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APM Spine & Sports Physicians

Intervertebral Discs

What are the intervertebral discs?

They are a circular series of ligament surrounding a gel-like system that functions as a shock absorber between the vertebrae. The upper discs start between the second and third vertebral joint and the lowest true discs end between the low back (lumbar vertebrae) and pelvis (sacrum). They are attached to the vertebra above and below by the hyaline cartilage plates. The discs make up about one-fourth of the height of the spinal column. They serve as cushions for the spine and allow for spinal mobility. Movement at each disc level is limited, but the combination of all the discs and vertebrae allow for specific spinal movements. Each disc contains an annulus fibrosus (outer ring) and nucleus pulposus (inner gel-like substance).

The discs are thinnest in the thoracic region and thickest in the lumbar region. Disc disorders are most common in the lumbar (low back) region.

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What is the annulus fibrosus?

It is the outer layer of the disc and it is comprised of cartilaginous bundles (collagen and protein) called the lamellae. Each layer of lamellae is angled approximately 30 degrees, and the angle alternates from layer to layer. This alternating pattern provides strength and flexibility for the annulus.

What is the nucleus pulposus?

The center of the disc is called the nucleus pulposus, and it is surrounded by the annulus fibrosus. It is semi-gelatinous and fluid-like. It is primarily composed of protein aggregates and water. At birth, the water content of a disc is about 90 percent, which decreases as we age. By the time we are in our fifties, the water content will have decreased to about 70 percent.

Degenerative Disc Disease

What is degenerative disc disease?

The term “degenerative disc disease” is really a misnomer. The degeneration of the disc is a natural process of aging and overuse, resulting in deterioration. The term “disease” is also a misnomer as it is not a disease, but a process. It is frequently referred to as “DDD” or spondylosis.

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How do the discs change as we age?

Due to age, genetics and environmental factors, changes occur within the discs. The blood supply to the discs decreases and the discs gradually deteriorate and lose water. The differentiation between the outer ligamentous annulus and the inner gel-like nucleus becomes less distinguishable. This deterioration results in:

  • Decreased spinal range of motion
  • Decreased ability for the disc to function as a shock absorber for the spine
  • Decreased vertebral column height
  • Increased weight-bearing and possible irritation to the facet joints
  • Risk of increased compression of the spinal nerves
  • Risk of development of pain as a result of the changes in the disc

 Internal Disc Disruption

Oftentimes age, genetics and environmental factors combine to cause a painful process within the discs that goes beyond normal aging. The discs may develop tears or fissures in the outer ligamentous part of the disc (annular fibers). As a result, the nucleus pulposus (the semi-gelatinous inner layer of the disc) can be forced into the tears/cracks, opening them wider. Nerve endings in the region may be sensitive to the nuclear material entering these tears, and pain may develop. This process is often responsible for the intermittent low back pain that many experience as “throwing their back out.” Typically this is caused by a bending forward and possibly a twisting motion, which place the lamellae fibers in the annulus at a mechanical disadvantage, allowing the opening up of a tear.

Herniated Disc

What is a herniated disc?

The fissures in the outer fibers (annulus pulposus) may become extensive, and the nucleus pulposus (the center of the disc) may start to squeeze through to the edge of the disc or beyond. This will cause the disc to bulge initially, and when the deterioration occurs through most or all of the layers, a true herniation will result. The herniation will be defined as a bulge protrusion or extrusion, depending upon the shape of the herniation. This protrusion may compress the spinal nerves or spinal cord, which can result in pain. Herniated discs are also referred to as “slipped” disc. A herniated disc can occur in any part of your spine, but it tends to occur more frequently in the lumbar spine (low back) than the cervical spine (neck) and less frequently in thethoracic spine (mid back).

What are the symptoms?

Internal disc disruption is best understood in the lumbar spine, because it is more common in occurrence and the anatomy is easier to understand. It can cause episodes of severe low back pain with muscle spasms. In rare instances the symptoms may become constant.

When a lumbar herniated disc presses against a nerve root, pain, numbness, and/or weakness can occur in the leg. If nerve compression occurs from a cervical disc herniation, the symptoms may occur in the arm.

How is a herniated disc diagnosed?

Pain from a disc problem can mimic other medical problems, particularly muscular problems. A diagnosis is made as a result of a thorough history and physical evaluation as well as other diagnostic testing, which may include:

How is it treated?

Symptoms from a herniated disc usually improve in a few weeks or months. To help you recover:

  • Stay active (walk or do other light activity).
  • Rest if you have severe pain.
  • For an acute injury, apply ice for 10-15 minutes, three times per day, for two to three days. After three days you can start to use heat help further reduce the pain.
  • Take medication to relieve pain. Medication will not cure a disc herniation.
  • Undergo physical therapy, for instruction in doing exercises properly.
  • Spinal injections may be recommended in certain cases.
  • Surgery may be recommended for cases that do not respond to conservative treatment.