Finite element analysis after rod fracture of the spinal hybrid elastic rod system

Hsieh, Ju‐Ton; Chen, Chin‐Sheng; Chuang, Shao-Ming; Wang, Jyh-Horng; Chen, Po-Quang; Huang, Yi‐You

doi:10.1186/s12891-022-05768-x

Cited by 3 publications

(1 citation statement)

References 23 publications

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“…In an in vitro study, it is difficult to obtain a cadaveric specimen and the individual difference that exist in a clinical experiment. Additionally, the stress flow of the lumbar spine, while giving to external moment, is difficult to be visualized in the in vitro study [ 34 , 35 ]. The FE technique was able to design a new orthopedic device and analyze its biomechanical features [ 36 , 37 , 38 , 39 ].…”

Section: Discussionmentioning

confidence: 99%

Biomechanical Effects of a Novel Pedicle Screw W-Type Rod Fixation for Lumbar Spondylolysis: A Finite Element Analysis

et al. 2023

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Lumbar spondylolysis involves anatomical defects of the pars interarticularis, which causes instability during motion. The instability can be addressed through instrumentation with posterolateral fusion (PLF). We developed a novel pedicle screw W-type rod fixation system and evaluated its biomechanical effects in comparison with PLF and Dynesys stabilization for lumbar spondylolysis via finite element (FE) analysis. A validated lumbar spine model was built using ANSYS 14.5 software. Five FE models were established simulating the intact L1–L5 lumbar spine (INT), bilateral pars defect (Bipars), bilateral pars defect with PLF (Bipars_PLF), Dynesys stabilization (Bipars_Dyn), and W-type rod fixation (Bipars_Wtyp). The range of motion (ROM) of the affected segment, the disc stress (DS), and the facet contact force (FCF) of the cranial segment were compared. In the Bipars model, ROM increased in extension and rotation. Compared with the INT model, Bipars_PLF and Bipars_Dyn exhibited remarkably lower ROMs for the affected segment and imposed greater DS and FCF in the cranial segment. Bipars_Wtyp preserved more ROM and generated lower stress at the cranial segment than Bipars_PLF or Bipars_Dyn. The injury model indicates that this novel pedicle screw W-type rod for spondylolysis fixation could return ROM, DS, and FCF to levels similar to preinjury.

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Section: Discussionmentioning

confidence: 99%

Biomechanical Effects of a Novel Pedicle Screw W-Type Rod Fixation for Lumbar Spondylolysis: A Finite Element Analysis

et al. 2023

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Changing rod stiffness to moderate stress of adjacent disc in oblique lumbar interbody fusion - A finite element analysis

Chou,

Chen,

Chen

et al. 2024

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Background OLIF (oblique lumbar interbody fusion) is a minimally invasive surgery to treat spinal instability. However, clinical studies indicated the early degeneration of adjacent segments after surgery. The rod stiffness of OLIF was associated with change at adjacent segments. Therefore, the study aimed to compare the biomechanical effects of OLIF with different rod material properties using the finite element (FE) method.Methods A validated L1-L5 lumbar spine was conducted in the biomechanical analysis using FE software ANSYS. The FE model of OLIF with a rod was created. Current biocompatible materials for the rod of the OLIF model were changed, including titanium alloy (OLIF_Ti), nickel-titanium alloy (OLIF_NiTi), and polycarbonate urethane (OLIF_PCU) rod. Four FE models, consisting of the intact model (INT) and implant models, were created. Hybrid control loads, such as flexion, extension, rotation, and lateral bending, were subjected to four models on the L1 vertebral body. The bottom of the L5 vertebral body was fixed.Results At the surgical level, while compared to the INT model, the OLIF_Ti and OLIF_NiTi model resulted in a ROM reduction of over 40% at least, but the OLIF_PCU changed about 10% in flexion and extension. At adjacent level L2-L3, the FE results indicated that the OLIF_Ti and OLIF_NiTi model increased more stress by about 12% at least than the INT model at the adjacent segment, but it demonstrated that the OLIF_PCU would not result in stress rise at the adjacent level L2-L3 in flexion and extension.Conclusion The study concluded that rod stiffness was associated with change at the adjacent segments. The use of OLIF surgery with PCU rods can minimize the impact of the adjacent segment after lumbar fusion.

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Comparison of the Optimal Design of Spinal Hybrid Elastic Rod for Dynamic Stabilization: A Finite Element Analysis

et al. 2022

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The spinal hybrid elastic (SHE) rod is a semi-rigid pedicle screw-based rod for spinal dynamic stabilization. This study investigated the biomechanical effects of different ratios of SHE rod using finite element analysis (FEA). A three-dimensional nonlinear FEA of an intact lumbar spine model (INT) was constructed. The SHE rod was composed of an inner nitinol stick (NS) and an outer polycarbonate urethane shell (PS). Four groups implanted at L3–L4 had the same outer diameter (5.5 mm) but different NS diameter/PS thickness ratios: Nt45, Nt35, Nt25, and Nt15. The resultant intervertebral range of motion (ROM), disc stress, facet joint contact force, screw stress, NS stress, and PCU stress were analyzed. The results indicated that ROM, disc stress, and facet force decreased moderately in the implanted L3–L4 levels and increased slightly in the adjacent L2–L3 levels. The NS stress and NS diameter trended towards inverse proportionality. Changing the ratio did not markedly influence screw or PS stress. The SHE rod system with elastic NS and insulated PS has a 5.5 mm diameter for universal pedicle screws. The SHE rod system provides sufficient spinal support and increases gentle adjacent segment stress. Considering the durability, the optimal NS diameter/PS thickness ratio of the SHE rod system is 3.5/2.0 mm.

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Finite element analysis after rod fracture of the spinal hybrid elastic rod system

Cited by 3 publications

References 23 publications

Biomechanical Effects of a Novel Pedicle Screw W-Type Rod Fixation for Lumbar Spondylolysis: A Finite Element Analysis

Biomechanical Effects of a Novel Pedicle Screw W-Type Rod Fixation for Lumbar Spondylolysis: A Finite Element Analysis

Changing rod stiffness to moderate stress of adjacent disc in oblique lumbar interbody fusion - A finite element analysis

Comparison of the Optimal Design of Spinal Hybrid Elastic Rod for Dynamic Stabilization: A Finite Element Analysis

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