title: Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-Duration Spaceflight on the International Space Station.
abstract: METHODS
  Prospective case series.
  
  
  OBJECTIVE
  Evaluate lumbar paraspinal muscle (PSM) cross-sectional area and intervertebral disc (IVD) height changes induced by a 6-month space mission on the International Space Station. The long-term objective of this project is to promote spine health and prevent spinal injury during space missions and here on Earth.
  
  
  BACKGROUND
  National Aeronautics and Space Administration (NASA) crewmembers have a 4.3 times higher risk of herniated IVDs, compared with the general and military aviator populations. The highest risk occurs during the first year after a mission. Microgravity exposure during long-duration spaceflights results in approximately 5 cm lengthening of body height, spinal pain, and skeletal deconditioning. How the PSMs and IVDs respond during spaceflight is not well described.
  
  
  METHODS
  Six NASA crewmembers were imaged supine with a 3 Tesla magnetic resonance imaging. Imaging was conducted preflight, immediately postflight, and then 33 to 67 days after landing. Functional cross-sectional area (FCSA) measurements of the PSMs were performed at the L3-4 level. FCSA was measured by grayscale thresholding within the posterior lumbar extensors to isolate lean muscle on T2-weighted scans. IVD heights were measured at the anterior, middle, and posterior sections of all lumbar levels. Repeated measures analysis of variance was used to determine significance at P < 0.05, followed by post-hoc testing.
  
  
  RESULTS
  Paraspinal lean muscle mass, as indicated by the FCSA, decreased from 86% of the total PSM cross-sectional area down to 72%, immediately after the mission. Recovery of 68% of the postflight loss occurred during the next 6 weeks, still leaving a significantly lower lean muscle fractional content compared with preflight values. In contrast, lumbar IVD heights were not appreciably different at any time point.
  
  
  CONCLUSIONS
  The data reveal lumbar spine PSM atrophy after long-duration spaceflight. Some FCSA recovery was seen with 46 days postflight in a terrestrial environment, but it remained incomplete compared with preflight levels.
  
  
  METHODS
  4.
authors: Department of Orthopaedic Surgery, University of California, San Diego, CA.
authors: Douglas G
authors: DG
authors: Chang
authors: Department of Orthopaedic Surgery, University of California, San Diego, CA.
authors: Robert M
authors: RM
authors: Healey
authors: Department of Orthopaedic Surgery, University of California, San Diego, CA.
authors: Alexander J
authors: AJ
authors: Snyder
authors: The Ola Grimsby Institute, Bellevue, WA.
authors: Jojo V
authors: JV
authors: Sayson
authors: KBRwyle, Houston, TX.
authors: Brandon R
authors: BR
authors: Macias
authors: Department of Orthopaedic Surgery, University of California, San Francisco, CA.
authors: Dezba G
authors: DG
authors: Coughlin
authors: Department of Orthopaedic Surgery, University of California, San Francisco, CA.
authors: Jeannie F
authors: JF
authors: Bailey
authors: School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ.
authors: Scott E
authors: SE
authors: Parazynski
authors: Department of Orthopaedic Surgery, University of California, San Francisco, CA.
authors: Jeffrey C
authors: JC
authors: Lotz
authors: Department of Orthopaedic Surgery, University of California, San Diego, CA.
authors: Alan R
authors: AR
authors: Hargens
mesh_terms: D018480:Astronauts; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000473:pathology*; D008161:Lumbosacral Region / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D064170:Paraspinal Muscles / Q000502:physiology*; D011446:Prospective Studies; D013026:Space Flight / Q000379:methods; D013997:Time Factors