Aragon Institute of Engineering Research, University of Zaragoza, María de Luna 3, 50018 Zaragoza, Spain.
Med Eng Phys. 2010 May;32(4):363-71. doi: 10.1016/j.medengphy.2010.01.010. Epub 2010 Mar 4.
The mechanical environment considerably affects the evolution of the bone healing process. However, the effect of an external cyclic stimulation on the process has not yet been fully clarified. The aim of the present work is to evaluate the distribution of different mechanical variables in the fracture callus when an external cyclic stimulation is applied at different frequencies, in order to investigate those stimuli most likely to regulate bone healing. To perform this analysis an axisymmetric poroelastic finite element model of a sheep metatarsus fracture has been developed and several mechanical variables quantified within the callus: deviatoric strain, octahedral strain, pore pressure and fluid flow velocity. The applied mechanical stimulus corresponds to a compression displacement of 0.02 mm at frequencies of 1, 50 and 100Hz. The fluid flow velocity experiences considerable variations in amplitude and peak value when the frequency of the external stimulus changes, while the rest of the mechanical variables are not significatively modified. We conclude that the change in the frequency of the external mechanical stimulus directly affects the interstitial fluid flow velocity in the fracture callus. This change in the fluid flow velocity may induce movement of wastes, feeds or growth factors, as well as stimulating cellular differentiation and proliferation by means of changes in the mechanical environment of the callus. In addition, the results of this work suggest that, to obtain a more significant effect of cyclic stimulation, higher frequencies with lower amplitude than those normally used in previous experimental works are needed.
机械环境会极大地影响骨愈合过程的演变。然而，外部循环刺激对该过程的影响尚未完全阐明。本工作的目的是评估在不同频率下施加外部循环刺激时，骨折痂中的不同力学变量的分布，以研究那些最有可能调节骨愈合的刺激。为了进行这种分析，开发了绵羊跖骨骨折的轴对称多孔弹性有限元模型，并在痂内量化了几种力学变量：偏应变、八面体应变、孔隙压力和流体流速。施加的力学刺激是在 1Hz、50Hz 和 100Hz 时施加 0.02mm 的压缩位移。当外部刺激的频率变化时，流体流速的振幅和峰值经历了相当大的变化，而其余的力学变量则没有显著改变。我们得出结论，外部机械刺激频率的变化直接影响骨折痂中的间质流体流速。这种流体流速的变化可能会通过改变痂的力学环境来诱导废物、饲料或生长因子的移动，并刺激细胞分化和增殖。此外，这项工作的结果表明，为了获得更显著的循环刺激效果，需要比以前的实验工作中通常使用的更高频率和更低振幅的刺激。
