Dooris A P, Goel V K, Grosland N M, Gilbertson L G, Wilder D G
Iowa Spine Research Center, Departments of Biomedical Engineering andOrthopaedics, University of Iowa, Iowa City, Iowa, USA.
Spine (Phila Pa 1976). 2001 Mar 15;26(6):E122-9. doi: 10.1097/00007632-200103150-00004.
A nonlinear three-dimensional finite element model of the osteoligamentous L3-L4 motion segment was used to predict changes in posterior element loads as a function of disc implantation and associated surgical procedures.
To evaluate the effects of disc implantation on the biomechanics of the posterior spinal elements (including the facet joints, pedicles, and lamina) and on the vertebral bodies.
Although several artificial disc designs have been used clinically, biomechanical data-particularly the change in loads in the posterior elements after disc implantation-are sparse.
A previously validated intact finite element model was implanted with a ball-and-cup-type artificial disc model via an anterior approach. The implanted model predictions were compared with in vitro data. To study surgical variables, small and large windows were cut into the anulus, and the implant was placed anteriorly and posteriorly within the disc space. The anterior longitudinal ligament was also restored. Models were subjected to either 800 N axial compression force alone or to a combination of 10 N-m flexion-extension moment and 400 N axial preload. Implanted model predictions were compared with those of the intact model.
Facet loads were more sensitive to the anteroposterior location of the artificial disc than to the amount of anulus removed. Under 800 N axial compression, implanted models with an anteriorly placed artificial disc exhibited facet loads 2.5 times greater than loads observed with the intact model, whereas posteriorly implanted models predicted no facet loads in compression. Implanted models with a posteriorly placed disc exhibited greater flexibility than the intact and implanted models with anteriorly placed discs. Restoration of the anterior longitudinal ligament reduced pedicle stresses, facet loads, and extension rotation to nearly intact levels.
The models suggest that, by altering placement of the artificial disc in the anteroposterior direction, a surgeon can modulate motion-segment flexuralstiffness and posterior load-sharing, even though the specific disc replacement design has no inherent rotational stiffness.
采用L3 - L4节段骨韧带复合体的非线性三维有限元模型，以预测作为椎间盘植入及相关手术操作函数的后部元件负荷变化。
评估椎间盘植入对脊柱后部元件（包括小关节、椎弓根和椎板）及椎体生物力学的影响。
尽管几种人工椎间盘设计已应用于临床，但生物力学数据，尤其是椎间盘植入后后部元件负荷的变化却很稀少。
通过前路将球窝型人工椎间盘模型植入先前经验证的完整有限元模型。将植入模型的预测结果与体外数据进行比较。为研究手术变量，在纤维环上切开小窗口和大窗口，并将植入物置于椎间盘间隙的前方和后方。同时修复前纵韧带。模型单独承受800 N轴向压缩力，或承受10 N·m屈伸力矩和400 N轴向预负荷的组合。将植入模型的预测结果与完整模型的预测结果进行比较。
小关节负荷对人工椎间盘的前后位置比对纤维环切除量更敏感。在800 N轴向压缩下，人工椎间盘置于前方的植入模型显示小关节负荷比完整模型观察到的负荷大2.5倍，而人工椎间盘置于后方的植入模型预测压缩时无小关节负荷。人工椎间盘置于后方的植入模型比人工椎间盘置于前方的完整模型和植入模型具有更大的灵活性。前纵韧带的修复将椎弓根应力、小关节负荷和伸展旋转降低至接近完整水平。
模型表明，即使特定的椎间盘置换设计没有固有的旋转刚度，通过改变人工椎间盘在前后方向上的位置，外科医生也可以调节运动节段的弯曲刚度和后部负荷分担。
