MHRA because a small number of patients implanted with these hips "may 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."
The MHRA went on to state that "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."
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To date no similar action has been taken to protect patient safety by the Irish Medicines Board (IMB).
Patients who are part of the DePuy Hip Implant Recall are being tested for abnormally high chromium and cobalt ion levels in their blood but not other metal on metal hip implant patients in Ireland are being tested. Given that the potential harm to patients is known and the manufacturing companies who have made substantial profits from selling these implants to the Irish market continue to be licensed by the IMB, it does not seem unreasonable that the IMB should insist that all MoM patients receive the appropriate blood tests.
In the UK meanwhile, the MHRA is sufficiently concerned about these widely used hip implant products to require that the following action be taken in all cases:
Action:
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 evaluationof 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.