A Cause of Pain
Spondylolisthesis is a condition in which one vertebral body slips forward over the one below (subluxation). This may be due to a congenital issue (present at birth), trauma to the spine or it can be a result of degenerative and aging changes to the spine.
A spondylolysis is a term to describe a gap or a nonunion of a portion of the spine known as the pars interarticularis. This gap may be congenital or it may result from trauma to the spine. Spondylolisthesis can also occur when the joints connecting the different components of the spine become weaker, and allow one bone to slip on the other; in these cases, a defect of the pars interarticularis does not exist.
When spondylolisthesis occurs, the nerves passing through the central canal may become compressed and the nerves leaving through the neural foramen at the level of the slip may become compressed as well. Also, a patient with spondylolysis has a higher likelihood of suffering from a slip of the spine.
Spondylolisthesis is graded depending on the amount of slippage of one bone on the other. Grade I refers to a slippage of one to 24%. Grade II refers to a slip of 25 to 49%. Grade III is a slip of 50 to 74%. Grade IV is a slip of 75 to 99%. Grade V is a slip
Spondylolisthesis may cause the patient to have pain in the back or in the neck as a result of the slip of the bones themselves. The patient may also experience radicular pain to the arms or legs if the nerves are being pressed as they leave the neural foramen. The patient may also experience a more generalized pain to the lower extremities if there is significant compression upon the nerves in the central canal. In the neck, a significant spondylolisthesis may cause pressure on the spinal cord itself, resulting in pain and paralysis.
As described above, spondylolisthesis may be a result of degenerative changes of the spine or may occur from a gap or defect in a portion of the spine known as the pars interarticularis. This gap or defect may result from trauma or it may be present from birth. Over time and as a result of stress on the spine and gravity, the gradual slippage of one bone on the other progresses. The progression may continue or may stabilize.
The first step in diagnosing spondylolisthesis is obtaining a complete history from the patient, followed by a detailed physical examination. If the physician is suspicious that a spondylolisthesis may be present, the next step is to confirm this with diagnostic studies.
An x-ray of the lumbar spine on a lateral view will easily confirm whether or not there is a slippage of one bone upon the other. It is often helpful to take this x-ray in a standing position as on occasion, the slip will reduce to a more neutral position when the patient is lying down (supine).
It is also helpful to have the patient obtain an extra x-ray of the lumbar spine, in the standing position, bending forward and backward. This is known as a flexion/extension x-ray. This x-ray will help to determine how much motion there is and whether the spine is stable or unstable.
An MRI scan is a very sensitive study which will also show not only the spondylolisthesis, but the degree of compression of the nerves as they exit the neural foramina and as they pass through the central spinal canal. If this does not give sufficient detail or if this still remains a question, a myelogram followed by a CT scan of the spine may provide more information.
A CT scan will also determine whether or not there is a spondylolysis (gap or defect in the bone) present. These imaging studies are excellent and showing the anatomy of the spine but they do not give information about the function of the nerves. If there is a question as to how the nerves are functioning, an EMG/nerve conduction study may help.
Depending upon the cause of the spondylolisthesis, the condition may or may not be avoidable. If it is due to a congenital gap in the bone (pars interarticularis), then there is not much that one can do to prevent the eventual effects of normal strain on the spine and gravity from causing a slip to develop. Certainly being at ideal body weight, staying in shape, exercising and keeping the back and abdominal muscles strong will help to decrease the likelihood of slip over time. Similarly, when the slip is due to degeneration and aging of the facet joints, there is not much that one can do except to try to keep close to ideal body weight and stay in shape. On the other hand, there are certain exercises that have a higher risk of causing a fracture of the pars interarticularis, thus resulting in the possibility of spondylolisthesis in the future. Certain athletic activities that cause extension of the spine (standing and arching the back backward) predispose one to such fractures, such as gymnastics and diving. However, they are uncommon in swimmers.
Nonsurgical management has a significant role in the treatment of spondylolisthesis. Those patients with low-grade spondylolisthesis (grade I or grade II) may respond to more conservative care.
• Activity modification to exclude activities that will place additional stress or flexion of the spine.
• Bracing of the spine space (cervical and lumbar)
• Physical medicine/physical therapy techniques
– Nonsteroidal anti-inflammatory medications
– Spinal epidural steroid injections
– Oral pain medications
– A short course of oral steroids
Surgical intervention may be needed when patients fail to respond to nonsurgical treatments, there is a progression of the slippage over 30%, the slip is grade III or higher, or when there are progressive neurological symptoms and physical deformity.
• Selective decompression of nerve roots and decompression of posterior spine space (known as the Gill procedure) has a 25% risk of leading to increased subluxation in the future.
• Decompression of the nerve roots and decompression of the posterior spine with a fusion. This procedure helps not only to decompress the nerves, but it also helps to stabilize the spine from slipping further in the future. In addition, it may be possible to help pull the spine back into a more neutral position, correcting the slip which had already occurred, and improving the patient’s posture. This can be done through a variety of fusion techniques which are discussed in the Surgical Procedures section of this website. Diffusion can be accomplished from the posterior approach (back of the body), through the anterior approach (through the abdomen), or through a combination thereof. An interbody fusion, graft placed between the vertebral bodies, may also be used.
In general, the prognosis for these patients is quite good when the slip is of a lower grade. When the spondylolisthesis is of grade III or higher, the risks of injury to the nerves during surgery and experiencing further slipping of the spine in the future are higher than in the lower grade slips.