title: A method to study lumbar spine response to axial compression during magnetic resonance imaging: technical note.
abstract: METHODS
  A magnetic resonance imaging (MRI)-compatible device was developed to apply calibrated compression loads to the lumbar spine during imaging. Experiments were performed to establish a protocol to measure lumbar load-response and estimate muscle-force contribution to spinal load.
  
  
  OBJECTIVE
  To develop experimental methodology for direct study of lumbar spine response to compression load.
  
  
  BACKGROUND
  Most lumbar MRI scans require subjects to lie relaxed and supine, but spinal stenosis has been demonstrated to increase during moderate compressive loading. Several devices have been used to load the spine during MRI, but they could not maintain and/or change calibrated loads during MRI experiments. Furthermore, artifact from viscoelastic creep during imaging was not considered.
  
  
  METHODS
  An MRI-compatible spine compression unit with pneumatic load elements was developed to produce calibrated compression loads. Young healthy men were loaded with 140% body weight for up to 10 minutes to establish an appropriate test protocol. Muscle force contribution to spinal load was estimated from electromyography experiments.
  
  
  RESULTS
  The spine compression unit produced specified loads +/- 29 N (standard deviation). Spine viscoelastic creep reached steady state by 6.5 minutes, leaving 3.5 minutes for image acquisition. The subjects could support 1.0 body weight for the requisite 10 minutes. Muscle compressive force estimates were only 135 N during application of 1.4 x body weight external compression load; thus, internal muscle forces during supine spine compression could be neglected.
  
  
  CONCLUSIONS
  The lumbar load/image protocol fits within the time constraints of creep deformation and subject endurance. These methods allow acute lumbar mechanical response measurements during loading.
authors.affiliation: Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone, North Carolina 28608-2071, USA. wislederd@appstate.edu
authors.forename: D
authors.initials: D
authors.lastname: Wisleder
authors.forename: S L
authors.initials: SL
authors.lastname: Werner
authors.forename: W J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: S J
authors.initials: SJ
authors.lastname: Fleck
authors.forename: V M
authors.initials: VM
authors.lastname: Zatsiorsky
mesh_terms: D000328:Adult; D019245:Compressive Strength / Q000502:physiology*; D004576:Electromyography; D005080:Exercise Test; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*