title: Disc herniations in astronauts: What causes them, and what does it tell us about herniation on earth?
abstract: OBJECTIVE
  Recent work showed an increased risk of cervical and lumbar intervertebral disc (IVD) herniations in astronauts. The European Space Agency asked the authors to advise on the underlying pathophysiology of this increased risk, to identify predisposing factors and possible interventions and to suggest research priorities.
  
  
  METHODS
  The authors performed a narrative literature review of the possible mechanisms, and conducted a survey within the team to prioritize research and prevention approaches.
  
  
  CONCLUSIONS
  Based on literature review the most likely cause for lumbar IVD herniations was concluded to be swelling of the IVD in the unloaded condition during spaceflight. For the cervical IVDs, the knowledge base is too limited to postulate a likely mechanism or recommend approaches for prevention. Basic research on the impact of (un)loading on the cervical IVD and translational research is needed. The highest priority prevention approach for the lumbar spine was post-flight care avoiding activities involving spinal flexion, followed by passive spinal loading in spaceflight and exercises to reduce IVD hyper-hydration post-flight.
authors.affiliation: Center of Muscle and Bone Research, Charité University Medicine Berlin, Hindenburgdamm 30, 12203, Berlin, Germany. belavy@gmail.com.|Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, VIC, 3125, Australia. belavy@gmail.com.
authors.forename: Daniel L
authors.identifier: http://orcid.org/0000-0002-9307-832X
authors.initials: DL
authors.lastname: Belavy
authors.affiliation: Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell Street, Bristol, BS2 8EJ, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Adams
authors.affiliation: Department of Orthopedics, Institute of Clinical Sciences, Sahlgrenska Academy, Gothenburg University, Gothenborg, Sweden.|Department of Orthopedics, Sahlgrenska University Hospital, Gothenborg, Sweden.
authors.forename: Helena
authors.initials: H
authors.lastname: Brisby
authors.affiliation: Department of Rehabiliation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, 9000, Ghent, Belgium.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cagnie
authors.affiliation: Department of Rehabiliation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, 9000, Ghent, Belgium.
authors.forename: Lieven
authors.initials: L
authors.lastname: Danneels
authors.affiliation: Nuffield Orthopaedic Centre, Headington, Oxford University Hospitals NHS Trust, Oxford, OX3 7HE, UK.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Fairbank
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, San Diego, CA, 92103-8894, USA.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Hargens
authors.affiliation: Bioengineering Building, Stony Brook University, Stony Brook, NY, 11794-5281, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Judex
authors.affiliation: Johnson Space Center, 2101 NASA Parkway SD4, Houston, TX, 77058, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Scheuring
authors.affiliation: Centre for Military Medicine, Satakunta Air Command, PO.Box 1000, 33961, Pirkkala, Finland.
authors.forename: Roope
authors.initials: R
authors.lastname: Sovelius
authors.affiliation: Department of Physiology, Anatomy and Genetics, Oxford University, Le Gros Clark Building, South Parks Road, Oxford, OX1 3QX, UK.
authors.forename: Jill
authors.initials: J
authors.lastname: Urban
authors.affiliation: Faculty of Human Movement Sciences, MOVE Research Institute Amsterdam, VU University Amsterdam, van der Boechorststraat 9, Amsterdam, 1081 BT, The Netherlands.
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
authors.affiliation: Institute of Orthopaedic Research and Biomechanics, University of Ulm, Helmholtzstrasse 14, 89081, Ulm, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Wilke
mesh_terms: D018480:Astronauts; D002574:Cervical Vertebrae / Q000503:physiopathology; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000209:etiology* / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000503:physiopathology; D012307:Risk Factors; D013026:Space Flight
keywords: Atrophy; Back pain; Bed rest; Inactivity; Muscle; Prolapse