单侧椎板开窗髓核摘除术对相邻节段椎间盘的生物力学影响

The Biomechanics Influence of unilateral laminectomy and discectomy surgery on the adjacent different grades of Disc Degeneration

目的应用非线性有限元分析研究单侧椎板开窗髓核摘除术对相邻节段不同程度退变椎间盘应力分布的影响。方法基于断层cT图像建立L3～L5节段三维非线性有限元模型，并依据13～L4椎间盘不同退变程度建立轻、中和重度退变有限元模型，以及单侧椎板开窗髓核摘除术后模型。在模拟前屈、后伸、左右侧弯和左右旋转六个主要生理活动条件下，分析相邻：宵段椎间盘L3～L4髓核和纤维环vonMises应力极值变化。结果行L4－L5左侧椎板肝窗髓核摘除后，相邻13～L4椎间盘为健康椎间盘时，髓核和纤维环基质内yonMises应力极值后伸最大，左侧弯时最小；轻度退变时，应力极值在左侧弯时增加最明显；中度退变时．髓核和纤维环基质vonMises应力极值减小，但仍高于健康椎间盘应力；重度退变时，髓核内VOllMises应力极值均较轻中度椎间盘退变时下降，除轴向旋转运动外，甚至低于健康椎间盘时的应力值；纤维环基质内vonMises应力值较轻中度退变时下降，但仍高于健康椎间盘内纤维环应力，尤以左侧弯时明显。结论当相邻节段椎间盘退变时，行单侧椎板开窗髓核摘除后避免同侧侧弯可以减少异常应力的产生，降低椎间盘退变加速的风险。

Objectives To study the stress distribution of the adjacent different grades of disc degeneration underwenting unilateral laminectomy and discectomy surgery using non-linear finite element analysis. Methods Based on the lumbar CT scans, the finite element model （FEM） of lumbar spinal segment（L3-L5） was established. According to L3-L4, intervertebral disc degeneration, different grades of disc degeneration （ healthy, mild, moderate and severe） models were established and unilateral laminectomy and discectomy surgery were also established. Physiological action such as flextion , extension , lateral bending and lateral rotation was simulated and the von Mises stress in the nucleus pulposus and annulus fibrosus matrix of L3-L4 disc was investagated. Results After unilateral laminectomy and discectomy surgery, the extremum value of von Mises stress of nucleus pulposus and annulus fibrosus matrix was maximum during extension and minimus left bending in the healthy intervertebral disc. Compared with healthy disc, the increment of extremum value was found during left bending in the mildly degenerated disc. When the value decreased in the moderately degenerated disc, but still higher than that in the healthy disc. When the adjacent disc is severly degenerated, the extremum value of nucleus pulposus decreased, in addition to axial rotation, and even lower than that of healthy disc. The value of annulus matrix decreased and still higher than that of healthy disc , especially during left bending. Conclusions After unilateral laminectomy and discectomy surgery, avoiding lateral bending will reduce the abnormal stress in the degenerated disc and decreased the risk of accelerating disc degeneration.