Two House Democrats introduced a bill to create a national database of patients who received artificial hips and knees, a system already used in some other countries to track how patients fare, reduce unnecessary surgeries, and weed out inferior products. The bill would establish a government-backed registry to track patients' results over time and help detect ineffective surgical practices and faulty devices. Patient registries are expected to play an important role in "comparative effectiveness" reviews that the Obama administration hopes will help identify which medical procedures and products work best.