'No proof' quarter of hip implants work Last year the Medicines and Healthcare products Regulatory Agency (MHRA) announced almost 50,000 patients with "metal-on-metal" hip replacements would need annual checks - including blood tests - over concerns they could cause serious health problems. In October regulators said most types of the devices should no longer be fitted, after a study found unacceptably high failure rates among implants used in 17,000 devices still on the market. It followed a series of investigations by The Daily Telegraph which uncovered the risks posed by some of the implants, and the ease with which failing models were allowed on the market. Metal-on-metal devices have been linked to muscle and bone damage and neurological issues, because tiny ions made up of cobalt and chromium can break off and leak into the blood. The research team, led Sion Glyn-Jones, a consultant orthopaedic surgeon and senior lecturer at the University of Oxford, said the figures about devices used in 2011 were "likely to be an underestimation of the true problem" because much of the evidence which is held on implants was of low quality, or related only to short-term outcomes. He said: "This is of great concern, particularly in light of the widespread publicity surrounding recent safety problems with regard to some resurfacing and other large diameter metal-on-metal joint replacements." In an accompanying editorial, researchers from Harvard Medical School call for restrictions to stop manufacturers promoting devices or drugs before they have rigorous data to suppot them. It says: "Physicians who adopt new technologies that have little or no evidence of superiority over existing products need to be educated about the implications of their choices. They should also ensure that their patients know about the benefits and risks of the new - but often unproved - medical devices that they are receiving. Devices named in the study as lacking evidence to support their use include the Corial Cemented stem, made by De Puy, the Charnley KS cemented stem, also made by De Puy, the MMC uncemented cup and the Maxera uncemented cup made by Zimmer. The British Hip Society said: "The number of hip implants used in this country without a proven track record is falling year on year. There are fewer unproven prostheses implanted in the UK compared with the practice in almost every other Western country, with the possible exception of Scandinavian countries.