Accurate 3D pose estimation method for polyethylene wear assessment in total knee replacement

This study describes a new method for evaluating polyethylene wear in total knee prosthesis. Since the amount of wear is dependent on a number of variables such as weight and activity of the patient, the amount should be estimated based on in-vivo measurement. A computer vision technique called 3D/2D matching is employed to perform in-vivo assessment using single-plane radiograph. By the 3D/2D matching algorithm the three-dimensional position and orientation (pose) of knee implants is estimated to measure the femorotibial distance which is defined as the shortest perpendicular distance from the tibial tray to the femoral component. The accuracy of the proposed 3D/2D matching method is demonstrated on some in-vitro investigations. Pose estimation errors are examined and the maximum error in in-plane/out-of-plane translations and rotations 0.28/4.17 mm and 0.33/0.26 degrees, respectively. That in femorotibial distance measurements is 0.14 mm.