Spondylolisthesis occurs when one vertebra slips forward over the vertebra below it. The term is pronounced spondy-low-lis-thesis and is derived from the Greek language: spondylo means vertebra and listhesis means to slip. There are several types or causes of spondylolisthesis; a few are listed below.
- Congenital spondylolisthesis means the disorder is present at birth.
- Isthmic spondylolisthesis occurs when a defect, such as a fracture occurs in a bony supporting vertebral structure at the back of the spine.
- Degenerative spondylolisthesis is more common and is often associated with degenerative disc disease, wherein the discs (eg, due to the effects of growing older) lose hydration and resilency.
How spondylolisthesis may develop
Spondylolisthesis usually develops in the spine's low back; your lumbar spine. The lumbar spine is exposed to directional pressures while it carries, absorbs, and distributes most of your body's weight at rest and during activity. In other words, while your lumbar spine is carrying and absorbing body weight, it also moves in different directions (eg, rotate, bend forward). Sometimes, this combination causes excessive stress to the vertebra and/or its supporting structures, and may lead to a vertebral body slipping forward over the vertebrae beneath.
Who may be at risk
If a family member (eg, mother, father) has spondylolisthesis, your risk for developing the disorder may be greater. Some activities make you more susceptible to spondylolisthesis. Gymnasts, linemen in football, and weight lifters all put significant pressure and weight on their low backs. Think about gymnasts and the positions they put their body in: They practically bend in half backwards—that's an extreme arched back. They also twist through the air quickly when doing flips and then land, absorbing the impact through their legs and low back. Those movements put substantial stress on the spine, and spondylolisthesis can develop as a result of repeated excessive strains and stress.
X-ray view of spondylolisthesis
The x-ray below shows you a good example of a lumbar spondylolisthesis. Look at the area the arrow is pointing to: You can see that the vertebra above the arrow isn't in line with the vertebra below it. It's slipped forward; it's spondylolisthesis.
Arrow points to a lumbar spondylolisthesis
Doctors "grade" the severity of a spondylolisthesis using five descriptive categories. Although there are several factors your doctor considers when evaluating your spondylolisthesis, the grading scale (below) is based on the far forward a vertebral body has slid forward over the vertera beneath. Often, the doctor uses a lateral (side view) x-ray to examine and grade a spondyloisthesis. Grade I is a smaller slip than Grade IV or V.
- Grade I: Less than 25% slip
- Grade II: 25% to 49% slip.
- Grade III: 50% to 74% slip.
- Grade IV: 75% to 99% slip.
- Grade V: The vertebra that has fallen forward off the vertebra below it. This is the most severe type of spondylolisthesis and is termed spondyloptosis.