Spondylolysis is a condition in which the there is a defect in a portion of the spine called the pars interarticularis (a small segment of bone joining the facet joints in the back of the spine). The pars interarticularis defect can be on one side of the spine only (unilateral) or both sides (bilateral). The most common level it is found is at L5-S1. It is typically caused by stress fracture of the bone, and is especially common in adolescents who over train in activities. Spondylolysis also runs in families and is more prevalent in some populations, suggesting a hereditary component such as a tendency toward thin vertebral bone.
Although this condition can be caused by repetitive trauma done to the lumbar spine or strenuous sports such as football or gymnastics, anatomy also plays a major role. Some topological changes in the shape of the vertebral column can reduce surface area and torsional range of motion during twists and bends, therefore increasing the stresses on the section.
When there is a deficit or fracture in the intervertebral joints, a range of vertebra slip can be expected anteriorly, as depicted in figure 1. The primary deficit causing the Spondylolisthesis is the formerly mentioned articulated deficit, Spondylolysis.
The severity of the slippage is usually measured after taking a side-view X-ray, and then graded on a scale of 1 to 4. The slippage is measured from the amount the upper vertebral body slips forward on the lower vertebral body.
- Grade 1: 25% or less of vertebral body has slipped forward
- Grade 2: 26% – 50%
- Grade 3: 51% – 75%
- Grade 4: 76% – 100%
Spondylolysis develops most commonly in adolescents, most typically in 10 to 15 year olds. The majority of adolescents with spondylolysis do not have symptoms, or their symptoms are mild and are often overlooked.
People with spondylolysis may feel pain and stiffness in the center of the low back. Bending fully backward increases pain. Symptoms typically get worse with activity and go away with rest.
Patients with Spondylolisthesis may eventually experience pain that radiates down one or both legs. This pain may come from the pressure and irritation on the nerves that exit the spinal canal near the fracture. When nerve pressure in the low back causes leg pain, doctors refer it as neurogenic pain.
The cause of this nerve pressure is a result of the body’s attempt to heal the stress fracture. Over time, the healing process may cause a bump of extra cartilage to grow at the site where the bones are trying to heal the overuse injury. The bump may squeeze the nerve. This can produce pain and weakness in the leg. Reflexes become slowed.
Doctors often begin by prescribing nonsurgical treatment for spondylolysis. This is because the symptoms from the fractures often resolve with rest or bracing. In some cases, doctors simply monitor their patients’ condition to see if symptoms improve. An X-ray may be taken every few months to check how well the area is healing.
If the doctor feels that the problem is due to a recent fracture, you may be placed in a rigid back brace or cast for three to four months. Keeping the spine from moving can help ease pain and inflammation.
When symptoms are not relieved with nonsurgical treatments, however, patients may require surgery. The main types of surgery for spondylolysis include:
- Posterior lumbar fusion
Laminectomy: Nerve compression can cause considerable pain and symptoms. If too much cartilage builds up where the fractured bones are trying to heal, the nerve that passes near the injured bone may get squeezed, as described earlier in the spinal canal stenosis. To fix this, a section of the bony ring is removed to take pressure off the nerve. The procedure to remove the lamina from the bony ring and release pressure on the nerve is called laminectomy.
Posterior Lumbar Fusion: A spinal fusion may be required after a surgeon performs a laminectomy procedure. Fusion is recommended when a spinal segment (a set of vertebrae) has become too loose or unstable.
A spinal fusion allows two or more bones to grow together, or fuse, into one solid bone. This keeps the bones and joints from moving. In this procedure, the surgeon lays small grafts of bone over the problem area on the back of the spine. Some surgeons also apply metal plates and screws to prevent the two vertebrae from moving. However, this practice is controversial because fusion occurs in about 90 percent of children with spondylolysis when the procedure is done without plates and screws.