The intervertebral disc is the largest avascular structure in the human body, with very low cellularity and largely without sensory innervation. It has a slow rate of tissue turnover and its viability depends primarily on transport of dissolved nutrients and metabolites, through long diffusion pathways. The disc has been implicated in painful conditions that affect a large proportion of the population. Epidemiological data suggest that long-term degenerative changes are more likely to produce these painful conditions than are acute overload injuries. Therefore, here we propose to combine existing and new information on disc tissue properties and structure into a coordinated theory of the whole disc behavior that can subsequently be applied to explain its healthy and pathological behavior. We will perform experiments to document intervertebral disc mechanical behavior, and compare these data with a new combined theory of mechanical, fluid, and chemical behavior of the disc's tissues and structure. This theory will be incorporated in a finite element model of the whole disc that will be refined based on the experimental data. Specifically: (1) Mechanical behavior will be documented by measurements of time-dependent load-displacement behavior of intervertebral discs and internal displacements. (2) Intervertebral disc swelling behavior will be documented over time by placing semi-constrained discs in baths of differing ionic concentrations and measuring volumetric increase, constraining force and intradiscal pressure. (3) Fluid flow and diffusion in the intervertebral disc will be measured under conditions of different end-plate permeability by recording the concentration of fluorescent dyes of different molecular weights. (4) Electrical potentials will be mapped at known positions in intervertebral discs subjected to time-varying displacements of the specimen with controlled boundary conditions (displacements and porosity of the end fittings). This theory will, in turn, provide a way to understand the relationships between the physical environment of the disc (mechanical, nutritional, etc.) and the local conditions that can influence its metabolism, eventual composition and function in three-dimensions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR049370-02
Application #
6767698
Study Section
Special Emphasis Panel (ZRG1-SSS-M (01))
Program Officer
Panagis, James S
Project Start
2003-08-01
Project End
2007-07-31
Budget Start
2004-08-01
Budget End
2005-07-31
Support Year
2
Fiscal Year
2004
Total Cost
$356,025
Indirect Cost
Name
University of Vermont & St Agric College
Department
Orthopedics
Type
Schools of Medicine
DUNS #
066811191
City
Burlington
State
VT
Country
United States
Zip Code
05405
Stokes, Ian A F; Gardner-Morse, Mack (2016) A database of lumbar spinal mechanical behavior for validation of spinal analytical models. J Biomech 49:780-785
Stokes, Ian A F; Laible, Jeffrey P; Gardner-Morse, Mack G et al. (2011) Refinement of elastic, poroelastic, and osmotic tissue properties of intervertebral disks to analyze behavior in compression. Ann Biomed Eng 39:122-31
Stokes, Ian A; Chegini, Salman; Ferguson, Stephen J et al. (2010) Limitation of finite element analysis of poroelastic behavior of biological tissues undergoing rapid loading. Ann Biomed Eng 38:1780-8
Iatridis, James C; Furukawa, Masaru; Stokes, Ian A F et al. (2009) Spatially resolved streaming potentials of human intervertebral disk motion segments under dynamic axial compression. J Biomech Eng 131:031006
Costi, John J; Stokes, Ian A; Gardner-Morse, Mack G et al. (2008) Frequency-dependent behavior of the intervertebral disc in response to each of six degree of freedom dynamic loading: solid phase and fluid phase contributions. Spine (Phila Pa 1976) 33:1731-8
Masuoka, Kazunori; Michalek, Arthur J; MacLean, Jeffrey J et al. (2007) Different effects of static versus cyclic compressive loading on rat intervertebral disc height and water loss in vitro. Spine (Phila Pa 1976) 32:1974-9
Iatridis, James C; MacLean, Jeffrey J; O'Brien, Mary et al. (2007) Measurements of proteoglycan and water content distribution in human lumbar intervertebral discs. Spine (Phila Pa 1976) 32:1493-7
Costi, J J; Stokes, I A; Gardner-Morse, M et al. (2007) Direct measurement of intervertebral disc maximum shear strain in six degrees of freedom: motions that place disc tissue at risk of injury. J Biomech 40:2457-66
Stokes, Ian A F; Windisch, Luke (2006) Vertebral height growth predominates over intervertebral disc height growth in adolescents with scoliosis. Spine (Phila Pa 1976) 31:1600-4
Stokes, Ian A F; Iatridis, James C (2004) Mechanical conditions that accelerate intervertebral disc degeneration: overload versus immobilization. Spine (Phila Pa 1976) 29:2724-32