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目的 研究卵巢切除大鼠皮质骨的几何学改变和力学性能改变 ,探讨雌激素缺乏时皮质骨改变的发生机制。方法 选雌性SD大鼠 5 6只 ,分为Sham组和OVX组 ,动物分别在 4、12、2 0和 2 8周时处死 7只 ,取其胫骨备用。左侧于近 3/ 5和远 2 / 5交界部切断 ,在电镜下摄片 ,计测截面总面积、皮质骨面积、骨外径周长、骨髓腔面积和骨内径周长。右侧以近 3/ 5与远 2 / 5交界点为加载点进行三点弯曲力学实验。结果 Sham组术后 4周至 2 8周胫骨截面总面积和骨外径周长逐渐增加 (P <0 .0 0 5 ) ,而髓腔面积和内径周长变化不明显。OVX组截面总面积和外径周长也有逐渐增加趋势 ,但差异无显著性。而内径周长和髓腔面积都明显增加 ,在相同时期显著大于Sham组 (P <0 .0 0 5 ) ,而皮质骨面积却与Sham组差异无显著性。三点弯曲试验结果表明从 4～ 2 8周实验对照两组抗弯强度和刚度均逐渐增加 ,但两组间差异无显著性。在各时期骨组织材料力学性能也无显著性差异。结论 卵巢切除对皮质骨的影响主要表现在使骨髓腔扩大 ,对骨外膜的影响较小 ,在短期内对皮质骨的力学性能无明显影响
Objective To study the geometric changes and mechanical properties of cortical bone in ovariectomized rats, and to explore the mechanism of cortical bone changes in estrogen-deficient rats. Methods Fifty-six female Sprague-Dawley rats were randomly divided into Sham group and OVX group. Seven animals were sacrificed at 4, 12, 20 and 28 weeks, respectively. The left side was cut off at the junction of 3/5 and 2/5 far away. The total area of the cross section, the area of the cortical bone, the perimeter of the bone, the area of the bone marrow cavity and the circumference of the bone were measured by electron microscopy. On the right side of the 3/5 and far 2/5 junction for the loading point for three-point bending test. Results The total area of the tibial cross section and the diameter of the external diameter of the Sham group increased gradually from 4 weeks to 28 weeks after operation (P <0.05), while the changes of the medullary cavity area and internal diameter did not change significantly. OVX cross-sectional area of the total area and the diameter of the circumference also increased gradually, but the difference was not significant. However, both the inner diameter and the medullary cavity area increased significantly, which was significantly higher than that of the Sham group (P <0.05) at the same period, while the cortical bone area was not significantly different from Sham group. Three-point bending test results show that from 4 to 28 weeks experimental control two groups of flexural strength and stiffness were gradually increased, but no significant difference between the two groups. There was no significant difference in the mechanical properties of bone tissue in all the time. Conclusion The effect of ovariectomy on cortical bone is mainly manifested in expanding the medullary cavity and less impact on the adventitia, and has no significant effect on the mechanical properties of cortical bone in a short period of time