Systems identification for material properties of the intervertebral joint.

Abstract An identification of the elastic solid properties of the intervertebral disc was achieved by the finite element method utilizing experimental data from the axial loading of a lumbar intervertebral joint. By assuming orthotropic material properties for the vertebra and disc, a 3-D finite element model resembling the test specimens was constructed and exercised. The model deformations were then compared to the experimental measurements and an initial correlation found between them. Finally, using an efficient optimization scheme, the overall material constants of the disc were optimally determined by minimizing the error between the experimental data and the predicted deformations from the finite element analysis. The material constants thus identified show the orthotropic elastic moduli of the lumbar intervertebral disc to be independent of segment level but decrease directly as a function of the severity of degeneration.

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