| Bone has functional adaptability,and it can respond to external stimuli that reach a certain level.Therefore,bone structure and bone mass distribution can be improved by vibration or drug stimulation.In the first part of this dissertation,the experiment of vibration in combination with drugs against osteoporosis was carried out to investigate the influence of vibration and drug stimuli on bone tissue.In the second part,the relationship between dynamic load and bone surface strain was studied through the tibia axial loading model.Osteoporosis is a disease characterized by decreased bone mass and deterioration of the bone microstructure,which occur frequently among postmenopausal women.Whole body vibration is safer than other sports.Xian-Ling-Gu-Bao is a new drug developed from non-governmental prescriptions.Both of them have a broad application prospect for the treatment of osteoporosis.In this study,35 female Wistar rats aged 8 months were randomly divided into five groups: control group(CON),ovariectomized group(OVX),vibration group(WBV),drug group(XGC)and vibration + drug group(WBV +XGC).Except the CON group,the other four groups of rats were ovariectomized bilaterally.After 2 weeks,the WBV group was subjected to whole-body vibration at a frequency of 35 Hz with an acceleration of 0.25 g for 15 min/d.The XGC group was gavage with Xian-Ling-Gu-Bao suspension via gavage needle at a dose of 1 1g/kg once daily.The WBV+XGC group was vibrated and gavaged.The vibration and gavage lasted for 21 days.The rats were sacrificed immediately and the right tibia and femur samples were taken.The microstructure of the tibial proximal cancellous bone was evaluated by Micro-computed tomography.The mechanical properties of the femoral cortical bone were measured by three-point bending test.The experimental results showed that for the microstructure of cancellous bone of tibia,the bone volume fraction of CON group was significantly higher than that of OVX group,WBV group and WBV+XGC group;the trabecular number in CON group was significantly higher than that in OVX and WBV groups,and the trabecular number was significantly higher in WBV+XGG group than that of OVX group;the structural model index of CON group was significantly lower than those of OVX group and WBV group,and that of WBV+XGC group was significantly lower than those of OVX group and WBV group;there were no significant differences among groups in bone mineral density,trabecular thickness,and trabecular separation.For femur cortical bone,there were no significant differences among groups in stiffness and apparent elastic modulus.The experimental results show that ovariectomy can lead to degeneration of the microarchitecture of tibial cancellous bone,and whole body vibration or Xian-Ling-Gu-Bao alone has no significant effect on it;whole body vibration in combination with Xian-Ling-Gu-Bao can counteract the ovariectomy-induced cancellous bone microstructure degradation.Ovariectomy had no significant effect on the femoral cortical bone mechanical properties.Whole body vibration or Xian-Ling-Gu-Bao alone,as well as whole body vibration in combination with Xian-Ling-Gu-Bao did not significantly affect femoral cortical bone mechanical properties.Compared to other loading models,direct loading on a single limb can be used to explore the response of bone tissue to specific mechanical loads by accurately controlling the magnitude,direction,and application point of the load.This model was used to investigate the relationship between loading and bone surface strain during axial loading of rat tibia in this study.Fifteen 5-month-old female Wistar rats were used,and the right legs were taken as experimental samples after sacrifice.Each sample was loaded three times and the maximum loading force was 30.00 N,40.00 N and 50.00 N,respectively.The position of the 0o/45o/90o strain gages was at third of the length of the lower leg close to the proximal end;the strain gauge is attached to the middle of the calf.The processed slope of the maximum strain-load fit straight line,the processedslope of the minimum strain-load fit straight line of the 0o/45o/90o strain gages and the processed strain-load fit straight line slope are 26.38±5.37με/N,-12.41±5.12με/N and 29.94±9.86με/N respectively;25.22±5.31με/N,-12.39±4.83με/N and 28.31±9.73με/N at 40N;23.50±5.64με/N,-11.36±4.61με/N and 27.26±9.39με/N at 50 N.At the ultimate compressive loads of 30,40,and 50 N,there were no significant differences among groups in the slopes of the strain-load fitted straight lines of the maximum principal strain,minimum principal strain,and strain.The strain-load relationship obtained in this experiment provided basis for determining the load of rat tibia in non-invasive loading experiments. |
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