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Degenerative Spondylolisthesis
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Spondylolisthesis
is defined as the movement of adjacent vertebra relative
to each other.
Although spondylolisthesis can be caused
by many pathologic entities, degenerative spondylolisthesis
is by far the most common. With aging, discs lose water
content and ultimately height. As the vertebra on either
side of the disc come closer to each other through
the loss of disc height, the upper vertebra slides
forward on the subadjacent vertebra producing spondylolisthesis.
High stresses and motion produce degeneration of the
disc and for this reason the most susceptible levels
of the lumbar spine, L4-L5, followed by L3-L4 and L5-S1
are the vertebral segments most commonly involved. |
Spondylolisthesis
is also associated with deterioration of the facet joints
connecting the two vertebra. As the facet joints become
arthritic due to this deterioration, they enlarge in
an attempt to confer stability. As the two rings of the
vertebral segments which make up the spinal canal, slide
past each other, the canal narrows in size (fig 1). The
combination of canal narrowing and enlargement of the
facet joints, produces the characteristic nerve compression
problems found in degenerative spondylolisthesis. The
nerves are compressed in two major areas at the site
of a degenerative spondylolisthesis It is believed that
a reduction in nerve blood flow accounts for the symptoms
produced from spinal canal narrowing (Spinal
stenosis).
Typically the legs ache or are
painful with activity. This is called neurogenic claudication.
Enlargement of the facet joints increases spinal canal
narrowing by encroachment into the lateral recesses (fig
2).The enlarged facet joints separate as the vertebra
moves forward producing spinal instability. Spinal instability
in degenerative spondylolisthesis has important implications
in the ultimate treatment of this disease Conservative
therapy is always the first treatment for any degenerative
spinal disorder. There is a new published in the New
England Journal of Medicine finds some advantage to choosing
surgery over non-invasive treatment for degenerative
spondylolisthesis. View
the abstract of the study.
Rarely does degenerative spondylolisthesis cause serious
weakness or numbness in the legs requiring emergency surgery.
Epidural steroid injections may help
alleviate the the inflammation of the nerve roots producing
symptomatic relief for periods of weeks or months. Physical
therapy may improve the back pain associated with the slipping
of the vertebra, but rarely improves the nerve compression
due to spinal stenosis. Those patients whose symptoms are
refractory to conservative treatments are candidates for
surgery.
The goals of surgery are to alleviate nerve compression
while maintaining spinal stability. If the spinal segments
are rigid despite their slipped position, then microscopic
decompression of the lateral recesses and nerve holes
(neuroforamen) can produce significant relief of nerve
pressure. This is in contradistinction to the laminectomy
(see Decompressive
Laminectomy) operation where stabilizing bone is
removed causing the slipped segment to be at risk of
further movement. In general most patients are not candidates
for decompression alone because enough bone needs to
be removed that the spinal segment is rendered more unstable.
Because most patients present with both back and leg
complaints, nerve decompression and fusion with or without
spinal instrumentation is usually required to adequately
treat degenerative spondylolisthesis.
During the operation, a microscope is
employed to adequately remove all encroaching bone from
around the affected nerves. Because the fusion operation
will reestablish stability after decompression, there
is no limitation to how much bone can be removed and
therefore a more complete decompression can be accomplished.
A posterior spinal fusion is then performed by transplanting
bone from the iliac crest to the bones of the back of
the spine.
The ultimate goal of this procedure is that as the fusion
heals, very much like a bone heals after it is fractured,
that the two vertebrae are connected by this healing
fusion mass and become stabilized together. We use spinal
instrumentation in degenerative spondylolisthesis for
a few reasons. Adequate scientific evidence exists to
indicate that fusions heal at a higher rate with the
addition of spinal instrumentation. To view an animation
of the surgery, click on the projector below.
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Anecdotally,
our patients seem to enjoy a smoother, less painful postoperative
course by the addition of an "internal brace." The instrumentation
is screws connected by rods which hold the vertebra together
while the fusion is healing. Postoperative care can be
found in an associated description. Surgery for degenerative
spondylolisthesis is one of the most gratifying spinal
operations from the surgeons standpoint. Done correctly
patients usually achieve excellent relief of both spinal
stenosis symptoms and back pain. Function is improved allowing
the individual a better quality of life. |
Related
links:
Posterior Spinal
Fusion
Anterior Spinal
Fusion
Spondylolisthesis surgical cases
performed by Dr. Pashman
Isthmic Spondylolisthesis
Back FAQ's
ASF/PSF
Improves Lumbar Sagittal Alignment in Multi-level Fusions
for Isthmic Spondylisthesis
Spinal Balance
Abnormal Anatomy
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