When an injured worker has low back pain along with leg pain or tingling, he or she may have a lumbar herniated disc. Sometimes this is referred to as a slipped disc, a ruptured disc or a pinched nerve.
The human spine is formed by 24 spinal bones, called vertebrae. The vertebrae are stacked one on top of another to form the spinal column. The spinal column is the body's main upright support and gives the body its form. The section of the spine in the lower back is known as the lumbar spine. The spinal cord resides in the spinal canal formed by the hollow center of the vertebrae assembled on top of each other. The spinal cord branches out into nerve roots, which pass through openings in the sides of each vertebra, called the neural foramina, before branching out further into the nerves that actuate the body.
The lumbar spine is made up of the lower five vertebrae, referred to as L1 to L5. These five vertebrae line up to give the low back a slight inward curve. The lowest vertebra of the lumbar spine, L5, connects to the top of the sacrum, a triangular bone at the base of the spine that fits between the two pelvic bones.
Between the vertebrae are shock absorbers called intervertebral discs, which separate the vertebrae. The discs are made of connective tissue. Connective tissue is the material that holds the living cells of the body together. Most connective tissue is made of fibers of a material called collagen. These fibers help the disc withstand tension and pressure.
A disc is made of two parts. The center, called the nucleus pulposus, is spongy. It provides most of the disc's ability to absorb shock. The nucleus is held in place by the annulus fibrosus, a series of strong ligament rings surrounding it. Ligaments are connective tissues that attach bones to other bones.
Healthy discs work like shock absorbers to cushion the spine. They protect the spine against the daily pull of gravity. They also protect it during strenuous activities that put strong force on the spine, such as jumping, running, and lifting.
Imagine a jelly doughnut, if you put enough pressure on the outside of the doughnut (annulus fibrosus), the jelly (nucleus pulposus) will pop out; the same thing may occur with the nucleus pulposus at the center of intervertebral discs when the annulus fibrosus is damaged or wears down. When the nucleus pulposus oozes out, it may come into contact with the nerve roots resulting in pain. The next McCormick Law Office post will discuss the causes of disc herniation.