Ann Marie Schmidt had knee replacement surgery last month. The operation was for an old injury that made walking painful, but the 71-year-old resident of Temple, Texas, has other, more serious conditions. She suffers from neuropathy (nerve pain), scoliosis and meningioma - a type of benign brain tumor. Schmidt is the kind of high-risk patient Medicare worries about as a candidate to land back in the hospital after surgery. Nearly one in five Medicare patients discharged from the hospital is readmitted within 30 days, at a cost of $17 billion every year to Medicare, according to the Centers for Medicare & Medicaid Services. Aside from the expense to Medicare, readmission presents serious health risks for patients. "It's a long list," says Dr Eric Coleman, associate professor of medicine and a geriatrician at the University of Colorado Health Sciences Center. "But the big ones include infection, falls that cause fractures, medication errors, confusion or delir