Comparative study of femoral component sizing in TKA between custom cutting block and intraoperative anterior reference sizing

BackgroundCorrect sizing of prostheses is a considerable factor regarding function and successful rate of total knee arthroplasty (TKA). The purpose of this study is comparing the accuracy of CT-based preoperative sizing in patient-specific guide (PSG) with the conventional femoral component-sizing instrument.MethodsFifty-four patients underwent TKA with CT-based PSG. Preoperative sizing was compared to the component size measured intraoperatively by conventional anterior reference femoral-sizing instrument. The actual sizes of implanted components were also recorded to analyze the accuracy of each measurement.ResultsBy comparing to CT preoperative planning, the measurement of femoral size with the conventional anterior reference instrument showed 55.6% of equivalent size, 37% of increased size and 7.4% of decreased size with interclass correlation of 0.914 (0.852–0.950). The measurement by two surgeons showed 42.6% and 57.4% equivalent to the actual size (53.7% and 38.9% larger sizes). The accuracy of CT preoperative sizing in femoral component on comparing to the actual size was 96.3%.ConclusionAccuracy of femoral component sizing with a conventional instrument remains questionable. It might lead to an oversized component. The accuracy of sizing in PSG is improved due to the advantage of preoperative CT sizing.