The effects of HTO for varus knee deformity on the amount/distribution of stresses in the articular cartilage were analysed using a 3D finite element model. It was shown that joint-line obliquity of more than 5° induced excessive shear stress in the tibial articular cartilage. A large amount of correction in OWHTO with a resultant joint-line obliquity of 5° or more may induce detrimental stress to the articular cartilage. Double-level osteotomy should be considered as a surgical option in this situation.

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There are many designs of the femoral stem of a cemented total hip arthroplasty, and mechanical failure of the stem is caused by several factors related to the cement, such as failure of the cement. Optimization of the shape of the stem, especially multiobjective optimization, is required to solve these design problems because a cement fracture is caused by multiple factors. The objective of this study was to determine a stem geometry considering multiple factors at the same time. A three-dimensional finite element model of the proximal femur was developed from a composite femur. A total of four objective functions--two objective functions, the largest maximum principal stress of proximal and distal sections in the cement mantle, for each of the two boundary conditions, walking and stair climbing--were used. The neighborhood cultivation genetic algorithm was introduced to minimize these objective functions. The results showed that the geometry that leads to a decrease in the proximal cement stress and the geometry that leads to a decrease in the distal cement stress were not the same. However, the results of the walking and the stair climbing conditions matched. Five dominant stem designs were considered to be the Pareto solution, and one design was identified as the "better design" for all objective functions. It was shown that multiobjective optimization using a genetic algorithm may be used for optimizing the shape of the femoral stem in order to avoid cement fracture.

The authors have been developing a newly-designed totally-implantable artificial myocardium using a covalent shape-memory alloy fibre (Biometal®, Toki Corporation), which is attached onto the ventricular wall and is also capable of supporting the natural ventricular contraction. This mechanical system consists of a contraction assistive device, which is made of Ti-Ni alloy. And the phenomenon of the martensitic transformation of the alloy was employed to achieve the physiologic motion of the device. The diameter of the alloy wire could be selected from 45 to 250μm. In this study, the basic characteristics of the fiber of 150μm was examined to design the sophisticated mechano-electric myocardium. The stress generated by the fiber was 400gf under the pulsatile driving condition (0.4W, 1Hz). Therefore it was indicated that the effective assistance might be achieved by using the Biometal shape-memory alloy fiber.