CORR Insights®: Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?

A s populations increase in size, and as total hip arthroplasty is increasingly performed in younger patients, the burden on healthcare systems grows. Implant survivorship beyond two decades is becoming an imperative. Unfortunately, many hip implants have been introduced—often as minor modifications of a successful design—only to fail catastrophically. Joint registries pioneered by the Scandinavian countries are powerful tools with which to compare implants in the long-term, but detection of underperforming implants sooner remains difficult because registries generally have focused on the endpoint of revision, rather than on signs of failure that may be evident earlier on. By the time it is apparent that an implant does not have acceptable long-term survival, many thousands, if not tens of thousands, have been implanted. Radiostereometric Analysis (RSA) has been shown to be adept at detecting implants that are prone to early failure long before the evidence was apparent from longitudinal studies or registry data [2]. However, RSA can be time consuming and labor intensive, and it calls for modified implants. For these reasons, RSA has not become established in many centers around the world. Traditionally, most studies came from those centers (mainly in Europe) where it has long been an integral part of the research program of institutions that have focused on it. This situation has recently changed with the advent of greater computing power and software that accelerates the process, and model-based systems eradicating the need for modified components. But, as with the continuing iteration of hip components potentially leading to a failed design, the modification of RSA must not diminish its accuracy in the quest for it to be easier and quicker.