Posterolateral gutter spine fusion surgery
There are multiple different methods for obtaining a spinal fusion, but the gold
standard is a posterolateral gutter fusion surgery. This type of spinal fusion,
which involves placing bone graft in the posterolateral portion of the spine
(a region just outside the spine), has a long history and is considered by many
surgeons to be the "tried and true" method of spinal fusion (see
Figure 1).
Posterolateral gutter spine fusion surgery description
In a posterolateral gutter fusion, the surgical approach
to the spine is from the back through a midline incision
that is approximately three inches to six inches long.
First, bone graft is obtained from the pelvis
(the iliac crest). Most spine surgeons work through
the same incision to obtain the bone graft and to perform
the spinal fusion.
Next, the harvested bone graft is laid out in the
posterolateral portion of the spine. This region lies
on the outside of the spine and is a very vascular
area, which is important because the fusion needs blood
to supply the nutrients for it to grow.
A small extension of the vertebral body in this area
(transverse process) is a bone that serves as a muscle
attachment site. The large back muscles that attach
to the transverse processes are elevated up to create
a bed to lay the bone graft on. The back muscles are
then laid back over the bone graft, creating tension
to hold the bone graft in place.
After spine fusion surgery, the body engages in a
natural process to repair itself, which usually means
growing bone. As the harvested bone graft grows and
adheres to the transverse processes, such as between
L4 and L5 (lumbar segment 4 and lumbar segment 5),
the spinal fusion is achieved and motion at that segment
is stopped. Spine surgery instrumentation (medical
devices, such as pedicle screws or cages) is sometimes
used as an adjunct to obtain a solid fusion.
However, a solid fusion is not always achieved. There
are two types of bone cells, one (osteoblast) that
grows bone and another (osteoclast) that removes bone.
It is a race between these two cell types for the spine
fusion to successfully set up. There are a couple of
key factors that patients can control that are important
in determining whether or not a fusion grows in solidly,
including:
-
Smoking cessation. It is generally advisable
to quit smoking prior to a spinal fusion surgery,
as nicotine is a direct toxin to bone graft and will
prevent the bone from forming.
-
Limited motion. Bone forms better if motion
is limited, so patients are advised to avoid bending,
lifting, and twisting for three months after spinal
fusion surgery.
Most spine fusions will set up within three months,
and will continue to get stronger for one to two years.
Once a solid fusion is achieved it is very unlikely
that it will ever break. Recurrent pain after a successful
spine fusion surgery is generally not from the fused
level, but can be from any of the other joints.
A "transfer" lesion can occur especially
if more than one level is fused. This is the result
of increased stress being transferred to the next level.
Although this has been well documented in multi-level
spine fusions, it is less clear if doing a one level
fusion leads to a higher incidence of joint breakdown
than in the general population (than for people who
have not had a spine fusion surgery).
Posterolateral gutter spine fusion risks and complications
The principal risk of this type of low back surgery
is that a solid fusion will not be obtained (nonunion)
and further surgery to re-fuse the spine may be necessary.
Nonunion rates of between 10% and 40% have been quoted
in the medical literature.
Nonunion rates are higher for patients who have had
prior surgery, patients who smoke or are obese, patients
who have multiple level spine fusion surgery, and for
patients who have been treated with radiation for cancer.
Not all patients who have a nonunion will need to
have another fusion procedure. As long as the joint
is stable, and the patient's symptoms are better, more
back surgery is not necessary.
Other than nonunion, the risks of a spinal fusion
surgery include infection or bleeding. These complications
are fairly uncommon (approximately 1% to 3% occurrence).
In addition, there is a risk of achieving a successful
fusion, but the patient's pain does not subside.
By: Peter
F. Ullrich, Jr., MD
September 8, 1999 (Updated January 20, 2004)
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