I CAN CAUSE YOU more double-barreled misery than any other part of your body. I am your backbone, and you have some pretty wild ideas about me. You think of me as a series of "joints" that go "out" - out where? I ask. Every year or so, when I flare up, you have me pummeled, heated and drugged - none of which does much good. The pains I give you are simply my response to the bad treatment you give to me. Ironically, there is very little wrong with me that you couldn't fix your self. You need never have another backache.
Trouble in my department began when your ancestors decided to stand erect. Instead of a nicely balanced suspension bridge, I became a tent pole. And quite a versatile tent pole at that: one that can bend, twist, swivel a head and support most of the body's weight.
I also must provide security for your l8-inch spinal cord. Let anything serious happen to this whitish, half-inch-thick cable and you will likely spend the rest of your life in a wheelchair, for the millions of messages which fly back and forth along it direct all your activities below the neck level. I protect the cord with three layers of sheathing, a fluid bath to take up shock, plus a bony housing. Thirty-one pairs of nerves branch out from the cord. Almost half are sensory, which convey information to the brain; the rest are motor, which transmit orders from the brain to the muscles. In some situations, the cord even does its own thinking. Your finger touches a hot stove. There's no time to waste conveying this information to the brain. My cord orders a reflex action - and the finger is jerked away.
The chances of my cord ever causing you any trouble are rather remote. But my 33 vertebrae and their supporting structures are another story. A wide range of things can cause pain here: trouble with kidneys, prostate or liver; arthritis and various infections; even emotions. For example, several times you had big worries that nagged at you for days. You developed a dull backache. You didn't connect any hurting with your worries. As usual, you thought I was "out." What was really happening was this: strong emotions tighten muscles; mildly tensed for several days, my muscles simply grew tired and announced it with dull pain. Once you stopped worrying, I ceased hurting.
If you would study my structure - really an marvel - you'd get a better idea of what causes backache. Starting at the top, I have seven cervical vertebrae, which are capable of an extraordinary range of movement. In addition to supporting your head, they can twist to let you look down at the ground or up at the stars. Laterally, they permit 180 degrees of motion, letting you look over either shoulder.
The 12 thoracic or chest vertebrae, which come next, aren't capable of such a wide range of movement; there's no need for it. The ribs are hooked to these. Trouble in this area is rare.
At the lower end are five heavy lumbar vertebrae, which carry most of your weight; five sacral segments, which are fused together to form the coccyx - all that is left of the tail once sported by your forebears. This lower area, particularly around the fourth and fifth lumbar vertebrae, is the big trouble spot.
When you were born, I was more or less straight. Then, when you began to hold your head erect, my vertebrae took on a curve in the neck area. Another curve developed lower down when you began to toddle. Result: I have a vague S shape today. Actually, this is far better than a perfectly straight spine, for the arches act as shock absorbers.