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Once the decision is made to proceed with the surgery, the goal is to
create a solid fusion. At each level in the spine, there is a disc space in
the front and paired facet joints in the back. Working together, these
structures define a motion segment and permit multiple degrees of motion.
Two vertebral segments need to be fused together to stop the motion at one
segment, so that an L4-L5 (lumbar segment 4 and lumbar segment 5) spinal
fusion is actually a one-level spinal fusion.
A spine fusion surgery involves using bone graft to cause two vertebral
bodies to grow together into one boney segment. Bone graft can be taken
from the patient’s hip (autograft bone) during the fusion surgery, or
taken from cadaver bone (allograft bone). Synthetic bone graft substitutes
are also in development, and one type - bone morphogenic proteins (which
helps the body create bone) - is currently being used for certain fusion
procedures.
Certain things can negatively impact the chances of obtaining a
successful fusion, including smoking (nicotine), obesity, osteoporosis,
chronic steroid use, diabetes mellitus or other chronic illnesses, prior
back surgery or attempted fusion, multi-level fusion, radiation for cancer
treatment, and malnutrition.
Spine fusion surgery options
·
Posterolateral gutter fusion—the
procedure is done through the back and the harvested bone graft is laid out
in the posterolateral portion (just outside) of the spine
·
Posterior lumbar interbody fusion
(PLIF)—the procedure is done from the back and includes removing
the disc between two vertebrae and inserting bone into the space created
between the two vertebral bodies
·
Anterior lumbar interbody fusion
(ALIF)—the procedure is done from the front and includes removing
the disc between two vertebrae and inserting bone into the space created
between the two vertebral bodies
·
Anterior/posterior spinal fusion—the
procedure is done from the front and the back and is a combination of the
ALIF and posterolateral gutter fusion procedures
·
Transforaminal interbody fusion
(TLIF)—fuses both the front and back portions of the spine
through a single approach through the back of the spine
While anterior fusions (from the front) are less invasive, not all
situations are appropriate for this approach.
A lumbar spinal fusion is most effective for those conditions involving
only one vertebral segment. Most patients will not notice any limitation in
motion after a one-level fusion. Fusing two segments of the spine may be a
reasonable option for treatment of pain if needed. Fusion of more than two
segments is unlikely to provide pain relief because it removes too much of
the normal motion in the back and places too much stress across the
remaining joints. Only in rare cases should a three (or more) level fusion
for pain alone be considered, although it may be necessary in cases of
scoliosis and lumbar deformity.
The principal risk of this type of surgery is that a solid fusion will
not be obtained (nonunion) and further surgery to re-fuse the spine may be
necessary. The patient should also be aware that even if fusion is
successful, that does not assure that the pain will go away. As with any
surgery, there is a chance of complications such as infection, bleeding,
and anesthetic complications. Another potential complication of fusion
surgery in the low back includes any type of nerve damage.
After a spine fusion surgery, it takes approximately three months for
the fusion to successfully set up and achieve its initial maturity. During
these first three months, it is necessary to follow the surgeon’s
postoperative care instructions and avoid activities that may place the
bone graft at risk. For many patients who undergo a one level fusion
further activity restrictions after three months may not be necessary.
Permanent restrictions are only needed in a few cases. Actually, since bone
is a live tissue, after it has set up it will get stronger with stress
(activity).
Fusion surgery success rates are quoted at between 70 and 95%. Surgery
for painful conditions that arise from gross instability tends to be more
reliable. Also, surgery in those individuals that have only one badly
degenerated disc (especially L5-S1) and otherwise have a normal spine tend
to fair well. Success rates drop for multilevel degenerative disc disease,
or in individuals that still have good maintenance of their disc heights.
It should be kept in mind that the vast majority of spine fusions are
elective in nature, and should only be considered in those individuals that
have failed conservative treatment, yet still have significant activity restrictions.
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