Knee and hip replacements are among the most frequently performed inpatient surgeries for Medicare beneficiaries. But the quality and cost of these procedures can vary wildly, and complications such as infections or implant failures are not uncommon. A new billing model unleashed this year by the Centers for Medicare and Medicaid Services aims to improve care and produce savings on these surgeries, and the Northeast Georgia Medical Center in Gainesville is one of just two pilot program hospitals in the state operating the alternative, bundled-payment system.