Spondylolisthesis

Lumbar disc Sacral canal stenosis Spondylolisthesis Perineum syndrome... 

There is a great deal of interest in spondylolisthesis and, in the worst case scenario, spondyloptosis. What is spondylolisthesis and what is spondylo-ptosis ... 

Spondylolisthesis is a slipping of one vertebra on the other. The thing to remember is that the vertebra that is slipping carries the trunk with it as it slips forward. What is spondyloptosis I think the best definition of spondyloptosis is when the cephalad vertebrae s posterior superior corner is caudal to the inferior vertebrae s anterior superior corner. It is usually difficult to assess the anterior superior corner because the sacrum has many adaptive changes and herein lies one of the controversies with spondylolisthesis. 

The Classification of Leon Wiltse has been used extensively in North America and I think that it may be one of the reasons that there is so much confusion about spondylolisthesis in the USA. A better classification is the Marchetti-Bartilozzi Classification. Basically there are only two types of spondylolisthesis, developmental and acquired. 

Fig.1. This table represents 16 patients surgically treated in the 1970s for developmental spondylolisthesis. All had over 50% slip so that the Meyerding Classification was Grade ill or Grade IV.

This is an important distinction when one is attempting to understand spondylolisthesis. Developmental spondylolisthesis is the one that severely progresses [6]. What causes spondylolisthesis and spondyloptosis If we agree that spondylolisthesis must be present before spondyloptosis occurs, then we have to use a classification to help us understand this. Spondyloptosis is usually seen in high grade dysplastic type of developmental spondylolisthesis. 

Fig. 2. Note severe spondyloptosis. Note the vertical sacrum and the rounded dome. Note complete block on myelogram. The consistent finding of vertical sacrum in spondyloptosis is of paramount importance. This position makes reduction difficult. It is important to recognize spondylolisthesis before the sacrum becomes vertical...

If we believe that the sacrum and the L5 vertebra are normal at one time in all spondylolisthesis patients, then we have to understand why there is such different anatomy of the sacrum, pars and lumbar vertebra 5. The sacrum may appear normal or it may show some degree of bend, or it may become clearly vertical in spondyloptosis (Fig. 2). We have witnessed over the years that the sacrum has deformed in spondylolisthesis (Fig. 3). We have studied the sacrum of many spondylolistheses and have divided them into 3 groups, depending upon how bent they are. Which ones do and which ones do not is difficult to understand. If we accept the statement... 

Fig. 3. These tracings are of spondylolisthesis sacrums. Note the multitude of shapes. The first several are very "benf and the sacral horizontal angle is almost 90 degrees...

Fig. 4. This tomogram illustrates the vertical sacrum and the trapezoidal L5. This is more of a spondylop-tosis than a spondylolisthesis. Yet, by our grading system, it would register as a more benign condition than it really is.

There is a similar situation with the L5. If we assume that L5 vertebra has a normal appearance at one time, then how do we explain the trapezoidal looking L5 in the various degrees of spondylolisthesis. Some think it hypoplasia - I disagree. 

The pars interarticularis in developmental spondylolisthesis may appear stretched, drawn and thin and sometimes may actually have a gross fracture (Fig. 5). 

How do you measure and how do you grade spondylolisthesis Frequently because of the many adaptive changes of the sacrum, false interpretation, usually on the mild side, is given by the radiologists that read plain x-rays. We need a better grading system ... 

Slip angle as used by the North Americans also tends to have a benign description of the spondylolisthesis. It is measured by the angle of a line constructed along the long axis of the sacrum to the top of L5. The top of L5 is used because the inferior portion of L5 is so distorted. 

Fig. 6. There are many ways to grade spondylolisthesis and maximum lordosis. We need to be consistent and revise measurements when it becomes apparent that the old measurements are no longer useful...

Fig. 8. This pain profile seems to indicate that pain is variable in time and intensity. There are many pain generators in spondylolisthesis and some may act at one time and not another...

