| Osteoporosis, characterized by decreasing bone mass and regressive microarchitectural deterioration of bone tissue, is a whole-body bone disease with a consequent increase in bone fragility and susceptibility to fracture. Currently, Osteoporotic fracture is a health hazards faced by human being, which has been listed as one of the three diseases of the old aged by the World Health Organization (WHO).For osteoporosis, whose occurrence is mainly influenced by the relative distribution of age factors, in particular the disease occurred in postmenopausal women. Disuse is also a key factor leading to osteoporosis.At present, the major methods for combating osteoporosis is physical training , improving the dietary patterns, drug treatment, artificial gravity. Improving diet and physical training of people has not very significant effects; drug treatment method has been quite successful, but generally will be accompanied by side effect, artificial gravity is not easy to achieve. Many experiments show that, almost unaware micro-incentives can promote bone growth, which is the actual high-frequency micro-incentives containing low vibration.This study takes the principle of bone adapt function - Wolff Law and Frost mechanical control system theory as the basis. We refer to the domestic and foreign literature of vibration against to osteoporosis, and do further in-depth study based on their experiment. We develop the vibration devices by ourselves, and use suspended rats simulating the model of osteoporosis caused by disuse. The suspended rats were imposed continuous and intermittent high frequency and low amplitude vibration, whose frequency is 0.32 Hz and acceleration is 0.3 g. Finally, we compare and analyze the mechanical strength, bone mass and the change of microstructure by biomechanical performance test and organization observation. The study is a further improvement and expansion of this method about high frequency and low amplitude vibration against osteoporosis and bone loss, and it is also a convenient,economical, and non-drug, non-invasive method of treating osteoporosis.The experimental uses female S-D rats, 6-month-old, weight 250±10g. Divided into 7 groups, each with 7 rats, called based group, suspended base group, continuous vibration group, intermittent 1 week group, intermittent 2 weeks group, intermittent 4 weeks group. Vibration loading frequency is 0.32 Hz, and the acceleration is 0.3 g, 15 min/ day, 5days/week, totaling 8 weeks. Finally, the right ulna do three-point bending test, the cortical bone and cancellous bone of the right tibia bone do compression test,and the cancellous bone of left tibia bone do non-decalcification slice observation.We use soft-ware SPSS14.0 for statistical analysis, the results are used mean±standard deviation (x±S)as the form , use single sample T test analysis within groups, use independent samples T-test and single-factor analysis variance between groups .If P <0.05, it is considered as statistically significant.The experimental results are as follows:1. On the right tibias do compress test. The tibias were divided into three parts, the middle parts of the backbone were made as a columniform sample about 6 mm high ,the cancellous bone in proximal tibia were made as a columniform sample about 5 mm high , each samples were do compression damage test, measuring their elastic modulus, compressive strength, and the greatest damage load. The elastic modulus, compressive strength and the greatest damage of suspended base group is significantly lower than based group (P <0.05).The elastic modulus, compressive strength, and the greatest damage of continuous vibration group and the intermittent vibration group are significantly higher than suspended base group (P <0.05), particularly intermittent 1 week group is more obvious, followed by continuous vibration group. Intermittent 2 weeks group, intermittent 4 weeks group, intermittent four weeks group are not very obvious. This shows that, after eight weeks of vibration we can increase ability of anti-compression destroy and improve the quality of bone.2. On the one side of ulna do three-point bending test. It shows that vibration can improve the mechanical properties. Compare with base group,on the elastic modulus ,continuous vibration group increased by 26.67%, intermittent 1 week group increased by 29.09%, intermittent 2 weeks group increased by 11.50%, intermittent 4 weeks group increased by 0.63%;On the bending energy, continuous vibration group increased by 3.82%, intermittent 1 week group decreased by 9.01%, intermittent 2 weeks group increased by 24.65%, intermittent 4 weeks group decreased by 26.22%; On rigid coefficient, continuous vibration group increased by 63.50%, intermittent 1 week group increased by 99.32%, intermittent 2 weeks group decreased by 24.52%, intermittent 4 weeks group decreased by 9.56% . Intermittent 1 week group the has the most obvious changes on the elastic modulus, intermittent 4 weeks group has not obvious changes. Bending energy and rigidity coefficient have more complex changes due to vary factors.3. Observation of dynamic histomorphometry test shows that vibration can promote bone growth and increase bone mineral apposition rate, intermittent vibration is better than continuous vibration group to stimulate bone growth, but the vibration cycle is very crucial. Intermittent 1 week group and intermittent 2 weeks group are relatively obvious, followed by a continuous vibration group, and intermittent 4 weeks.4. Observation of static histomorphometry test shows that the change in percentage of trabecular area (%Tb.Ar), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were observed. After 8-week's vibration, for the group which receives vibration, the number of the %Tb.Ar, the Tb.Th and the Tb.N were enhanced, but the number of the Tb.Sp decreases. This means that the area of trabecular is larger, the thickness of trabecular is stronger, the number of trabecular is increased, and the structure of trabecular is tighter. The results of intermittent 1 week group are obviously changed, followed by continuous vibration group, intermittent 2 weeks group, and intermittent 4 weeks group.Through measurement of the bone's mechanical properties and observation of static histomorphometry test, it is showed the elastic moduluses , compressive strength and the greatest damage of the compact bone and the spongy bone in the tibia are enhanced after eight-week's vibration( f = 32Hz, a = 0.3g); also the elastic moduluses and bending strength in ulna, and bone mineral apposition rate in the area , the thickness, and the number of trabecular are heightened; the structure of trabecular was tighter. That means the mechanical properties of the bone are enhanced, and the fine and microcosmic structure of the bone are enhanced after the eight-week's vibration. In other words, the vibration ( f = 32Hz, a = 0.3g)can be used to fight against the osteoporosis.
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