title: Nucleus pulposus glycosaminoglycan content is correlated with axial mechanics in rat lumbar motion segments.
abstract: The unique biochemical composition and structure of the intervertebral disc allow it to support load, permit motion, and dissipate energy. With degeneration, both the biochemical composition and mechanical behavior of the disc are drastically altered, yet quantitative relationships between the biochemical changes and overall motion segment mechanics are lacking. The objective of this study was to determine the contribution of nucleus pulposus glycosaminoglycan content, which decreases with degeneration, to mechanical function of a rat lumbar spine motion segment in axial loading. Motion segments were treated with varying doses of Chondroitinase-ABC (to degrade glycosaminoglycans) and loaded in axial cyclic compression-tension, followed by compressive creep. Nucleus glycosaminoglycan content was significantly correlated (p < 0.05) with neutral zone mechanical behavior, which occurs in low load transition between tension and compression (stiffness: r = 0.59; displacement: r = -0.59), and with creep behavior (viscous parameter eta(1): r = 0.34; short time constant tau(1): r = 0.46). These results indicate that moderate decreases in nucleus glycosaminoglycan content consistent with early human degeneration affect overall mechanical function of the disc. These decreases may expose the disc to altered internal stress and strain patterns, thus contributing through mechanical or biological mechanisms to the degenerative cascade.
authors.affiliation: McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6081, USA.
authors.forename: John I
authors.initials: JI
authors.lastname: Boxberger
authors.forename: Sounok
authors.initials: S
authors.lastname: Sen
authors.forename: Chandra S
authors.initials: CS
authors.lastname: Yerramalli
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Elliott
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D019765:Chondroitin ABC Lyase / Q000494:pharmacology; D015299:Discitis / Q000503:physiopathology; D004195:Disease Models, Animal; D006025:Glycosaminoglycans / Q000378:metabolism*; D006801:Humans; D007403:Intervertebral Disc / Q000187:drug effects / Q000378:metabolism*; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D009068:Movement / Q000187:drug effects / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013131:Spine / Q000502:physiology
chemical_list: D006025:Glycosaminoglycans; D019765:Chondroitin ABC Lyase