Shirazi-Adl A
Department of Mechanical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada.
Spine (Phila Pa 1976). 1992 Feb;17(2):206-12.
The effect of alteration in the nucleus fluid content on the mechanics of a lumbar motion segment was analyzed by a finite-element model. Various combined loads were applied on the lumbar segment and were then kept constant while the disc-confined fluid was changed incrementally to a maximum of 12% gain or loss in its original volume. Change in the nucleus volume directly affected the intradiscal pressure. Loss of nucleus fluid content increased the contact forces on the facets and diminished tensile forces in the anulus fiber layers. The inner anulus layers were more affected than the outer ones. Reverse trends were computed when the nucleus fluid content was increased. Except in combined extension and compression loading, fluid gain increased the segmental stiffness while the overall stiffness lessened with loss of fluid content. Loss of the nucleus fluid caused inward bulge at the inner anulus layers and altered the stress distribution in the vertebral bodies. The nucleus material normally carries a portion of the applied compression and stresses and supports the surrounding anulus layers. A loss in the nucleus-confined fluid disrupted the normal mechanical function of the nucleus, whereby disc anulus layers were predisposed to lateral instability and disintegration, and hence to further degeneration; facets were subjected to significant additional loads; and vertebral bodies underwent a markedly different stress distribution.
通过有限元模型分析了髓核液体含量变化对腰椎运动节段力学性能的影响。对腰椎节段施加各种组合载荷，然后保持恒定，同时椎间盘内的液体以其原始体积最多增加或减少12%的幅度逐渐变化。髓核体积的变化直接影响椎间盘内压力。髓核液体含量的减少增加了小关节上的接触力，并减小了纤维环层中的拉力。纤维环内层比外层受影响更大。当髓核液体含量增加时，计算结果呈现相反趋势。除了在伸展和压缩联合加载时，液体增加会增加节段刚度，而随着液体含量的减少，整体刚度会降低。髓核液体的流失导致纤维环内层向内膨出，并改变了椎体中的应力分布。髓核物质通常承受一部分施加的压缩力和应力，并支撑周围的纤维环层。髓核内液体的流失破坏了髓核的正常力学功能，从而使椎间盘纤维环层易于发生侧向不稳定和崩解，进而导致进一步退变；小关节承受显著的额外载荷；椎体的应力分布也明显不同。
