title: Kinematics of the canine lumbar intervertebral joint. An in vivo study before and after adjacent instrumentation.
abstract: METHODS
  In vivo, canine lumbar spine intervertebral motion was measured before and after instrumentation of caudal segments. The three-dimensional kinematics of the intervertebral joint were described using helical axes and Fourier series.
  
  
  OBJECTIVE
  The in vivo three-dimensional kinematics of the intervertebral joint were measured and described. An animal model where intervertebral motion could be repeatedly changed was developed.
  
  
  BACKGROUND
  The kinematics of intervertebral joints have been described from results of extensive in vitro testing, some limited in vivo testing, and clinically by evaluation of flexion/extension films. In the canine, in vivo intervertebral motion has been described previously, but the method possessed some measurement artifact.
  
  
  METHODS
  In vivo, four canines had motion data collected (L2-L3) while the animals walked on a treadmill. L3 To L7 were instrumented in all of the animals and motion testing was repeated 1 and 12 weeks later. Helical axes of motion were determined for each gait cycle. Fourier series were fit to the motion data, helical axis parameters, and Fourier coefficients were all statistically compared (pre- and postinstrumentation).
  
  
  RESULTS
  Vertebral rotations (coronal plane) and excursion of the L2/3 facet increased significantly (P < 0.01) after caudal instrumentation. Helical axes were oriented in a ventral direction and only the angle of rotation about the axis changed significantly (P < 0.05) after instrumentation of caudal segments. The Fourier coefficients (amplitudes) showed a significant (P < 0.05) increase in the coronal plane rotations only, after adjacent instrumentation.
  
  
  CONCLUSIONS
  The in vivo kinematics of the intervertebral joint have been completely defined in this study. Some motion characteristics compare very well to human motion. Since motion at an intervertebral joint now can be repeatedly altered, this animal model shows promise as a useful tool for investigation of tissue response to changes in motion at a joint.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Schendel
authors.forename: M B
authors.initials: MB
authors.lastname: Dekutoski
authors.forename: J W
authors.initials: JW
authors.lastname: Ogilvie
authors.forename: J M
authors.initials: JM
authors.lastname: Olsewski
authors.forename: L J
authors.initials: LJ
authors.lastname: Wallace
mesh_terms: D000818:Animals; D001863:Bone Screws; D004285:Dogs; D005583:Fourier Analysis; D007091:Image Processing, Computer-Assisted; D007596:Joints / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology