Significance of orientation and determination of cummulative damage measures during cyclic testing of human thoracolumbar spine

Determining the mechanical properties of the spine is a significant step in understanding the behavior of the spine under normal conditions. Although a limited amount of data for cyclic loading is currently available, the tests are not completely documented and the loads, spine segment positioning, and frequency are not representative of those typically found during normal activities. The purpose of this study is to develop an understanding of the relationship between loads and the development of fatigue failure in thoracolumbar motion segments.; Motion segments separated from human cadaveric spine were tested in two series. Compression series applied a pure compression load quasi-statically in the neutral position. The load was increased and the specimen was observed to determine failure. Motion segments were also tested without orientation (axially aligned).; The results from the tests show that mechanical properties of the disc depend on the orientation of the motion segments at neutral angle. Results also suggest that energy dissipation could be potentially a good damage measure unlike creep. (Abstract shortened by UMI.)...