Age related differences in the mechanical properties of the mouse lumbar motion segments

In previous studies mouse lumbar spines have been used to model the human lumbar spine in order to investigate disc degeneration. While disc stiffness has been know to increase with age in humans, how mouse mechanical properties change with respect to age has not been examined. Uniaxial mechanical testing was performed utilizing motion segments that were harvested from lumbar spines representing two age groups. Force and displacement data were normalized using disc geometry and used to calculate neutral zone and stiffness. Results showed a significant difference between the neutral zones of the two age groups and trends were found in normalized stiffness. Studies in human disc mechanics use stiffness as a measure of change in disc mechanics, but our testing methods have allowed us to generate a stress/strain curve that utilizes three parameters for measuring change in disc mechanics instead of one.