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目的观察模拟失重尾部悬吊大鼠模型松质骨骨密度、骨小梁结构及力学性能变化。方法 3个月龄雄性SD大鼠24只,随机分为3组,尾部悬吊14d、28d和空白对照组。到期处死动物,测定L_4椎体、股骨髁部骨密度,并进行显微CT及生物力学测试。结果尾部悬吊组较对照组椎体、股骨髁部骨密度均显著下降,且尾部悬吊大鼠骨质疏松随时间加重,松质骨的骨体积分数(BV/TV)、骨小梁厚度(Tb.Th)、骨小梁数目(Tb.N)较对照组显著降低(P<0.05),股骨髁部表面积体积比(BS/BV)、椎体骨小梁间隙(Tb.Sp)则较对照显著增高。生物力学测试表明,尾部悬吊14d、28d组腰椎的最大压缩应力分别较空白对照组下降11.8%、26.3%,股骨抗弯曲载荷较空白对照组下降13.9%,24.6%,力学强度显著下降。结论尾部悬吊大鼠从14d即表现出明显的松质骨骨密度下降,骨小梁三维微结构破坏,椎体力学强度也显著下降,并随时间发展不断加重,理论上骨折风险性增加。
Objective To observe the changes of cancellous bone density, trabecular structure and mechanical properties in a rat model of simulated weightlessness tail suspension. Methods Twenty-four male SD rats, 3 months old, were randomly divided into 3 groups and were suspended for 14 days, 28 days and blank control group respectively. The animals were sacrificed at the expiration, bone mineral density of the L4 vertebral body and femoral condyles were measured, and micro-CT and biomechanical tests were performed. Results Compared with the control group, the BMD of the vertebral body and the femoral condyle in the tail suspension group decreased significantly. The osteoporosis in the tail suspension rats increased with time, the bone volume fraction (BV / TV) of cancellous bone, the trabecular thickness (Tb.Th), the number of trabecular (Tb.N) decreased significantly compared with the control group (P <0.05). The ratio of BS / BV to Tb.Sp Significantly higher than the control. Biomechanical tests showed that the maximal compressive stress of the lumbar vertebrae on the 14d and 28d tail suspensions decreased by 11.8% and 26.3% respectively compared with the blank control group, and the flexural strength of the femur decreased by 13.9% and 24.6% compared with the blank control group, respectively. Conclusion The tail-suspended rats showed a significant decrease of cancellous bone mineral density, the destruction of the three-dimensional micro-structure of trabecular bone and the decrease of mechanical strength of vertebral bodies from 14th day after birth, which was aggravated with time. In theory, the fracture risk increased.