Tissue Mechanics Laboratory, Bioengineering Graduate Program, University of Notre Dame, IN 46556, USA.
J Biomech. 2012 Aug 31;45(13):2222-9. doi: 10.1016/j.jbiomech.2012.06.020. Epub 2012 Jul 9.
Low-magnitude high-frequency (LMHF) loading has recently received attention for its anabolic effect on bone. The mechanism of transmission of the anabolic signal is not fully understood, but evidence indicates that it is not dependent on bone matrix strain. One possible source of signaling is mechanostimulation of the cells in the bone marrow. We hypothesized that the magnitude of the fluid shear stress in the marrow during LMHF loading is in the mechanostimulatory range. As such, the goal of this study was to determine the range of shear stress in the marrow during LMHF vibration. The shear stress was estimated from computational models, and its dependence on bone density, architecture, permeability, marrow viscosity, vibration amplitude and vibration frequency were examined. Three-dimensional finite element models of five trabecular bone samples from different anatomic sites were constructed, and a sinusoidal velocity profile was applied to the models. In human bone models during axial vibration at an amplitude of 1 g, more than 75% of the marrow experienced shear stress greater than 0.5Pa. In comparison, in vitro studies indicate that fluid induced shear stress in the range of 0.5 to 2.0Pa is anabolic to a variety of cells in the marrow. Shear stress at the bone-marrow interface was as high as 5.0Pa. Thus, osteoblasts and bone lining cells that are thought to reside on the endosteal surfaces may experience very high shear stress during LMHF loading. However, a more complete understanding of the location of the various cell populations in the marrow is needed to quantify the effects on specific cell types. This study suggests the shear stress within bone marrow in real trabecular architecture during LMHF vibration could provide the mechanical signal to marrow cells that leads to bone anabolism.
低频高幅（LMHF）加载因其对骨骼的合成代谢作用而受到关注。传递合成代谢信号的机制尚未完全了解，但有证据表明，它不依赖于骨基质应变。信号传递的一个可能来源是骨髓细胞的力刺激。我们假设在 LMHF 加载过程中骨髓中的流体切应力幅度处于力刺激范围内。因此，本研究的目的是确定 LMHF 振动过程中骨髓中的切应力范围。切应力是通过计算模型估计的，并研究了其对骨密度、结构、渗透性、骨髓粘度、振动幅度和振动频率的依赖性。构建了来自不同解剖部位的五个小梁骨样本的三维有限元模型，并将正弦速度分布应用于模型。在 1g 轴向振动的人体骨模型中，超过 75%的骨髓经历的切应力大于 0.5Pa。相比之下，体外研究表明，在 0.5 至 2.0Pa 范围内的流体诱导切应力对骨髓中的各种细胞具有合成代谢作用。骨-骨髓界面处的切应力高达 5.0Pa。因此，被认为位于骨内膜表面的成骨细胞和骨衬细胞在 LMHF 加载期间可能经历非常高的切应力。然而，需要更全面地了解骨髓中各种细胞群体的位置，以量化对特定细胞类型的影响。本研究表明，在真实小梁结构中 LMHF 振动过程中骨髓内的切应力可以为骨髓细胞提供导致骨合成代谢的机械信号。
