title: Biomechanical comparison of effects of the Dynesys and Coflex dynamic stabilization systems on range of motion and loading characteristics in the lumbar spine: a finite element study.
abstract: BACKGROUND
  The primary purpose of dynamic stabilization is to preserve the normal range of motion (ROM) by restricting abnormal movement in the spine. Our aim was to analyze the effects of two different dynamic stabilization systems using finite element modeling (FEM).
  
  
  METHODS
  Coflex and Dynesys dynamic devices were modeled and implanted at the L4-L5 segment using virtual FEM. A 400 N compressive force combined with 6 N flexion, extension, bending and axial rotation forces was applied to the L3-4 and L4-5 segments. ROM and disc loading forces were analyzed.
  
  
  RESULTS
  Both systems reduced ROM and disc loading forces at the implanted lumbar segment, with the exception of the Coflex interspinous device, which increased ROM by 19% and did not change disc-loading forces in flexion.
  
  
  CONCLUSIONS
  The Coflex device prevented excessive disc loading, but increased ROM abnormally in flexion. Neither device provided satisfactory motion preservation or load sharing in other directions.
authors: Department of Orthopedics and Traumatology, Gazi Mustafa Kemal State Hospital, Ankara, Turkey.
authors: Ahmet
authors: A
authors: Kulduk
authors: Department of Orthopedics and Traumatology, Gazi University Faculty of Medicine, Ankara, Turkey.
authors: Necdet S
authors: NS
authors: Altun
authors: Department of Orthopedics and Traumatology, Gazi University Faculty of Medicine, Ankara, Turkey.
authors: Alpaslan
authors: A
authors: Senkoylu
mesh_terms: D019245:Compressive Strength / Q000502:physiology; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D020342:Finite Element Analysis; D006801:Humans; D016268:Internal Fixators; D007403:Intervertebral Disc / Q000502:physiology* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000502:physiology* / Q000601:surgery*; D008954:Models, Biological; D065289:Pedicle Screws; D016059:Range of Motion, Articular / Q000502:physiology; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology
keywords: Coflex; Dynesis; Finite element modeling; dynamic stabilization; interspinous devices; spinal column