title: An in vivo magnetic resonance imaging study of changes in the volume (and fluid content) of the lumbar intervertebral discs during a simulated diurnal load cycle.
abstract: METHODS
  Magnetic resonance imaging was used to measure the changes in volume of the lumbar intervertebral disc in vivo during a load cycle.
  
  
  OBJECTIVE
  To measure changes in volume of the lumbar intervertebral disc during a load cycle and relate these changes to changes in fluid content.
  
  
  BACKGROUND
  There have been very few experiments conducted to measure the volume and fluid changes in intervertebral discs in vivo.
  
  
  METHODS
  Five healthy subjects were recruited (aged 27, 29, 31, 34, and 52 years) in a study using magnetic resonance imaging to measure the changes in volume of the lumbar intervertebral disc in vivo, during a load cycle. The experiment was designed to simulate a diurnal load cycle, but over less time. The load cycle consisted of bed rest, followed by walking with a 20-kg backpack for 3 hours, followed by bed rest for 3 hours. Magnetic resonance imaging scans of the lumbar spine were obtained 10 times during this load cycle. The disc volume was calculated by summing the disc area contained in each slice of the scan. The changes in volume of the discs (L2-L3, L3-L4, and L4-L5) recorded at the 10 times were then related to the fluid changes.
  
  
  RESULTS
  Load-induced changes in disc volume can be detected and measured using MR imaging. The average volume increase 3 hours after removing a highly compressive load was 5.4%. The water content of the nucleus and anulus in the disc of the young human is said to be approximately 80% and 70%, respectively. If the disc gained 5.4% of its initial total volume, and assuming that the initial fluid content was approximately 75%, then it gained approximately 7% (i.e., 5.4%/75% x 100% approximately 7%) of its fluid.
  
  
  CONCLUSIONS
  Load-induced changes in disc volume can be detected and measured using magnetic resonance imaging.
authors.affiliation: Department of Radiology, Emory University School of Medicine, Atlanta, Georgia, USA. jmalko@emory.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Malko
authors.forename: W C
authors.initials: WC
authors.lastname: Hutton
authors.forename: W A
authors.initials: WA
authors.lastname: Fajman
mesh_terms: D000328:Adult; D001510:Bed Rest; D001834:Body Water / Q000378:metabolism*; D002940:Circadian Rhythm; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D018495:Fluid Shifts / Q000502:physiology; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016138:Walking / Q000502:physiology; D016474:Weight-Bearing