Spondylolisthesis can be caused by degeneration, trauma or congenital defects. It most commonly occurs in the lowest lumbar vertebra on the bony ring formed by the pedicle and lamina bones, which protects the spinal cord and spinal nerves. The bone is weakest in an area called the “pars interarticularis,” which joins the upper and lower joints. This pars defect or fracture is called spondylolysis and is believed to be a stress fracture that results from repeated strain on a bone. At first, the body can heal the damage produced by strain on the bone. However, if repeated strains occur faster than the body can respond, the bone will eventually fracture. If the pars is fractured, the condition is called spondylolysis.
Spondylolisthesis occurs if a vertebra shifts as a result of a widening fracture when the muscles and ligaments holding a vertebra in place become overworked; the vertebral body can then slide forward onto the vertebra below. The forward slip makes the spinal canal smaller, leaving less room for the nerve roots and often causing a pinched nerve.
Teenagers sometimes develop a unique type of spondylolisthesis in which one vertebra slips forward and slides completely off the vertebra below. Spondylolisthesis can also occur in the cervical spine and may result from a neck injury or rheumatoid arthritis. Cervical spondylolisthesis usually causes neck pain and stiffness.
Your physician will take a history, perform a physical exam, and will likely request an X-ray. X-rays are often all that are needed to diagnose a pars defect or forward slip of a vertebra. Sometimes however, bone scans and CT scans are preferred.
Treatment for spondylolisthesis is similar to treatment for other causes of mechanical and compressive back pain. Doctors may prescribe rest during the acute phase, including avoidance of sports, to help relieve symptoms. Special braces, casts, or corsets may be used to help heal a stress fracture and to ease pain. Your doctor may also encourage you to work with a physical therapist and/or prescribe pain medication. Specific exercises are important for rehabilitation and return to sport.
If conservative treatments fail to manage your pain, your doctor may recommend surgery. Surgical treatment should relieve both mechanical and compressive pain as well as any pressure on spinal nerves. The surgical procedure for spondylolisthesis is known as decompressive laminectomy of the lumbar spine, and will free up or "decompress" the affected nerves. The surgeon will remove a section of bone from the back of the spine (lamina) and/or a portion of the facet joints. Because the lamina and facet joints provide stability to the spine, removing them can cause the spine to become loose and unstable. When this occurs, doctors will include spinal fusion as part of the procedure.
Spondylolysis and Spondylolisthesis are unstable conditions. Fusion is almost always a part of the surgical plan. Sometimes decompression is also necessary. In adolescents and children with spondylolysis only and no spondylolisthesis, direct repair of the pars defect without fusion may be appropriate.