The intervertebral disc (IVD) is a composite structure consisting of three distinct components: the nucleus pulposus (NP), the annulus fibrosus (AF), and the cartilaginous endplates. Decreased tissue cellularity and altered matrix architecture characterize intervertebral disc degeneration. The disc derives its structural properties largely through its ability to attract and retain water. The AF is the main torque converter in the spine while the NP provides hydrostatic pressure. Delamination of the annulus is the key pathoetiologic feature that produces a herniated nucleus pulposus (HNP) (Fig. 2). Rotary strain sets the stage for herniation. Overt trauma has a variable and questionable role but may be the precipitating event superimposed on underlying degeneration. Collectively, these features can lead to abnormal spine biomechanics and pain. Degenerated discs are thought to cause pain in several ways, including mechanical instability (stretching of pain fibers), compressive impingement on adjacent nerves (radiculopathy) (Fig. 3), and biochemical irritation via the release of inflammation mediators such as phospholi-pase A2, causing primary dural pain (11).
Was this article helpful?