title: In vivo measurement of lumbar spinal creep in two seated postures using magnetic resonance imaging.
abstract: METHODS
  A magnetic resonance imaging technique was developed to measure creep in the lumbar spine in different seated postures. Owing to the fixed size and horizontal orientation constraints of the magnetic resonance imaging system bore, gravitational force was simulated in the horizontal plane while the subject assumed each of two near-seated postures: 1) flexed lumbar, and 2) extended lumbar.
  
  
  OBJECTIVE
  One experimental subject was used to determine the feasibility of this technique designed to correlate spinal creep with different seated postures.
  
  
  BACKGROUND
  Although epidemiologic and pathologic studies have linked the seated posture with low back pain and disc degeneration, few in vivo studies have explored the mechanical response of the lumbar spine to seated postures.
  
  
  METHODS
  Creep displacement of four lumbar discs (L3-S1) was measured from unloaded and loaded scans separated by 30 minutes of constant loading. Forty-eight images were measured from three trials in each posture, four sagittal slices per trial.
  
  
  RESULTS
  Creep while in an extended posture (3.58 mm) was greater than creep while in a flexed posture (2.92 mm). System resolution was 0.78 mm.
  
  
  CONCLUSIONS
  This technique can be used to discern between creep displacements in different postures.
authors.affiliation: Department of Orthopaedics, University of Southern California, Los Angeles, USA.
authors.forename: T P
authors.initials: TP
authors.lastname: Hedman
authors.forename: G R
authors.initials: GR
authors.lastname: Fernie
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D007403:Intervertebral Disc / Q000033:anatomy & histology* / Q000502:physiology; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D011187:Posture; D016683:Supine Position / Q000502:physiology*