REVISION RATES AFTER KNEE REPLACEMENT IN THE UNITED-STATES

OBJECTIVES. Each year approximately 100,000 Medicare patients undergo knee replacement surgery. Patients, referring physicians, and surgeons must consider a variety of factors when deciding if knee replacement is indicated. One factor in this decision process is the likelihood of revision knee replacement after the initial surgery. This study deter mined the chance that a revision knee replacement will occur and which factors were associated with revision. METHODS. Data on all primary a nd revision knee replacements that were performed on Medicare patients during the years 1985 through 1990 were obtained. The probability tha t a revision knee replacement occurred was modeled from data for all p atients for whom 2 full years of follow-up data were available. Two st rategies for linking revisions to a particular primary knee replacemen t for each patient were developed. Predictive models were developed fo r each linking strategy. ICD-9-CM codes were used to determine hospita lizations for primary knee replacement and revision knee replacement. RESULTS. More than 200,000 hospitalizations for primary knee replaceme nts were performed, with fewer than 3% of them requiring revision with in 2 years. The following factors increase the chance of revision with in 2 years of primary knee replacement: (1) male gender, (2) younger a ge, (3) longer length of hospital stay for the primary knee replacemen t, (4) more diagnoses at the primary knee replacement hospitalization, (5) unspecified arthritis type, (6) surgical complications during the primary knee replacement hospitalization, and (7) primary knee replac ement performed at an urban hospital. CONCLUSIONS. Revision knee repla cement is uncommon. Demographic, clinical, and process factors were re lated to the probability of revision knee replacement.