Kumar Naresh, Judith Meakin R, Kumar Aravind, Mishra Viren, Robert Mulholland C
New Cross Hospital, Wolverhampton, United Kingdom.
Spine (Phila Pa 1976). 2005 Aug 1;30(15):1731-5. doi: 10.1097/01.brs.0000172160.78207.49.
A 2-dimensional axisymmetric finite element model of an intervertebral segment was used to investigate the stress patterns in the adjacent vertebrae of fused spinal segment incorporating 4 common cage designs. The same was used to study the effect of maturation of bone graft on stress distribution pattern.
To study and compare the stress distribution patterns in a normal spinal segment and in the adjacent vertebrae of a fused spinal segment. The effect of bone graft incorporation around the mesh cage was also investigated.
Lumbar fusion surgery is thought to relieve discogenic low back pain by eliminating the abnormal intersegmental movement at the level of disc degeneration. Successful spinal fusion does not guarantee symptomatic pain relief. Discogenic pain is also known to be associated with an abnormal load transmission pattern across the degenerate disc. We hypothesized that the lumbar interbody fusion results in relief of discogenic pain by normalizing the load distribution pattern.
We used a 2-dimensional axisymmetric finite element model of an intervertebral segment to investigate the stress patterns in the vertebrae adjacent to a fused spinal segment incorporating 4 common cage designs: (1) anterior lumbar interbody fusion, (2) posterior lumbar interbody fusion rectangular, (3) posterior lumbar interbody fusion threaded, and (4) mesh cage.
High stress concentrations and abnormal overall stress patterns were noted for all the cage designs studied. The anterior lumbar interbody fusion cage with its larger contact area showed the least abnormal stress magnitude in comparison with the other cages. Incorporation of bone in and around the mesh cage increased the area of contact and decreased the abnormal high stresses. The spine fusion model representing final bony healing showed restoration of near physiologic stress pattern.
Interbody fusion cages with larger area of contact between cage and vertebral endplate produces a lower stress distribution pattern. A successful bony fusion restores near physiologic stress distribution pattern. Restoration of near normal load distribution pattern may become an important aim of surgery for discogenic low back pain.
采用二维轴对称有限元模型来研究椎间节段，以探讨融合脊柱节段相邻椎体中4种常见椎间融合器设计的应力模式。同样利用该模型研究植骨成熟对应力分布模式的影响。
研究并比较正常脊柱节段和融合脊柱节段相邻椎体中的应力分布模式。还研究了网式融合器周围植骨融合的影响。
腰椎融合手术被认为可通过消除椎间盘退变节段的异常节段间运动来缓解椎间盘源性下腰痛。成功的脊柱融合并不能保证症状性疼痛缓解。椎间盘源性疼痛也已知与退变椎间盘上异常的负荷传递模式有关。我们假设腰椎椎间融合通过使负荷分布模式正常化来缓解椎间盘源性疼痛。
我们使用椎间节段的二维轴对称有限元模型来研究融合脊柱节段相邻椎体中4种常见椎间融合器设计的应力模式：（1）前路腰椎椎间融合；（2）后路矩形腰椎椎间融合；（3）后路带螺纹腰椎椎间融合；（4）网式融合器。
在所研究的所有融合器设计中均观察到高应力集中和异常的整体应力模式。与其他融合器相比，前路腰椎椎间融合器因其较大的接触面积显示出最小的异常应力大小。网式融合器内部及其周围的植骨增加了接触面积并降低了异常高应力。代表最终骨愈合的脊柱融合模型显示接近生理应力模式得以恢复。
椎间融合器与椎体终板之间接触面积较大时会产生较低的应力分布模式。成功的骨融合可恢复接近生理的应力分布模式。恢复接近正常的负荷分布模式可能成为椎间盘源性下腰痛手术的一个重要目标。
