Survival of Hip and Knee Arthroplasty in the United States Using Medicare Data

Survivorship of hip and knee arthroplasty has been investigated for the Scandinavian population with the aid of implants registries [1-2]. This study examines the use of Medicare data to evaluate survival of hip and knee implants. The 5% sample of Medicare claims from 1997 to 2004 was examined for hip and knee arthroplasty claims. Medicare beneficiary ID was used to follow patients longitudinally between primary and revision surgery. During the 8-year study period, 30600 and 62882 primary total hip or knee arthroplasties, respectively, were extracted. We further excluded patients with traumatic fractures, bone cancer, health maintenance organization enrollees, and those who did not receive both parts A and B coverage. Survivorship was assessed by the Kaplan-Meier and Cox regression methods. Overall, the Kaplan-Meier estimate showed that after 8 years since the primary surgery, 93.6% of total hip arthroplasties and 96.2% of total knee arthroplasties remained revision-free among the elderly Medicare population. Men had a significantly higher risk of knee revision than women, but no significant sex difference among hip revision. Older patients had a reduced risk of revision as compared with younger patients. This study demonstrated the feasibility of Medicare data as a source of hip and knee implant survival. However, Medicare data are lacking in certain critical information such as the reasons for revision, the design of implants, and the bearing materials used. These deficiencies could be addressed with a formal US registry and more specific, mandated reporting requirements. The study also identified some interesting and significant differences in prosthesis outcome that warrant further investigation.