Confused about spondylolisthesis vs. spondylolysis? These two medical terms are so close in spelling (not to mention their equally challenging pronunciations) that it can be difficult to recall which term refers to what, exactly.
As you’ve probably surmised, they are very closely related, and are even interconnected. The best way to understand both terms is to start with an explanation of spondylolysis.
Spondylolisthesis Vs. Spondylolysis
What is spondylolysis?
Spondylolysis is a combination of the prefix spondylo, meaning “vertebra or the spinal column” and lysis, meaning “decomposition, separation, or breaking down.” The breakdown starts at a very young age, usually somewhere between the ages of 4 and 7, as the result of common childhood activities—running, jumping, stretching, twisting, and bending. If at any point the spine becomes hyperextended (by bending backwards, for example), it’s possible that it could set the stage for spondylolysis.
Let’s take a deeper look at this process: Your spine is made up of vertebrae cushioned by discs and held together by facet joints. Each spinal segment has two facet joints—the upper one is called superior and the lower one inferior—and a bone in between connects them. That connecting bone is called the pars interarticularis.
When the spine is hyperextended, the superior joint “pecks” into the connecting bone; if it happens often enough the persistent pecking fatigues and eventually breaks the bone. Because the bone has a very poor blood supply, it can be difficult or even impossible for the break to heal completely. The resulting defect in the bone is called spondylolysis. When the condition first develops, there is no pain—nor any awareness of the defect at all.
The Progression Of Spondylolysis
Though it’s difficult for the bone to heal, it will try to repair itself. It does so by filling in the affected area with very dense scar tissue containing free nerve endings. When those nerve endings are stimulated, the result is back pain.
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For most people affected with spondylolysis, the pain first presents in their teenage years, most typically for those who are active in high school sports (think gymnasts and football players in particular). As time goes by the condition changes, causing another spike of pain around the ages of 30-40.
Let’s take a closer look at what’s happening in the spine during this progression: The spine has a front anterior column that consists of the vertebral bodies and the discs, which carry 80% of the body load. In the back are the lamina (bony structures that protect the spinal cord) and the facets (where the defect is located), which carry 20% of the load.
Because of the defect, the 20% load normally carried by the facet joints shifts forward to the anterior column, degenerating the discs due to the extra load. Normally, the disc holds the bones above and below it and provides stability, helping the bones to move together as a unit; but if you wear the disc out enough, it loses its stabilizing effect and the bones above and below the disc start slipping back and forth, no longer moving as one. That forward slippage is called spondylolisthesis. The slippage itself causes pain; also, the disc itself can herniate or rupture, or trap or pinch a nerve.
There is a second, more common, type of spondylolisthesis called degenerative spondolysthesis. Degenerative spondylolisthesis is not caused by a defect but by slippage of the spine due to natural wear and tear of the disc. In other words, there is no spondylolysis—no defect—that causes it. Instead, a disc simply wears out, loses its ability to stabilize the spine, and the spine slips forward. Most people with degenerative spondolysthesis feel a noticeable pain around the age of 50+.
How is spondylolisthesis treated?
If spondylolisthesis is caught during the teenage years, it could potentially be treated like a regular fracture (as long as there’s active bone growth at the fracture site).
For later-in-life treatments, physical therapy (such as trunk-strengthening exercises) and anti-inflammatories can be helpful. Avoiding certain activities that aggravate the condition (like certain sports or weight-lifting that may hyperextend your back) could also help to manage the pain.
Degenerative spondylolisthesis is less responsive to physical therapy because it is usually accompanied by some degree of spinal stenosis. Epidural injections are sometimes used to relieve the pain.
For both conditions, surgery could be necessary to stabilize the spine; in many cases, that means fusion.
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