Isolated human thoracic vertebral bodies were systematically subjected to compressive loads at three different strain rates over four orders of magnitude. Each vertebra was crushed to 50% of its original length. High-speed motion picture films were taken of each test event. Static, quasistatic, and dynamic material property data were collected and included ultimate load, deformation to ultimate load, stiffness, and energy to ultimate load. Analysis and interpretation of high-speed motion films indicated that whenever the vertebral body is loaded in compression it deforms, and the deformation applies pressure on the marrow contents. This internal hydraulic effect may be a contributory factor to the observed nonlinear increase in strength as strain rate increases. The response of the marrow with respect to the deformation of the vertebral centrum is described. When the compressive load was removed, all vertebrae began a recovery process. The general features of this restoration process are described. The mechanism or mechanisms by which recovery takes place are not fully understood.
Keywords: compressive load, vertebral body, deformation, stress and strain