Mechanical damage to the intervertebral disc annulus fibrosus subjected to cyclic tensile loading

Damage progression in the the circumferential direction of the disc annulus is likely to occur in vivo in response to cyclic loading with associated degradation in tensile material properties, yet this information is not available in the literature. We hypothesize that damage of the annulus will be increased by the number of cycles and magnitude of strain applied to the tissue. Therefore, the objective of this study is to obtain a quantitative relationship between number of cycles and magnitude of tensile strain and damage on the annulus fibrosus. Damage to the annulus is assessed through measurement of permanent deformation (% elongation) and peak stress in the tissue under cyclic loading conditions.