Predicted survival curves for hip replacements for two male and two female hypothetical individuals with different levels of blood cobalt at 2 and 5 µg/l. Predicted survival curves for hip replacements for two male and two female hypothetical individuals with different levels of blood cobalt at 2 and 5 µg/l. Device is the Birmingham Hip Resurfacing. Time period is in months. Survival curves shown with 95% CI. David J Langton et al. BMJ Open 2013;3:e001541 ©2013 by British Medical Journal Publishing Group