椎体后凸成形术对邻近节段的生物力学影响

目的 通过分析椎体后凸成形术对脊柱功能单位(FSU)的生物力学作用,探讨椎体后凸成形术对邻近节段的生物力学影响.方法 将16个胸椎FSU交替分配至两组,制成压缩骨折模型,对骨折椎体行椎体后凸成形术,分别用磷酸钙骨水泥(CPC)和聚甲基丙烯酸甲酯(PMMA)骨水泥灌注.测量手术前后FSU强度和刚度,不同载荷下椎间盘、椎体和后部结构的应力、应变值以及椎间盘的位移值.结果 术后CPC组和PMMA组FSU强度较术前分别增加14%和16%,刚度分别减少13%和12%.两组FSU未强化椎体的应力应变值均高于术前(P＜0.05),CPC组未强化椎体应力应变值低于PMMA组(P＜0.05).两组FSU术后椎间盘位移比术前明显减少(P＜0.01),CPC组椎间盘位移值大于PMMA组(P＜0.01).结论 椎体后凸成形术增强了FSU的生物力学性能,但可促使邻近节段退变,改变灌注剂材料特性可以改善对邻近节段的影响.

Biomechanical effect of kyphoplasty on adjacent segment

Objective To explore the effect of kyphoplasty on the adjacent segment.Methods Sixteen thoracic functional spine units(FSUs) were evenly assigned to one of two cement groups (CPC group and PMMA group). After the fracture models were established, the fractures were repaired using kyphoplasty with CPC or PMMA. Initial and postoperative strength and stiffness of FSUs, stress and strain of nucleus pulposus, vertebral bodies and posterior elements, and the values of displacement of nucleus pulposus were determined. Results Postoperative strength of two groups was significantly greater than the initial value, postoperative stiffness of two groups was significantly smaller than the initial value. Postoperative stress and strain of non-augmented vertebrae of two groups were significantly greater than the initial values,which of PMMA group were higher than those of CPC group. Postoperative displacement of the disks of two groups was significantly smaller than the initial value,which of PMMA group was lower than that of CPC group. Conclusion Kyphoplasty may facilitate the subsequent fracture of adjacent non-augmented vertebrae. Changes of biomechanical properties of cement could improve the effect on adjacent levels.