Spinal Fusion Surgery
Considering spinal fusion surgery as treatment for a spinal condition
like degenerative disc disease? Call the specialists at United Spine &
Joint.
Contact us to determine what option
is best for you, what your insurance will cover and any additional
surgery costs.
What is Lumbar Spine Fusion?
A
lumbar spine fusion is a type of back surgery designed to treat
low
back pain from degenerative disc disease. It is called a “spine fusion”
because the surgery involves placing small morsels of bone either in the
front of the spine (in the disc space) and/or along the back of the spine
(in the posterolateral gutter) so that the bone grows together and fuses
that section of the spine.
The fusion is designed to eliminate motion in that fused segment of the
spine, thereby decreasing or eliminating the back pain created by the
motion.
The spine is not actually fused at the time of the surgery. Instead, the
surgery creates the conditions for the spine to be able to fuse and
the
fusion is a process that will set up over a 3 to 6 month (and up to 18
month) period of time following the spinal fusion surgery (see figure 1).
Lumbar spinal fusion surgery for low back pain caused by
degenerative
disc disease is usually considered an
option for patients who:
- Have not found sufficient pain relief from extensive—usually at
least six months—of non-surgical treatment (such as physical therapy,
medications, and other treatments)
- Have
ongoing low back pain that limits their ability to function in
their daily activities at work and/or at home
- Have received a diagnosis that a specific disc space is the pain
generator and other possible causes of the patient’s low back pain have
been considered and ruled out
It is important to stress that the decision to undergo a fusion procedure
for low back pain is entirely the patient’s decision and he or she needs to
carefully weigh the risks and possible complications along with the
potential benefits of surgery, as well as consider the full range of
alternatives to a spine fusion surgery.
It is often a good idea for patients to get a second (or third) opinion from
other surgeons and/or other types of spine specialists prior to deciding
whether or not to have spinal fusion.The decision to have a spine fusion
procedure to treat low back pain from degenerative disc disease is a very
personal one. Degenerative disc disease is for the most part a
non-crippling, non-progressive type of back condition, although in a
minority of cases it can cause severe back pain and can significantly impact
on an individual’s ability to function.
History of Spinal Fusion Surgery
Fusion surgery for the treatment of
lower back pain has been done since
the early 1900’s. At that time, spine fusion procedures were done to limit
the deformity created by tuberculosis infections, and it was found that not
only did the fusion procedure limit the deformity, it also reduced the
patient’s low back pain as well.
Since then, spine fusion procedures have had variable popularity for the
treatment of pain from
lumbar degenerative disc disease and remain somewhat
controversial in the medical community.
Surgeons and researchers span the
spectrum in terms of their beliefs as to how useful spine fusion surgery is
and when and how it should be performed.
- Some spine surgeons do not believe fusion surgery is at all useful
and is never indicated for the treatment of low back pain from lumbar
degenerative disc disease.
- Some spine surgeons are very willing to offer patients a fusion
procedure, and some are even willing to do multiple level fusion
surgery.
As with most things in medicine, the truth lies somewhere in between the
two far ends of the spectrum of beliefs about spine fusion surgery as a
treatment for low back pain
from degenerative disc disease. In general, when
done by a skilled surgeon for a patient with the right indications, spinal
fusion surgery is usually an effective treatment that brings significant
relief from severe, ongoing low back pain caused by degenerative disc
disease.
Each patient has to weigh the risks of a major surgical procedure and a long
healing process with the potential benefits. The spine fusion surgery works
best for treating one level of the spine, although two levels can be fused
if the patient has severe low back pain. As the number of levels fused
increases, the risks of the procedure increase (e.g. a nonunion) and the
potential benefits decrease. Only rarely and in extreme cases would most
spine surgeons recommend or even offer a three or four-level spine fusion
surgery.
Who is a good candidate for Spinal Fusion Surgery?
The biggest risk for spine fusion procedure is continued pain, meaning
that the surgery did not substantially reduce or eliminate the patient’s
pain. The number one reason this occurs is that the fused disc was
improperly identified as the cause of the patient’s pain, so fusing the disc
was unnecessary and irrelevant. This is why getting an accurate diagnosis is
critical.
One of the most difficult and crucial parts of any type of low back
surgery is selecting the patients who will do well with a certain procedure.
It is especially critical to select the right patients for a lumbar spine
fusion surgery for two reasons:
- Lumbar spine fusion is an extensive surgery and the healing process
takes a long time (about 3 to 6 months, and up to 18 months)
- The spine fusion forever changes the biomechanics of the back and is
thought to increase the stress placed on the other (non-fused) joints in
the lower spine and possibly lead to degeneration of the adjacent levels
of the spine.
Lumbar spine fusion surgery is generally not recommended until a patient
has tried 6 to 12 months of adequate non-surgical care. Spinal fusion is
best for treating
low back pain caused by severe degenerative disc changes
and is best for treating one, or maybe two, levels of the lower spine
(typically the L4-L5 level and/or L5-S1 level).
