A key government experiment that set out to lower costs and coordinate care for Medicare patients — now the blueprint for an innovation the Obama administration is trying to move to a national scale — has failed to save a substantial amount of money.

The five-year test enlisted 10 leading health systems around the country and offered financial bonuses if they could save enough by treating older patients more efficiently while providing high-quality care…

The uneven progress is significant because the experiment involves “accountable care organizations,” one of the hottest trends in health policy and an idea included in the year-old federal law intended to overhaul the nation’s health-care system.