title: Instantaneous center of rotation behavior of the lumbar spine with ligament failure.
abstract: OBJECTIVE
  The goal of this study was to investigate the effect of ligament failure on the instantaneous center of rotation (ICR) in the lower lumbar spine.
  
  
  METHODS
  A 3D finite element model of the L4-5 segment was obtained and validated. Ligament failure was simulated by reducing ligaments in a stepwise manner from posterior to anterior. A pure bending moment of 7.5 Nm was applied to the model in 3 anatomical planes for the purpose of validation, and a 6-Nm moment was applied to analyze the effect of ligament failure. For each loading case, ligament reduction step, and load increment, the range of motion of the segment and the ICR of the mobile (L-4) vertebra were calculated and characterized.
  
  
  RESULTS
  The present model showed a consistent increase in the range of motion as the ligaments were removed, which was in agreement with the literature reporting the kinematics of the L4-5 segment. The shift in the location of the ICR was below 5 mm in the sagittal plane and 3 mm in both the axial and coronal planes.
  
  
  CONCLUSIONS
  The location of the ICR changed in all planes of motion with the simulation of multiple ligament injury. The removal of the ligaments also changed the load sharing within the motion segment. The change in the center of rotation of the spine together with the change in the range of motion could have a diagnostic value, revealing more detailed information on the type of injury, the state of the ligaments, and load transfer and sharing characteristics of the segment.
authors.affiliation: Department of Mechanical Engineering, Yildiz Technical University, Istanbul.
authors.forename: Yunus
authors.initials: Y
authors.lastname: Alapan
authors.forename: Cihan
authors.initials: C
authors.lastname: Demir
authors.forename: Tuncay
authors.initials: T
authors.lastname: Kaner
authors.forename: Rahmi
authors.initials: R
authors.lastname: Guclu
authors.forename: Serkan
authors.initials: S
authors.lastname: Inceoğlu
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D008023:Ligaments, Articular / Q000473:pathology / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology*; D008953:Models, Anatomic; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation