Strauss P J, Novotny J E, Wilder D G, Grobler L J, Pope M H
Spine Institute of New England, Williston, Vermont.
Spine (Phila Pa 1976). 1994 Apr 15;19(8):965-72. doi: 10.1097/00007632-199404150-00016.
To assess the biomechanical influences of the Graf fixation system on the spine, motion segments were tested. In normal spines, destabilized and restabilized with the Graf system conditions, the range of motion and flexibilities were found under various loading conditions.
These results should explain how the Graf Fixation system affects the biomechanical response of a motion segment.
Motion segments (L2-3) and (L4-5) were subjected to these loading conditions: compressive loading, flexion-extension, lateral bending, and axial rotation moments. During the loading, the main and coupled motions were measured, and flexibilities were computed. The position of the balance point in axial loading was also determined. The motion segments were tested under three conditions: intact, destabilized, and restabilized. The destabilization consisted of a bilateral total laminectomy (pedicle-to-pedicle). Restabilization was affected with the Graf stabilization system, consisting of polyester bands between pedicle screw implants.
The total laminectomy significantly changed the balance point location by moving it forward. The restabilized motion segment had a balance point more similar to normal conditions. The mean compressive compliance was significantly less after application of the Graf system compared with destabilization. The range of motion for flexion-extension and axial rotation was significantly reduced for the main motion with the Graf system. For lateral bending, the main and coupled rotations were affected significantly, with lateral bending and flexion-extension motion reduced and axial rotation increased after restabilization. Restabilization decreased the flexibility of the destabilized motion segment for all of the moments.
The Graf fixation system reduced the range of motion and the flexibility values in some loading conditions. These results only assess the immediate stabilization characteristics of this implant system in cadaveric material. Further research should address the fatigue characteristics.
为评估格拉夫固定系统对脊柱的生物力学影响，对运动节段进行了测试。在正常脊柱、使用格拉夫系统使其失稳后再稳定的情况下，在各种加载条件下测定了运动范围和柔韧性。
这些结果应能解释格拉夫固定系统如何影响运动节段的生物力学反应。
对（L2 - 3）和（L4 - 5）运动节段施加以下加载条件：压缩载荷、屈伸、侧弯和轴向旋转力矩。在加载过程中，测量主要运动和耦合运动，并计算柔韧性。还确定了轴向加载时平衡点的位置。运动节段在三种条件下进行测试：完整、失稳和再稳定。失稳包括双侧全椎板切除术（椎弓根至椎弓根）。使用格拉夫稳定系统进行再稳定，该系统由椎弓根螺钉植入物之间的聚酯带组成。
全椎板切除术通过使平衡点向前移动显著改变了其位置。再稳定的运动节段的平衡点与正常情况更相似。与失稳相比，应用格拉夫系统后平均压缩顺应性显著降低。使用格拉夫系统时，主要运动的屈伸和轴向旋转运动范围显著减小。对于侧弯，主要和耦合旋转受到显著影响，再稳定后侧弯和屈伸运动减少，轴向旋转增加。再稳定降低了失稳运动节段在所有力矩下的柔韧性。
格拉夫固定系统在某些加载条件下减小了运动范围和柔韧性值。这些结果仅评估了该植入系统在尸体材料中的即时稳定特性。进一步的研究应关注疲劳特性。
