Analysis of large head-neck motions.

Abstract An eleven-element lumped-parameter two-dimensional model of the human head-neck system was developed to predict the motion of the head and neck under impact loadings and upper torso accelerations that represent “whiplash” conditions. This model incorporates mechanical analogies for the intervertebral disks, muscles, ligaments and articular facets. These simulations are composed of springs and dashpots with both linear and nonlinear moduli. The forces developed in these substructures are calculated as functions of the deformation of the system, and employed in the equations of motion. The model was tested by comparing the experimental and analytical results for the head motion determined from force inputs and data reported by other researchers for three different experiments. In general, highly satisfactory agreement was found to exist between predictions and data despite parameter matching problems. The forces and stresses extant in the individual subsystems were also examined for one of the test runs. Force histories were plotted for elements which were representative of the maximum force levels calculated. A procedure was also developed to approximate the strain in the spinal nerve. Strains greater than the current biological material test ranges were predicted, indicating the need for extended testing of these materials and the acquisition of more accurate element strength parameters. Methods to improve and expand the model are discussed, with particular reference to the extension of the model to three dimensions.