Modeling Degenerative Disk Disease in the Lumbar Spine: A Combined Experimental, Constitutive, and Computational Approach
Modeling Degenerative Disk Disease in the Lumbar Spine: A Combined Experimental, Constitutive, and Computational Approach
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DOI：
10.1115/1.4007632
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发表时间：
2012-10-01
影响因子：
1.7
通讯作者：
Puttlitz, Christian M.
中科院分区：
文献类型：
--
作者：
Ayturk, Ugur M.;Gadomski, Benjamin;Puttlitz, Christian M.
使用连续体方法对椎间盘纤维环的本构力学行为进行建模，具有促进这种临床重要组织的形态学和生物力学相关性的潜力。将椎间盘组织的连续表示应用到计算模型中，将为研究退行性疾病的影响提供一个特别有价值的工具。然而，到目前为止，在文献中朝着这个目标的相关努力已经受到限制，由于缺乏一个计算上易处理和可实现的本构函数。为了解决这一问题，在平面双轴拉伸下对从总共15个健康和退化椎间盘中采集的环形样本进行了测试。应变能函数的预测，这是以前被证明是无条件凸，适合的实验数据，和优化的系数被用来修改以前验证的有限元模型的L4/L5功能脊柱单元。优化的材料系数的基础上的实验结果表明，在微观层次的取向分散的胶原纤维和这些纤维的机械非线性，由于变性的增加。另一方面，有限元模型预测，由于最初的核，然后整个磁盘的逐步退化，在纤维环中的应力产生的逐步增加。在所有旋转载荷方向（轴向旋转除外），预计活动范围最初随髓核退化而增加，然后随瓣环退化而减少。总体而言，观察到退化会特别影响瓣环胶原纤维网络的功能有效性，导致组织水平和运动节段水平的生物力学行为发生变化。[DOI电话：10.1115/1.4007632]
Using a continuum approach for modeling the constitutive mechanical behavior of the intervertebral disk's annulus fibrosus holds the potential for facilitating the correlation of morphology and biomechanics of this clinically important tissue. Implementation of a continuum representation of the disk's tissues into computational models would yield a particularly valuable tool for investigating the effects of degenerative disease. However, to date, relevant efforts in the literature towards this goal have been limited due to the lack of a computationally tractable and implementable constitutive function. In order to address this, annular specimens harvested from a total of 15 healthy and degenerated intervertebral disks were tested under planar biaxial tension. Predictions of a strain energy function, which was previously shown to be unconditionally convex, were fit to the experimental data, and the optimized coefficients were used to modify a previously validated finite element model of the L4/L5 functional spinal unit. Optimization of material coefficients based on experimental results indicated increases in the micro-level orientation dispersion of the collagen fibers and the mechanical nonlinearity of these fibers due to degeneration. On the other hand, the finite element model predicted a progressive increase in the stress generation in annulus fibrosus due to stepwise degeneration of initially the nucleus and then the entire disk. Range of motion was predicted to initially increase with the degeneration of the nucleus and then decrease with the degeneration of the annulus in all rotational loading directions, except for axial rotation. Overall, degeneration was observed to specifically impact the functional effectiveness of the collagen fiber network of the annulus, leading to changes in the biomechanical behavior at both the tissue level and the motion-segment level. [DOI: 10.1115/1.4007632]