A 3D kinematic estimation of knee prosthesis from fluoroscopic images

We have developed two innovative techniques for estimating 3D motion of the knee prosthesis from its 2D perspective 'projections. One is a two-step estimation algorithm and the other is a way to solve overlapping problem. In our two-step estimation algorithm, the first step estimation was done, in the same way as Banks and Hodge's on, the assumption of pseudo-orthogonal projection. hen, the second step estimation was succeeded based upon the perspective projection to accomplish;more accurate estimation. The other is an estimation method to solve such a problem, as our algorithm did not function when the silhouettes of tibio and femoral components overlapped with each other. Here first, interpolated the missing parts of silhouette contour and then applied the clipping method. Simulation results demonstrated that our two-step estimation algorithm improved accuracies much, and also sufficient accuracies could be assured even for the overlapped silhouettes; Equivalent to those without overlap. Finally, we applied our algorithm to the fluoroscopic images. We introduced not only the absolute positions/orientations for each component but also the relative positions/orientations between the both components. Estimation results of the clinical applications demonstrated that our algorithm worked well as like as theoretical.