Surgery For Lumbar Spinal Stenosis - "Sometimes
less is more"
Spinal Stenosis literally means “narrowing” of
the spinal canal. It is a common condition
that sometimes accompanies the natural degeneration of the spine. In
fact, it is the most
common condition leading to spine surgery in people over the age of
sixty.
The narrowing or stenosis is caused by changes in several elements
of the spine:
the disc, the facet joint, and the ligamentum flavum. Together these
three structures comprise
the “walls” of the spinal canal.
The disc is the shock absorber for the spine. As the
disc undergoes the natural process
of degeneration, it begins to desiccate or dry up. The result is loss
of structural integrity
whereby the disc can no longer support the weight of the spine. As a
consequence, the disc
bulges much the same way as a tire bulges when it is low on air. The
bulging of the front or
anterior wall of the spinal canal results in narrowing of the canal.
The second structure involved in spinal stenosis is the facet
joint. There are actually two
facet joints for each level of the spine, one on each side. The facet
joints allow motion, mostly
during flexion and extension of the spine. The lining of the facet joint
is comprised of the
same type of cartilage as hip or knee joints. As such, this lining is
susceptible to the same
arthritic changes as with other cartilaginous joints. These changes
involve erosion and
narrowing of the joint space. The inflammatory response leads to growth
of bone around the
joint. The end result is narrowing of the sides of the spinal canal
and the small holes or
foramen through which the nerves exit the canal.
The third structure making up the posterior or back wall of
the spinal canal is called the
ligamentum flavum. It is also called the yellow or elastic
ligament. This ligament is a dynamic
structure, meaning that it changes its shape depending on the position
of the spine. When the
spine is flexed as during sitting, the ligament is stretched or narrowed.
This opens the spinal
canal creating more space for the spinal nerves. When the spine is extended
however as when
standing, the ligament is shortened and thickened creating less space
for the spinal canal. This
is why patients with spinal stenosis have symptoms when standing or
walking but have almost
instant relief from sitting down.
The symptoms of spinal stenosis are very consistent. Simply,
standing and walking become
intolerable but sitting or driving a car is no problem. A super market
can only be navigated by
leaning on the shopping cart. A patient with spinal stenosis learns
every bench and chair in the
mall or doesn’t venture there at all. The symptoms usually involve
the legs more than the back
and in fact may be misdiagnosed as a problem with the blood vessels
in the legs. The legs
become painful or cramped after a short period of standing or walking.
They may become weak
and numb or “feel like wood” due to the impingement of the
nerves. Back pain may accompany
the leg symptoms due to the facet arthritis or from muscle fatigue resulting
from bending forward
to keep the spinal canal open. Over time, it becomes more comfortable
to sit than stand and life
becomes more sedentary. Rarely, a wheel chair becomes the only means
of transportation.
Early treatment for spinal stenosis includes physical
therapy to remain active, and anti-
inflammatory medication such as NSAIDs. Injections such as epidural
steroid injections can
be dramatic in relieving the symptoms. Unfortunately the relief is often
short lived. When
non-surgical treatment is no longer successful, it is time to consider
surgical decompression.
Historically, the surgical treatment of choice has been the laminectomy.
This operation involves
removing the structures that comprise the posterior or back of the spine.
This includes the spinous
processes, the bones that stick out from the back of the spine. The
spinous processes are the
bumps that one feels when they run their finger up and down the spine.
Between the spinous
processes runs a ligament that extends from the base of the skull to
the bottom of the spine or the
sacrum. When leaning forward, this ligament is under significant tension.
This allows for a person
to lean forward without fatiguing the back muscles. The ligament acts
in much the same way as the
cable on a crane that runs down the back of the swing arm allowing it
to extend out without falling
over. Unfortunately, by removing the spinous processes, the ligament
is also removed. This can
create instability in the spine resulting in chronic back pain and recurrence
of the leg symptoms.
Studies on the long term results of laminectomy often show deteriorating
outcomes several
years after the surgery. A review of the existing literature in 1991
showed an average success of
only 64%.
Normal Spine Operated
Spine following Laminectomy
In 1992, Dr. Kleeman developed and tested a surgical procedure
for spinal stenosis
called the “port-hole” decompression. Instead of
performing a laminectomy and removing the
spinous processes, the spinal canal was decompressed through openings
or “port-holes” that
left the spinal structures intact.
Area of Decompression Laminectomy
Decompression Port-hole Decompression
The long-term results were presented at The North American Spine Society
meeting in 1997,
receiving the Outstanding Poster award for that year. At 4 years after
surgery 98% of the patients
were still satisfied with the results of the operation. Before the surgery
only 6% of the
patients could stand or walk for more than 15 minutes. At 4 years from
the time of the surgery,
96% of the patients could stand or walk for more than 15 minutes. Since
that time, hundreds of
patients have benefited from this less invasive procedure. The full
research article can be found in
the journal Spine 2000;25:865-870.
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