How The Spine Works

…and what happens when it doesn’t

Your spine moves like a semirigid gooseneck lamp, with the greatest movement in your neck—which might move three hundred times a day—and your lower back. Whether you run a marathon or pick up a book from the floor, the discs lying between the bones (vertebrae) of your spine absorb the shocks of pressure and cushion the bones of your back to protect you from injury and pain. The wear and tear to these bones, discs, and related structures as we age is at the root of most back pain. Bones get arthritic, discs shrink or press on a nerve, supporting ligaments calcify, and so on.

There are thirty-two or thirty-three vertebrae in your spine. The seven top vertebrae, which support the skull and neck, are called the cervical spine and numbered Cl to C7. The next twelve vertebrae, which go down the back of the chest and connect to the ribs, are the thoracic spine (T1 to T12). The next five compose the lumbar spine (L1 to LS). Finally, the sacrum consists of five fused vertebrae, and the coccyx, or tailbone, is three or four fused vertebrae at the bottom of the spine. Each vertebra has a solid oval part in the front and a hollow arch pointing toward the back. The sides of the arch are called lamina. A system of interlocking small joints called facets, located on the side of each vertebra, prevents us from turning too far and looking like the girl in The Exorcist who could spin her head all the way around. A U-shaped layer of thick yellow ligaments, just inside the arch and facets, further stabilizes the spine. The muscles of the back are attached to the back of the spine and, by pulling on these bones, stabilize and move the spine.

The vertebrae and interspersed discs support the weight of your spine. Within the vertebrae, under the arch and underlying ligaments, there is the spinal canal. In this protective, bony canal lies the delicate spinal cord, a cable of nerves about the thickness of your finger, and the nerves going into and out of the cord. The nerves within the cord carry messages up and down its length, to and from the brain, linking the brain with the peripheral nerves. There are 62 nerve roots that come off the side of the cord in pairs, 31 on the right and 31 on the left. A little hole, called a foramen on either side of each vertebra, allows the nerve roots to exit the spinal canal. One pair exits at the level of each vertebra. Just below the place where the ribs reach the spine, the spinal cord ends and gives off a collection of nerve roots called the cauda equina (“horse’s tail” in Latin), that control feeling and movement from the groin down, as well as bowel, bladder, and sexual function. The brain, spinal cord, cauda equina, and roots within the canal and foramen are wrapped in protective covering. Closest to the nervous tissue is an ultra thin membrane surrounded by colorless water-like spinal fluid, which is contained by another thin membrane, the arachnoid, which looks like a spiderweb. A thick protective outer layer, the dura, completes the wrap. In the spinal canal, the dura is surrounded by the fat and veins of the epidural space.

How Wear and Tear Creates Pain

Painful spinal disorders occur, in order of descending frequency, in the lumbar, cervical, and thoracic spine. The 23 discs between the vertebrae play a major role in the gradual process of spinal degeneration, pain, and disability. These semiflexible shock absorbers resemble checker pieces, with a shoe-leather overing called the annulus. They are filled with a substance like hard rubber called the nucleus. Discs contain a large percentage of water, and after you turn 30, they begin to dry out and become brittle and flatten. Degenerated discs may crack and fissure, a potential cause of intrinsic disc-related or discogenic, pain. More seriously, they may herniate. The nucleus may ooze through a rip in the covering causing pain or other neurological problems, especially if it presses on a sensitive nearby nerve root or the spinal cord.

Age and wear-and-tear-related loss of disk height also results in minor instability of the affected areas, with one vertebral body wiggling over another.  To compensate for this instability, the supporting yellow ligaments thicken and compress the spinal canal and foramina. As we age, these bulging ligaments harden due to calcification and we develop pressure on the cord, the cauda equina, or the nerve roots exiting the spine. The narrowing process results in what we call stenosis, which can cause pain, weakness, or numbness. Sometimes the instability becomes serious and bones slip over one another significantly, causing narrowing of the spinal canal and foramina, which also results in stenosis. This instability can cause or worsen scoliosis. If discs could be prevented from degenerating and losing height, or could be restored when they do degenerate, most spinal problems could be avoided. This is a serious challenge for preventive medicine and the Biotechnology industry.

Yet, there is hope… Here we discuss our procedures to relieve discogenic pain.

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Emile M. Hiesiger, M.D.

The Corinthian
345 East 37th Street
Suite 320
New York, NY 10016
• Phone (212) 697-1411 or
• Phone (212) 263-6123
• Fax (212) 697-1399

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