title: Finite element analysis of the biomechanical effect of coflex™ on the lumbar spine.
abstract: OBJECTIVE
  The biomechanical properties of the Coflex™ (Paradigm Spine, NY, USA), a device designed to provide dynamic stabilization without lumbar fusion, have not been clearly defined. The purpose of this study was to determine the efficacy and biomechanical effect of Coflex™ using finite element model (FEM).
  
  
  METHODS
  A 3D geometric model of the L3-L5 was created by integrating computerized tomography (CT) images. Based on the geometric model, a 3D FEM was created and the Coflex™ model was incorporated into the base model. Mechanical load dependent on the postural changes and boundary conditions, were imposed to simulate various 3D physiological states. The simulation analysis included stress and strain distributions, intervertebral disc deformation, and the range of motion of the facet joint and lumbar spinous process.
  
  
  RESULTS
  Coflex™ significantly restrained displacement in extension, lateral bending and compression of joint between the L4-5 as one in the experimental group was observed -1.3% of flexion, -24.5% of extension, -44.5% of lateral bending and -37.2%. The average intradiscal pressure of the L4-5 decreased by 63% and the average facet contract force of the L4-5 decreased markedly by 34% in the experimental group. A load of 120 MPa from extension was observed at the base of spinous process in the experimental group.
  
  
  CONCLUSIONS
  The Coflex™ can be safely used for achieving functional dynamic stabilization of the lumbar vertebral column while preserving the intactness of the other components. However, the fatigue fracture of the L4 spinous process should be carefully monitored.
authors.affiliation: Department of Medical System Engineering and School of Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors.forename: Dong-Hak
authors.initials: DH
authors.lastname: Byun
authors.affiliation: Department of Medical System Engineering and School of Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea. ; Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Dong Ah
authors.initials: DA
authors.lastname: Shin
authors.affiliation: Department of Medical System Engineering and School of Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors.forename: Jin-Myung
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Medical System Engineering and School of Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors.forename: So-Hee
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Medical System Engineering and School of Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors.forename: Hyoung-Ihl
authors.initials: HI
authors.lastname: Kim
keywords: Finite element analysis; Interspinous implant; Lumbar vertebrae; Spinous process