Abstract
Purpose
Correct sizing of prostheses is a considerable factor regarding function and successful rate of total knee arthroplasty (TKA). Patient-specific guide (PSG), using CT preoperative planning for sizing, alignment and bone cutting, has been developed to improve the accuracy and reproducibility of TKA. The purpose of this study is comparing the accuracy of CT-based preoperative sizing in PSG with the conventional femoral sizing instrument.
Methods
From January 2012 to December 2012, fifty-four patients underwent TKA with CT-based PSG. Preoperative sizing was compared to the component size measured intra-operatively by conventional anterior reference femoral sizing instrument. The actual sizes of implanted components were also recorded to analyze the accuracy of each measurement.
Results
By 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 and tibial components comparing to the actual size was 96.3% (95%CI: 87–99%) and 88.9% (95%CI:77–5), respectively.
Conclusions
Femoral component sizing with a conventional instrument is a simple and commonly used technique, but its accuracy remains questionable. It should be recognized by the surgeons that the instrument might lead to an oversized component. The accuracy of sizing in PSG is improved due to the advantage of preoperative CT sizing.
