Pathology of symptomatic lumbar disc protrusion.

There has been considerable advance in our understanding of lumbar disc protrusion. Contrary to popular belief, the healthy lumbar disc is remarkably resilient to trauma. Its nutrition is the key to failure. A fissure alone will not predispose a disc to protrusion, unless a free fragment also develops. The first symptoms of protrusion are often dramatic (the free fragment is displaced posteriorly), but this has been preceded by a long period of symptomless pathology. Protrusion is often inevitable: an incident and not an accident. Space in the vertebral canal is a major factor determining whether there is nerve root compromise. Mediators from the nucleus cause root inflammation and root tension signs. These inflammatory changes and the symptoms can resolve even though the protrusion remains. Imaging to identify the level, and surgery, are required only when conservative measures fail.