Shogo Ariyoshi

A 3D kinematic estimation of knee prosthesis using X-ray projection images: clinical assessment of the improved algorithm for fluoroscopy images

In this paper, we propose three ideas to improve a kinematic estimation algorithm for total knee arthroplasty. The first is a two-step estimation algorithm that improves estimation accuracy by excluding certain assumptions needed for the pattern matching algorithm reported by Banks and Hodge. The second is incorporating a 3D geometric articulation model into the algorithm to improve estimation accuracy substantially for the depth translation, and to introduce contact points’ trajectories between the articular surfaces. The third is an algorithm to process estimation even when the silhouettes of two components overlap. To assess our algorithm’s potential for clinical application, we carried out two experiments. First, we used a robot to position the prosthesis. Estimation accuracy was checked by comparing input data to the robot with the estimates from X-ray photographs. Incorporating our articulation model remarkably reduced the error in the depth translation. Next, we performed a clinical assessment by applying the algorithm and articulation model to fluoroscopy images of a patient who had recently had TKA.

The performance of a new measuring method for three-dimensional ball motion in a ball-bearing

Abstract Recently, a new method for measuring ball motions three dimensionally was developed by one of the present authors and its principle was reported in the previous paper. Before its practical applications were examined, the calibration tests were carried out and the outputs obtained by this new method were compared with the values expected theoretically. By compensating for some undesirable effects, it was confirmed that the outputs were sufficient to analyse actual ball motions within an experimental error of 5%. In order to demonstrate its usefulness, an example of experimental results obtained by this new technique is shown.

Periodic ball behaviour in a deep groove ball-bearing under conditions of low radial load and low shaft speed

Abstract The actual ball behaviour during one cage revolution was investigated by using a new measuring method for three-dimensional ball motion. From the experimental results, periodic ball motion with slip was recognized and according to the differences in ball behaviour distinct peripheral regions of the bearing could be discerned.

Proposal to Improve Kinematic Estimation Algorithm of Knee Prosthesis

We will propose two innovative techniques for estimating 3D motion of the knee prosthesis from its 2D perspective projections such as X-ray images. One of our proposing techniques 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 orthogonal projection. Then, the second step estimation was succeeded based upon the perspective projection to accomplish more accurate estimation. The other is a novel 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 the estimation was processed in two steps in associate with the above-mentioned two-step estimation. First, the missing part of silhouette contour due to overlap was interpolated using free-formed curvatures. In the next step, a clipping window was set in the projective coordinate so as to separate the overlapped silhouette. 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.

Experiment on the Kinematic Estimation of Knee Prosthesis using X-ray Photographic Apparatus and Robot

We have developed a technique for estimating 3D motion of knee prosthesis from its 2D perspective projections. Our estimation algorithm includes some innovations such as a two-step estimation algorithm, incorporative use of a geometric articulation model and an algorithm to solve two silhouettes’ overlapping problem. When we attempt to apply our algorithm to a clinical setting, we face a problem such that we can not assess the algorithm because the actual positions and orientations are not known. Thus we built an experimental system using an X-ray photography and a robot for assessing the algorithm. The system is also promising for developing a variety of experiments such as the wear tests of the prosthetic articulating surfaces and the contact stress analyses from photoelastic measurement

A 3D Kinematic Measurement of Knee Prosthesis Using X-ray Projection Images (Countermeasure to the Overlap between Tibio-femoral Component Silhouettes)

We have developed a technique for estimating 3D motion of knee prosthesis from its 2D perspective projections. As Fourier descriptors were used for compact representation of library templates and contours extracted from the prosthetic X-ray images, the entire silhouette contour of each prosthetic component was required. This caused such a problem as our algorithm did not function when the silhouettes of tibio and femoral components overlapped with each other. Here we planned a novel method to overcome it ; which was processed in two steps. First, the missing part of silhouette contour due to overlap was interpolated using a free-formed curvature such as Bezier. Then the first step position/orientation estimation was performed. In the next step, a clipping window was set in the projective coordinate so as to separate the overlapped silhouette drawn using the first step estimates. After that the localized library whose templates were clipped in shape was prepared and the second step estimation was performed. Computer model simulation demonstrated sufficient accuracies of position/orientation estimation even for overlapped silhouettes ; equivalent to those without overlap.