Stress Fractures

With such big words in the medical world, you may be asking what exactly is Isthmic Spondylolisthesis. Well, Spondylolisthesis is the Latin term for a slipped vertebral body, and Isthmic refers to the fact that the slip is due to a stress fracture through a piece of bone in the back (the pars interarticularis). Approximately 5% of the population experiences a stress fracture in the lowest lumbar vertebral segment (L5), usually between the ages of five and seven. That segment then slides forward, encroaching on the first sacral vertebral body (S1). This is almost never due to an injury. The L5-S1 segment is the most likely to slip but it can also occur at L4-L5 or L3-L4.

This condition is the leading cause of back pain in adolescents, though most adolescents that have the condition will not experience any back pain because of it. It is not a very dangerous condition as there are almost never any neurological problems associated with it.

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Spondylolisthesis - person hunched over showing spine


Probably 80% of people who have this condition never have any symptoms and therefore never even realize they have it. For those who do develop low back pain, the cause may be from the vertebrae sliding forward and compressing a nerve or from resulting disc degeneration. With the bony segments of the spine not working properly the disc has to work harder. The disc is designed to work very well under normal compression, but the forward force applied to the disc in the case of spondylolisthesis can cause the disc to break down.

In addition to the low back pain, some patients also experience leg and foot pain due to the nerve being pinched (almost always the L5 nerve). This leg pain will generally be worse when the patient stands or walks.

Pain can also come from the fracture, and the tissue in that area may become irritated and painful. Within the pars interarticularis the nerve endings (nociceptors) can become sensitized and create pain. Most of the pain will be activity related. Pain with rest is not typical.

Spondylolisthesis - two doctors looking at x-ray


If, upon physical exam at a pain clinic, symptoms indicate a possible isthmic spondylolisthesis, an imaging study will be needed to confirm the diagnosis. Isthmic spondylolisthesis can be seen on a regular X-ray, and on a Magnetic Resonance Imaging (MRI) scan. As noted, the spondylolisthesis will almost always occur at the juncture of the L5 and S1 vertebral segments, so that is where the most attention will be focused on the images. The imaging study can also detect if there is degenerative disc disease leading to a nerve root being pinched.

Treatment need only be considered if the pain limits the patient’s pain to any great extent. It is not a dangerous situation, and the pain is generally not progressive.

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