外周定量CT对大鼠骨骼结构和力学特性的评价

目的　为探讨和评估外周定量CT(pQCT)在骨组织结构和力学特性测量中的价值。方法　将 5 0只 4月龄雌性未交配的健康Wistar大鼠 ,经适应性喂养 8周后 ,随机分成 6组 ,其中 1组处死作为基线组 (Base ,n =8) ,其余大鼠行去卵巢手术 (Ovariectomy ,OVX)或假手术 (Sham)。OVX组共16只 ,Sham组共 8只 ,雌激素干预组 (O +E)共 18只。处死时留取右侧胫骨和股骨分别进行骨组织形态计量学分析、pQCT测量、股骨远端凹入实验和股骨中段三点弯曲试验。结果　大鼠经OVX后胫骨近端骨小梁体积显著降低 (8 1%± 1 4 %比 19 5 %± 1 5 % ,OVX比Sham ,P <0 0 1)和pQCT检查股骨远段的小梁骨骨矿含量 (1 7± 0 3比 3 2± 0 5mg/mm ,OVX比Sham ,P <0 0 1) ,骨矿盐密度(TrabBMD ,15 8± 32比 32 0± 39mg/mm3 ,OVX比ShamP <0 0 1)显著减少 ,同时松质骨的力学特性下降 ,最大载荷和刚度均显著低于假手术组。经雌激素干预后以上各指标均得以改善。皮质骨骨量和结构主要表现为增龄性的改变 ,OVX和雌激素干预对其影响不明显 ,相关分析表明pQCT测得的股骨远端骨密度和组织计量学指标骨小梁的体积和数目呈显著正相关 (r分别为 0 88和 0 73,P <0 0 1) ,股骨松质骨骨量和骨密度与凹入实验的最大载荷和刚度也呈显著正相关 (r为 0

Evaluation of bone architecture and biomechanic properties by peripheral quantitative computed tomography in rats

OBJECTIVES: To evaluate the value of peripheral quantitative computed tomography (pQCT) in measuring bone architecture and biomechanic properties. METHODS: 50 virgin female Wistar rats six months old were randomly divided into 4 groups: (1) 8 rats were killed as baseline group; (2) 8 rats underwent sham operation and then were killed 14 weeks after (sham operation group); (3) 16 rats underwent bilateral ovariectomy (OVX) without further intervention. Six and 14 weeks after the operation each 8 rats were killed (OVX group); and (4) 18 rats underwent OVX too. After the OVX 9 of the 18 rats were treated with 17beta-estradiol 20 micro g/kg/d IH and 9 rats were treated with estradiol valerate 800 micro g/kg/d po for 8 weeks respectively. Then the 18 rats were killed (OVX plus estrogen group, O + E group). The right tibiae of the rats were taken for histomorphometric analysis, and the right femora were prepared for pQCT scanning and bone biomechanical measurement with indentation test and three-point bending test. RESULTS: Histomorphometric analysis showed that the trabecular volume of proximal tibia (Cn-BV/TV) in the OVX group was 8.1 +/- 1.4%, significantly lower than that in the sham operation group (19.5 +/- 1.5%, P < 0.01). pQCT scanning showed that the femoral trabecular bone mineral content (Trab BMC) in the OVX group was 1.7 +/- 0.3 mg/mm, significantly lower than that in the sham operation group (3.2 +/- 0.5 mg/mm, P < 0.01) and the femoral trabecular bone mineral density (Trab BMD) in the OVX group was 158 +/- 32 mg/mm(3), significantly lower than that in the sham operation group (320 +/- 39 mg/mm(3), P < 0.01). The cancellous maximal load (Can load) of the distal shaft of femur in the OVX group was 12.5 +/- 2.5 N, significantly lower than that in the sham operation group (45.9 +/- 3.2 N, P < 0.01). The cancellous stiffness (Can Stiff) of the distal shaft of femur in the OVX group was 226 +/- 48 N/mm, significantly lower than that in the sham operation group (396 +/- 72 N/mm, P < 0.01). The Can load of O + E group was 21.8 +/- 3.7 N, significantly higher than that in the OVX group (P < 0.05). The Can Stiff of the O + E group was 382 +/- 54 N/mm, significantly higher than that in the OVX group (P < 0.05). There were no significant differences in cortical bone determined by pQCT as well as biomechanic properties in measured by three point test after OVX and estrogen treatment. A significant positive correlation was shown between Trab BMD and Cn-TV/BV and between Trab BMD and Tb N (r = 0.88 and 0.73, both P < 0.01). Similarly, both Trab BMC and Trab BMD of the femur were significantly correlated with the Can load and Can Stiff determined by indentation test (r = 0.47 - 0.68, all P < 0.01). There was also a significant correlation of parameters measured by pQCT in cortical bone with the maximal load and stiffness for the femur midshaft, and the best correlation was found between the maximal load of femur midshaft and Crt BMC and Crt A (both r = 0.76 and P < 0.01). CONCLUSION: The geometric, densitometric and mechanical properties in cortical and trabecular bones of rat can be well described by pQCT.