随着我国人口老龄化的加剧，骨质疏松症已成为影响公众健康的重要因素之一。对于骨折后的骨质疏松患者，一旦手术方案规划不当，则将导致手术失败，且难以翻修。使用仿真骨进行术前规划是提高手术成功率的重要手段。目前市面上应用最广泛的仿真骨为国外合成骨。研究表明，该产品的皮质骨材料在力学性能上与人体皮质骨相当，但其内部填充的用于模拟松质骨的聚氨酯泡沫是均匀密度且各向同性的，而真实松质骨具有密度梯度变化及各向异性特点。另外，其形态参数及骨质特点与中国人骨骼有较大差距，且不便于制作骨折模型，因此在临床中的应用具有一定的局限性。完成力学等效仿真骨的研制，首先要对骨的力学性能进行精准预测。临床上往往通过骨密度来预测骨的力学性能。但研究表明，无论是作为金标准的双能X射线还是定量CT立体骨密度测定，其检测结果与临床表现中的骨折风险并不一致，在一定程度上反映了骨密度并不能直接代表骨力学性能的好坏。骨是多尺度生物材料，内部松质骨结构复杂。除体积分数（对应骨密度）外，其微结构特点也是宏观力学性能的重要度量之一。显微CT成像可以获得松质骨的微结构信息。以往研究中也曾对松质骨微结构特点与宏观力学性能间的关系进行了相关研究，但因其辐射剂量大，无法直接应用于临床。因此，如何既能考虑松质骨的微结构特点，又在人体安全的情况下准确预测松质骨的力学性能，并研制适合中国人的力学等效仿真骨是亟待解决的问题。

针对以上问题，本文建立了一种预测松质骨力学性能的多尺度模型，并以此为基础，进行力学等效仿真骨的研制。主要研究内容及结论如下：

1. 建立了基于临床CT信息且考虑松质骨微结构特征的力学性能预测模型。首先建立松质骨微结构参数、各向异性的量化算法，并通过织构张量描述松质骨微结构信息，计算松质骨正交各向异性力学参数。进一步地，建立临床CT灰度值与松质骨正交各向异性力学参数间的回归关系，分析解剖部位、各向异性程度差异对预测模型的影响。最后以松质骨的圆盘压缩实验进行验证。结果表明，较传统应用广泛的各向同性力学模型，该方法大大提高了松质骨宏观弹性模量及屈服强度的预测准确性。
2. 建立了依据CT信息个性化设计松质骨力学等效微结构的方法。以三周期极小曲面为基础，进行不同结构模式、体积分数、各向异性程度的微结构设计，并通过有限元计算，得出结构参数对宏观力学参数的影响规律。进一步地，结合松质骨力学性能预测模型，建立CT与等效微结构参数间的关系。最后通过股骨头大尺度球头压入实验、股骨头-螺钉耦合性能实验进行验证。实验结果表明，等效微结构可在85%以上的水平复现松质骨在特定情况下的综合力学响应。
3. 分别开展定制型、常规型两类力学等效仿真骨的研制。两类仿真骨内部均通过等效微结构设计达到松质骨的力学等效。定制型仿真骨借助3D打印技术实现畸形与骨折模型，而常规型仿真骨则进一步优化复合材料实现皮质骨的力学等效。最后将仿真骨与尸体骨、国外合成骨进行实验对比。实验结果表明：力学等效仿真骨除了在整体压缩、扭转刚度上与尸体骨及国外合成骨接近外，还能反映出中西方人因股骨颈前倾与股骨前弓角度的不同而产生的骨周应变分布的差异，以及可以复现股骨颈骨折、股骨近端劈裂骨折、假体周围螺旋形骨折等经典骨折形态。

综上所述，本文所建立的松质骨力学性能预测多尺度模型较传统方法可以更为准确的预测松质骨的宏观弹性模量、屈服强度，可为临床骨折风险预测、骨科虚拟诊疗提供依据。另一方面，本文研制的力学等效仿真骨因其在整体力学性能、断裂载荷、局部松质骨力学响应、骨周围应变分布等方面均表现出良好的力学等效性，且较国外合成骨更贴合中国人骨型，可以替代进口产品作为骨科术前规划及科研实验的通用耗材。

