A WORLDWIDE investigation into medical implants has found that millions of patients are at risk from poorly tested devices. It is time to face the problem.

If a drug has adverse effects or is ineffective, the medication is changed. But it is more difficult and dangerous to remedy an implanted device, such as a cardiac valve, pacemaker, breast implant or artificial joint. Why then is it so much easier to gain approval for medical devices?

The European Medicines Agency evaluates evidence of efficacy and safety in controlled clinical trials before licensing drugs. Most of the …