骨陷窝-骨细胞形状和方向对骨单元内液体流动行为的影响

骨组织内的流体流动不仅为骨细胞的生存提供了充足营养供应及代谢物排放途径,也在骨重建过程中起到关键作用. 为了更精确地阐明骨内液体流动的具体形式,这项研究利用骨陷窝-骨细胞的密度,形态和方向等参数来计算骨单元内液体的流动行为. 首先,计算出不同形状和方向的骨陷窝周围骨小管的数量及分布情况,其次利用算出的参数以及骨组织其他微结构数据来估计骨组织的渗透率和孔隙率等参数,最后根据计算所得的参数建立骨单元的多孔弹性力学有限元模型,并分析了在轴向位移载荷作用下骨陷窝形状和方向对骨单元内液体渗流行为的影响. 结果表明,在所研究的参数范围内不同骨单元模型的相同区域上,骨陷窝形状影响下的骨单元最大压力和流速比最小的分别增加了86%和18%;骨陷窝方向影响下的最大压力和流速比最小的分别增加了125%和56%. 伸长形骨陷窝对单个骨单元局部压力的影响远大于扁平形和圆形骨陷窝. 骨陷窝从0°绕$x$轴旋转到90°过程中压力是逐渐降低的,且30°,45°和60°的模型对骨单元内局部流速有显著影响. 该模型表示骨陷窝的形状和方向以及骨小管的三维分布对骨单元内液体压力和流速幅值及沿不同方向的流动差异有显著的影响. 这项研究将有助于精确量化描述骨内液体的流体行为. 

EFFECT OF OSTEOCYTE-LACUNAE SHAPE AND DIRECTION ON THE FLUID FLOW BEHAVIOR IN OSTEON1)

In order to accurately describe the fluid flow in osteon, this study developed a method to describe the fluid anisotropic flow based on the density, shape and direction of lacunae. Firstly, the number and distribution of the bone canaliculi around the lacunae were calculated. Secondly, the permeability and porosity were estimated by using the calculated parameters and other microstructure data of bone tissue. Finally, the poroelastic finite element model of osteon was established according to the calculated parameters, and the influence of lacunae shape and direction on the fluid flow behavior in osteon under the axial displacement load was analyzed. The results showed that the lacunae shape and direction had a significant effect on the value and distribution of fluid pressure and velocity in osteon. For the range of parameters investigated, the influence of the lacunae shape on the maximum pressure and flow velocity in the same region of different osteon models can reach 86% and 18%, respectively, and the influence of the lacunae direction on that can reach 125% and 56%, respectively. In addition, the lacunae shape and direction had a great influence on the local pressure and velocity of a single osteon (up to 62% difference in fluid pressure between regions due to the influence of the lacunae shape, and up to 58% and 50% difference in fluid pressure and flow velocity due to the influence of the lacunae direction, respectively). The model showed that the lacunae shape and direction and the three-dimensional distribution of the canaliculus can determine the degree of anisotropy fluid flow in osteon. This study help to accurately quantify the anisotropic flow behavior of interstitial fluid of bone.