Pain seems to be an intermittent condition in spondylolisthesis. If we construct a time line, the intensity of pain symptoms seems to vary not only in time but in duration and in magnitude (Fig. 8). 

There are many pain generators in spondylolisthesis. Some are acting at one time while others are acting at another. 

If we construct this time line, we can see that if we believe spondylolisthesis may progress to spondyloptosis, we can project various and sundry reasons for a painful situation and a situation when pain completely resolves. These pain generators are microfracture, annular stretch, sacral molding, L5 molding, degenerative disc, nerve root entrapment, caudi entrapment. 

Fig. 9 a, b. This illustration reveals a patient with a bent sacrum, degenerative disc, and spondylolisthesis... 

The x-rays show a macrofracture of an elongated pars interarticularis. These films illustrate the many pain generators in spondylolisthesis microfractures causing elongation of the pars, degenerative annular stretch, degenerative disc disease, and the sudden macro fracture of the pars causing the acute syndrome... 

Figure 9 a shows a spondylolisthesis with a bent sacrum and a dehydrated disc. The chief complaint was sudden and severe low back pain and if we look closely at this x-ray (Fig. 9 b) we can see an acute pars fracture superimposed on the elongated pars interarticularis. Further questioning of the patient revealed that yes he had chronic low back pain but never thought much about it until this episode. 

The research recently done by the Iowa group is fascinating to me. In my mind it confirms all my ideas about spondylolisthesis [8]. They simply potted immature calf spines and stressed them. The slip of the vertebra occurred at the growth plate much like slipped capital femoral epiphysis. If we can use this model as we think about high dysplastic spondylolisthesis with increased lordosis we begin to realize why the sacrum and L5 look the way they do in spondylolisthesis [3]. 

As the growth plate is subjected to forces, the sacrum will deform. It will round off and dome and L5 will become trapezoidal because of Heuter Volkman and Wolff s laws. The pars interarticularis will become elongated through repeated stress fractures [7]. If the posterior tether is weak L5 slips off. We can understand the entire event of spondylolisthesis from birth to spondyloptosis with this thinking. We can also understand the various spinal pathoanatomies that are seen at various times with x-rays. 

Fig. 10 a, b. Normal bony hook in Fig. a. a Normal strong inferior facet of L5 and normal strong sacral facet, b Thin pars and a deficient superior sacral facet. This is the dysplasia of developmental spondylolisthesis. The degree of dysplasia coupled with increased lordosis begins the cascade of spondylolisthesis... 

Fig. 11-14. These MRIs of 4 different patients illustrate the variety of changes seen in spondylolisthesis. Note the increasing disc space at the S1-S2 region. Note how the best MRI is the topogram. Radiologists need to be instructed for spondylolisthesis MRIs...

It is clear that severe spondylolisthesis is seen in growing children. The developmental type of spondylolisthesis with high dysplasia is the problem (a poor bony hook). For whatever reason the pelvis rotates and lordosis increases. This now causes stress on the growth of the plates of L5 and SI. These deform because of Heuter Volkman Rule and Wolff s law. The dys-plastic bony hook may stretch or separate or both. The sacrum may bend. The disc may fail. Eventually in the worst case scenario the spondylolisth-... 

These MRIs show progressive spondylolisthesis with the sacral bending and the S1-S2 disc becoming wide posteriorly (Figs. 11-14). These are 4 different patients. If the restraining elements posteriorly do not hold, L5 slips forward and the sacrum becomes vertical and we have a spondyloptosis. 

To identify x-ray markings to predict which will become severe spondylolisthesis. This might mean the introduction of new imaging techniques in order to make this prognosis. 

To make recommendations on how to image patients in order to easily view the markers that we have identified. Too many times the sacrum is cut off on the x-rays or the label is placed in a bad position. We need to make specific recommendations on how to take appropriate spondylolisthesis x-rays. Maybe early MRIs are needed. 

A better system of grading spondylolisthesis so the radiologist will be able. 

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