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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
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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. |
