Accuracy of a novel, automated 2D-3D registration software for measuring cup position in total hip arthroplasty

This study evaluated the accuracy of an automated 2D-3D registration software for matching preoperative 3D models of the pelvis and acetabular component to intraoperative 2D fluoroscopy images in total hip arthroplasty (THA).

We developed a 2D-3D registration software that registers a 3D model of the pelvis from preoperative CT and a 3D model of the acetabular implant to intraoperative fluoroscopic imaging, thereby calculating the implant position relative to the 3D pelvic reference frame. A total of 145 datasets were used including 65 digitally reconstructed radiographs, 20 dry bone phantoms datasets and 60 clinical datasets with preoperative CT and intraoperative fluoroscopy imaging. Achieved acetabular positions from the clinical images were determined from post-operative CT using a 3D/3D registration method. Accuracy was assessed by comparing the calculated acetabular position from the 2D-3D software to the ground truth data.

Mean absolute difference between ground truth and the 2D-3D software was 1.9° [signed error range: -4.4, 4.8] for inclination, 1.5° [-7.3, 4.1] for anteversion, 1.6 mm [-5, 3.8] for cup height and 1.8 mm [-7.3, 4.1] for depth across all datasets. In total, 100% of inclination results and 98% of anteversion results were within 5° while 90% of height and 81% of depth results were within 3 mm.

We validated the accuracy of an automated 2D-3D registration software for use in THA. While our method requires preoperative data from CT, the results are comparable to robotics and image-based navigation, and present a promising, simple technology that can be easily integrated into an operating room for THA.