What is the difference between absolute and relative stenosis?

The difference between an absolute and a relative spinal canal stenosis lies in the diameter of the constricted spinal canal. In relative spinal canal stenosis, the mean diameter is between 10-14mm. In absolute spinal canal stenosis, the diameter is even more narrowed.

Here, it is already less than 10 mm. However, the criterion of the mean diameter is usually not sufficient for a final assessment of the severity of spinal canal stenosis, since the spinal canal may be sufficiently wide in the middle, while it is strongly narrowed in the outer region. Since the nerves that move into defined areas of the body are located in the outer area of the spinal canal, a narrowing there can lead to enormous pain on the one hand and on the other hand, it can be used to determine the location of the stenosis.

For example, in the case of pain moving from the lower leg to the tip of the foot, a narrowing of the spinal canal in the lower lumbar region can be inferred, since the corresponding nerve exits the spinal canal in the area of the fifth lumbar vertebra. In principle, however, it can be said that absolute spinal canal stenosis is a more advanced stage than relative spinal canal stenosis. Therefore, absolute stenosis is usually associated with relatively severe pain and should be treated by a doctor as soon as possible to avoid possible permanent damage.

Anatomy of the lumbar spine

The lumbar spine (lumbar spine) is formed by the five lumbar vertebrae of the spinal column. Since they are located in the lower part of the spine, they must bear the highest proportion of weight. For this reason, they are also considerably thicker than the other vertebrae.

However, this does not prevent the signs of wear and tear that are particularly common in this area. For example, joint wear and slipped discs are most common in the lumbar spine. The lumbar spine also differs in its structure from the other areas of the spine. For example, from the second lumbar vertebrae onwards, there is no longer a spinal cord, but only individual nerve roots, which move further down and emerge from their designated nerve root cell holes (neuroforamas).This area, where the spinal cord ends and the spinal canal is filled by nerves, is called the “horse’s tail”, or cauda equina in medical terms.