骨质疏松绵羊模型松质骨及皮质骨的微观结构及力学性能变化的研究

目的观察去势手术对绵羊皮质骨和松质骨的骨密度、骨小梁结构及力学性能的影响。方法20只雌性成年绵羊（4±1.5）随机分为去势4个月组（OVX-4months）（4只）、去势12个月组（OVX-12months）（8只）和假手术（Sham）组（8只）。OVX组行双侧卵巢切除术,假手术组仅显露双侧卵巢,术中测定腰椎骨密度。分别与术后4、12个月处死动物,测定股骨颈、股骨干及股骨髁的骨密度,并行MicroCT分析及生物力学测试。结果去势12个月后（OVX-12months）组腰椎、股骨颈及股骨髁的骨密度较对照组显著降低,而皮质骨骨密度无明显降低。其松质骨的相对骨体积（BV/TV）、骨小梁厚度（Tb.Th）、骨小梁数目（Tb.N）较对照组显著降低,表面积体积比（BS/BV）、骨小梁间隙（Tb.Sp）则较对照显著增高。生物力学测试表明,去势12个月后,腰椎松质骨的最大压缩应力分别较Sham组和OVX-12months组下降82.5%和85.9%,力学强度显著下降,而皮质骨的力学强度无显著变化。结论去势12个月后,绵羊腰椎、股骨部的松质骨BMD及骨小梁空间结构参数明显降低,力学强度也显著下降,可以作为骨质疏松的大动物模型。而皮质骨的骨密度和力学强度下降不明显,需要更长的去势时间。

The trabecular and cortical bone difference in ovariectomized sheep: a densitometric, histomorphometric and biomechanical study

Objective To observe the trabecular and cortical bone changes in ovariectomized (OVX) sheep. Methods 20 adult sheep were randomly divided into three groups: sham-operated group(Sham, 8 sheep), OVX-Month 4 group(n=4) and OVX-Month 12 group(n=8). At the time of operation, all sheep underwent dual energy x-ray absorptiometry (DXA) of the lumbar vertebrae. Sheep were sacrificed 4 months and 12 months after operation respectively, and BMD at lumbar spine, femoral neck, femoral shaft and femoral condyle was measured using DXA. The trabecular bone (spine, femoral neck and condyle) and cortical bone (femoral shaft) were harvested and for micro-CT scanning. Compression test was performed for trabecular bone, while the 3-point bending test was conducted for cortical bone. Results After OVX for 12 months, the BMD in trabecular bone was significantly lower than that of Sham group and OVX-Month 4 group (P<0.01). The BS/BV, Tb.Th and Tb.N was significantly lower while the Tb.N and BVF was significantly higher (P<0.01 for both) compared with OVX-Month 12 group and Sham controls. The maximum compressive strength of trabecular bone in OVX-Month 12 group was significantly lower than that of the other two groups (P<0.01). 3-point bending test for cortical bone showed no difference among 3 groups. Conclusion BMD, micro-architecture and biomechanical properties of the trabecular bone decreased significantly after OVX for 12 months. OVX sheep was a suitable animal model for studying estrogen depletion osteoporosis.