title: Human cartilage endplate permeability varies with degeneration and intervertebral disc site.
abstract: Despite the critical functions the human cartilage endplate (CEP) plays in the intervertebral disc, little is known about its structural and mechanical properties and their changes with degeneration. Quantifying these changes with degeneration is important for understanding how the CEP contributes to the function and pathology of the disc. Therefore the objectives of this study were to quantify the effect of disc degeneration on human CEP mechanical properties, determine the influence of superior and inferior disc site on mechanics and composition, and simulate the role of collagen fibers in CEP and disc mechanics using a validated finite element model. Confined compression data and biochemical composition data were used in a biphasic-swelling model to calculate compressive extrafibrillar elastic and permeability properties. Tensile properties were obtained by applying published tensile test data to an ellipsoidal fiber distribution. Results showed that with degeneration CEP permeability decreased 50-60% suggesting that transport is inhibited in the degenerate disc. CEP fibers are organized parallel to the vertebrae and nucleus pulposus and may contribute to large shear strains (0.1-0.2) and delamination failure of the CEP commonly seen in herniated disc tissue. Fiber-reinforcement also reduces CEP axial strains thereby enhancing fluid flux by a factor of 1.8. Collectively, these results suggest that the structure and mechanics of the CEP may play critical roles in the solute transport and disc mechanics.
authors.affiliation: Department of Biomedical Engineering, University of Delaware, Newark, DE, United States.
authors.forename: John F
authors.initials: JF
authors.lastname: DeLucca
authors.affiliation: Department of Biomedical Engineering, University of Delaware, Newark, DE, United States.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Cortes
authors.affiliation: Department of Mechanical Engineering, University of Pennsylvania, Philadelphia, PA, United States.
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Jacobs
authors.affiliation: Penn State Hershey Bone and Joint Institute Pennsylvania State University, Hershey, PA, United States.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Vresilovic
authors.affiliation: Department of Biomedical Engineering, University of Delaware, Newark, DE, United States; Department of Biological Sciences, University of Delaware, Newark, DE, United States.
authors.forename: Randall L
authors.initials: RL
authors.lastname: Duncan
authors.affiliation: Department of Biomedical Engineering, University of Delaware, Newark, DE, United States. Electronic address: delliott@udel.edu.
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Elliott
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002356:Cartilage / Q000378:metabolism*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007403:Intervertebral Disc / Q000378:metabolism* / Q000503:physiopathology; D055959:Intervertebral Disc Degeneration / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D055595:Mechanical Phenomena; D008875:Middle Aged; D010539:Permeability; D013314:Stress, Mechanical
keywords: Biphasic; Cartilage endplate; Intervertebral disc; Permeability; Spine