Lumbar Degenerative Disk Disease

Between each vertebral body of the spine are pads of fibrocartilage-based structures that provide support, flexibility, and minor load-sharing, known as the intervertebral discs. These are primarily composed of two layers: (1) a soft, pulpy nucleus pulposus on the inside of the disc and (2) a surrounding firm structure known as the annulus fibrosus. A disruption of the normal architecture of these round discs can lead to a disc herniation or a protrusion of the inner nucleus pulposus, possibly applying pressure to the spinal cord or nerve root and resulting in radiating pain and specific locations of weakness. Slightly more than 90% of herniated discs occur at the L4-L5 or the L5-S1 disc space, which will impinge on the L4, L5, or S1 nerve root. This compression produces radiculopathy into the posterior leg and dorsal foot. If the disc injury progresses to the point of neurologic compromise or limitations with activities of daily living, then surgical intervention may be required to decompress and stabilize the affected segments. In the absence of motor deficits, a nonoperative course of analgesia, activity modification, and injections should be tried for several months. The surgical results for the primarily sciatic pain that has failed conservative treatment are predictable and favorable.