A novel method to characterize the compressive, tensile, and neutral zone stiffness of the intervertebral disc

Mechanical properties of organ-cultured rat tail intervertebral discs were characterized across the entire range of axial tension-compression. Rather than assuming the shape of the axial force-deformation curve, the stiffness-deformation relationship was assumed to follow a double logistic (U-Shaped) function, consistent with disc mechanical theory [1]. The novel model strongly fit all data (min R2 = 0.9533) and was sensitive to mechanical changes caused by injection of decorin—an innate immune system stimulant. Decorin injection induced similar mechanical changes as mild disc degeneration.