Spondylolisthesis refers to forward slippage of one vertebra on the one below it. In image on left, L5 is slipped forward on S1. In image on right, L4 is slipped forward on L5. Note the L2, L3 and L4 vertebrae all line up and are stacked on top of each other. L4 and L5 do not line up because L4 has moved forward on L5. This “slip” occurs because of wearing out of the joints in the spine. With severe arthritis, these joints become “incompetent” and the vertebra starts to slip forward. It is a sign of instability at that level. Most common levels for this to occur are L4-5 and L5-S1.
The term “spondylolisthesis” refers to one vertebra slipping forward on the vertebra below it. There are several causes of spondylolisthesis, but by far the most common cause is severe arthritis in the spine. A common phrase used to refer to this condition is a “slipped vertebra”. This should not be confused with “slipped disc”, which refers to a disc herniation or rupture of a disc. Spondylolisthesis is a form of “instability” in the spine, which really means abnormal motion at the involved level.
Spondylolisthesis is most common in the lumbar spine, particularly at L4-5 and L5-S1, the two lowest levels in the spine. Spondylolisthesis is often accompanied by spinal stenosis. For more on spinal stenosis, click here.
Patients may have back pain that is worse with activity. Many patients have pain or numbness in the legs or buttocks because of the presence of spinal stenosis. As mentioned, most patients with spondylolisthesis have some degree of spinal stenosis. The spondylolisthesis makes the stenosis more severe. So many patients with these coexisting conditions have leg discomfort, especially when walking. The symptoms are identical to patients with spinal stenosis. Patients usually have worsening leg pain after walking a certain distance, and feel some relief when they bend forward on a cart or walker (shopping cart sign).
Spondylolisthesis is diagnosed with X-rays of the lumbar spine in the standing position. MRI is helpful in evaluating for spinal stenosis. Note that X-rays show the slipped vertebra but do not show the degree of spinal stenosis.
The initial treatment for spondylolisthesis with spinal stenosis consists of anti-inflammatory medications (ibuprofen, naproxen), physical therapy and epidural steroid injections. Of these, epidural injections are most likely to provide pain relief.
Patients who do not respond to the above treatments and who continue to experience pain that is affecting their quality of life are candidates for surgery. It is very rare for patients to become paralyzed or wheel-chair bound if they do not have surgery. Pain is the most common symptom, and patients may end up having difficulty walking distances because of the leg pain. But frank paralysis is rare and should not be a reason patients seek surgery. The main reason to have surgery is if the pain and discomfort is to such a degree that it is affecting your quality of life and keeping you from doing things you enjoy.
The key principles to remember regarding the surgical treatment of spondylolisthesis and stenosis are the following:
- If patient has spinal stenosis without spondylolisthesis, lumbar decompression alone leads to excellent results. In such cases, fusion is not necessary unless the surgeon has to remove an excessive amount of bone that would render the spine unstable.
- If patient has spinal stenosis AND spondylolisthesis, then lumbar decompression AND fusion leads to excellent results.