Degenerative Disc Disease & Sciatica
Medical Author: William C. Shiel Jr., MD, FACP, FACR
How is the spine designed?
The vertebrae are the bony building blocks of the spine. Between
each of the largest part of the vertebrae are the discs. Ligaments
are situated around the spine and discs. The spine has seven
vertebrae in the neck (cervical vertebrae), 12 vertebrae in the
mid-back (thoracic vertebrae), and five vertebrae in the low back
(lumbar vertebrae). In addition, in the mid-buttock, beneath the fifth lumbar vertebra, is sacrum followed by the tailbone (coccyx).
What is the purpose of the spine and its discs?
The bony spine is designed so that vertebrae "stacked"
together can provide a movable support structure while also
protecting the spinal cord (nervous tissue that extends down the
spinal column from the brain) from injury. Each vertebra has a
spinous process, which is a bony prominence behind the spinal cord
that shields the cord's nerve tissue. The vertebrae also have a
strong bony "body" in front of the spinal cord to provide a platform
suitable for weight-bearing.
The discs are pads that serve as "cushions" between each vertebral
body that serve to minimize the impact of movement on the spinal column. Each
disc is designed like a jelly donut with a central softer component
(nucleus pulposus). This softer component can rupture (herniate)
through the surrounding outer ring (annulus fibrosus) and irritate
adjacent nervous tissue. Ligaments are strong fibrous soft tissues
that firmly attach bones to bones. Ligaments attach each of the
vertebrae and surround each of the discs. When ligaments are injured
as the disc degenerates, localized pain in the area affected can result.
Picture of herniated disc between L4 and L5
Cross-section picture of herniated disc between L4 and L5
Picture of stapled incision post-surgery
What is degenerative disc disease? What are the symptoms?
As we age, the water and protein content of the cartilage of the body
changes. This change results in weaker, more fragile and thin
cartilage. Because both the discs and the joints that stack the
vertebrae (facet joints) are partly composed of cartilage, these
areas are subject to wear and tear over time (degenerative changes).
The gradual deterioration of the disc between the vertebrae is referred to as degenerative
disc disease. Wear of the facet cartilage and the bony changes of the adjacent joint is referred to as degenerative facet joint disease or osteoarthritis of the spine.
Degeneration of the disc is medically referred to as spondylosis.
Spondylosis can be noted on x-ray tests or MRI scanning of the spine
as a narrowing of the normal "disc space" between the adjacent vertebrae.
Degeneration of the disc tissue makes the disc more susceptible to
herniation. Degeneration of the disc can cause local pain in the affected area. Any level of the spine can
be affected by disc degeneration. When disc degeneration affects the
spine of the neck, it is referred to as cervical disc disease. When
the mid-back is affected, the condition is referred to as thoracic
disc disease. Disc degeneration that affects
the lumbar spine is referred to as lumbago. Lumbago causes pain
localized to the low back and is common in older people.
Degenerative arthritis (osteoarthritis) of the facet joints is also a
cause of localized lumbar pain that can be detected with plain x-ray
testing. The pain from degenerative disc or joint disease of the
spine is usually treated conservatively with intermittent heat, rest,
rehabilitative exercises, and medications to relieve pain, muscle
spasm, and inflammation.
Next: What are radiculopathy and sciatica? What are the symptoms? »
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