新型可吸收骨水泥的制备及其应用于小牛椎体标本压缩性骨折椎体成形术的生物力学研究

目的 探讨聚富马酸丙二醇酯（PPF）/β-磷酸三钙（β-TCP）制备新型可吸收骨水泥的配方及其应用于小牛椎体标本压缩性骨折椎体成形术的生物力学性能研究。方法 采用两步法制备PPF,使用凝胶渗透色谱仪测量PPF的数均分子量、重均分子量及聚合度分布指数,使用MR氢谱对PPF进行结构分析。将制备好的PPF与β-TCP按照10∶1、5∶1、3∶1、2∶1配制不同热交联反应体系,制备4种不同配方的PPF/β-TCP可吸收骨水泥,选择抗压强度和压缩模量均较高的骨水泥进行后续实验。选取2~3岁健康小牛腰椎L₁~L₄节段标本4具,分离出16个椎体,使用牙托粉填平每个椎体的椎板凹陷部位,测量每个椎体的受力面积。选择椎体受力面积相近的10个椎体,按数字表法随机分为PPF/β-TCP组和甲基丙烯酸甲酯（PMMA）组,每组5个。PMMA组和PPF/β-TCP组椎体使用MTS-858力学机器制备压缩性骨折模型,对比2组完成模型制备时的椎体高度、抗压强度和刚度。PPF/β-TCP组和PMMA组分别使用PPF/β-TCP骨水泥和标准PMMA骨水泥对压缩骨折模型行椎体成形术,对比2组骨水泥注入量,术后椎体高度、椎体恢复百分比,椎体抗压强度、刚度。结果 PPF数均分子量为1 637±55,重均分子量为1 741±68,聚合分布指数为1.06。MR氢谱结构分析提示反应产物为PPF。配方1~4 PPF/β-TCP可吸收骨水泥抗压强度分别为（53.5±1.5）、（63.2±0.4）、（97.9±5.5）、（100.8±3.2）MPa,压缩模量分别为（0.97±0.04）、（1.05±0.05）、（1.10±0.10）、（0.45±0.18）GPa。选取压缩模量与抗压强度均高的配方3 PPF/β-TCP可吸收骨水泥用于椎体成形术。PPF/β-TCP组和PMMA组小牛椎体标本的椎体体积、高度、受力面积差异均无统计学意义（P值均>0.05）。PPF/β-TCP组和PMMA组的椎体压缩性骨折后高度、椎体成形术后椎体高度以及椎体高度恢复百分比差异均无统计学意义（P值均>0.05）。组内比较：PPF/β-TCP组椎体压缩性骨折椎体成形手术前后椎体抗压强度分别为（2 282±341）N和（1 848±219）N,椎体刚度分别为（215±27）N/mm和（182±15）N/mm,差异均无统计学意义（t=2.14、2.13,P值均>0.05）;PMMA组压缩性骨折椎体成形手术前后抗压强度分别为（2 350±289）N和（3 105±452）N,椎体刚度分别为（221±26）N/mm和（296±37）N/mm,差异均有统计学意义（t=2.81、3.21,P值均<0.05）。组间比较：PPF/β-TCP组与PMMA组术中骨水泥注入量差异无统计学意义（P>0.05）;PPF/β-TCP组与PMMA组发生压缩性骨折时椎体抗压强度和刚度差异均无统计学意义（P值均>0.05）,椎体成形术后椎体抗压强度和刚度PMMA组均大于PPF/β-TCP组,差异均有统计学意义（t=4.99、5.61,P值均<0.05）。结论 PPF与β-TCP按照3∶1配制的可吸收骨水泥具有与人椎体力学性能相近、交联温度低等特点。在治疗小牛椎体压缩性骨折模型时,PPF/β-TCP可吸收骨水泥与PMMA骨水泥术中注入量相近,两者恢复椎体高度的效果相当;且PPF/β-TCP可吸收骨水泥注入后椎体力学性能优于注入PMMA骨水泥者,具有替代PMMA骨水泥治疗椎体压缩性骨折的潜力。     

基于有限元的骨组织工程支架结构力学性能优化分析

目的 分析骨组织工程支架微孔参数对支架力学性能的影响,为支架微孔结构的优化设计提供参考依据。方法 利用ANYSY软件建立支架微孔结构有限元模型,计算最大等效应力、最大总变形与孔隙率的关系,并分析比较不同孔径、孔间距结构对支架最大等效应力、最大总变形、内部应变的影响。结果 x、y轴方向孔间距的影响规律一致,随着孔间距从0.6 mm增加到2.0 mm,最大等效应力从63.1 MPa减小到46.3 MPa,最大总变形从23.8 μm减小到21.8 μm,最佳应变比从80%增大到84%;但随着z轴方向孔间距的增大,最大等效应力从38.3 MPa增大到47.8 MPa,最大总变形从20.8 μm增大到22.8 μm,最佳应变比在82%~85%波动。x,y轴方向孔径从0.1 mm增加到1.0 mm时,最大等效应力从32.4 MPa增大到78.4 MPa,最大总变形从19.9 μm增大到38.2 μm,最佳应变比从90%减小到53%;z轴方向孔径的增大会引起支架的最大等效应力从58.8 MPa减小到37.9 MPa,而最大总变形从23.3 μm增大到25.9 μm,最佳应变比从82%增大到87%。结论 支架孔隙率和最佳应变比越大,最大等效应力、最大总变形越小,支架生物性能和力学性能越好。研究结果对支架的结构设计和优化具有参考价值。     

Composite scaffolds for bone tissue engineering: Application review and future direction北大核心

BACKGROUND: In general, a single-type artificial bone is difficult to meet the requirements for bone defect repair and extracellular matrix of bone tissue engineering. Compositing and processing the materials with different properties can form the composite-type artificial bone, which can either ensure the biological activity or effectively improve its mechanical properties. OBJECTIVE: To summarize the present situation of the application of composite-type artificial bone and prospects the development trend. METHODS: The literatures were retrieved from CNKI, ScienceDirect, PubMed, SpingerLink, EI Village, Wiley databases from January 2000 to April 2017. The key words were “composite scaffold, tissue engineering, artificial bone” in Chinese and English, respectively. The selected literatures were analyzed according to the inclusion and exclusion criteria. RESULTS AND CONCLUSION: The requirements for the scaffolds used for bone tissue engineering are complex and it should carefully consider and control various factors used in the design and preparation of scaffolds, including microporous structure, mechanical strength, degradation rate, porosity, growth factor, morphology and surface chemistry, so as to meet the bone tissue engineering applications. The preparation of tissue-engineered bone scaffold is based on biological active substances and matrix materials through a reasonable manner. It simulates the components of natural bone matrix, promotes the adhesion, proliferation and differentiation of bioactive substances, and gives play to its functions of osteogenesis. Although existing techniques and methods have made significant progress in the preparation of composite scaffolds, there is no technique or method to fully meet all the requirements for preparation of tissue-engineered bone scaffold. © 2018, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.