Abstract

Biomechanical responses of the geriatric cervical spine with varying degrees of degeneration were studied using an anatomically accurate three-dimensional nonlinear detailed finite model of the human lower cervical spine. The geometrical details of the bony structure of the cervical spine model were obtained from the computed tomography images and the soft tissue details from cryomicrotome anatomic sections. The finite element model was validated under physiologic compression, flexion, extension and eccentric complex loading modes in terms of the angular stiffness, and the localized strain in the vertebral body and bilateral facet masses. Different levels of degenerated conditions in the cervical spine model were simulated by altering the material properties of the intervertebral nucleus pulposus, fiber content in the annulus fibrosus and decrease in the height of the disc. The external stiffness and internal stress responses of geriatric degenerated spines were compared with the adult normal spine. The overall stiffness of the geriatric spine increased with increasing severity of degeneration. Similarly, the stress magnitudes in the vertebral body increased with increasing levels of degeneration.

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