OP进程中腰椎松质骨微观空间结构和力学特性的变化规律及与宏观力学强度的相关性

Changes in the microscopic spatial structure and mechanical properties of lumbar cancellous bone during OP progression and their correlation with macroscopic mechanical strength

目的基于骨质疏松兔模型,研究骨质疏松(OP)进程中松质骨微观空间结构、微观力学特性与宏观力学特性的变化规律及相关性。方法选用64只雌性大白兔随机分为假手术组(Sham组,n=32)和骨质疏松模型组(OP组,n=32)。将Sham组和OP组的白兔分别随机分为基线(Pre-ovx)、1、2、4个月4个组(n=8)。于术后0、1、2、4个月利用双能X线骨密度仪(DXA)分别测量各组骨密度(BMD)。采集腰椎标本并采用纳米压痕法测量微观力学参数,采用显微计算机断层扫描技术(Micro-CT)测量微观空间结构参数,采用轴向压缩实验测量宏观力学强度参数。结果随着建模时间延长,BMD、最大载荷(Lmax)、骨小梁的弹性模量、硬度、骨小梁厚度(Tb.Th)骨小梁数量(Tb.N)逐渐降低,骨小梁间隔(Tb.Sp)逐渐升高。Pearson直线相关分析显示,Tb.Th与Lmax(r=0.926,P=0.000)、弹性模量(r=0.938,P=0.000)及硬度(r=0.921,P=0.000)的相关性最强呈正相关。微观力学特性中,弹性模量与Lmax(r=0.940,P=0.000)相关性最强呈正相关。多元线性回归显示Tb.Th(β=0.369,P=0.038)和弹性模量(β=0.594,P=0.002)均与Lmax呈正相关。结论Tb.Th以及骨小梁的弹性模量为骨宏观力学强度的影响因素,弹性模量对于骨宏观力学强度的影响最为显著,可以将弹性模量作为OP骨折的预测因子。

Objective This study aims to explore the changing patterns and correlation of the microscopic spatial structure,micromechanical properties,and macromechanical properties of cancellous bone in the process of osteoporosis(OP)based on the os-teoporotic rabbit model.Methods 64 female white rabbits were selected and randomly divided into a sham operation group(Sham group,n=32)and an osteoporosis model group(OP group,n=32).White rabbits in the Sham and OP groups were randomized into 4 groups(n=8)at baseline(Pre-ovx),1,2,and 4 months,respective-ly.Bone mineral density(BMD)was measured by dual-energy X-ray absorptiometry(DXA)at 0,1,2,and 4 months after surgery.Lum-bar vertebrae specimens were collected and the micromechanical pa-rameters were measured by nanoindentation method,the microspatial structural parameters were measured by micro-computed tomography(Micro-CT),and the macromechanical strength parameters were mea-sured by axial compression test.Results With the extension of modeling time,BMD,maximum load(Lmax),elastic modulus of bone trabeculae,stiffness,hardness,trabecular thickness(Tb.Th)and trabecular number(Tb.N)gradually decreased,while the trabec-ular spacing(Tb.Sp.)gradually increased.Pearson′s linear correlation analysis showed that Tb.Th had the strongest positive correla-tion with Lmax(r=0.926,P=0.000),modulus of elasticity(r=0.938,P=0.000),and hardness(r=0.921,P=0.000),all positively cor-related.Among the micromechanical properties,modulus of elasticity and Lmax(r=0.940,P=0.000)had the strongest positive correla-tion.Multiple linear regression showed that both Tb.Th(β=0.369,P=0.038)and elastic modulus(β=0.594,P=0.002)were positive-ly correlated with Lmax.Conclusion Tb.Th and the elastic modulus of the bone trabeculae are the factors that influence the macro-scopic mechanical strength of bone,and the elastic modulus has the most significant impact on the macroscopic mechanical strength of bone.So the elastic modulus can be used as a predictor of OP fracture.