Voide Romain, van Lenthe G Harry, Müller Ralph
Institute for Biomedical Engineering, University and ETH Zürich, Moussonstrasse 18, 8044, Zurich, Switzerland.
Calcif Tissue Int. 2008 Jul;83(1):61-9. doi: 10.1007/s00223-008-9120-y. Epub 2008 Jun 11.
The femoral neck is a relevant and sensitive site for studying the degree of osteopenia. Engineering principles predict that bone structural parameters, like cross-sectional geometry, are important determinants of bone mechanical parameters. Mechanical parameters are also directly affected by the material properties of the bone tissue. However, the relative importance of structural and material properties is still unknown. The aim of this study was to compare bone competence and structural parameters between a murine strain showing a low bone mass phenotype, C57BL/6 (B6), and another one showing a high bone mass phenotype, C3H/He (C3H), in order to better determine the role of bone structure and geometry in bone failure behavior. Murine femora of 12- and 16-week-old B6 and 12- and 16-week-old C3H inbred strains were mechanically tested under axial loading of the femoral head. In order to assess the structural properties, we performed three-dimensional morphometric analyses in five different compartments of the mouse femur using micro-computed tomography. The mechanical tests revealed that B6 femora became stiffer, stronger, and tougher at 12-16 weeks, while bone brittleness stayed constant. C3H bone stiffness increased, but strength remained constant, work to failure decreased, and bone became more brittle. These age effects indicated that B6 did not reach peak bone properties at 16 weeks of age and C3H did reach maximal skeletal biomechanical properties before 16 weeks of age. Our investigations showed that 83% of the strength of the femoral neck in the B6 strain was explained by cortical thickness at this location; in contrast, in C3H none of the mechanical properties of the femoral neck was explained by bone structural parameters. The relative contributions of bone structural and material properties on bone strength are different in B6 and C3H. We hypothesize that these different contributions are related to differences at the ultrastructural level of bone that affect bone failure.
股骨颈是研究骨质减少程度的一个相关且敏感的部位。工程学原理预测，骨结构参数，如横截面几何形状，是骨力学参数的重要决定因素。力学参数也直接受骨组织材料特性的影响。然而，结构和材料特性的相对重要性仍然未知。本研究的目的是比较表现出低骨量表型的小鼠品系C57BL/6（B6）和表现出高骨量表型的另一品系C3H/He（C3H）之间的骨强度和结构参数，以便更好地确定骨结构和几何形状在骨破坏行为中的作用。对12周龄和16周龄的B6和12周龄和16周龄的C3H近交系小鼠股骨在股骨头轴向加载下进行力学测试。为了评估结构特性，我们使用微型计算机断层扫描对小鼠股骨的五个不同区域进行了三维形态分析。力学测试表明，B6股骨在12 - 16周时变得更硬、更强且更坚韧，而骨脆性保持不变。C3H骨硬度增加，但强度保持不变，破坏功降低，且骨变得更脆。这些年龄效应表明，B6在16周龄时未达到峰值骨特性，而C3H在16周龄之前确实达到了最大骨骼生物力学特性。我们的研究表明，B6品系股骨颈强度的83%可由该部位的皮质厚度解释；相比之下，在C3H中，股骨颈的力学性能均无法由骨结构参数解释。骨结构和材料特性对骨强度的相对贡献在B6和C3H中有所不同。我们推测这些不同的贡献与影响骨破坏的骨超微结构水平的差异有关。
