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Human Annulus Fibrosus Dynamic Tensile Modulus Increases with Degeneration
Sounok Sen1, Nathan T Jacobs, John I Boxberger
1Department of Orthopaedic Surgery University of Pennsylvania Philadelphia, PA 19104.
Mechanics of Materials : an International Journal
|January 17, 2012
Summary
Degeneration increases the stiffness of the annulus fibrosus (AF) in the spine, affecting its ability to absorb energy during cyclic loading. This study quantifies these changes in dynamic viscoelastic properties.
Area of Science:
- Biomechanics
- Biomaterials Science
- Orthopedic Research
Background:
- The annulus fibrosus (AF) is crucial for intervertebral disc (IVD) mechanical function.
- Disc degeneration alters AF composition, impacting its mechanical properties.
- Understanding AF viscoelasticity is key to explaining IVD energy dissipation.
Purpose of the Study:
- Quantify dynamic viscoelastic properties of human AF in tension.
- Determine the impact of degeneration on these properties.
Main Methods:
- Tested non-degenerated and degenerated human AF samples in uniaxial tension.
- Applied cyclic loading across frequencies (0.01Hz-2Hz) at various equilibrium strains.
- Utilized a linear viscoelastic model to determine dynamic modulus and phase angle.
Main Results:
- AF dynamic modulus increased with higher equilibrium strain.
- Higher frequencies led to more elastic AF behavior (decreased phase angle).
- Degeneration increased AF dynamic modulus but did not affect phase angle.
Conclusions:
- Degeneration stiffens the annulus fibrosus.
- Altered viscoelastic properties influence the disc's energy dissipation capacity.
- Findings provide insight into the AF's mechanical role under cyclic loading.
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