3X-Knee: A Novel Technology for 3D Preoperative Planning and Postoperative Evaluation of TKA Based on 2D X-Rays

This chapter introduces a solution called "3X-knee" that can robustly derive 3D models of the lower extremity from 2D long leg standing X-ray radiographs for preoperative planning and postoperative treatment evaluation of total knee arthroplasty (TKA). There are three core components in 3X-knee technology: (1) a knee joint immobilization apparatus, (2) an X-ray image calibration phantom, and (3) a statistical shape model-based 2D-3D reconstruction algorithm. These three components are integrated in a systematic way in 3X-knee to derive 3D models of the complete lower extremity from 2D long leg standing X-ray radiographs acquired in weight-bearing position. More specifically, the knee joint immobilization apparatus will be used to rigidly fix the X-ray calibration phantom with respect to the underlying anatomy during the image acquisition. The calibration phantom then serves two purposes. For one side, the phantom will allow one to calibrate the projection parameters of any acquired X-ray image. For the other side, the phantom also allowsone to track positions of multiple X-ray images of the underlying anatomy without using any additional positional tracker, which is a prerequisite condition for the third component to compute patient-specific 3D models from 2D X-ray images and the associated statistical shape models. Validation studies conducted on both simulated X-ray images and on patients' X-ray data demonstrate the efficacy of the present solution.