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首页> 外文期刊>Journal of Biomechanics >The poro-elastic behaviour of the intervertebral disc: A new perspective on diurnal fluid flow
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The poro-elastic behaviour of the intervertebral disc: A new perspective on diurnal fluid flow

机译：椎间盘的孔隙弹性行为：日间流体流动的新观点

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Diurnal disc height changes, due to fluid in- and outflow, are in equilibrium while daytime spinal loading is twice as long as night time rest. A direction-dependent permeability of the endplates, favouring inflow over outflow, reportedly explains this; however, fluid flow through the annulus fibrosus should be considered. This study investigates the fluid flow of entire intervertebral discs. Caprine discs were pre-loaded in saline for 24 h under four levels of static load. Under sustained load, we modulated the disc's swelling pressure by exchanging saline for demineralised water (inflow) and back to saline (outflow), both for 24 h. We measured disc height creep and used stretched exponential models to determine time constants. During inflow disc height increased in relation to applied load, and during outflow disc height decreased to preload levels. When comparing in- and outflow phases, there was no difference in creep, and time-constants were similar indicating no direction-dependent resistance to fluid flow in the entire intervertebral disc. Results provoked a new hypothesis for diurnal fluid flow: in vitro time-constants for loading are shorter than for unloading and in vivo daytime loading is twice as long as night time unloading, i.e. in diurnal loading the intervertebral disc is closer to loading equilibrium than to unloading equilibrium. Per definition, fluid flow is slower close to equilibrium than far from equilibrium; therefore, as diurnal loading occurs closer to loading equilibrium, fluid inflow during night time unloading can balance fluid outflow during daytime loading, despite a longer time-constant. (C) 2015 Elsevier Ltd. All rights reserved.
机译：由于液体的流入和流出，昼间盘高度变化达到平衡，而白天的脊柱负荷是夜间休息时间的两倍。据报道，端板的与方向有关的渗透性有利于流入而不是流出，这解释了这一点。但是，应考虑流经纤维环的液体。这项研究调查了整个椎间盘的流体流动。在四个水平的静态负荷下，将山羊圆盘在盐水中预负荷24小时。在持续的负载下，我们通过将盐水交换为软化水（流入）和回盐水（流出）为时24小时，来调节椎间盘的溶胀压力。我们测量了圆盘高度的蠕变，并使用了拉伸指数模型来确定时间常数。相对于施加的载荷，流入盘的高度增加，而流出盘的高度减小至预载水平。比较流入和流出阶段时，蠕变没有差异，并且时间常数相似，表明在整个椎间盘中对流体的流动没有方向依赖性。结果激发了昼夜流体流动的新假设：体外负荷的时间常数比卸荷的时间常数短，而白天的体内负荷是夜间负荷的两倍，即在白天负荷下，椎间盘更接近负荷平衡而不是负荷。卸荷平衡。按照定义，接近平衡状态的流体流动要比远离平衡状态的流体慢。因此，由于昼夜负荷接近负荷平衡，尽管时间常数较长，但夜间卸货期间的流体流入可以平衡白天负荷下的流体流出。 （C）2015 Elsevier Ltd.保留所有权利。

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