不同骨水泥量在PKP术后对相邻节段生物力学影响的有限元分析

Biomechanical finite element analysis of adjacent vertebral bodies following percutaneous kyphoplasty with different amount of bone cement

目的采用三维有限元方法分析生理载荷作用下不同骨水泥量对伤椎及相邻节段生物力学影响的差异。方法利用MIMICS软件对60例骨质疏松性胸腰段单椎体压缩骨折行椎体后凸成形(PKP)手术前后的CT数据进行预处理,然后导入ABAQUS软件中建立三维有限元模型,设置0.3 MPa轴向载荷进行生物力学分析,评价不同骨水泥量PKP术后相邻节段生物力学差异及变化趋势。结果用三维重建软件Mimics 10.01和有限元软件Ansys 11.0成功进行三维模型有限元网格划分。椎体应力分布:术前应力主要分布于椎体前部,PKP术后应力集中于骨水泥附近,椎体整体前后应力改变。骨水泥增强后的伤椎应力明显增加,平均增加约15%(4 ml为8%,5 ml为13%,6 ml为17%,7 ml为22%),轴向刚度比术前骨质疏松椎体增加了约30%。在中立位时,伤椎成形后下位椎体的应力增加约18%(4 ml为15%,5 ml为18%,6 ml为20%,7 ml为23%)。椎间盘应力分布:在轴向施加载荷时,有局部后凸畸形的椎间盘前部会承受更大应力。结论 PKP术后可引起上下相邻节段生物力分布的改变,随着骨水泥注入量的增加,对生物力学的影响有增强趋势。

Objective To explore the biomeehanical effects of percutaneous kyphoplasty （PKP） on adjacent vertebrae and analyze biomechanical differences with different amount of bone cement for injured vertebra and the adjacent vertebrae. Methods There were CT scans data of 60 patients with compression fractures who underwent PKP. Three-dimensional finite element models of 60 patients were built in the MIMICS and the ABAQUS software. The stress on the vertebrae, disc and endplate under axial pressure （0.3 MPa） were analyzed to evaluate the influence of PKP on injured vertebrae and the adjacent vertebrae. Results Three-dimensional reconstruction software Mimics 10.01 and finite element software Ansys 11.0 were used to establish successfully three-dimensional model with finite element mesh. Vertebral stress distribution： Preoperative stress mainly distributed in front of the vertebral body. After PKP surgery, the stress concentration was around the bone cement, the whole vertebral body before and after the change of stress. Vertebral overall stress changed before and after surgery. After vertebroplasty, vertebrae stress damage was significantly increased, with an average increase of about 15%（4 ml of 8%, 5 ml of 13%, 6 ml of 17%, 7 ml of 22%）. Axial stiffness was increased by about 30% over the osteoporotie vertebral before surgery. In the neutral position, Vertebral fractures after vertebroplasty surgery, lower vertebral stress increased by about 18%（4 ml of 15%, 5 ml of 18%, 6 ml of 20%, 7 ml of 23%）. Disc stress distribution： When an axial load was applied, local kyphosis front discs were subjected to even greater stress. Conclusion The pereutaneous kyphoplasty changes the biomechanieal distribution on adjacent vertebrae. With the amount of bone cement increases, the biomeehanieal effect has the increasing trend.