Osteoarthritis of the hip is a common disease, and in the past 50 years it has been possible to treat it successfully with joint replacement surgery. Surgery in younger people with higher demands for activity is increasingly being undertaken owing to modern implants and refined surgical techniques. However, in such situations, implants need to have extended longevity and no long term adverse effects. Two linked research studies examine large national datasets from Finland (doi:10.1136/bmj.e4646) and the United Kingdom (doi:10.1136/bmj.e2383) to estimate the risk of cancer in patients with metal-on-metal hip implants.1 2

With potentially lower wear,3 lower risk of dislocation, and better outcomes than metal-on-polyethylene articulations,4 modern metal-on-metal implants, including large metal heads and hip resurfacing, have become popular. These implants currently account for 35% of hip replacements in United States and 14% in the United Kingdom. Recent reports of peri-prosthetic adverse soft tissue reactions and high blood metal ion concentrations have raised concern that exposure …