Construction of rabbit anatomical three-dimensional models of large segmental tibial defects

doi:10.3969/j.issn.2095-4344.2016.24.002

Abstract

Abstract:

BACKGROUND: Tissue-engineered bone has been considered to be a promising candidate for the repair and reconstruction of load-bearing large segmental bone defects. Currently, the studies on the application of tissue-engineered bone mainly focus on cell-scaffold or cytokine-scaffold constructs, which have shed light upon the repair of large segmental bone defects.
OBJECTIVE: To establish simple and convenient tissue engineering of anatomically shaped tibial bone defect models using three-dimensional rapid prototyping technology to manufacture rabbit tibia biomimetic artificial bone scaffolds.
METHODS: Three-dimensional electronic models were constructed using Mimic software. Hydroxyapatite/polycaprolactone scaffolds were manufactured by fused deposition modeling equipment. Fifty rabbits aged 6 months were randomly divided into three groups: blank control (n=3), control (n=6) and experimental groups (n=6), respectively. Tibial defects ranged 1.2 cm were made in all groups. No treatment was given in blank control group. The bone defects in control and experimental groups were repaired with autogenous osteotomized bone and anatomical tissue-engineered bone, respectively, and fixed with plates and screws.
RESULTS AND CONCLUSION: (1) Rabbit tibial bone measurements: tibial length was (93.77±0.59) mm, tibiofibular transverse diameter (8.36±0.13) mm, sagittal diameter (5.97±0.12) mm, average thickness of bone cortex (1.20±0.10) mm, average diameter of the medullary cavity (4.30±0.06) mm. Angle between the connection line of the midpoints of superior and inferior articular surfaces at the side of tibial bone models and the connection line of the midpoints of superior and inferior intersecting surfaces at the side of osteotomized bone models was α=(5.97±0.13)°. (2) X-ray in bone defects: at postoperative 4 and 12 weeks, no obvious displacement and angulated deformity were found in bone grafts, suggesting the good bone defect repair. (3) Histological examination: at postoperative 4 weeks, bone scaffolds were filled with new bone in the experimental group. Furthermore, considerably increased new bone formation and mineralization were observed at postoperative 12 weeks. (4) General observation: no obvious displacement and angulated deformity occurred in bone defect grafts at postoperative 4 and 12 weeks. These findings suggest that rabbit anatomical models of large segmental tibial bone defects with good stability were constructed using three-dimensional prototyping technology, which may simulate the structure and function of bone tissue and be used for guiding the new bone regeneration.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: Tissue Engineering, Anatomy, Biomechanics

CLC Number:

R318

Bao Xiao-gang, Xu Guo-hua. Construction of rabbit anatomical three-dimensional models of large segmental tibial defects[J]. Chinese Journal of Tissue Engineering Research, 2016, 20(24): 3508-3515.

Figures/Tables 2

2.1 实验动物数量分析纳入新西兰大白兔15只(另有3只取材制作电子模型)，空白组3只均存活，对照组6只中有1只于术后10 d因腹泻死亡；实验组6只中有1只于术后约8 d腹泻死亡，1只于术后约24 d无明显诱因死亡；后及时补充实验组及对照组样本量恢复到6只，饲养过程无脱失者，最后15只新西兰大白兔进入结果分析。 2.2 模型创新性目前可利用成骨支架材料的研究较多，包括天然材料(同种异体骨、海藻酸盐、纤维蛋白等)，合成材料(聚己内酯和生物陶瓷等)，复合材料(聚己内酯/羟基磷灰石等)等[14-15]，这些支架材料都有其优点和缺陷，实验更关注的是材料的复合、加工和新的复合材料的利用，课题组前期研究的聚己内酯/羟基磷灰石复合材料已被证实具有良好的生物相容性、一定的可降解性、一定的机械负荷、适宜成骨细胞和内皮细胞等黏附和增殖等[4，16-18]；现拟利用成熟的3D打印技术制备结构、形状可控的组织工程骨支架，将有利于个性化的根据不同的骨缺损部位制备人工骨支架，有利于研究机械力学对负重部位骨缺损修复影响，同时也为一些结构不规则的骨缺损修复提供了可能，这种具备一定可降解性、一定机械负荷的解剖型组织工程骨支架可能更适合作为负重部位组织工程骨的研究基质[19-20]。 2.3 模型稳定性骨科生物医用材料自二战以后至今广泛研究，但真正能用于临床负重部位骨缺损修复的支架材料还未有报道。关于负重部位大段骨缺损修复文献的报道多为部分骨缺损的材料充填式成骨研究，包括课题组前期利用聚己内酯/羟基磷灰石复合材料修复山羊胫骨部分缺损研究。Diab等[7]利用电纺聚己内酯纳米纤维管装载骨形态发生蛋白2作为骨支架修复大鼠股骨大段完全骨缺损，但其模型对支架力学性却不做要求，并且行髓内钉和螺钉固定支架，其局部成骨作用基本靠骨形态发生蛋白2诱导成骨，其支架的意义并未体现。Liu等[8]利用DBB作为骨支架装载骨形态发生蛋白2修复山羊胫骨大段完全骨缺损；Yasuda等[9]利用同种异体骨装载骨形态发生蛋白2修复小鼠股骨大段完全骨缺损。目前这些研究并未考虑机械力学对负重部位骨缺损模型的重要影响，也未考虑骨支架与机体自体骨的解剖学匹配问题，其支架重建、修复过程中常出现局部畸形等缺陷，不具备广泛应用的特点[21-24]。其次，临床因为感染、创伤、肿瘤等所致骨缺损部位、形状及大小各不一致，实验通过计算机辅助技术设计3D打印的符合样本个体化解剖特点的组织工程骨支架，是组织工程骨支架个体化发展的必然要求。一方面，实验从结构上优化与控制组织工程三维支架，具有与骨缺损部位吻合的外形，有利于个性化的根据不同的骨缺损部位制备人工骨支架，同时也为一些结构不规则的结构部位的修复提供了可能[25-26]。 2.4 兔胫骨标本测量结果使用复旦大学高分子材料重点实验室MicroCT对3只新西兰大白兔双侧胫骨进行三维重建，得出长度(93.77±0.59) mm；胫腓交界横径(8.36±0.13) mm，矢状径(5.97±0.12) mm；骨皮质平均厚度(1.20±0.10) mm；髓腔平均直径(4.30±0.06) mm；胫骨模型侧面上下关节面中点连线与截骨模型侧面上下截面中点连线的夹角[α=(5.97±0.13)°]。根据图像结果分析出兔胫骨解剖参数，用于指导内固定安置。实验用自行设计的钢板在体外进行兔胫骨的固定，侧面和背面观可见钢板固定牢靠，长度和弧度适合兔胫骨(图2)。 2.5 解剖型组织工程骨构建及其生物力学测试见图3A-E。兔胫骨行CT扫描后，利用Mimic软件基于CT断层扫描计算机三维重建技术获得缺损骨的三维电子模型(图3B)。再对电子模型数据进行处理得到STL格式的文件，将此文件输入熔融沉积成型设备(FDM)制备解剖仿生人工骨支架(图3E)。该打印的解剖型组织工程骨抗压强度、弹性模量均接近自体骨且较临床常用的骨诱导人工骨有显著提高，具有较好的支持作用(表1)。"

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