Statistical analysis of failure times in total joint replacement

Time to revision is an important criterion describing the quality of implan ts in total joint surgery. Estimates of failure probabilities are required to inform a patient about the risk of suffering a reoperation. Also, regres sion models are used for comparing different prosthesis designs. Typically, patients dying before a revision are considered as censored for time to pr osthesis failure. We argue that this technique is inadequate for estimation of failure probabilities and insufficient for comparison of different desi gns. We propose a new approach based on a competing risk model to account f or concurrent mortality. We describe differences in the estimation of failu re probabilities and in the interpretation of regression models for implant failure. Additionally, we introduce a random effects term in the regressio n model to account for potential dependencies in the failure times of bilat erally treated patients. The new approach is illustrated with fictitious da ta and data from an observational study conducted at a specialized hospital in Switzerland. (C) 2001 Elsevier Science Inc. All rights reserved.