Nonlinear Biomechanical Model of the Cervical-Thoracic Transregional Joint.
AEROSPACE MEDICAL RESEARCH LAB WRIGHT-PATTERSON AFB OHIO
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A two dimensional model of the cervical-thoracic transregional joint is developed, which incorporates vertebra geometry and the measured material response properties of the ligaments and intervertebral disc. The model provides a useful tool for the parametric study of the effects of anatomical elements on the overall joint motion. In the model, the joint motion is restricted to the sagital plane, and the articulating facet surfaces for the adjacent vertebrae are represented by two curves. The requirement that point contact be maintained between these curves constitutes a kinematic constraint on the relative motion between the two vertebrae. The model considers the vertebrae to be rigid bodies and the masses of the vertebrae are neglected. The characterization of the velocity dependent response of the anterior and posterior longitudinal ligaments is based on a set of experiments in which load versus deflection data were generated at deflection rates of 0.5 and 1 inch per second. From these data, a constitutive equation is derived, consisting of a third order polynomial of the deflection plus a fifth term, the product of an arbitrary constant, the deflection and the deflection velocity.