Pose estimation of artificial knee implants in fluoroscopy images using a template matching technique

The paper describes an algorithm to estimate the position and orientation (pose) of artificial knee implants from X-ray fluoroscopy images using computer vision. The resulting information is used to determine the kinematics of bone motion in implanted knees. This determination can be used to support the development of improved prosthetic knee implants, which currently have a limited life span due to premature wear of the polyethylene material at the joint surface. The algorithm determines the full 6 degree of freedom translation and rotation of knee components. This is necessary for artificial knees which have shown significant rotation out of the sagittal plane, in particular internal/external rotations. By creating a library of images of components at known orientation and performing a template matching technique, the 3D pose of the femoral and tibial components are determined. The entire process, when used at certain knee angles, gives a representation of the positions in contact during normal knee motion.