Papers by Author: Toshiyuki Tateiwa

Abstract: In simulator studies, the Biolox-forte hip prosthesis were run for 5 million cycles (Mc) using 50% new born calf serum for both the standard test (STD) mode and the micro-separation test (MSX) mode. Wear measurements were carried out every 0.5 Mc. The wear patterns were mapped and observed by SEM. In a clinical study, the OstealTM hip prostheses which were implanted for 15 to 19 years and 17 year BioloxTM hip prostheses were analyzed. According to the same technique as the simulator study, the wear patterns were analyzed using SEM. The steady-state wear rates for alumina THR ranged from 0.16 to 0.65 mm3/Mc in the MSX mode and 0.011 mm3/Mc in the STD mode. The MSX simulator mode produced two narrow wear scars (stripes) of dull appearance on the ball. In the SEM analysis, the stripe scars showed mild wear after 5 Mc duration. In the Biolox and the Osteal retrieval alumina ball, the stripe scars showed severe wear. The Osteal retrievals had one grade lower wear in the main worn area than the Biolox retrievals on SEM analysis. The stripe wear and its location in the retrieval balls were seen in the simulator study. The area and wear severity of the stripe wear were influenced by the quality of alumina, design of THA and various actual motions in patients.

Abstract: The surface of retrieved alumina (Al2O3) femoral heads was investigated by piezo-spectroscopic techniques based on confocal photo-stimulated fluorescence. The micrometric spatial resolution of the laser beam impinging on the investigated joint surface (typically about 1 $m in lateral resolution) enabled us estimating patterns and magnitude of residual stress in extremely narrow zones, at least comparable with the grain size of the material. According to a statistical collection of data on a microscopic level, it was possible to assess the retrieved femoral heads in-toto, thus extending the microscopic analysis to the entire surface of the joint. A stress field was found, which mainly arose from loading history, and displacements acting on the femoral head during its lifetime. Residual stress data enabled us to draw interesting conclusions about the role of the material microstructure and the peculiar kinetic mechanisms involved with the use of the joint. Spectroscopic techniques, which are complementary to in vitro testing procedures and theoretical stress analyses based on finite-element methods, can be very useful in improving the design of the femoral head and in optimizing the microstructural characteristics of the ceramic materials employed.

Abstract: A survey of confocal Raman/fluorescence microprobe spectroscopic techniques is presented with emphasis placed on surface analysis of artificial hip joints. Suitable instrumental configurations are first explained in some details in order to describe the versatility of the spectroscopic microprobes to biomedical materials analyses. Then, these notions, which represent the foundation for structural and mechanical analyses of joint surfaces, are applied to selected cases of paramount importance in hip arthroplasty.