Pose estimation of mobile-bearing total knee arthroplasty using X-ray fluoroscopic images and 3D knematic analysis

To achieve 3D kinematic analysis of total knee arthroplasty (TKA), 2D 3D image registration techniques, which use X-ray fluoroscopic images and computer aided design (CAD) model of the knee implant, have attracted attention in recent years. These techniques could provide information regarding the movement of radiopaque femoral and tibial components but could not provide information of radiolucent polyethylene insert, because the insert silhouette on X-ray image did not appear clearly. Therefore, it was difficult to obtain 3D kinemaitcs of the polyethylene insert, particularly the mobile-bearing insert that move on the tibial component. This study presents a technique and the accuracy for 3D kinematic analysis of the mobile-bearing insert in TKA using X-ray fluoroscopy, and finally performs clinical applications. For a 3D pose estimation technique of the mobile-bearing insert in TKA using X-ray fluoroscopy, tantalum beads and CAD model with its beads are utilized, and the 3D pose of the insert model is estimated using a feature-based 2D 3D image registration technique. In order to validate the accuracy of the present technique, experiments including computer simulation test were performed. The results showed the pose estimation accuracy was sufficient for analyzing mobile-bearing TKA kinematics, and the estimation errors were within 1. 0 mm and 1. 0 degree except for translation parameter perpendicular to X-ray fluoroscopic images. In the clinical applications, seven patients with the mobile-bearing TKA in deep knee bending motion were studied and analyzed. Consequently, the present technique enables us to better understand mobile-bearing TKA kinematics, and this type of evaluation was thought to be helpful for improving implant design and optimizing TKA surgical techniques.