椎体后凸成形对邻近节段力学影响的有限元分析

Biomechanical effects of percutaneous kyphoplasty on adjacent vertebrae: A finite element analysis

背景：椎体后凸成形术自应用临床以来取得了令人鼓舞的临床效果,但是术后邻近椎体发生骨折时有报道。从生物力学角度来分析邻近椎体发生骨折的可能原因具有重要价值。目的：以有限元方法观察椎体后凸成形术对相邻椎体生物力学的影响,分析相邻椎体继发骨折的原因。方法：利用MIMICS软件对1例T12压缩骨折椎体后凸成形术前后的CT图片进行预处理,后导入ABAQUS软件中建立T10~L2的三维有限元模型,设置0.3,1.0,4.0MPa三种轴向载荷进行生物力学分析,观察不同载荷下模型整体及各部分的Von Mises应力,重点评价椎体后凸成形术对骨折相邻椎体生物力学的影响。结果与结论：成功建立了椎体后凸成形术前后的三维有限元模型,当轴向压力以0.3,1.0,4.0MPa增加后,椎间盘、软骨终板和椎体整体的应力也成比例增加。椎体后凸成形术后脊柱胸腰段各部位的应力开始重新分布,增强椎体（T12）的相邻椎间盘（T11~12、T12~L1）及相邻终板（T11下终板、L1上终板）的应力增强区域增加;T12相邻椎体（T11,L1）所受最大应力明显增加,但远端椎体（T10,L2）的最大应力明显减少。提示椎体后凸成形术后引起上下相邻椎体继发骨折可能与术后生物力学行为的改变有关。

BACKGROUND： Kyphoplasty has obtained favorable clinical effects, but adjacent vertebral fracture has been reported. Therefore, it is important to analyze the possible reasons for adjacent vertebral fracture based on biomechanics. OBJECTIVE： To explore the biomechanical effectsof percutaneous kyphoplasty （PKP） on adjacent vertebrae and analyze causes for adjacent vertebral fracture. METHODS： T10-L2 segment data were obtained from CT scans of a female with single T12 compressed fracture who underwent PKP. A three-dimensional finite element model of thoracolumbar Spine （T10-L2） was built in the MIMICS and the ABAQUS software. The stress on the annulus fiber, nucleus pulposus, endplate and facet joints under axial pressure （0.3, 1.0, and 4.0 MPa） were analyzed to evaluate the influence of PKP on the vertebrae adjacent to fractures. RESULTS AND CONCLUSION： The 3D finite element models before and after PKP were successfully established. The stresses were increased with increasing axial pressure. In the model after PKP, the stress augmentation scope on adjacent end plates （T11 low plate and L1 top plate） and intervertebral disc （T11-12 and T12-L1） increased. The maximum Von Mises stress on adjacent vertebrae （T11 and L1） increased, but the maximum Von Mises stress on end vertebrae （T10 and L2） decreased. Postoperative adjacent vertebral fracture after PKP may be related to the changes of biomechanical effects on adjacent vertebrae.