Biomechanics of the Intervertebral Disc: The Effects of Load History on Mechanical Behavior

Abstract

Degenerative disc disease is associated with back pain, and can be a debilitating disorder. In addition to the biological contributions of genetics and aging, mechanical factors have been implicated in accelerating the progression of disc degeneration. Two studies were performed in order to explore the effects of various loading conditions on disc biomechanics. The first study explores the effects of compressive historical loads and disc hydration on subsequent creep loading and recovery. The second study investigates the restorative powers of creep distraction between compressive loading periods. In both cases three commonly applied mathematical models were employed to characterize disc behavior and the effectiveness of each model was validated. The studies confirm that hydration level has a significant impact on disc stiffness and time dependent behavior. Distraction and conditioning phases are shown to have a significant impact on hydration level and thus subsequent mechanical behavior.