| Osteoporosis is a bone disease characterized by decreased bone mass,deterioration of bone microstructure and increased fracture risk.Bone structure and mechanical properties can be improved by whole-body vibration.The hip and lumbar vertebrae are the sites most vulnerable to fracture,so the intervention time of wholebody vibration is of great significant for the treatment of osteoporosis in the lumbar vertebrae.The study aimed to explore the effects of whole-body vibration before and after ovariectomy on the bone microstructural and mechanical properties of the lumbar vertebrae in rats,and to analyze the maintenance effect of vibration.The study aimed to investigate the effect of high frequency and low load vibration on lumbar spine and lumbar intervertebral disc,respectively.In this study,180 female Wistar rats aged 3 months were randomly divided into four groups: pre-ovariectomized vibration group(WBV),post-ovariectomized vibration group(OW),ovariectomized group(OVA)and control group(CON).After 2 weeks of adaptation,the WBV group was subjected to whole-body vibration at a frequency of 35 Hz with an acceleration of0.25 g for 30 min/d,5 days/week and a total of 8 weeks.At the end of the 8th week,15 rats in each group were sacrificed and the lumbar vertebrae samples were taken.At the9 th week,rats in the WBV group,OW group and OVA group were ovariectomized and recovered for 2 weeks.At the 11 th week,the OW group was subjected to whole-body vibration with the same vibration parameters as the WBV group at 1-8 weeks.At the end of the 18 th week,15 rats in each group were sacrificed and the lumbar vertebrae samples were taken.For 8 weeks from the 19 th week on,no intervention was done for the four groups.At the end of the 26 th week,15 rats in each group were sacrificed and the lumbar vertebrae samples were taken.Firstly,the spines of rats were scanned and reconstructed by Micro-computed tomography(Micro-CT)to obtain the microstructure parameters.Secondly,a compression test was performed on the L5 vertebral body to obtain the elastic modulus and stiffness.Thirdly,a creep test was performed on the L3-L4 segment to obtain the maximum displacement and time constant.Finally,a microindentation test was performed on the annulus fibrosus of the L1-L2 annulus fibrosus to obtain the indentation depth and elastic modulus.The results were compared by one-way analysis of variance,and the interaction between groups and time was analyzed by two-way analysis of variance.Results showed that,at the 8th week,there were no significant differences among groups in microstructure parameter of L4 vertebral body(p>0.05);the stiffness of L5 vertebral body in WBV group was significantly higher than those in OW group and CON group(p<0.05);the displacement of L3-L4 segment in WBV group was significantly higher than those in the other groups(p<0.05);the elastic modulus of L1-L2 annulus fibrosus in WBV group was significantly higher than that in CON group(p<0.05);the indentation depth of L1-L2 annulus fibrosus in WBV group was significantly lower than that in CON group(p<0.05).At the 18 th week,the BMD,BV/TV and Tb.N of L4 vertebral body in CON group were significantly higher than those in the other groups(p<0.05);the SMI and Tb.Sp of L4 vertebral body in CON group were significantly lower than those in the other groups(p<0.05);the stiffness of L5 vertebral body and the elastic modulus of L1-L2 annulus fibrosus showed WBV group > OVA group > OW group,but the difference was not significant(p>0.05);the indentation depth of L1-L2 annulus fibrosus in WBV group was significantly lower than that in the other groups(p<0.05).At the 26 th week,the BMD,BV/TV and Tb.N of L4 vertebral body in CON group were significantly higher than those in the other groups(p<0.05);the SMI and Tb.Sp of L4 vertebral body in CON group were significantly lower than those in the other groups(p<0.05);the stiffness of L5 vertebra in CON group was significantly higher than that in WBV group and OW group(p<0.05).The BMD,BV/TV and Tb.N of L4 vertebral body all showed a significant change at the 8th week < 18 th week < 26 th week in WBV group,OW group and OVA group(p<0.05);the Tb.Sp of L4 vertebral body showed a significant change at the 8th week >18th week> 26 th week in WBV group,OW group and OVA group(p<0.05);the elastic modulus and stiffness of the L5 vertebral body at 26 th week were significantly lower than those at 8th week in WBV group and OW group(p<0.05);the stiffness of the L5 vertebral body at 26 th week were significantly lower than those at 18 th week in WBV group and OW group(p<0.05).These results demonstrate that,the degeneration degree of the microstructure and mechanical properties in osteoporotic rats gradually increased with age;the whole-body vibration improved the stiffness of the lumbar vertebrae and viscoelasticity of the lumbar intervertebral disc of normal rats,but did not have a significant effect on the microstructure of the lumbar vertebrae of normal rats;the whole-body vibration treatment before and after osteoporosis did not significantly improve the microstructure and mechanical properties of the vertebral body of rats in all groups.However,it significantly improved the mechanical properties of the annulus fibrosus,but this positive effect did not continue with age. |
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