The Medicines and Healthcare products Regulatory Agency (MHRA) of the United Kingdom has issued a Medical Device Alert (MDA) providing updated advice to assist the early detection of soft tissue reactions in patients implanted with metal-on-metal (MoM) hip replacements.

MHRA, in consultation with its independent Metal-on-Metal Expert Advisory Group (MoM EAG), has continued to monitor the performance of MoM hip joint articulations for the occurrence of soft tissue reaction associated with these devices. The majority of patients with MoM hip replacements currently have well-functioning hips. However, some patients will develop progressive soft tissue reactions to the wear debris associated with MoM articulations. Data from the 13th Annual Report of the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man, published in 2016, continued to show a risk of adverse soft tissue reaction to particulate debris. MHRA's clinical orthopaedic experts have also observed that soft tissue necrosis may occur in both asymptomatic and symptomatic patients, and believe early detection of these events should give a better revision outcome should this becomes necessary. This MDA is being sent to general practitioners (GPs) for information only, in case patients ask about the contents of this notice. GPs need take no further action on receipt of this alert.

MHRA is instructing users to take the following actions:-

• Put updated systems in place for the follow-up and investigation of all patients implanted with MoM hip replacements.
• Follow the patient management advice given in table 1* of the appendix of the MDA in conjunction with the following guidance notes:
  • MARS MRI scans or ultrasound scans should carry more weight in decision-making than isolated blood metal levels alone.
  • Patients with muscle or bone damage shown on MARS MRI are those of most concern.
  • An isolated fluid collection (unless very large) around the joint in an asymptomatic patient, can be observed with interval scanning and clinical review.
  • Local symptoms may occur in otherwise well-functioning hips; these should be investigated for other causes.
  • Rising blood metal levels may indicate potential for soft tissue reaction.
  • After revision surgery, whole blood metal levels of chromium and/or cobalt are expected to fall and symptoms to improve. Persistent symptoms should be investigated for potential causes that include: failure of fixation, component loosening, infection and instability. If no cause is found, further blood metal level measurement and cross-sectional imaging should be considered.
  • The advice in table 1 has been produced based on current knowledge, it will not necessarily cover all clinical situations. Each patient must be assessed individually.

* In all cases, the benefit of ionising radiation screening should be weighed against the risks from radiation exposure on an individual patient basis, in line with the requirements of The Ionising Radiation (Medical Exposure) Regulations 2000.

For details, please refer to the MHRA's website:
https://www.gov.uk/drug-device-alerts/all-metal-on-metal-mom-hip-replacements-updated-advice-for-follow-up-of-patients

Posted on 30 June 2017