Background: National and regional arthroplasty registries have been used to study the results of primary total knee arthroplasties. The purpose of this paper was to present the results of revision total knee replacements and describe predictors of survival of those replacements, with repeat revision as the end point.
Methods: The nationwide Finnish Arthroplasty Registry included 2637 revision total knee arthroplasties from 1990 through 2002. Survivorship of the revision total knee arthroplasties was analyzed, with repeat revision as the end point. The survivorship analyses comprised evaluations of the proportional hazards assumption followed by calculations of univariate and multivariate statistics and model diagnostics as appropriate.
Results: The survival rate following the revision total knee arthroplasties was 95% (95% confidence interval, 94% to 96%) at two years (1874 knees), 89% (95% confidence interval, 88% to 90%) at five years (944 knees), and 79% (95% confidence interval, 78% to 81%) at ten years (141 knees). Multivariate regression analysis showed the most significant predictors of prosthetic survival to be the age of the patient and the life in service of the primary total knee replacement (that is, the time between the primary total knee replacement and the revision). Survivorship was also significantly predicted by the year of the first revision total knee arthroplasty and the reason for the revision.
Conclusions: An age greater than seventy years, revision five years or more after the primary arthroplasty, and absence of patellar subluxation are positive indicators of survival of a revision total knee replacement. We believe that normal aging as well as the deconditioning effect of disease (osteoarthritis and rheumatoid arthritis) and its treatment (primary total knee replacement) may lead to a reduced activity level, which, together with a presumed reluctance to operate on elderly patients, protects against repeat revisions.
Level of evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.