title: The role of endplate poromechanical properties on the nutrient availability in the intervertebral disc.
abstract: OBJECTIVE
  To investigate the relevance of the human vertebral endplate poromechanics on the fluid and metabolic transport from and to the intervertebral disc (IVD) based on educated estimations of the poromechanical parameter values of the bony endplate (BEP).
  
  
  METHODS
  50 micro-models of different BEP samples were generated from μCTs of lumbar vertebrae and allowed direct determination of porosity values. Permeability values were calculated by using the micro-models, through the simulation of permeation via computational fluid dynamics. These educated ranges of porosity and permeability values were used as inputs for mechano-transport simulations to assess their effect on both the distributions of metabolites within an IVD model and the poromechanical calculations within the cartilaginous part of the endplate i.e., the cartilage endplate (CEP).
  
  
  RESULTS
  BEP effective permeability was highly correlated to local variations of porosity (R(2) ≈ 0.88). Universal patterns between bone volume fraction and permeability arose from these results and from other experimental data in the literature. These variations in BEP permeability and porosity had negligible effects on the distributions of metabolites within the disc. In the CEP, the variability of the poromechanical properties of the BEP did not affect the predicted consolidation but induced higher fluid velocities.
  
  
  CONCLUSIONS
  The present paper provides the first sets of thoroughly identified BEP parameter values that can be further used in patient-specific poromechanical studies. Representing BEP structural changes through variations in poromechanical properties did not affect the diffusion of metabolites. However, attention might be paid to alterations in fluid velocities and cell mechano-sensing within the CEP.
authors.affiliation: Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Malandrino
authors.affiliation: INSIGNEO Institute for in silico Medicine, Department of Mechanical Engineering, University of Sheffield, Sheffield, UK.
authors.forename: D
authors.initials: D
authors.lastname: Lacroix
authors.affiliation: Institute for Mechanics of Materials and Structures, Vienna University of Technology, Vienna, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Hellmich
authors.affiliation: Orthopedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Ito
authors.affiliation: Institute for Biomechanics, ETH, Zurich, Switzerland.
authors.forename: S J
authors.initials: SJ
authors.lastname: Ferguson
authors.affiliation: Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, Barcelona, Spain. Electronic address: jnoailly@ibecbarcelona.eu.
authors.forename: J
authors.initials: J
authors.lastname: Noailly
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology*; D003198:Computer Simulation; D006801:Humans; D057446:Hydrodynamics; D007403:Intervertebral Disc / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology*; D008875:Middle Aged; D008954:Models, Biological; D009752:Nutritional Status / Q000502:physiology*; D010539:Permeability
keywords: Bone porosity; Bony endplate; Hydraulic permeability; Intervertebral disc metabolites; Poromechanics; Spine mechanobiology