The Lumbar Disc | The Lumbar Discs
The lumbar discs are the intervertebral discs that separate the vertebral bodies in the lumbar spine. The lumbar spine includes the vertebra (spinal bones) in our lower back, which include the last five vertebral bones, and the joint between the last lumbar vertebra and the base (top) of the sacrum. The weight bearing portions of the lumbar spine, including the lumbar discs and lumbar intervertebral discs, are thicker to support the heavy loads that they must absorb, due to their location at the bottom of the spine and torso. So these load-bearing elements in the lower back are built thicker and stronger to endure the weights and pressures, though they may still be vulnerable to wear and tear over a long life. Also, the rate of this wear and tear of these weight-bearing elements may accelerated by factors such as poor nutrition, smoking, bad posture, weight gain, and trauma. Here we will take a closer look at the chemistry and anatomy of the lumbar disc, how they may become degenerated, and the available options for people who suffer from back pain conditions related to degenerative disc disease.
The Lumbar spine. Before we take a closer look at the lumbar discs, let's look at the shape of the lumbar spine.
The basic element of the lumbar spine are the five lumbar vertebra that meet up with the bottom of the thoracic spine above, and the top of the sacrum below. The lumbar spine is the second lordotic curvature from the top of the spine, which means that it is concave anteriorly and convex posteriorly. Both the lordotic curvatures in the cervical and lumbar spine are also known as secondary curves of the spine, meaning that they are not present at birth and develop afterwards.
Both of the weight-bearing parts of the lumbar spine - the vertebral bodies and the discs, must bear more and more weight the closer they are to the trunk of the body (pelvis). For this reason, the vertebral bodies and discs become thicker the lower they go towards the pelvis. The lumbar vertebral bodies and discs, which are roughly bean-shaped, become thicker anteriorly (towards the front of the body) than posteriorly the closer they are to the sacrum. This increase in thickness and height towards the front of the vertebral bodies and discs accommodate the curvature of the lumbar spine as it turns inwardly to articulate with the base (top) of the sacrum.
The weight bearing elements are designed to take on the added loads, due to their location in the bottom of the spine. Nevertheless, they may succumb to wear and tear over time. Degenerative changes to these weight-bearing elements that perhaps cause the most lower back pain and related dysfunction include herniated discs. Herniated discs are conditions where rips in the outer layer of the disc causes inner nucleus material to pour out of it. If this ejected material presses into the spinal nerves, the resulting pain may be painful and could result in nerve damage. This type of condition is known as a compressed nerve or nerve root compression. The theory behind this condition is that we don't experience pain as a result of the herniated disc, but by the result of its affect on the adjacent nerve the disc material presses into.
The location of the pain in the back and associated body structures that are affected depend on which nerves have been compressed. Often the spinal nerves that are the most commonly affected are the ones between the 4th and 5th lumbar vertebrae, and the 5th lumbar vertebra and the 1st sacral body. The nerve between lumbar vertebra 4 and 5 is known as the L5 nerve. The nerve between the 5th lumbar vertebra and the top sacral body is known as the S1 nerve.
L5 nerve impingement: can result in lower back pain as well as weakness in the big toe and ankle. Advanced cases may result in a condition known as foot drop, which is the inability to extend the foot (push off the ground).
S1 nerve impingement: may result in lower back pain as well as the loss of the ankle reflex and weakness in the ankle. Advanced cases may involve the inability to do toe rises.