Degenerative Disc Disease of the Spine: Anatomic and Imaging Considerations

Traditionally, disc degeneration has been linked to mechanical loading. The importance of mechanical factors has been emphasized by experiments on cadaver spines with both severe single-event and relentless loading [1–5]. Disc failure is more common in areas where there are the heaviest mechanical stresses, such as the lower lumbar region. It has been suggested that mechanical factors produce endplate damage, the antecedent to disc degeneration [6]. The disc is metabolically active, and the metabolism is dependent on diffusion of fluid either from the marrow of the vertebral bodies across the subchondral bone, the cartilaginous endplate, or through the annulus fibrosus from the surrounding blood vessels. Morphologic changes in vertebral bone and cartilaginous endplate, which occur with advancing age or degeneration, can interfere with normal disc nutrition and further the degenerative process. This disruption of the normal endplate results in deformation when under loading. Compressive damage to the vertebral body endplate alters the distribution of stresses in the adjacent disc.