Correlations between nanostructure and micromechanical properties of healing bone
Correlations between nanostructure and micromechanical properties of healing bone
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DOI：
10.1016/j.jmbbm.2017.08.022
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发表时间：
2018-01-01
影响因子：
3.9
通讯作者：
Wagermaier, Wolfgang
中科院分区：
文献类型：
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作者：
Hoerth, Rebecca M.;Kerschnitzki, Michael;Wagermaier, Wolfgang
已知骨中的所有等级水平都对其力学行为有贡献。基本构建块是矿化的胶原原纤维，其组装成具有不同原纤维组织的较大结构。在骨发育和愈合过程中，胶原组织从骨痂中的无序编织骨逐渐增加，逐渐被更高有序的板层骨取代，最终导致组织化程度最高的皮质板层骨。我们研究了股骨截骨小鼠模型，并分析了新形成的骨痂组织和皮质中成熟的板层骨。该模型显示了具有不同纤维组织的三种骨类型：（i）编织型、（ii）中度板层型和（iii）板层型。使用高分辨率同步辐射小角X射线散射结合背散射电子成像，我们的特点是不同地区的矿化程度，平均矿物颗粒厚度和矿物颗粒取向的超微结构。我们进一步使用显微压痕将硬度、诱导裂纹长度和裂纹模式与骨超微结构相关联。新形成的骨痂组织含有高度矿化的编织骨岛，具有厚但有序性差的矿物颗粒。这些岛被具有低矿化水平和薄但排列良好的颗粒的层状骨层包围。愈伤组织的硬度值较皮质低，裂纹较皮质长。骨痂编织骨比骨痂板层骨具有更短的裂纹。然而，由于其非常相似的层状组织和高度的矿物质颗粒orientation.In结论，我们证明，编织和越来越高的定向板层骨不仅在胶原纤维组织，而且数量，与板层骨相比，矿物颗粒的取向和不同形状也可能导致编织骨的机械能力降低。这可能解释了为什么许多生物体用更高组织的骨替代组织更少的骨类型。
All hierarchical levels in bone are known to contribute to its mechanical behavior. The basic building block is the mineralized collagen fibril which is assembled into larger structures with varying fibrillar organization. The collagen organization increases from unordered woven bone in the callus which is gradually replaced by higher ordered lamellar bone during bone development and healing and finally results in cortical lamellar bone with highest degree of organization. The structural and mechanical description of these organizational motifs is not yet complete.We investigated a femoral osteotomy mouse model and analyzed newly formed callus tissue and mature lamellar bone in the cortex. This model exhibits three bone types with different fibrillar organization: (i) woven, (ii) moderate lamellar and (iii) lamellar. Using high resolution synchrotron small angle X-ray scattering in combination with back-scattered electron imaging we characterized the ultrastructure of the different regions in terms of degree of mineralization, averaged mineral particle thickness and mineral particle orientation. We further used microindentation to correlate hardness, induced crack lengths and crack patterns with the bone ultrastructure.The newly formed callus tissue contains highly mineralized woven bone islands, featuring thick but poorly ordered mineral particles. Such islands are surrounded by layers of lamellar bone with a low mineralization level and thin but well aligned particles. Callus tissue shows lower hardness valties and longer cracks than the cortex. Callus woven bone exhibits shorter cracks than callus lamellar bone. However, the poorly mineralized callus lamellar bone shows crack propagation mechanisms similar to cortical bone due to its very similar lamellar organization and high degree of mineral particle orientation.In conclusion we demonstrate that woven and increasingly higher oriented lamellar bone do not only differ in collagen fibril organization, but also that the amount, orientation and different shape of mineral particles are also likely to contribute to the reduced mechanical competence of woven as compared to lamellar bone. This may explain why many organisms replace less organized bone types with higher organized ones.