title: Influence of biochemical composition on endplate cartilage tensile properties in the human lumbar spine.
abstract: Endplate cartilage integrity is critical to spine health and is presumably impaired by deterioration in biochemical composition. Yet, quantitative relationships between endplate biochemical composition and biomechanical properties are unavailable. Using endplate cartilage harvested from human lumbar spines (six donors, ages 51-67 years) we showed that endplate biochemical composition has a significant influence on its equilibrium tensile properties and that the presence of endplate damage associates with a diminished composition-function relationship. We found that the equilibrium tensile modulus (5.9 ± 5.7 MPa) correlated significantly with collagen content (559 ± 147 µg/mg dry weight, r(2)  = 0.35) and with the collagen/GAG ratio (6.0 ± 2.1, r(2)  = 0.58). Accounting for the damage status of the adjacent cartilage improved the latter correlation (r(2)  = 0.77) and indicated that samples with adjacent damage such as fissures and avulsions had a diminished modulus-collagen/GAG relationship (p = 0.02). Quasi-linear viscoelastic relaxation properties (C, t1 , and t2 ) did not correlate with biochemical composition. We conclude that reduced matrix quantity decreases the equilibrium tensile modulus of human endplate cartilage and that characteristics of biochemical composition that are independent of matrix quantity, that is, characteristics related to matrix quality, may also be important.
authors.affiliation: Orthopaedic Bioengineering Laboratory, Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, S-1157, San Francisco, California, 94143-0514.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Fields
authors.forename: David
authors.initials: D
authors.lastname: Rodriguez
authors.forename: Kaitlyn N
authors.initials: KN
authors.lastname: Gary
authors.forename: Ellen C
authors.initials: EC
authors.lastname: Liebenberg
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Lotz
mesh_terms: D000368:Aged; D002356:Cartilage / Q000737:chemistry* / Q000473:pathology / Q000503:physiopathology*; D055119:Elastic Modulus; D005260:Female; D006025:Glycosaminoglycans / Q000032:analysis; D006801:Humans; D006909:Hydroxyproline / Q000032:analysis; D007403:Intervertebral Disc; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D013718:Tensile Strength; D014867:Water / Q000032:analysis
chemical_list: D006025:Glycosaminoglycans; D014867:Water; D006909:Hydroxyproline
keywords: biomechanical properties; cartilage endplate; intervertebral disc degeneration; low back pain; spine