With the intensification of the aging population in China, osteoporosis has become one of the important factors affecting the public health. For the fractured patients with osteoporosis, the surgery must be well planned to avoid the fixation failure and the repair difficulties. Using simulated bone to rehearse the surgical plan before surgery is an important means to improve the success rate of surgery. At present, the most widely used simulated bone is imported composite bone. Previous studies have shown that the mechanical properties of the cortical bone material of this composite bone are equivalent to those of human cortical bone, but the polyurethane foam to simulate cancellous bone is isotropic and uniform, which is different from the real cancellous bone with anisotropy and heterogeneity. In addition, its bone shape parameters and bone characteristics are designed for European races which has a large gap with Chinese bones, and is not convenient to make fracture models. Therefore, the application of this kind of composite bone in preoperative planning has various limitations. To complete the development of mechanical equivalent simulated bone, it is first necessary to accurately predict the mechanical properties of the bone. In clinical practice, bone mineral density is often measured to predict the mechanical properties of bone. However, studies proved that the gold standard methods such as dual-energy X-ray and quantitative CT measured three-dimensional bone mineral densities are not consistent with the fracture risk in clinics, indicating that bone mineral density does not directly represent the bone mechanical properties. Bone is a typical multiscale biomaterial, with complex internal cancellous bone structure. In addition to volume fraction (corresponding to bone density), its microstructure characteristics are also an important measure of the macroscopic mechanical properties of bone. Micro CT can obtain the microstructure information of cancellous bone. In previous studies, the relationship between microstructure characteristics and macroscopic mechanical properties of cancellous bone has also been studied. However, due to its large radiation dose, it can not be directly applied in clinical practice. Therefore, how to accurately predict the mechanical properties of cancellous bone while considering its microstructure characteristics and ensuring human safety, and develop a mechanical equivalent simulated bone suitable for Chinese people is an urgent problem to be solved.

In solving the above drawbacks, this paper established a multi-scale model for predicting the mechanical properties of cancellous bone. Based on this, the mechanical equivalent simulated bone was developed. The main research contents and conclusions are as follows:

1. A prediction model for mechanical properties of cancellous bone was established based on clinical CT information by considering the microstructure characteristics. Firstly, an algorithm for quantifying the microstructure parameters and anisotropy of cancellous bone was established, and the microstructure information of cancellous bone is described by fabric tensor to calculate the orthotropic mechanical parameters. Further, a regression relationship between clinical CT grayscale values and orthotropic mechanical parameters of cancellous bone was established, and the effects of anatomical location and anisotropy on the prediction model were analyzed. Finally, an experimental verification is carried out using the disc-compression of cancellous bone. The results show that this method greatly improves the prediction accuracy of the macroscopic elastic modulus and yield strength of cancellous bone compared to the widely used isotropic mechanical models.
2. A method for personalized design of mechanical equivalent microstructure of cancellous bone based on CT information was established. Based on the triply periodic minimal surfaces, microstructure designs with different structural modes, volume fractions, and anisotropic degrees are performed. Through finite element simulation, the influence of structural parameters on macroscopic mechanical parameters is obtained. Furthermore, combined with the prediction model for mechanical properties of cancellous bone, the relationship between CT and equivalent microstructure parameters was established. Finally, it was verified by large-scale indentation experiments and screw insertion experiments of femoral head. The experimental results show that the equivalent microstructure can reproduce the comprehensive mechanical response of cancellous bone under specific conditions at a level of over 85%.
3. Developing customized and regular mechanical equivalent simulated bones. The mechanical equivalence of cancellous bone is achieved through microstructure design in both types of simulated bones. Customized simulated bones are manufactured using 3D printing technology to reproduce deformities and fracture models, while regular simulated bones further optimize composite materials to achieve mechanical equivalence of cortical bone. Finally, experimental comparisons were made between simulated bone, cadaver bone, and imported composite bone. The results show that the mechanical equivalent simulated bone has similar overall compression and torsional stiffness as cadaveric bone and imported composite bone, it also reveals the differences in the distribution of periosseous strain caused by the differences in femoral neck anteversion angle and femoral bow angle between Chinese and Western people. Besides that, the simulated bones can reproduce classic fracture patterns such as femoral neck fractures, proximal femoral split fractures, and spiral fractures around the prosthesis.

In summary, a multi-scale model for predicting mechanical properties of cancellous bone is established which can more accurately predict the macroscopic elastic modulus and yield strength of cancellous bone than traditional methods. It provides criteria for clinical fracture risk prediction, orthopedic virtual diagnosis and treatment. The mechanical equivalent simulated bone shows good consistency with actual bone in overall mechanical properties, fracture load, local cancellous bone mechanical response, and periosseous strain distribution, and is more suitable for Chinese bone characteristics than imported composite bones. It can replace imported products as a necessary choice for orthopedic preoperative planning and biomechanical testing.