Epidemiology of total knee replacement in the United States Medicare population

Background: There are limited population-based data on the utilization and outcomes of total knee replacement. The aim of the present study was to describe the rates of primary and revision total knee replacement and selected outcomes in persons older than sixty-five years of age in the United States. Methods: Using Medicare claims, we computed annual incidence rates of unilateral elective primary and revision total knee replacement among United States Medicare beneficiaries in the year 2000. Poisson regression was used to assess the relationships between demographic characteristics and the incidence rates of primary and revision knee replacement. Proportional hazards models were used to examine the relationships between the ninety-day rates of complications and demographic and clinical factors. Results: The rate of primary knee replacement was lower in blacks than in whites and in those qualifying for Medicaid supplementation than in those with higher incomes. The complications observed during the ninety days following primary knee replacement included mortality (0.7%), readmission (0.9%), pulmonary embolus (0.8%), wound infection (0.4%), pneumonia (1.4%), and myocardial infarction (0.8%). The complications observed during the ninety days following revision knee replacement were mortality (1.1%), readmission (4.7%), pulmonary embolus (0.5%), wound infection (1.8%), pneumonia (1.4%), and myocardial infarction (1.0%). Blacks had higher rates of mortality, readmission, and wound infection after primary knee replacement than whites did. Patients who qualified for Medicaid supplementation had higher complication rates, particularly after primary knee replacement. Conclusions: Overall, the rates of postoperative complications during the ninety days following total knee replacement are low. In the United States, blacks and individuals with low income undergo total knee replacement less frequently and generally have higher rates of adverse outcomes following primary knee replacement. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.