Spondylolisthesis occurs when one vertebra slips forward on the adjacent vertebrae. This will produce both a gradual deformity of the lower spine but also a narrowing of the vertebral canal. It is often associated with pain.
There are five major types of spondylolisthesis:
Type I is called dysplastic spondylolisthesis and is secondary to a congenital defect of either the superior sacral or inferior L5 facets or both with gradual slipping of the L5 vertebra. *
Type II, isthmic or spondylolytic, in which the lesion is in the isthmus or pars interarticularis, has the greatest clinical importance in persons under the age of 50. If a defect in the pars interarticularis can be identified but no slipping has occurred, the condition is termed spondylolysis. If one vertebra has slipped forward on the other (horizontal translation), it is referred to as spondylolisthesis.
Type II can be divided into three subcategories: Type II A is sometimes called Lytic or stress spondylolisthesis and is most likely caused by recurrent micro-fractures caused by hyperextension. It is also called a "stress fracture" of the pars interarticularii and is much more common in males.
Type II B probably also occurs from micro-fractures in the pars. However, in contrast to Type II A, the pars interarticularii remain intact but stretched out as the fractures fill in with new bone.
Type II C is very rare in occurrence and is caused by an acute fracture of the pars. Nuclear imaging may be needed to establish diagnosis.
Type III is a degenerative spondylolisthesis, and occurs as a result of the degeneration of the lumbar facet joints. The alteration in these joints can allow forward or backward vertebral displacement. This type of spondylolisthesis is most often seen in older patients. In Type III, degenerative spondylolisthesis there is no pars defect and the vertebral slippage is never greater than 30%.
Type IV, traumatic spondylolisthesis, is associated with acute fracture of a posterior element (pedicle, lamina or facets) other than the pars interarticularis.
Type V, pathologic spondylolisthesis, occurs because of a structural weakness of the bone secondary to a disease process such as a tumor or other bone diseases.
The most common symptom of spondylolisthesis is low back pain. Many times a patient can develop the lesion (spondylolysis) between the ages of five and seven and not present symptoms until they are 35-years-old, when a sudden twisting or lifting motion will cause an acute episode of back and leg pain.
Usually the pain is relieved by extension of the spine and made worse when flexed. The degree of vertebral slippage does not directly correlate with the amount of pain a patient will experience. Fifty percent of patients with spondylolisthesis will associate an injury with the onset of their symptoms.
In addition to back pain, patients may complain of leg pain. In this situation, there can be associated narrowing of the area where the nerves leave the spinal canal that produces irritation of a nerve root.
Many patients with spondylolisthesis will have vague symptoms and very little visible deformity. Often, the first physical sign of spondylolisthesis is tightness of the hamstring muscles in the legs. Only when the slip reaches more than 50 percent of the width of the vertebral body will there begin to be a visible deformity of the spine.
There may be a dimple at the site of the abnormality. Sometimes there are mild muscle spasms and usually some local tenderness can be felt in the area. Range of motion is often not affected, but some pain can be expected on hyperextension. Laboratory test results are normal in patients with one or both disorders.
Plain roentgenograms of the lumbar spine are best initial X-rays for diagnosing spondylolysis or spondylolisthesis. Spondylolisthesis is most easily seen on the lateral view of the spine, but in some cases specialized imaging studies such as a bone scan or CT scan (CAT scan) are needed to make the diagnosis. Patients with a dysplastic pars have an elongated interarticular region along with altered pedicles. This is usually best visualized by CT scan.
A spondylolisthesis is graded according to the amount that one vertebral body has slipped forward on another. A grade I slip means that the upper vertebra has slipped forward less than 25 percent of the total width of the vertebral body, a grade II slip is between 25 and 50 percent, a grade III slip between 50 and 75 percent, a grade IV slip is more than 75 percent, and in the case of a grade V slip, the upper vertebral body has slid all the way forward off the front of the lower vertebral body. This is a special situation that is called a spondyloptosis.Differential Diagnosis
The diagnosis of spondylolysis is confirmed by the discovery of a pars defect on a lateral roentgenogram and spondylolisthesis is confirmed by noting the forward position of one vertebral body on another.
Flexion and extension views of the lumbar spine may help to identify the presence of instability of the spine. This subtle movement may be an important part of the pain experienced and be essential to the planning for further treatment.
The conservative non-surgical treatment for spondylolysis and spondylolisthesis is most commonly rest, followed by trunk and abdominal strengthening exercises. A physical therapist is often helpful in getting you back on your feet and can instruct you in the proper way to do these exercises without exacerbating your symptoms. If there is significant leg pain, patients can also take an anti-inflammatory medication. Braces are rarely indicated but may be helpful in reducing symptoms.
For patients with spondylolysis, surgery to repair the defect in the pars intra-articularis is indicated only after non-operative measures such as physical therapy and exercises have failed to relieve symptoms. In younger patients, surgery may be used to directly repair the pars defect; in older patients or in those with some degree of instability, a fusion may be required.
If you have spondylolisthesis with the slippage greater than 50 percent of the width of the adjacent vertebral body, then a fusion is required to stop further slippage and provide relief from the associated symptoms of instability and nerve root irritation. Surgeons using a technique called a "fusion in-situ" can do this. What this means is that the surgeon will fuse the two abnormal vertebra together to prevent further slippage, but no attempt will be made to bring the vertebrae back into their original alignment. This is an area of considerable debate among spine surgeons, because although there are now techniques available that will allow the surgeon to "reduce" the slipped vertebra back to is normal, "anatomic" position, these techniques carry the risk of causing an injury to the surrounding nerve roots in the process. You should discuss these issues carefully with your doctor before surgery.
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