Spondylolisthesis

About Spondylolisthesis

In spite of its difficult name spondylolisthesis (pronounced spon” -di-lo-lis-thee’-sis) is a fairly straightforward structural disease of the spine. Spondyl- comes from the Greek word for vertebra, and -olisthesis from the Greek word for slip. Spondylolisthesis thus means slipped vertebra, and that is exactly what this back disease is. As noted earlier in this website, the term “slipped disc” is a misnomer for a herniated disc; our intervertebral discs cannot slip out of place. Yet our vertebrae can on occasion do just that.

In this website it was mentioned that the weight-bearing surfaces of our vertebrae do not generally lie horizontally—that is, parallel to the ground. Most of them lie at a distinct slant, and the upper surface of the sacrum in particular slopes, on the average, nearly 45 degrees, as shown in the illustration on below image. This tilted surface of the sacrum helps set the stage for spondylolisthesis.

A normal, intact vertebra, however, could not slip. The small facet joints at its rear firmly lock it to the vertebra below. For slippage to occur, the vertebra must be defective, with a crack across it in such a way that the rear portion of the vertebra, with its facet joints, is detached from the front portion. Such a defect is called spondylolysis {spondyl-, again, from the Greek word for vertebra, and -olysis from the word for dissolve or loosen). The cause of such a crack seems to be some hereditary weakness combined with prolonged mechanical stresses, which gradually produce what physicians call a fatigue fracture.

If a person has this crack, it is possible for it slowly to widen (as is shown in the illustration on image) under the weight of the upper body, allowing the detached front portion of the vertebra gradually to slip on the vertebra below. In most cases it is the lowermost lumbar vertebra, as shown here, that slides down the sloping upper surface of the sacrum, distorting the intervening disc and carrying along with it the entire upper spinal column.

Such spondylolisthesis is one back disease that seems to be unique to our human species. No other animal is known to develop it quite in this way, points out Leon L. Wiltse, M.D., of Memorial Hospital Medical Center in Long Beach, California, who for many years has made a special study of this disease. Four-footed animals, with horizontal spines, do not experience this exact sort of slippage, nor do even our closest relatives, the great apes. Human spondylolisthesis thus does seem to be caused in part by our upright posture. Only in humans does the weight of the upper body chronically press upon the lower spine, where —once the crack occurs—it can impel the downward slippage characteristic of spondylolisthesis.

Physicians have recognized spondylolisthesis for at least two centuries. In 1782, a Belgian obstetrician noticed patients with slippage so great it interfered with childbirth. Not until after the widespread introduction of x-ray diagnosis during the early part of this century, however, were physicians able to learn much about the condition.

The underlying defect (spondylolysis), which is harmless in itself, is surprisingly common; about one out of twenty of us has this crack across the back of our lowermost lumbar vertebra. In some population groups, the prevalence of this defect is even higher, notably among some Eskimos in northern Alaska. In one x-ray survey of 153 northern Eskimos admitted to the Alaska Native Service Hospital in Anchorage for reasons other than back problems, researchers found that 28 percent of them had the crack.

Only in about half the people with the crack, however, does any slippage occur, according to studies by Dr. Wiltse, and in most of these people it usually does not produce any significant symptoms. “There are probably many people with this condition who don’t know they have it and never have any trouble from it,” says Dr. Wiltse. “And we don’t actually know what percentage of people who do have it develop enough pain to cause them to see a doctor. But among people with back pain severe enough to consult a doctor, this is a fairly common cause of the pain.”

Most people with backaches from spondylolisthesis are able to keep it under control by conservative means—bed rest and pain-relieving drugs when pain is bad; wearing an orthopedic corset at times; and exercising after the pain subsides to strengthen the abdominal muscles supporting the spine. A small minority, however, may have so much trouble that they ultimately need surgery.

Lloyd Eagleton, for instance, is a compact, dark-haired man who began having aches in his lower back when he was a teenager. In his twenties, he recalls, they became “terrible” at times. He worked in a meat-packing plant, and his job at the time involved heavy lifting. He was constantly bruising his lower back and getting “sharp pains back there, which eventually would go down to a steady ache.” When he was x-rayed at work, he recalls being told “that I had a misalignment there, that the vertebrae were not lined up. It was a defect in my back I would have to live with.” He had noticed he had “a dip in the small of the back you could lay your thumb in. It was really caved in.” About that time he happened to change his particular job within the plant, and his back started to feel better.

When Lloyd was in his mid-thirties, however, he began to experience numbness in his legs, “down through the thigh, through the knee, down into the ankle.”

While he was driving on vacation one spring, his right leg and foot—the one on the gas pedal—would go numb. “It continued to get worse. At work, I’d have to sit down sometimes to relieve the pain and numbness. Later, it got so sitting wasn’t comfortable, and I’d have to get up and move around to relieve it. Soon it got so I couldn’t climb stairs.” He tried heat treatments and wearing an orthopedic corset, but they did not help enough.

Finally, that fall, he visited a specialist, who for the first time told him that he had spondylolisthesis and that in his case the defective vertebra was pinching nerves in his lower back. “He told me that the pain might get worse and that the solution was to undergo surgery. ‘You can have your surgery now,’ he told me, ‘or you can wait. It’s up to you. Eventually you will probably have to have something done.’ ”

Lloyd pondered this advice and then the next month did undergo surgery to fuse his slipping vertebra to the one below. This meant spending three months in a long body cast, and being off work for six months. Since he is now a supervisor, he no longer does heavy physical work on his job. “There is always some strain there, and still some tingling and a little bit of numbness, but I feel fortunate to be able to lead a normal life. I can do just about anything I want to do. It seems as solid as a bolt back there, probably stronger than it’s ever been.”

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