Spondylolysis is the medical term for a spine fracture or defect that occurs at the region of the pars interarticularis. The pars interarticularis is region between the facet joints of the spine, and more specifically the junction of the superior facet and the lamina.
Spondylolisthesis is the medical term used to describe the forward slippage (anterior translation or displacement) of one spine bone (vertebrae) on another.
Quite often, a person who has spondylolysis (pars fracture) will also have some degree of spondylolisthesis (forward slippage of one spine bone on another). However, a person may have a spondylolysis without having spondylolisthesis, and a person may have spondylolisthesis without having a spondylolysis.
It is more common for a child or young adult to have a spondylolysis (pars fracture) without having spondylolisthesis, whereas adults are frequently diagnosed with spondylolisthesis without spondylolysis. Although it is confusing, both of these conditions are frequently seen in combination, and the treatments for both conditions are often the same. However, it is much more common for adults to be treated surgically; children with spondylolysis/spondylolisthesis rarely require surgery unless the slippage is severe.
There are a number of causes of spondylolisthesis, and a classification system was developed by Wiltse. There are six types (or causes): Type I is congenital (birth defect) or dysplastic (developed abnormally early in life), Type II is isthmic (caused by a pars fracture and instability), Type III is degenerative (caused by arthritis), Type IV is traumatic (acute facet fracture/injury to the facet complex), Type V is pathologic (caused by a tumor, cancer, or infection), and Type IV is postsurgical (iatrogenic bone removal).
Back pain is the most common presenting symptom, particularly in adults. Children may or may not have significant back pain; the predominant symptom(s) may be difficulty walking, postural deformity, and/or hamstring tightness. Adults frequently have leg pain, numbness, and/or weakness (sciatica, radiculitis, or radiculopathy) while children rarely have leg symptoms.
Children with spondylolysis and spondylolisthesis often have a stiff-legged gait and backward pelvic tilt, causing the buttocks to appear very flat. If the spondylolisthesis is severe, a “step-off” may be felt over the lower back region. The hamstring tightness may be so severe in some children that forward bending is limited and picking something off the floor is impossible. The neurological examination of strength, sensation, and reflexes is usually always normal in children.
Adults with spondylolysis and/or spondylolisthesis frequently have lumber tenderness and an antalgic gait (pain causing abnormal walking), but rarely have a noticeable deformity unless the slippage is severe or has been present since childhood. Adults may have numbness, weakness, and/or neurogenic claudication, especially if the associated arthritis and spinal stenosis is severe.
Spondylolysis and spondylolisthesis is frequently identified with regular lumbar x-rays, especially the lateral (side view) x-rays. It is sometimes difficult to see a non-displaced or minimally displaced pars fracture (spondylolysis), therefore oblique and flexion/extension x-rays are usually obtained. A Computed Tomography (CT) scan is the best test to verify that a pars defect/fracture is or is not present. The amount of forward translation (spondylolisthesis) is quantified by evaluating the percentage of slippage of one bone on another. The Meyerding classification is used determine whether it is a Grade I (0-25%), Grade II (25-50%), Grade III (50-75%), Grade IV (75-100%), or Grade V (more than 100%). The slip angle is determined by how angulated the L5 bone is on S1.
An MRI test is useful to evaluate the severity of nerve compression, but is less accurate at detecting a pars fracture than a CT scan. A bone scan may be ordered to determine if the spondylolysis pars fracture is recent (acute), or if it is old (chronic). A recent fracture would generally have a significant radionucleotide uptake and appear as a “hot spot” in the lower lumbar region.
There are no laboratory tests used to diagnose spondylolysis or spondylolisthesis. Occasionally, specific tests are ordered to rule out infection or other medical/rheumatologic conditions.
A discogram may useful in an adult patient to determine if the discs adjacent to the spondylolysis/spondylolisthesis are also causing pain. A doctor performs this procedure by injecting radiopaque dye, under pressure, into the discs of the lumbar spine. The procedure is performed using fluoroscopy, a special x-ray machine that allows x-ray images to be viewed instantly on a television monitor. A discogram would not be recommended for an adolescent or child.
If a patient has significant leg pain, weakness, and/or numbness, electromyography and nerve conduction velocity (EMG/NCV) tests may be recommended. EMG/NCV tests are useful to determine which nerve is affected, and how severely it is damaged or irritated. The test will often clarify where a nerve is actually being compressed – whether it is in the back, buttock, or leg.
The diagnosis of spondylolysis and/or spondylolisthesis may be suspected, particularly if the above-mentioned physical findings are present. An x-ray or CT scan is required to confirm the diagnosis, as well as to grade the severity of the condition.
The treatment of children with spondylolysis and/or spondylolisthesis depends on the severity of the pain, nerve compression, and slippage. A patient diagnosed with an acute (recent) spondylolysis, especially one with a positive “hot” bone scan, should be treated with a brace or cast so as to maximize the chance for bone healing of the fracture. Nearly all patients are recommended for conservative treatment initially unless there is a severe neurologic deficit such as leg weakness and numbness. Physical therapy and oral medications (non-steroidal anti-inflammatory medications, and rarely pain medications and muscle relaxant medications) are prescribed. Epidural steroid injections and/or nerve root blocks are usually not necessary, but may also be ordered for severe pain or moderate pain that is no longer responding to other conservative measures. Patients who fail these conservative measures, especially those children with a Grade III spondylolisthesis or higher, are usually candidates for surgical intervention.
The recommended surgery for children with spondylolysis and/or spondylolisthesis who have failed nonoperative measures is spinal fusion. The goal of surgery is to stabilize the levels of the spine that are “slipping” by placing bone graft and fusing (mending) the spine bones together. Small metal rods/screws (instrumentation) may also be used, and are recommended for older children and adolescents with significant slippage (Grade III or higher). The instrumentation fixes and holds the bones in place immediately, while the bone graft fuses (mends) the unstable spine bones together. After the fusion surgery is performed, it takes approximately 4-8 months for the fusion to “take” and the bones to solidly mend together. Prior to using metal instrumentation, patients were often required to be placed in body cast for 8 months to help the fusion mend. Nowadays, most patients are recommended to wear only a small plastic brace or soft corset, if anything, for 2-3 months after surgery to help the fusion solidify. The success rate for patients undergoing surgery is very high, and there are new minimally invasive surgery techniques that have been developed to allow patients to have an even faster recovery.
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