Three-dimensional Finite Element Analysis of a Human Lumbar Spinal Surgery: Topology Optimization Design of the Dynamic Spinal Fixator
Date Issued
2014
Date
2014
Author(s)
Lin, Hung-Ming
Abstract
Surgeons often use spinal fixators to manage spinal instability. Dynamic spinal fixators, such as the Dynesys (DY) and K-ROD (KD) systems, are designed to restore spinal stability and to provide flexibility. The long-term complications of implant breakage and the biomechanics of the adjacent and the bridged levels using KD system are still unknown. In addition, it is important to optimize the dynamic implant stiffness for desired spinal range of motion (ROM) achievement. As first, this study investigates stiffness of KD system and shows the stiffer structure from KD system. Afterwards, this study is to design a new spinal fixator using topology optimization (topology design (TD) system) to reduce the overall stiffness. Also, this study proceeds to investigate and compare the biomechanical effects of DY, KD, and TD system. Here, this study constructed finite element (FE) models of degenerative disc disease (DDD), DY, KD, and TD system. A hybrid-controlled analysis was applied to each of the four FE models. The rod structure of the topology optimization was modeled at a 39% reduced volume compared with the rigid rod. The FE results indicated that KD system supplies the greater stiffness during extension and the lower stiffness during flexion, in contrast to DY system. In contrast to DY system, KD system increased zygapophysial joint force of adjacent level, but this system decreased the cranial adjacent disc and pedicle screw stress during flexion. Additionally, KD and DY systems increased stiffness to within 47% of the value in the DDD model in all motions. As for TD system, it provided the softer rigidly structure during flexion in contrast to KD and DY system and was similar to DY system in terms of rigidly construct during extension, lateral bending, and torsion. TD system reduced the load in cranial adjacent disc and adjacent zygapophysial joint. The implant was burdened with TD system. Hence, topology design system is possible to avoid early adjacent disc and zygapophysial joint degeneration. Nevertheless, in contrast to KD and DY system, the lower load in the pedicle screw of TD system may prolong the life of pedicle screw in fatigue performance.
Subjects
拓樸最佳化
有限元素分析
脊椎生物力學
動態脊椎穩定器
Dynesys
K-ROD
SDGs
Type
thesis
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