BMJ 2018;360:k566

Follow-up for patients with metal-on-metal hip replacements: are the new MHRA recommendations justified?

Gulraj S Matharu, orthopaedic registrar1 2, Andrew Judge, professor of translational statistics1 2 3, Hemant G Pandit, professor of orthopaedic surgery1 4, David W Murray, professor of orthopaedic surgery1

Hip

Recent MHRA guidance for the surveillance of people with metal-on-metal hip replacements are onerous, costly, and insufficiently evidence based, argue Gulraj Matharu and colleagues

Metal-on-metal hips were commonly used in young active patients with arthritis, with about 1.5 million implanted worldwide.1 2 3 However, the devices experienced high short term failure rates,4 5 and many patients have had to have revision surgery because of abnormal reactions to materials generated by the implants (collectively termed adverse reactions to metal debris).1 2 6 Metal-on-metal hip implants are now rarely used.1 2

Failure of conventional hip implants is associated with symptomatic bone damage and requires revision with a larger implant. However, adverse reactions to metal debris from metal-on-metal implants are associated with destruction of soft tissue (muscles, tendons, neurovasculature) as well as bone. The soft tissue destruction is often irreparable,7 8 resulting in many patients doing poorly after revision procedures.8 Furthermore, irreversible bone and soft tissue damage can occur without noticeable symptoms.9 A few patients also develop systemic symptoms from exposure to high levels of metal ions, though these usually resolve after revision surgery (box 1). Reassuringly, large cohort studies have reported that patients with metal-on-metal hips are not at increased risk of cancer, heart failure, or death compared with patients with conventional hip replacements.13 14 15 16 17

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