Prior to recommending or offering spine surgery, a surgeon must also
consider other causes of low back pain that can closely mimic the symptoms
of degenerative disc disease. These conditions include:
If a patient’s
low back pain and other symptoms do not improve with
extensive conservative (nonsurgical) treatment and other causes of low back
pain have been ruled out, then he or she may be considered for a spine
fusion surgery. Importantly, while failing conservative treatment is a
necessary prerequisite for spine fusion surgery, it is not sufficient. Prior
to recommending spine fusion surgery, a
spine surgeon has to be confident
that he or she is fusing the segment of the spine that is generating the
patient’s pain (the “pain generator”). Obviously, fusing a structure that
does not cause pain will not reduce the patient’s low back pain or lead to a
successful outcome.
MRI scans have greatly increased the spine surgeon’s
ability to diagnose degenerative disc disease. Unfortunately, a lot of the
changes that are seen on MRI scans are more related to normal aging than to
a pathologic and painful disc. Differentiating a painful disc from an aging
disc is often difficult but there are some clues that help. In general, a
painful disc will be severely degenerated whereas the rest of the discs will
be well preserved. Other characteristics of a painful disc on an MRI scan
include:
- Disc space collapse, which means that the disc has
gotten shorter/flatter
- Endplate erosion, which is erosion of the top and bottom outer
material of the disc
- Edematous changes in the vertebral body (Modic changes), which is
when the MRI shows irritation of the bone marrow, may be an indicator of
a painful disc. There is a characteristic bright signal on the MRI scan
when this occurs.
If a spine surgeon is uncertain as to whether or not a disc is painful, a
CT-discogram may be ordered. A discogram is a direct pain
provocation test that is designed to try to elicit the patient’s pain by
injecting a dye into the disc space. If the test creates the patient’s
normal pain, it can be assumed that the test is positive and the disc is
generating the patient’s pain. Some major drawbacks of the procedure are:
- It involves an injection into the spine, which has several risks
(albeit rare)
- It is usually painful
- It is a subjective test, and both false positives and false
negatives can occur
- Accuracy of the test is largely dependent on the skill of the
discographer
Discograms are used by some
surgeons before every spine fusion, and it is
certainly warranted to gather as much information as possible before
undergoing a fusion procedure. However, discograms are probably not
necessary on a routine basis, and the test itself is somewhat controversial.
The test should only be used if the results are going to change the
surgeon’s recommendations (e.g. if negative, spine surgery will not be
recommended). If the results are ignored and the surgical choice is made off
of the MRI findings, then a discogram does not serve any useful purpose.
Increasing Success of Spine Fusion Surgery
Once a correct diagnosis has been made and the patient has decided to
proceed with spinal fusion surgery, then obtaining a solid fusion is the
next focus. Pseudoarthrosis, which means lack of a solid
fusion, is becoming a less common outcome of spinal fusion surgery thanks to
modern instruments and surgical techniques. However, there are a number of
fusion risks that can adversely create this outcome, including the patient’s
own health and personal habits (host factors) and the technique of the spine
surgeon.
Factors that Affect Spinal Fusion
There are a number of factors that negatively impact on obtaining a solid
fusion following spinal fusion surgery, including:
Of all these factors, the one that most negatively impacts the fusion
rate and is under the control of the patient is smoking. Nicotine has been
shown to be a bone toxin and it inhibits the ability of the bone growing
cells in the body (osteoblasts) to grow bone. A fusion is basically a race
between the bone growing cells and the bone eating cells (osteoclasts).
Continuing to smoke after a spine fusion surgery, especially immediately
after surgery, favors the bone eating cells and significantly undermines the
body’s ability to grow the bone need to create a fusion.
Since having a spinal fusion surgery for
low back pain is almost always
the patient’s decision, it only makes sense for patients to make a concerted
effort to allow the body its best chance possible of allowing the bone to
heal by not smoking. While
quitting smoking is difficult, it is definitely
worth it when considering a lumbar fusion surgery.
In addition to not smoking, most
surgeons will restrict a patient’s activity
level for several months following the surgery. Typically, mild activity
such as walking is encouraged as it promotes healthy circulation and aids in
the healing process. However, activities such as repetitive bending,
lifting, and twisting, are usually not permitted. Once the bone fuses, the
patient is encouraged to gradually resume normal activities as bone is a
living tissue and will become stronger when appropriate stress is applied to
it over a period of time.
Another factor that may contribute to obtaining a solid spine fusion is
the type of bone that is used. Typically, bone graft is taken from the
patient’s hip. Several types of bone graft substitutes and supportive
materials are currently either in use or in various stages of development,
and researchers are hopeful that new materials will help improve the success
rate of obtaining a solid fusion, especially for patients who are at high
risk for non-fusion.
Spinal Fusion Approaches
Technically, there is a wide variety of surgical procedures that can be done
to fuse the spine. The spine fusion surgery can be done with the following
approaches:
With any type of spine surgery, the specific technique used is largely
dependent on the spine surgeon’s experience and his or her comfort level
with the approach.
