This consent form covers the ongoing surveillance and potential revision of metal-on-metal hip resurfacing or large-diameter metal-on-metal total hip replacements. Regular monitoring is essential due to the risk of adverse reactions to metal debris.
Surveillance involves regular blood tests for cobalt and chromium metal ion levels, cross-sectional imaging (MARS-MRI — Metal Artefact Reduction Sequence) to assess for soft tissue reactions (pseudotumour, ALVAL), and clinical assessment. If revision is needed, the metal-on-metal components are removed and replaced with conventional implants through an incision over the hip. Revision takes two to three hours.
The MHRA mandates annual follow-up for all patients with metal-on-metal hip implants. Revision is recommended when there is evidence of adverse reaction to metal debris (ARMD) — including rising metal ion levels, soft tissue mass on imaging, progressive symptoms, or component malposition.
Continued surveillance without revision if the implant is functioning well, metal ions are low, and imaging is normal. Asymptomatic patients with well-positioned implants and low metal ions may not need revision.
For revision: full pre-assessment, blood metal ion levels, MARS-MRI, CT scan to assess bone stock, planning for potential bone loss and complex reconstruction.
For surveillance: early detection of adverse reactions before irreversible damage occurs. For revision: removal of the source of metal debris, resolution of soft tissue reactions, and restoration of hip function.
Longer operating time, more blood loss, and higher complication rates than primary hip replacement.
Metal debris and pseudotumour may have eroded bone, requiring bone grafting or specialised implants.
The gluteal muscles and capsule may be damaged by the pseudotumour.
Higher risk than primary replacement due to soft tissue damage.
Sciatic or femoral nerve may be damaged during revision.
Higher risk than primary replacement.
Periprosthetic fracture during revision.
Even after revision, metal ions may remain elevated for months.
For revision: general or spinal anaesthesia. Significant blood loss requires transfusion capability.
For revision: hospital stay two to five days. Hip precautions for six to twelve weeks depending on the reconstruction. Physiotherapy for hip rehabilitation. Full recovery six to twelve months. Continued metal ion monitoring until levels normalise.
Annual blood metal ions and clinical review (MHRA requirement). MARS-MRI every one to two years or if symptoms change. Ongoing even if asymptomatic.
Not necessarily. Many metal-on-metal hips function well for years. Revision is only recommended when there is evidence of adverse reaction — rising metal ions, abnormal imaging, or progressive symptoms. Ongoing surveillance identifies who needs revision.
Cobalt and chromium are released from the bearing surfaces of metal-on-metal implants. In most patients, levels are very low. Elevated levels may indicate increased wear or adverse tissue reaction.
Most metal-on-metal hips function well. Regular monitoring ensures any problems are detected early. If your metal ion levels are low and imaging is normal, the risk is low.