Finite element analysis of the biomechanical characteristics of ankylosing kyphosis osteotomy using the vertebral column decancellation and the vertebral column resection

doi:10.3969/j.issn.2095-4344.2017.31.017

Abstract

Abstract:

BACKGROUND: Patients with severe ankylosing kyphosis are often treated with orthopedic osteotomy, but with high surgical risk, treatment schemes are individualized, and the biological morphology and mechanical properties of the deformed spine are complex. Meanwhile, the finite element model is more adaptable for biomechanical analysis of the spinal deformity. However, its application in the treatment of ankylosing kyphosis in China was little reported.

OBJECTIVE: To establish an ankylosing kyphosis finite element model so as to investigate the relationship between different osteotomy methods and the deformation and stress distribution of the spine.

METHODS: A three-dimensional finite element model of ankylosing kyphosis was established, and then imported into ANASYS software, to simulate vertebral column decancellation and vertebral column resection at T₁₂ and L₁levels, respectively. The vertebrae and screw were loaded with the same load, and deformation and stress nephograms were obtained.

RESULTS AND CONCLUSION: (1) The deformation of the osteotomy at T₁₂ level was significantly larger than that at L₁ level. (2) The stress distribution of the decancellation osteotomy concentrated on the pedicle screw and titanium bar; the stress concentration of vertebral column resection was the intervertebral cage. (3) Individualized surgical treatment of ankylosing kyphosis may influence the selection of the osteotomy segment and osteotomy operation. The osteotomy segment may affect the stability of the spine, and stress distribution of internal fixation is likely related to the method of internal fixation. (4) This conclusion may provide theoretical reference for the biomechanical study of analysing ankylosing kyphosis.

中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程

Key words: Kyphosis, Osteotomy, Finite Element Analysis, Biomechanics, Tissue Engineering

CLC Number:

R318

Duan Yan-ji, Ma Jun-yi, Li Hui, Li Li, Ma Yuan. Finite element analysis of the biomechanical characteristics of ankylosing kyphosis osteotomy using the vertebral column decancellation and the vertebral column resection [J]. Chinese Journal of Tissue Engineering Research, 2017, 21(31): 5019-5024.

Figures/Tables 3

2.1 各种模拟截骨全脊柱模型的整体位移趋势结果显示，T12的两种截骨方式最大变形位移在5.0 mm以上，L1的变形位移在3.3 mm左右，该强直性脊柱后凸患者在4种工况下的全脊柱位移趋势分布云图显示，无论是全脊椎截骨术还是去松质骨截骨术，T12椎体的整体位移趋势都大于L1椎体(图4)。提示截骨节段对位移的影响显著。而分别在L1和T12选用去松质骨截骨及全脊椎截骨时，发现全脊椎截骨术位移趋势均略大于去松质骨截骨术(表2)。 2.2 椎弓根螺钉及钛棒的应力分布趋势在4种工况下，螺钉、钛棒的最大主应力、等效应力均出现在L1节段的去松质骨截骨，分别为241.99和285.52 MPa(表3)。L1全脊椎截骨模型中，最强等效应力及主应力较小，为72.149和83.195 MPa，其中螺钉的最强等效应力出现在L2的左侧的椎弓根螺钉，最大主应力表现为L2椎体右侧椎弓根螺钉(图5)。4种截骨方式下，L1椎体去松质骨截骨钛棒的应力最大，L1椎体的全脊椎截骨内固定棒的最大主应力及等效应力最小，其应力最大点位于钛棒置入螺钉节段的右侧，且集中于截骨节段的邻近节段，并显示越远离截骨节段的置钉节段，Mises云图最大主应力逐渐递减，而4种工况下的椎弓根螺钉及钛棒呈现出的应力分布趋势类似(表4)。 2.3 截骨接触面椎体(或钛笼)的应力分布在去松质骨截骨术截骨中，截骨椎体后方闭合，两椎体之间形成接触面，截骨接触面应力(等效应力与最大主应力)分别见表3。L1截骨接触面为9.976 3与6.340 8 MPa(图6)，T12截骨接触面分别为11.860和4.831 2 MPa。全脊椎截骨的截骨椎体使用钛笼支撑，因此模型将钛笼设置为刚性固定，分析钛笼所承受应力，该模型L1的全脊椎截骨钛笼等效应力与最大主应力分别是43.886和51.075 MPa(图6)，L1去松质骨截骨术模型则为42.534 MPa(等效应力)和31.213 MPa(最大主应力)。"

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