Villemure I, Cloutier L, Matyas J R, Duncan N A
Department of Mechanical Engineering, Ecole Polytechnique of Montreal, P.O. Box 6079, Station Centre-ville, Montreal, Que., Canada H3C 3A7.
J Biomech. 2007;40(1):149-56. doi: 10.1016/j.jbiomech.2005.11.008. Epub 2005 Dec 27.
Growth plates are highly inhomogeneous in morphology and composition. Mechanical loading can modulate longitudinal bone growth, though the mechanisms underlying this mechanobiology are poorly understood. The proximal tibial growth plates of six rats were tested in vitro under uniaxial compression to 5% strain, and confocal microscopy was used to track and capture images of fluorescently labeled cell nuclei with increasing applied strains. The local strain patterns through the growth plate thickness were quantified using texture correlation analysis. The technique of texture correlation analysis was first validated by comparing theoretical simulated strain maps generated from numerically distorted images. The texture correlation algorithm was sensitive to the grid size superimposed on the original image, but remained insensitive to parameters related to the size of the final image mask, which was searched by the correlation algorithm for each grid point of the original image. Within the growth plate, experimental strain distributions were non-uniform in all six specimens. Growth plates were mostly under compression strains. The strain distributions differed among the histomorphological zones of the growth plate, which was most obvious in specimens with regular growth plate shape: higher compressive strains (4-8 times higher than the applied 5% strain) were located mainly in regions overlapping the reserve and hypertrophic zones with lower compressive strains in the proliferative zone. This study documents the non-uniform mechanical behavior of growth plate across its three histological zones when exposed to compression. Further investigation is required to establish the significance of non-uniform strain fields during growth in vivo.
生长板在形态和组成上高度不均匀。机械负荷可调节纵向骨生长，但其背后的力学生物学机制仍知之甚少。对六只大鼠的胫骨近端生长板进行体外单轴压缩至5%应变测试，并使用共聚焦显微镜跟踪和捕获随着施加应变增加的荧光标记细胞核图像。通过纹理相关分析对生长板厚度上的局部应变模式进行量化。纹理相关分析技术首先通过比较由数字失真图像生成的理论模拟应变图进行验证。纹理相关算法对叠加在原始图像上的网格大小敏感，但对与最终图像掩码大小相关的参数不敏感，该掩码由相关算法针对原始图像的每个网格点进行搜索。在生长板内，所有六个标本的实验应变分布均不均匀。生长板大多处于压缩应变状态。生长板组织形态学区域之间的应变分布不同，这在生长板形状规则的标本中最为明显：较高的压缩应变（比施加的5%应变高4 - 8倍）主要位于与储备区和肥大区重叠的区域，而增殖区的压缩应变较低。本研究记录了生长板在受到压缩时其三个组织学区域的非均匀力学行为。需要进一步研究以确定体内生长过程中非均匀应变场的意义。
