Risk factors for long-term failure of orthopaedic medical devices: taking advantage of RSA as an early detection tool

Abstract

The longevity of total knee implants may be impaired by aseptic loosening of the components within the bone. Aseptic loosening remains the leading cause of revision surgery. In the past decades, many implant design aspects and surgical techniques have been changed in an attempt to decrease the risk of loosening. Given that radiostereometric analysis (RSA) is a highly accurate method to detect early implant migration which is predictive for late loosening, new implant designs should ideally be tested with RSA before widespread introduction onto the market. In this thesis, we present the results of four randomized controlled trials studying the effect of such changes in design on implant migration with use of RSA. We also pooled several RSA studies to be able to analyze the effect of other possible risk factors, including patient characteristics and surgical technique. We show that slight changes in implant design may increase the risk of loosening considerably, while other factors that are often thought to be associated with an increased risk (such as a high body mass index) do not appear to have a large effect.