Spondylolysis and Spondylolisthesis

The spine is made up of a series of connected bones called "vertebrae." In about 5% of the population, there is a developmental deficiency which ultimately results in a break in the junction between the front and back of one of the lower vertebrae of the lumbar spine. The anatomic name for this section of the vertebra where the fracture occurs is the “pars interarticularis.” This most commonly occurs in the lowermost vertebra, where the lower (lumbar) part of the spine joins the tailbone (sacrum), also known as the L5-S1 segment. Young athletes, such as gymnasts, football players, or wrestlers, through repetitive stress and loading of the lower lumbar segments may also develop a stress fracture in this region. Because of the constant forces the low back experiences, this fracture may not completely heal. In either case, whether the origin be predominantly developmental or traumatic / stress related from overuse, this condition of fracture is referred to as “spondylolysis.” Spondylolysis is simply a crack in the pars interarticularis of the vertebra which may result in lumbar pain or may cause no symptoms at all. However, sometimes the cracked vertebra does slip forwards or backwards over the vertebra below it. This displacement of one vertebra upon the one below is known as a “spondylolisthesis.”

It should be noted that a spondylolisthesis can also arise in the absence of a fracture or spondylolysis. In the older adult population, a spondylolisthesis can arise in the setting of wear and tear- or osteo-arthritis. In this scenario, degenerative changes affecting the intervertebral discs and facet joints are believed to initiate a cascade which ultimately leads to a slippage of one vertebral body upon another. A degenerative spondylolisthesis is most commonly observed in older females and at the L4-5 segment, one level above the lowermost level of the lumbar spine.

What are the symptoms?
Spondylolysis or acute fracture of the pars interarticularis in the younger (adolescent) patient population typically presents with low back pain. Patients will often describe pain reproduced with extension, or rearward leaning, of the lumbar spine. Spondylolisthesis itself may not cause any symptoms for years (if ever) after the slippage has occurred. Often, it can be the resulting sequelae, not the actual spondylolisthesis, that leads to symptoms. The most common consequences of spondylolisthesis include spinal stenosis, disc degeneration, facet joint arthrosis, and synovial cyst formation. The resultant spinal stenosis, or compression of the spinal nerves, can arise from mechanical pressure placed upon the nerves either in the central canal of the lumbar spine or as the nerves exit within the neural foramen. Patients who experience symptoms from nerve involvement may describe both low back and buttock pain as well as radiating symptoms such as numbness, tingling, pain, or weakness affecting the lower limb(s). For the most part, such stenosis related symptoms are usually aggravated by standing, walking and other activities, while sitting or relative rest will provide temporary relief.

Studies have shown that 5-10% of patients seeing a spine specialist for low back pain will have either a spondylolysis or spondylolisthesis. However, because spondylolisthesis is not always painful, the presence of a crack (spondylolysis) and slip (spondylolisthesis) on the x-ray image does not mean that this is the source of your symptoms. For this reason, it is essential that your treating physician properly evaluate your symptoms and personally interpret your radiographic studies to ensure that your spinal condition is properly diagnosed and that appropriate treatment is prescribed. The physiatrists at Long Island Spine Rehabilitation Medicine, fellowship trained in comprehensive non-surgical spine care, will personally evaluate each patient to determine whether these imaging findings may, in fact, be responsible for your symptoms.

How is it diagnosed?
Your doctor will begin by taking a history and performing a detailed physical examination. X-rays (plain radiographs) are also often ordered when a spondylolysis or spondylolisthesis is suspected. However, sometimes it is difficult to see a small fracture or more subtle slippage on an x-ray image, so additional tests may be needed. X-rays taken with your spine in a flexed and extended position, often also referred to as “dynamic” or “bending” films may demonstrate if the slippage is mobile or accentuated with postural change. A computed tomography (CT) scan can best and more clearly show a fracture or defect in the bone. A magnetic resonance imaging (MRI) scan may be ordered to demonstrate an acute fracture or stress reaction (i.e. swelling or edema) in the bone while also clearly revealing the soft tissue structures, including the intervertebral discs and spinal nerves, which might also be contributing to the overall pain syndrome. Bone scans such as a SPECT scan are also utilized and often considered a “gold standard” for revealing an acute fracture or spondylolysis.

If a spondylolisthesis is present, it is graded as I, II, III or IV based on how far forward or backward the vertebra has slipped.

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