European Spine Journal

, Volume 20, Issue 11, pp 1850–1858 | Cite as

Effect of the cord pretension of the Dynesys dynamic stabilisation system on the biomechanics of the lumbar spine: a finite element analysis

  • Chien-Lin Liu
  • Zheng-Cheng Zhong
  • Hung-Wei Hsu
  • Shih-Liang Shih
  • Shih-Tien Wang
  • Chinghua Hung
  • Chen-Sheng Chen
Original Article

Abstract

The Dynesys dynamics stabilisation system was developed to maintain the mobility of motion segment of the lumbar spine in order to reduce the incidence of negative effects at the adjacent segments. However, the magnitude of cord pretension may change the stiffness of the Dynesys system and result in a diverse clinical outcome, and the effects of Dynesys cord pretension remain unclear. Displacement-controlled finite element analysis was used to evaluate the biomechanical behaviour of the lumbar spine after insertion of Dynesys with three different cord pretensions. For the implanted level, increasing the cord pretension from 100 to 300 N resulted in an increase in flexion stiffness from 19.0 to 64.5 Nm/deg, a marked increase in facet contact force (FCF) of 35% in extension and 32% in torsion, a 40% increase of the annulus stress in torsion, and an increase in the high-stress region of the pedicle screw in flexion and lateral bending. For the adjacent levels, varying the cord pretension from 100 to 300 N only had a minor influence on range of motion (ROM), FCF, and annulus stress, with changes of 6, 12, and 9%, respectively. This study found that alteration of cord pretension affects the ROM and FCF, and annulus stress within the construct but not the adjacent segment. In addition, use of a 300 N cord pretension causes a much higher stiffness at the implanted level when compared with the intact lumbar spine.

Keywords

Lumbar spine Biomechanics Dynesys dynamic stabilisation system Finite element method Cord pretension 

Notes

Acknowledgments

This study was partly supported by National Science Council (NSC 99-2221-E-075-001-MY2) and Veterans General Hospitals (V98C1-078).

Conflict of interest

None.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Chien-Lin Liu
    • 1
  • Zheng-Cheng Zhong
    • 2
  • Hung-Wei Hsu
    • 2
  • Shih-Liang Shih
    • 3
  • Shih-Tien Wang
    • 1
  • Chinghua Hung
    • 4
  • Chen-Sheng Chen
    • 2
  1. 1.Department of Orthopaedic SurgeryTaipei-Veterans General HospitalTaipeiTaiwan
  2. 2.Department of Physical Therapy and Assistive TechnologyNational Yang-Ming UniversityTaipeiTaiwan
  3. 3.Department of Orthopaedic SurgeryTaipei-City HospitalTaipeiTaiwan
  4. 4.National Chiao-Tung UniversityTaipeiTaiwan

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