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Effect of mechanical loading on electrical conductivity in human intervertebral disk
Alicia R Jackson1, Francesco Travascio, Wei Yong Gu
1Department of Biomedical Engineering, Tissue Biomechanics Laboratory, University of Miami, Coral Gables, FL 33146, USA.
Journal of Biomechanical Engineering
|April 25, 2009
Summary
Mechanical loading decreases electrical conductivity in human intervertebral discs (IVD). Conductivity is direction-dependent in the annulus fibrosus (AF) and higher in the nucleus pulposus (NP) than AF.
Area of Science:
- Biomedical Engineering
- Tissue Mechanics
- Biophysics
Background:
- The intervertebral disc (IVD) is a charged, hydrated avascular tissue crucial for spinal mechanics.
- Mechanical loading influences IVD electromechanical transduction and transport properties.
- Electrical conductivity is a key material property influenced by tissue composition and structure.
Purpose of the Study:
- To investigate the impact of mechanical loading on the electrical conductivity of human IVD tissues.
- To determine if electrical conductivity is strain-dependent, inhomogeneous, and anisotropic in human IVD.
- To correlate tissue structure with observed electrical conductivity patterns.
Main Methods:
- Human lumbar IVDs were harvested, and specimens from annulus fibrosus (AF) and nucleus pulposus (NP) were prepared.
- Electrical conductivity was measured using a four-wire sense-current method under varying compressive strains (0%, 10%, 20%).
- Scanning electron microscopy (SEM) was used to analyze AF tissue morphology.
Main Results:
- Increasing compressive strain significantly decreased electrical conductivity in all tested IVD tissues (p<0.05).
- Electrical conductivity in the AF was significantly anisotropic, being lower in the radial direction compared to axial and circumferential directions (p<0.05).
- Nucleus pulposus (NP) tissue exhibited significantly higher electrical conductivity than annulus fibrosus (AF) tissue (p<0.05).
Conclusions:
- Electrical conductivity of human IVD tissues is dependent on mechanical strain and is inhomogeneous.
- The annulus fibrosus (AF) displays anisotropic electrical conductivity, which correlates with its layered structure and observed microtubule orientation.
- Findings provide crucial insights into mechanical loading effects on solute transport and electrical properties within IVD tissues.
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