Unicompartmental knee arthroplasty: 11-year experience from 3929 implants in RIPO register

BackgroundSince 2000, the Register of Prosthetic Orthopedic Implants (RIPO) has been following all hip, knee, and shoulder arthroplasties in the Emilia-Romagna region, comprising 4.5 million inhabitants, in northern Italy. The aim of the present analysis was to present the main figures of unicompartmental knee implants processed from the Registry.MethodsDuring the period 2000-2011, 3929 unicompartmental knee arthroplasties were performed on 3645 resident patients, of which 71% were females. The medial condyle was treated in 94% of cases, where mean age at surgery was 67.3 years and mean body weight was 76.6 kg. The main outcome measure was time to revision of at least one single component. The Kaplan-Meier survival and Cox multivariate analyses have been applied.ResultsAt 10-year follow-up, the percentage of survival was 86.8% (confidence interval (CI) at 95% was 84.1-89.5); total aseptic loosening represented 42% of the causes of failure, pain represented 15%, and sepsis represented 11%. Age at surgery significantly influences the survival of the prosthesis, whatever the reason for revision, while the type of tibial component (monoblock or metal tray) does not appear to be a determinant. Septic failure is not prevented by the use of antibiotic-loaded cement.ConclusionResults are comparable to main orthopedic registries from Scandinavia, Australia, and New Zealand, even if some differences can be highlighted.