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Mechanical properties of the intervertebral discThis project focuses on the determination of the mechanical characteristics of the intervertebral disc (IVD). We investigate the ability of different material models (paper in preparation) to rationalize observations from different experiments, such as: uniaxial tests on functional spinal units (FSU), compression tests on annulus fibrosus or nucleus polposus and biaxial tests on planar annulus fibrosus tissue probes.
The intervertebral disc is characterized by high densities of collagen and proteoglycan. A low fluid permeability enables the tissue to carry compressive loads. The complex morphology results in non-homogeneous and anisotropic mechanical properties. Experiments showed the mechanical response of the IVD being nonlinear, time- and charge-dependant. Uniaxial cyclic tests on ovine FSU’s showed the time-dependent nature of the response, clearly hysteresis is apparent. For the simulations a geometrically correct numerical model of the disc and its surrounding vertebras was obtained from CT-scans.
In literature a vast number of material models are described that can be used in terms of finite deformations. Different types of constitutive models are evaluated using data from our experiments: hyperelastic fiber reinforced, viscoelastic with time dependent bulk modulus and poroelastic. An inverse finite element approach is used for the determination of the respective material parameters. NCCR CO-MEContactjoerg.helfenstein@imes.mavt.ethz.ch [Top] | |||||||||||||||||||||||||
