The change of sagittal alignment of the lumbar spine after dynesys stabilization and proposal of a refinement

Won Man Park, Chi Heon Kim, Yoon Hyuk Kim, Chun Kee Chung, Tae Ahn Jahng

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Objective: Dynesys® is one of the pedicle-based dynamic lumbar stabilization systems and good clinical outcome has been reported. However, the cylindrical spacer between the heads of the screws undergoes deformation during assembly of the system. The pre-strain probably change the angle of instrumented spine with time and oblique-shaped spacer may reduce the pre-strain. We analyzed patients with single-level stabilization with Dynesys® and simulated oblique-shaped spacer with finite element (FE) model analysis. Methods: Consecutive 14 patients, who underwent surgery for single-level lumbar spinal stenosis and were followed-up more than 24 months (M: F=6: 8; age, 58.7±8.0 years), were analyzed. Lumbar lordosis and segmental angle at the index level were compared between preoperation and postoperative month 24. The von Mises stresses on the obliquely-cut spacer (5°, 10°, 15°, 20°, 25°, and 30°) were calculated under the compressive force of 400 N and 10 Nm of moment with validated FE model of the L4–5 spinal motion segment with segmental angle of 16°. Results: Lumbar lordosis was not changed, while segmental angle was changed significantly from -8.1±7.2° to -5.9±6.7° (p<0.01) at postoperative month 24. The maximum von Mises stresses were markedly decreased with increased angle of the spacer up to 20°. The stress on the spacer was uneven with cylindrical spacer but it became even with the 15° oblique spacer. Conclusion: The decreased segmental lordosis may be partially related to the pre-strain of Dynesys. Further clinical and biomechanical studies are required for relevant use of the system.

Original languageEnglish
Pages (from-to)43-49
Number of pages7
JournalJournal of Korean Neurosurgical Society
Volume58
Issue number1
DOIs
StatePublished - 1 Jul 2015

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Lordosis
Spine
Spinal Stenosis
Finite Element Analysis
Head

Keywords

  • Degenerative disease
  • Dynamic
  • Finite element analysis
  • Lumbar
  • Spine
  • Stabilization

Cite this

@article{050861f470d946c59253b3cd5859707f,
title = "The change of sagittal alignment of the lumbar spine after dynesys stabilization and proposal of a refinement",
abstract = "Objective: Dynesys{\circledR} is one of the pedicle-based dynamic lumbar stabilization systems and good clinical outcome has been reported. However, the cylindrical spacer between the heads of the screws undergoes deformation during assembly of the system. The pre-strain probably change the angle of instrumented spine with time and oblique-shaped spacer may reduce the pre-strain. We analyzed patients with single-level stabilization with Dynesys{\circledR} and simulated oblique-shaped spacer with finite element (FE) model analysis. Methods: Consecutive 14 patients, who underwent surgery for single-level lumbar spinal stenosis and were followed-up more than 24 months (M: F=6: 8; age, 58.7±8.0 years), were analyzed. Lumbar lordosis and segmental angle at the index level were compared between preoperation and postoperative month 24. The von Mises stresses on the obliquely-cut spacer (5°, 10°, 15°, 20°, 25°, and 30°) were calculated under the compressive force of 400 N and 10 Nm of moment with validated FE model of the L4–5 spinal motion segment with segmental angle of 16°. Results: Lumbar lordosis was not changed, while segmental angle was changed significantly from -8.1±7.2° to -5.9±6.7° (p<0.01) at postoperative month 24. The maximum von Mises stresses were markedly decreased with increased angle of the spacer up to 20°. The stress on the spacer was uneven with cylindrical spacer but it became even with the 15° oblique spacer. Conclusion: The decreased segmental lordosis may be partially related to the pre-strain of Dynesys. Further clinical and biomechanical studies are required for relevant use of the system.",
keywords = "Degenerative disease, Dynamic, Finite element analysis, Lumbar, Spine, Stabilization",
author = "Park, {Won Man} and Kim, {Chi Heon} and Kim, {Yoon Hyuk} and Chung, {Chun Kee} and Jahng, {Tae Ahn}",
year = "2015",
month = "7",
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language = "English",
volume = "58",
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TY - JOUR

