Degenerative spondylolisthesis
Osteoarthritis of the facet joints can also lead to
instability of a vertebral segment. Typically, as continued
degeneration weakens the facet joints, the L4 vertebral
body slips forward on the L5 vertebral body (see Figure
1). Since the L4-L5 segment has substantial flexion-extension
type movement, this area is most likely to slip. The
next most likely level is L3-L4, and rarely L5-S1.
As the body tries to capture the unstable segment,
the facet joints get bigger and place pressure on the
nerve root (lumbar spinal stenosis). Therefore, both
the symptoms and conservative treatment are essentially
identical as for patients with lumbar spinal stenosis.
In considering surgery for potential treatment, both
the lumbar spinal stenosis and the instability need
to be addressed. A lumbar laminectomy (open decompression—taking
pressure off the nerve root) is done along with a posterolateral
gutter fusion (eliminating the motion at a painful motion
segment).
There are some surgeons who recommend only doing the
laminectomy/decompression, but literature on the subject
seems to favor doing both the fusion and laminectomy/decompression
at the same time. Ironically, even though this represents
more surgery, results for a fusion and decompression
for a degenerative spondylolisthesis are better than
for a decompression alone for spinal stenosis, with
a 90-95% expected success rate.
Additionally, the results of the combined surgery tend
to last because the fusion provides the following advantages:
- It stops the progression of the stenosis.
- It stops motion in the joint and therefore stops
the arthritic pain.
However, the combined surgery is more extensive and
the healing times are longer. Specifically:
-
There is more soft tissue (e.g. muscle) dissection
that is related to the fusion surgery, which takes
longer to heal.
-
Obtaining the bone graft for the fusion (from the
pelvis) can also cause postoperative pain, although
modern techniques seem to limit this complication.
In experienced hands, pedicle screws may be safely
used to enhance the fusion. They probably do not affect
the final success rate, but do allow for earlier rehabilitation,
and prevent the need for a back brace after surgery.
By: Peter
F. Ullrich, Jr., MD
September 8, 1999
Updated February 28, 2001
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