Goto Keisuke, Tajima Naoya, Chosa Etsuo, Totoribe Koji, Kubo Shinichiro, Kuroki Hiroshi, Arai Takashi
Department of Orthopaedic Surgery, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki, 889-1692, Japan.
J Orthop Sci. 2003;8(4):577-84. doi: 10.1007/s00776-003-0675-1.
The risk of accelerating the degeneration of adjacent disc levels after lumbar spinal fusion is a controversial issue. A finite element model consisting of L1 to L5 lumbar spines was used to assess the effect on adjacent disc level after lumbar spinal fusion. We compared intact, L4/5 posterior interbody fusion (PLF), and L4/5 posterior lumbar interbody fusion (PLIF) models. The loading conditions applied were compressive force, compressive force plus flexion moment, and compressive force plus extension moment. Evaluations were made for von Mises stress on each vertebral end-plate, Tresca stress of all the annulus fibrosus, and Tresca stress of the annulus fibrosus from the posterior surface of the disc to the neural foramen. As the result, the von Mises stress adjacent to the fusion level was higher than the other nonfusion levels; it was higher under conditions of flexion moment loading plus compression loading [112% (2.59 PMa) in the PLF model and 117% (2.72 Mpa) in the PLIF model] than in the intact model. The Tresca stress of all the annulus fibrosus adjacent to the fusion level was higher than that on other nonfusion intervertebral levels; it was higher under conditions of flexion moment loading plus compression loading [127% (0.57 PMa) in the PLF model and 209% (0.89 Mpa) in the PLIF model] than in the intact model. The Tresca stress of the annulus fibrosus from the posterior surface of the disc to the neural foramen adjacent to the fusion level was higher than that on other nonfusion intervertebral levels; and it was higher under conditions of flexion moment loading plus compression loading [107% (1.48 PMa) in the PLF model and 112% (1.54 Mpa) in the PLIF model] than in the intact model. These findings demonstrate that with lumbar fusion, stresses on the vertebral end-plate and the annulus fibrosus were high adjacent to the fusion level; furthermore, stresses were higher in the PLIF model than in the PLF model. These results suggested that lumbar spinal fusion might bring with it a risk of damage to the annulus fibrosus and the vertebral end-plate adjacent to the fusion level.
腰椎融合术后相邻椎间盘节段加速退变的风险是一个存在争议的问题。使用包含L1至L5腰椎的有限元模型来评估腰椎融合术后对相邻椎间盘节段的影响。我们比较了完整模型、L4/5后外侧椎间融合（PLF）模型和L4/5后路腰椎椎间融合（PLIF）模型。施加的载荷条件为压缩力、压缩力加屈曲力矩以及压缩力加伸展力矩。对每个椎体终板的冯·米塞斯应力、所有纤维环的特雷斯卡应力以及从椎间盘后表面至神经孔的纤维环特雷斯卡应力进行了评估。结果显示，融合节段相邻处的冯·米塞斯应力高于其他未融合节段；在屈曲力矩加载加压缩加载条件下（PLF模型中为112%（2.59 PMa），PLIF模型中为117%（2.72 Mpa））高于完整模型。融合节段相邻处所有纤维环的特雷斯卡应力高于其他未融合椎间节段；在屈曲力矩加载加压缩加载条件下（PLF模型中为127%（0.57 PMa），PLIF模型中为209%（0.89 Mpa））高于完整模型。从椎间盘后表面至融合节段相邻神经孔的纤维环特雷斯卡应力高于其他未融合椎间节段；在屈曲力矩加载加压缩加载条件下（PLF模型中为107%（1.48 PMa），PLIF模型中为112%（1.54 Mpa））高于完整模型。这些发现表明，腰椎融合时，融合节段相邻处椎体终板和纤维环上的应力较高；此外，PLIF模型中的应力高于PLF模型。这些结果提示，腰椎融合可能会带来融合节段相邻处纤维环和椎体终板受损的风险。
