Unicompartmental Knee Arthroplasty: Does a Selection Bias Exist?

Unicompartmental knee arthroplasty (UKA) is a minimally invasive option reported to allow a more rapid recovery and better patient outcomes. However, whether these outcomes are related to selection bias has not been fully investigated. This study examines whether a bias existed in selection of UKA candidates. We compared outcomes of patients who were scheduled for UKA but had the plan changed intraoperatively to total knee arthroplasty (TKA) to two randomly selected contemporaneous control groups: 1) patients planned as UKA who received UKA and 2) patients planned as TKA who received TKA. Our results not only showed a selection bias existed, but also showed patients converted to TKA intraoperatively had similar clinical results to patients receiving UKAs and better results than patients originally scheduled for TKA.