There has been a recent trend in spine surgery toward trying to do more
minimally invasive types of procedures. Anterior fusions—approached from the
front—are done through a laproscope or a mini-open incision and carry less
morbidity (unwanted aftereffects) than spine fusion surgery done through a
posterior incision. However, there are a number of considerations with
anterior spine fusion, including:
- Some types of pathology do not lend themselves well to an anterior
fusion alone
- Not all spine surgeons are comfortable with the approach or do not
believe it is the best approach
- There are some unique risks associated with approaching the spine
fusion surgery from the front
No matter how the spine fusion surgery is done, the goal is to obtain a
solid fusion and stop the motion at the level fused.
Spine Fusion Alternatives
There are a couple of alternatives to spine fusion surgery that may
be considered for patients with
low back pain from lumbar
degenerative disc
disease. Currently, the main fusion alternatives include:
- IDET, or Intradiscal electrothermal coagulation (or
annuloplasty). This procedure involves inserting a needle into the
lumbar disc space, passing a catheter through the needle, and heating up
the annulus (the outer core of the disc space). The exact mechanism by
which the procedure relieves pain has not been clearly established, but
it is theorized that the heat contracts and thickens collagen fibers in
the disc wall, which in turn seals up painful tears and cracks and
reduces pain. The procedure also cauterizes nerve endings which is
thought to make them less sensitive. Not all patients benefit from IDET,
and the treatment is more likely to help people with less severe
degenerative disc disease than people with significant disc
degeneration. IDET is minimally invasive and usually done on an
outpatient basis (no overnight hospital stay) under mild sedation and a
local anesthetic. Although the procedure is minimally invasive it has
largely fallen out of favor in the spine world as it has marginal
clinical efficacy. Most insurance companies no longer cover the
procedure.
- Artificial discs.
Disc replacement surgery
involves
replacing the painful disc in the spine with an
artificial disc. As of
August 2006, two brands of lumbar artificial disc are available for use
in patients in the U.S.: the Charite lumbar artificial disc and the
PRODISC-L lumbar artificial disc. A number of other artificial disc
brands are in the clinical trial testing phase. The goal of artificial
disc replacement surgery is to preserve the normal motion of the spine
(unlike fusion, which eliminates motion at the painful spinal segment).
Artificial disc surgery has two primary theoretical advantages over
spinal fusion; 1) it is thought that preserving spinal motion reduces
the risk that other segments of the lumbar spine will wear down
prematurely; 2) it is believed that artificial disc surgery may achieve
better pain reduction than fusion. However, these potential benefits
come at the expense of greater risk with the surgery. Any motion
preservation device can fail by extrusion or wearing out with time.
Revision surgeries are expensive and extremely dangerous. The
risk/benefit ratio of artificial disc versus fusion is still largely
unknown, and currently many insurance companies are not covering the
procedure.
- Posterior dynamic stabilization. This treatment is
different from fusion in that posterior dynamic stabilization seeks to
preserve motion in the spine while also taking pressure off the diseased
vertebral disc. The theory is that removing pressure from the painful
disc will create a favorable healing environment and
reduce pain. The
devices used in the surgery are designed to unload pressure from the
vertebral disc in the same way a dynamic (moveable) brace unloads
pressure from an
injured knee
or ankle to allow it to heal. Various
forms of posterior dynamic stabilization devices are still in the
investigative or testing phase or early in use, and their efficacy and
potential risks and complications have not yet stood the test of time.
- Disc regeneration. Researchers in cellular and
molecular biology are exploring ways to use gene therapy to stimulate
regeneration of the vertebral disc and/or to slow or prevent
degeneration of the disc. The hope is that this therapy could prevent
the need for surgery. For example, in animal studies, the BMP-12 gene
(bone morphogenetic protein) has dramatically increased the generation
of cells in both the nucleus and the annulus of the vertebral disc.
BMP-12 is a molecule that, among other duties, promotes formation of
embryonic joints. Research is also being performed on gene therapy that
could inhibit the degeneration process. Gene therapy for treatment of
the intervertebral disc is still in the early stages of research.
Patient's Decision: Spinal Fusion
The decision to have a spine fusion procedure done to treat
low back pain
is
a very personal one, and it is entirely the patient’s decision. Degenerative
disc disease is for the most part a non-crippling, non-progressive type of
back condition and does not lead to neurological deficits or result in a
progressive crippling condition.
The natural history is for the low back pain to improve with time
(although it may take many years) as the natural aging process leads the
disc space to have less motion. With continued degeneration, bony growth
around the disc will try to capture the excess motion. Therefore, continuing
non-surgical treatments (such as medication, exercise) to manage the painful
symptoms and living with the discomfort is always an option.
Unlike many other types of surgery, with spinal fusion surgery only the
patient can decide if the pain and inability to complete one’s normal daily
activities is bad enough to warrant spinal fusion (or any other) type of
surgery. And the best way for a patient to make an informed decision about
whether or not to have spinal fusion is
to fully understand the trade-offs between spinal fusion and other
non-surgical and surgical treatment options.
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