Two-dimensional (2-D)/three-dimensional (3-D) registration techniques using single-plane fluoroscopy are highly important for analyzing 3-D kinematics in applications such as total knee arthroplasty (TKA) implants. The accuracy of single-plane fluoroscopy-based techniques in the determination of translation perpendicular to the image plane (depth position), however, is relatively poor because a change in the depth position causes only small changes in the 2-D silhouette. Accuracies achieved in depth position using conventional 2-D/3-D registration techniques are insufficient for clinical applications. Therefore, we propose a technique for improving the accuracy of depth position determination in order to develop a system for analyzing knee kinematics over the full six degrees of freedom (6 DOF) using single-plane fluoroscopy. In preliminary experiments, the behaviors of errors for each free variable were quantified as evaluation curves by examining changes in cost function with variations in the free variable. The evaluation curve for depth position was more jagged, and the curve peak less pointy, compared to the evaluation curves of the other five variables, and the curve was found to behave differently. Depth position is therefore optimized independently of the other variables, using an approximate evaluation curve of depth position prepared after initial registration. Accuracy of the proposed technique was evaluated by computer simulation and in vitro tests, with validation of absolute position and orientation performed for each knee component. In computer simulation tests, root-mean-square error (RMSE) in depth position was improved from 2.6 mm (conventional) to 0.9 mm (proposed), whereas for in vitro tests, RMSE improved from 3.2 mm to 1.4 mm. Accuracy of the estimation of the remaining two translational and three rotational variables was found to be almost the same as that obtained by conventional techniques. Results of in vivo tests are also described in which the possibility of full 6 DOF kinematic analysis of TKA implants is shown.

The purpose of this study was to compare midterm results of mobile-bearing and fixed-bearing in bilateral total knee arthroplasty (TKA). Twenty-two patients underwent bilateral TKA with a mobile-bearing prosthesis (Rotaglide, Corin, UK) on one side and a fixed-bearing prosthesis (NexGen-CR, Zimmer, USA) on the other. There were 21 female patients, and in 18 patients, the diagnosis was rheumatoid arthritis. The average age was 59.6 (35-78) years. In all procedures, the posterior cruciate ligament was retained and patella re-surfaced. The average followup in the mobile-bearing group was 98 (79-107) months and 96 (79-107) months in the fixed-bearing group. At the final follow-up, the knee score was 91.8 points and 91.1 points, respectively, and the function score 65.5 points.

No abstract

No abstract

We have investigated transport properties of carriers excited in high-quality homoepitaxial diamond (100) films by 5.6eV photons or 15keV electrons. The high-quality single-crystalline diamond films were homoepitaxially grown on type-Ib diamond substrates at a rate of 2.5μm∕h by high-power microwave-plasma chemical-vapor-deposition (MPCVD). In cathodoluminescence (CL) measurements, strong free-exciton recombination emissions were observed at room temperature from the almost whole specimen surface, indicating the grown films have substantially high quality. It is found through an analysis of the visible emission band originating from the type-Ib substrate that decay constants estimated for excited carriers were ∼5μm in the depth direction. This is consistent with the fact that the intensity of spotlike CL images varied with an exponential function of the lateral length. From transient photocurrent measurements using ultrashort pulse laser excitations, decay times τ for the present high-quality diamond were estimated to be 15 and 100ns for electrons and holes, respectively. Charge collection distances at an electric field E of 830V∕cm were deduced to be ∼190μm and over 1.2mm for electrons and holes, respectively. The former may give a high electron drift mobility of μ∼1600cm2∕Vs while the diffusion coefficients estimated for electrons are 55±14cm2∕Vs, which is comparable with or even higher than those of Si. These physical quantities demonstrate high quality of the diamond films grown by means of the high-power MPCVD method.