Proper patient selection for spine fusion surgery
The most difficult and crucial part 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:
-
Healing from a spine fusion procedure takes a long
time (about 3 to 6 months, and up to 18 months)
-
The spine fusion forever changes the biomechanics
of the back by increasing the stress placed on the
other (non-fused) joints in the lower spine.
Lumbar spine fusion surgery is generally not recommended
until a patient has tried 6 to12 months of adequate
conservative care (such as physical therapy, medications).
For more details on non-surgical treatment options, please
see Degenerative
disc disease - non-surgical treatment options.
If a patient’s low back pain and other
symptoms do not improve with extensive conservative
treatment, 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.
Identifying the pain generator before having
spine fusion
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 (see figure
1)
-
Endplate erosion
-
Edematous changes in the vertebral
body (Modic changes)
-
An associated isthmic spondylolisthesis
-
A tear
into the posterior annulus (high intensity zone)
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. 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:
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.
Prior to recommending or offering spine surgery, a
surgeon must also consider other causes of back pain
that can mimic the symptoms of degenerative disc disease.
These conditions include:
|
|
