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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.

Bovine articular chondrocytes dedifferentiated and lost their ability to express articular cartilage-specific extracellular matrices such as type II collagen and aggrecan when cultured in a culture flask during in vitro multiplication. A poly(DL-lactic-co-glycolic acid) (PLGA)–collagen hybrid mesh was prepared and used to redifferentiate the dedifferentiated cells. The two passaged dedifferentiated chondrocytes were seeded in a PLGA–collagen hybrid mesh and cultured in vitro in Dulbecco’s modified Eagle’s medium containing 10% fetal bovine serum. The cells adhered to the hybrid mesh, distributed evenly, and proliferated to fill the spaces in the scaffold. The gene expression of type I collagen, type II collagen, and aggrecan was analyzed after the cells were cultured in the hybrid mesh for 2–12 weeks. The expression of the gene encoding type I collagen was downregulated, whereas those of type II collagen and aggrecan were upregulated. Histological examination by hematoxylin–eosin and safranin O/fast green staining indicates that the cells regained their original round morphology. In addition, a homogeneous distribution of articular cartilage extracellular matrices was detected around the cells. These results suggest redifferentiation of the differentiated chondrocytes in the hybrid mesh. The hybrid mesh, which facilitated the redifferentiation of the dedifferentiated multiplied chondrocytes, would be an effective scaffold for the assembly of cells to regenerate three-dimensional cartilaginous tissue.

The investigation of the effect of direct current on the mechanical properties of experimental fractures was conducted by applying 7-10 microA of constant current to the osseous defect of the rabbits' fibulae. The fibulae were tested mechanically with the combined methods of nondestructive technique and breaking-strength measurement. The result was analyzed in relation to the volume of the newly formed callus, which was estimated by roentgenographic appearance and calculation. There is no accurate proof that an electrically stimulated callus is superior in mechanical strength. A more massive callus in a relatively earlier stage suggests that the stimulated callus may have some advantages over the nonstimulated callus.

In considering the pathophysiology of hydrocephalus in children, it is necessary to consider properties of brain tissue itself in addition to circulation of cerebrospinal fluid. The first step of biomechanical approach to hydrocephalus is to clarify the mechanical properties of brain tissue.

Amphoteric PVA hydrogels were made from mixed aqueous solutions of poly(acrylic acid), poly(allylamine) hydrochloride and poly(vinyl alcohol) by repetitive freezing and thawing. The hydrogen bond induced gelation produced an elastic and tough microporous hydrogel which generated tension as high as 0.3MPa corresponding to the solvent exchange from water to acetone. In this paper we show the microscopic structure of hydrogels determined by means of cryo-SEM technique and X-ray analysis.

New bone for the repair or the restoration of the function of traumatized, damaged, or lost bone is a major clinical need, and bone tissue engineering has been heralded as an alternative strategy for regenerating bone. A novel web-like structured biodegradable hybrid sheet has been developed for bone tissue engineering by preparing knitted poly(DL-lactic-co-glycolic acid) sheets (PLGA sheets) with collagen microsponges in their openings. The PLGA skeleton facilitates the formation of the hybrid sheets into desired shapes, and the collagen microsponges in the pores of the PLGA sheet promote cell adhesion and uniform cell distribution throughout the sheet. A large number of osteoblasts established from marrow stroma adhere to the scaffolds and generate the desired-shaped bone in combination with these novel sheets. These results indicate that the web-like structured novel sheet shows promise for use as a tool for custom-shaped bone regeneration in basic research on osteogenesis and for the development of therapeutic applications.

To examine the effects of direct electric current on ligament healing in rabbits, a full-thickness defect of the patellar ligament was electrically stimulated for time periods of up to seven weeks. The rabbits were randomly assigned to biomechanical and biochemical studies, and healing was evaluated by these parameters. Electrical stimulation was shown to restore tensile stiffness in a short period of time and to decrease the relative proportion of Type III collagen more rapidly than in the control group. However, electrical stimulation did not change the collagen content of newly formed tissue. Electricity enhances the repair process of the ligament by changing the ratio of collagen types.