Anatomy of the Spine

The spinal column is made up of small bones (vertebrae) stacked on top of one another, creating the natural curves of the back. Between the vertebrae are flat, round, rubbery pads (intervertebral disks) that act as shock absorbers and allow the back to flex or bend. Muscles and ligaments connecting the vertebrae allow motion while providing support and stability for the spine and upper body. Each vertebra has an opening (foramen) in the center and these line up to form the spinal canal. Protected by the vertebrae, the spinal cord and other nerve roots travel through the spinal canal. Nerves branch out from the spinal column through vertebral openings, carrying messages between the brain and muscles. Facet joints align at the back of the spinal column, linking the vertebrae together and allowing for rotation and movement. Like all joints, cartilage covers the surface where facet joints meet.

The spine contains three segments: cervical, thoracic and lumbar.

  • Cervical—The cervical spine includes the neck and consists of seven small vertebrae, beginning at the base of the skull and ending at the upper chest.
  • Thoracic—The thoracic spine consists of 12 vertebrae and begins at the upper chest, extending to the middle back and connecting to the rib cage.
  • Lumbar—The lumbar spine consists of five vertebrae located in the lower back; lumbar vertebrae are larger because they carry more of the body’s weight. The pars interarticularis is a part of the lumbar spine that joins the upper and lower joints; it is found in the posterior portion of the vertebra.

What Are Spondylolysis and Spondylolisthesis?

  • Spondylolysis—Often the result of excessive or repeated strain to this area of the spinal column, this occurs when there is a stress fracture of the pars portion of the vertebra, usually affecting the fifth lumbar vertebra (L5), or much less commonly, the fourth lumbar vertebra (L4). Spondylolysis is a common cause of low back pain in adolescent athletes, particularly those participating in sports or activities that place stress on the spine through repetitive spinal motion or hyperextention (overstretching). These may include: football, soccer, tennis, wrestling, weight lifting, gynmastics, volleyball, diving, rowing, figure skating or dancing.
  • Spondylolisthesis—If the stress fracture (spondylolysis) weakens the bone to such an extent that it can no longer maintain its proper position, the vertebra can start to shift out of place—this condition is called spondylolisthesis. If too much slippage occurs, the bones may begin to press on nerves. Surgery may be necessary to correct the condition. Spondylolisthesis is rarely due to trauma, however it is typically discovered when an athlete’s trauma or prolonged back pain prompts radiographic studies. In many cases of spondylolytic spondylolisthesis, the original fracture that occurred during adolescence remains unnoticed into adulthood. It isn’t until normal, age-related disk degeneration further stresses the pars fracture that the vertebra slip forward. This type of spondylolisthesis is most common in middle-aged men.

Causes

  • Genetics—Hereditary may be a contributing factor in spondylolysis, as individuals born with thin vertebral bone are more vulnerable to this condition. Significant periods of rapid growth may also encourage slippage.
  • Overuse—Certain sports place a great deal of stress on bones in the lower (lumbar) back due to repetitive spinal motion or constant hyperextention (overstretching) of the spine, resulting in a stress fracture on one or both sides of the vertebra. These activities may include: football, soccer, tennis, wrestling, weight lifting, gynmastics, volleyball, diving, rowing, figure skating or dancing.

Symptoms

Many people with spondylolysis and spondylolisthesis do not experience any obvious symptoms or pain. Often, a patient visits the doctor for activity-related, lower back pain, only to be surprised by the diagnosis. Patients may experience what feels like a muscle strain, with pain that spreads across lower back, and is sometimes accompanied by leg pain. Spondylolisthesis can also cause spasms that stiffen the back and tighten hamstring muscles, resulting in changes to posture and gain. Compression of the nerves and narrowing of the spinal canal may also occur, if the slippage is significant.

Diagnosing Spondylolysis and Spondylolisthesis

X-rays of the lower back (lumbar spine) will be required to show the position of the vertebrae. By measuring standing lateral spine X-rays, your physican can verify widening of the fracture gap at the pars, and the amount of forward slippage of the vertebra. If the vertebra is pressing on nerves, additional imaging studies, such as computed tomography (CT) or magnetic resonance imaging (MRI) may be needed to further assess your condition before treatment begins.

Nonsurgical Treatment

The initial treatment for spondylolysis is always nonsurgical. The patient will be be asked to refrain from physical activities until symptoms disappear on their own, which is common. Ibuprofin or other anti-inflammatory medications may be recommended to help alleviate back pain. A spine conditioning program, low back exercises, and exercises to stretch and strengthen back and abdominal muscles may also be recommended to help prevent incidences of pain in the future. Occasionally, a back brace and physical therapy may be prescribed. In most cases, activities can be gradually resumed, with few complications or reoccurances. Periodic X-rays will allow the physician to see if the vertebra is changing position.

Surgery

Surgery may be required if the slippage progressively worsens, or if back pain does not respond to nonsurgical treatment and begins to interfere with daily activities. In such cases, spinal fusion may be performed between the lumbar vertebra and the sacrum. An internal brace of screws and rods may be used, if needed, to hold vertebrae together as the fusion heals.

Complications

As with any surgery, there are some risks, and these vary from person to person. Complications are typically minor, treatable and unlikely to affect your final outcome. For most people, surgery can provide relief of symptoms and return to function with relatively low risk of complications. Overall, elderly patients have higher rates of complications from surgery, as do patients who are overweight, diabetics, smokers, or suffering from multiple medical problems. Among the general, potential risks associated with surgery are infection, bleeding and blood clots, and reactions to anesthesia. Be sure to discuss the potential risks and benefits with your surgeon prior to surgery.

Outcomes

For most patients with either spondylolysis or spondylolisthesis, conservative, nonsurgical measures provide excellent clinical outcomes and allow patients to resume all normal activities. Surgical intervention is rarely required.