No bias of ignored bilaterality when analysing the revision risk of knee prostheses: Analysis of a population based sample of 44590 patients with 55298 knee prostheses from the national Swedish Knee Arthroplasty Register

摘要

BackgroundThe current practice of the Swedish Knee Register is not to take into consideration if one or both knees in a patient are subject to surgery when evaluating risk of revision after arthroplasty. Risk calculations are typically done by statistical methods, such as Kaplan-Meier analyses and Cox's proportional hazards models, that are based on the assumption that observed events are independent, and this is rarely appreciated. The purpose of this study was to investigate if ignoring bilateral operations when using these methods biases the results.