Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis

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5 Citations (Scopus)

Abstract

Background data Combined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear. Methods Using a validated lumbosacral finite-element model, three variations at the L4–L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedicle screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated. Findings The adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6%, 47.3%, and 59.6%, respectively. However, these changes were reduced to 30.1%, 22.7%, and 27.0% after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms. Interpretation Fixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons.

Original languageEnglish
Pages (from-to)115-120
Number of pages6
JournalClinical Biomechanics
Volume43
DOIs
Publication statusPublished - Mar 1 2017

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Finite Element Analysis
Intervertebral Disc Degeneration
Disease Progression
Spine
Head
Pedicle Screws
Surgeons
Intervertebral disc disease

Keywords

  • Adjacent segment disease
  • Finite element
  • Interbody fusion
  • Spinal fixator

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine

Cite this

@article{3210bf0dde33411abbdd06cb72f560db,
title = "Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion: A finite element analysis",
abstract = "Background data Combined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear. Methods Using a validated lumbosacral finite-element model, three variations at the L4–L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedicle screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated. Findings The adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6{\%}, 47.3{\%}, and 59.6{\%}, respectively. However, these changes were reduced to 30.1{\%}, 22.7{\%}, and 27.0{\%} after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms. Interpretation Fixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons.",
keywords = "Adjacent segment disease, Finite element, Interbody fusion, Spinal fixator",
author = "Hsieh, {Yueh Ying} and Chen, {Chia Hsien} and Tsuang, {Fon Yih} and Wu, {Lien Chen} and Lin, {Shang Chih} and Chiang, {Chang Jung}",
year = "2017",
month = "3",
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doi = "10.1016/j.clinbiomech.2017.02.011",
language = "English",
volume = "43",
pages = "115--120",
journal = "Clinical Biomechanics",
issn = "0268-0033",
publisher = "Elsevier Limited",

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T1 - Removal of fixation construct could mitigate adjacent segment stress after lumbosacral fusion

T2 - A finite element analysis

AU - Hsieh, Yueh Ying

AU - Chen, Chia Hsien

AU - Tsuang, Fon Yih

AU - Wu, Lien Chen

AU - Lin, Shang Chih

AU - Chiang, Chang Jung

PY - 2017/3/1

Y1 - 2017/3/1

N2 - Background data Combined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear. Methods Using a validated lumbosacral finite-element model, three variations at the L4–L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedicle screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated. Findings The adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6%, 47.3%, and 59.6%, respectively. However, these changes were reduced to 30.1%, 22.7%, and 27.0% after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms. Interpretation Fixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons.

AB - Background data Combined usage of posterior lumbar interbody fusion and transpedicular fixation has been extensively used to treat the various lumbar degenerative disc diseases. The transpedicular fixator aims to increase stability and enhance the fusion rate. However, how the fused disc and bridged vertebrae respectively affect adjacent-segment diseases progression is not yet clear. Methods Using a validated lumbosacral finite-element model, three variations at the L4–L5 segment were analyzed: 1) moderate disc degeneration, 2) instrumented with a stand-alone cage and pedicle screw fixators, and 3) with the cage only after fusion. The intersegmental angles, disc stresses, and facet loads were examined. Four motion tests, flexion, extension, bending, and twisting, were also simulated. Findings The adjacent-segment disease was more severe at the cephalic segment than the caudal segment. After solid fusion and fixation, the increase in intersegmental angles, disc stresses and facet loads of the adjacent segments were about 57.6%, 47.3%, and 59.6%, respectively. However, these changes were reduced to 30.1%, 22.7%, and 27.0% after removal of the fixators. This was attributed to the differences between the biomechanical characteristics of the fusion and fixation mechanisms. Interpretation Fixation superimposes a stiffer constraint on the mobility of the bridged segment than fusion. The current study suggested that the removal of spinal fixators after complete fusion could decrease the stress at adjacent segments. Through a minimally invasive procedure, we could reduce secondary damage to the paraspinal structures while removing the fixators, which is of utmost concern to surgeons.

KW - Adjacent segment disease

KW - Finite element

KW - Interbody fusion

KW - Spinal fixator

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