Influence of dynesys system screw profile on adjacent segment and screw

Chien Lin Liu, Zheng Cheng Zhong, Shih Liang Shih, Ching-Hua Hung, Yong Eng Lee, Chen Sheng Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Objective: This study aimed to investigate whether different depths of screw placement of Dynesys would affect load sharing of screw, range of motion (ROM), annulus stress, and facet contact force. Summary of background data: In clinical follow-up, a high rate of screw complications and adjacent segment disease were found after using Dynesys. The pedicle screw in the Dynesys system is not so easy to implant into the standard position and causes the screw to protrude more prominently from the pedicle. Little is known about how the biomechanical effects are influenced by the Dynesys screw profile. Methods: The Dynesys was implanted in a 3-dimensional, nonlinear, finite element model of the L1 to L5 lumbar spine. Different depths of screw position were modified in this model by 5 and 10mm out of the pedicle. The model was loaded to 150N preload and controlled the same ROMs by 20, 15, 8, and 20 degrees in flexion, extension, torsion, and lateral bending, respectively. Resultant ROM, annulus stress, and facet contact force were analyzed at the surgical and adjacent level. Results: Under flexion, extension, and lateral bending, the Dynesys provided sufficient stability at the surgical level, but increased the ROM at the adjacent level. Under flexion and lateral bending, the Dynesys alleviated annulus stress at the surgical level, but increased annulus stress at the adjacent level. Under extension, the Dynesys decreased facet loading at the surgical level but increased facet loading at the adjacent level. Conclusions: This study found that the Dynesys system was able to restore spinal stability and alleviate loading on disc and facet at the surgical level, but greater ROM, annulus stress, and facet loading were found at the adjacent level. In addition, profile of the screw placement caused only a minor influence on the ROM, annulus stress, and facet loading, but the screw stress was noticeably increased.

Original languageEnglish
Pages (from-to)410-417
Number of pages8
JournalJournal of Spinal Disorders and Techniques
Volume23
Issue number6
DOIs
StatePublished - 1 Aug 2010

Keywords

  • adjacent segment effect
  • displacement-controlled method
  • dynamic stabilization system
  • finite element method
  • screw complications
  • screw profile
  • spine biomechanics

Fingerprint Dive into the research topics of 'Influence of dynesys system screw profile on adjacent segment and screw'. Together they form a unique fingerprint.

Cite this