T1 - The change of sagittal alignment of the lumbar spine after dynesys stabilization and proposal of a refinement

AU - Park, Won Man

AU - Kim, Chi Heon

AU - Kim, Yoon Hyuk

AU - Chung, Chun Kee

AU - Jahng, Tae Ahn

PY - 2015/7/1

Y1 - 2015/7/1

N2 - Objective: Dynesys® is one of the pedicle-based dynamic lumbar stabilization systems and good clinical outcome has been reported. However, the cylindrical spacer between the heads of the screws undergoes deformation during assembly of the system. The pre-strain probably change the angle of instrumented spine with time and oblique-shaped spacer may reduce the pre-strain. We analyzed patients with single-level stabilization with Dynesys® and simulated oblique-shaped spacer with finite element (FE) model analysis. Methods: Consecutive 14 patients, who underwent surgery for single-level lumbar spinal stenosis and were followed-up more than 24 months (M: F=6: 8; age, 58.7±8.0 years), were analyzed. Lumbar lordosis and segmental angle at the index level were compared between preoperation and postoperative month 24. The von Mises stresses on the obliquely-cut spacer (5°, 10°, 15°, 20°, 25°, and 30°) were calculated under the compressive force of 400 N and 10 Nm of moment with validated FE model of the L4–5 spinal motion segment with segmental angle of 16°. Results: Lumbar lordosis was not changed, while segmental angle was changed significantly from -8.1±7.2° to -5.9±6.7° (p<0.01) at postoperative month 24. The maximum von Mises stresses were markedly decreased with increased angle of the spacer up to 20°. The stress on the spacer was uneven with cylindrical spacer but it became even with the 15° oblique spacer. Conclusion: The decreased segmental lordosis may be partially related to the pre-strain of Dynesys. Further clinical and biomechanical studies are required for relevant use of the system.

AB - Objective: Dynesys® is one of the pedicle-based dynamic lumbar stabilization systems and good clinical outcome has been reported. However, the cylindrical spacer between the heads of the screws undergoes deformation during assembly of the system. The pre-strain probably change the angle of instrumented spine with time and oblique-shaped spacer may reduce the pre-strain. We analyzed patients with single-level stabilization with Dynesys® and simulated oblique-shaped spacer with finite element (FE) model analysis. Methods: Consecutive 14 patients, who underwent surgery for single-level lumbar spinal stenosis and were followed-up more than 24 months (M: F=6: 8; age, 58.7±8.0 years), were analyzed. Lumbar lordosis and segmental angle at the index level were compared between preoperation and postoperative month 24. The von Mises stresses on the obliquely-cut spacer (5°, 10°, 15°, 20°, 25°, and 30°) were calculated under the compressive force of 400 N and 10 Nm of moment with validated FE model of the L4–5 spinal motion segment with segmental angle of 16°. Results: Lumbar lordosis was not changed, while segmental angle was changed significantly from -8.1±7.2° to -5.9±6.7° (p<0.01) at postoperative month 24. The maximum von Mises stresses were markedly decreased with increased angle of the spacer up to 20°. The stress on the spacer was uneven with cylindrical spacer but it became even with the 15° oblique spacer. Conclusion: The decreased segmental lordosis may be partially related to the pre-strain of Dynesys. Further clinical and biomechanical studies are required for relevant use of the system.

KW - Degenerative disease

KW - Dynamic

KW - Finite element analysis

KW - Lumbar

KW - Spine

KW - Stabilization

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U2 - 10.3340/jkns.2015.58.1.43

DO - 10.3340/jkns.2015.58.1.43

M3 - Article

AN - SCOPUS:84939249369

VL - 58

SP - 43

EP - 49

JO - Journal of Korean Neurosurgical Society

JF - Journal of Korean Neurosurgical Society

SN - 2005-3711

IS - 1

ER -