title: Load sharing in lumbar spinal segment as a function of location of center of rotation.
abstract: OBJECTIVE
  The center (axis) of rotation (COR) in the lumbar spine has been studied well. However, there is limited information on the kinetic and kinematic consequences of imposed shift in the location of the COR, although this type of shift can be seen after surgeries using motion preservation or dynamic stabilization devices. The objective of this study was to assess the kinetic and kinematic changes in the lumbar spinal segment due to various imposed CORs.
  
  
  METHODS
  A 3D finite element model of the L4-5 segment was constructed and validated. The segment was loaded under a 7.5-Nm bending moment while constrained to rotate about various imposed CORs in the sagittal and axial motion planes. Range of motion, ligament forces, facet loads, and disc stresses were measured.
  
  
  RESULTS
  The present model showed an agreement with previous in vitro and finite element studies under the same load and boundary conditions. Range of motion, facet forces, disc stresses, and ligament loads showed a strong association with the location of the COR.
  
  
  CONCLUSIONS
  Acute alterations in the location of the COR can significantly change the load sharing characteristics within the spine segment. The normal location of the COR is a result of the tendency of the vertebra to move in the path of least cumulative resistance.
authors.affiliation: Department of Mechanical Engineering, Yildiz Technical University;
authors.forename: Yunus
authors.initials: Y
authors.lastname: Alapan
authors.forename: Semih
authors.initials: S
authors.lastname: Sezer
authors.forename: Cihan
authors.initials: C
authors.lastname: Demir
authors.forename: Tuncay
authors.initials: T
authors.lastname: Kaner
authors.forename: Serkan
authors.initials: S
authors.lastname: İnceoğlu
mesh_terms: D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D014057:Tomography, X-Ray Computed