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.
The Intervertebral Disc:
The intervertebral disc (IVD) is found between two subsequent vertebral bodies allowing the spine to flex and twist while supporting gravitational and muscular loads. A motion segment is comprised of an intervertebral disc and its two neighboring vertebral bodies. The mechanical properties of the disc are imperative to its normal operation. The disc is comprised of several components that each contribute to the mechanical properties. Degradation of these components can lead to reduced mechanical performance as well as pain.
The disc degenerates naturally as a normal part of aging, but the relationship between degeneration and pain is not fully understood. Studies are focused on differentiating between natural aging and the debilitating effects of more extreme degeneration. The effects of degeneration on the mechanical behavior of the disc may be a contributing factor to pain. Degeneration can lead to degraded biomechanics in terms of increased flexibility, decreased fluid pressurization, and lower disc height. Severe disc degeneration involves the degradation of the components of the disc and can lead to herniation, spinal stenosis, and degenerative spondylolisthesis.
Author: Adam Shabtai Gabai
Source: University of Maryland