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Damaged articular cartilage has a very limited capability of self-healing. The need for improved treatment of cartilage defects, which involve over 1 percent of population in Japan, has motivated research to create regenerated cartilage. Regenerated cartilage is engineered by culturing autologous chondrocytes on biodegradable scaffolds. We studied changes in biomechanical property, especially dynamic visco-elasticity during 6 weeks of in vitro culture. The results suggest that the ability of water holding was increased by new extracellular matrix (ECM) synthesis during 4 weeks of in vitro culture, although the ability of solid matrix (ECM and scaffold) to resist compression elastically was reduced.

To study the in vivo damage of the polyethylene acetabular cup retrieved at revision surgery was investigated, Mechanical properties were measured by a viscoelastic spectrometer and a universal Instron type testing machine with a torque meter. The following results were obtained ; 1) There was a positive quadratic correlation between stiffness of the acetabular cup and the duration from the implantation until the revision surgery in the case of the Weber type artificial hip joint. 2) There was a negative qudratic correlation between tan δ and the duration from the implantation until the revision surgery in the case of the Weber type artificial hip joint. 3) There was positive correlation between stiffness of the acetabular cup and the duration from the implantation until the revision surgery in the case of the Kyocera type artificial hip joint. 4) There was a negative correlation between tan δ and the duration from the implantation until the revision surgery in the case of the Kyocera type artificial hip joint. 5) There was a positive correlation between linear wear and the duration from the implantation until the revision surgery in the case of both the Weber and the Kyocera type artificial hip joints. 6) There was a positive correlation between torque and the duration from the implantation until the revision surgery in the case of both the Weber and Kyocera type artificial hip joints.

In order to understand the mechanical properties of human patella, regional differences of viscoelasticity and compressive strength have been investgaited in normal and pathological human patella by viscoelastic spectrometer and a testing machine of the Instron type. In the normal human patella cancellous bone, the averaged compressive elastic modulus at the lateral side was 417.2 MPa and that at the medial side was 243.3 MPa. Comparing normal and pathological patella, we find that the normal patella stiffness and tan δ value were higher than the pathological ones. This fact implies that the normal patella is stiffened as a result of functional adaption.

微少電流を通電することにより生ずる電気仮骨は骨折の治療に新機軸を持たらすものとして注目されているが, 電気仮骨形成の定量的評価法に適当なものがないため, X線による主観的判断によっているのが現状である. 10μAの直流電流通電後6～8週に出現した仮骨を, 微少荷重クリープおよび動的粘弾性試験により, 仮骨のX線像体積と力学的特性との間に明確な関連を発見した.

When shape memory alloys, such as Ni-Ti, Cu-Al-Zn are loaded, after initial elastic deformation, inelastic deformations sets in due to stress induced martensite transformation. To examine impact characteristics of NiTi, a high speed compression testing system using split Hopkinson pressure bar was developed. Specific examples of interaction between the stress induced and temperature induced martensite and the associated rate effect are presented for NiTi, based on the statistical continuum theory of martensite mechanics. Through these studies, the elastic modulus, the solid viscosity and the effect of temperature on mechanical characteristics of NiTi are clarified.

Relaxation tests provide the most direct means of obtaining the mechanical properties and evaluating the fixation function of mechanical elements involved in the pseudoelastic materials such as NiTi shape memory alloy. The tests are applied to uniaxial deformation and canti-lever conditions whereby the appropriate constitutive equation like Malvern Equation is given by the rate type equation.

Mechanical properties and bone density of bone from the horse were studied. Two kinds of bone samples were used : one was taken from legs of horses suffering in racing (fractured sample) and the other from legs horses which were killed for other reasons (non fractured sample). The dynamic stiffness and tan δ were measured by a viscoelastic spectrometer. A bone densitometer was used in density measurement. No substantial difference in values of dynamic stiffness and density was observed in two kinds of samples. On the other hand, the values of tan δ for the fractured sample were definitely lower than those for the non fractured one. It was inferred that the fractured sample was more brittle than the non fractured sample.