Spinal Fusion Options: Roads to Recovery
By Dr. Jeffrey R. Carlson

Spinal fusion has become a very common surgical procedure in
the United States over the past 10 years. There are many
diagnoses that range from fractures of the spine to severe
degenerative disc disease that prevent patients from being able
to stand or walk are best treated with a surgical remedy. This
article is intended to provide a basic review of the many spinal
fusion options that are available. It is best to talk to a
fellowship-trained spine surgeon who will be able to give you a
complete picture of all of the devices available that are
recognized for quality and reliability or to help you rule out
those that are not recommended.

As the number of spinal fusions has increased, the variety of
procedures and hardware alternatives that are available has also
increased. It may be easier to understand why there are so many
types of fusions if you consider how fractures need to be fixed
with fusion. With broken bones, there is usually little question
about the wisdom of providing casts or plates and screws to
stabilize bones that need to be realigned or stabilized.  Spinal
fusion provides the same stability for the spine as is used for
other fractured bones. What is a spinal fusion? Screws and rods
in the spine are used to keep bones from moving as the bone
graft that is placed allows the stabilized bones to form a
connection across a previously mobile disc space. The growth of
bone between 2 previously mobile bones is called fusion.

Standard fusion technique: Initially, fusion of the vertebral
bones was done by laying bone graft between the bones, to
provide a scaffolding across which the native bone cells could
grow. As the patient’s bone cells move across the bone graft,
they are able to incorporate the bone graft into the patient’s
own bone structure, forming a complete connection called a
fusion. Bone graft is of primary importance in allowing the
vertebral bones to fuse across a previously mobile segment.
Studies of patient’s with fusions done with bone graft alone
have shown a relatively good rate of incorporation when patients
are placed in back braces for 3 months or more. Because of the
inconvenience and discomfort of the bracing, pedicle screws and
rods have been added to provide an internal support that
obviates the need for external supports. Internal screws and
rods have increased successful fusion rates, as well as allowed
patients to become mobile very quickly after the spinal fusion.

Interbody fusion cages: As the skill of the surgeon’s has grown
when applying screws and rods to the spine, we have, in turn,
looked for better ways to gain improved results. Now, we are
able to put bone graft around the back of the spine, as well as
into the disc spaces. With these improved grafting methods, we
are able to safely access the lumbar disc from the back of the
spine. Adding bone graft to the disc increases the surface area
for healing and should improve the overall success rate of the
spinal fusion. Interbody grafting can be done from several
different approaches, as access to the disc space can be
achieved from multiple directions.

XLIF: This acronym stands for extreme lateral interbody fusion.
XLIF is a newer device designed to provide a carrier for bone
graft and support to the disc space. It is placed through an
incision on the patient’s flank. By making an incision on the
patient’s side, the abdominal contents can be moved out of the
way for a good view of the spine. Unfortunately, there are some
significant nerves in the front of the spine that are very
sensitive to being moved. This type of access to the spine can
lead to weakness in one leg because of the sensitivity of these
nerves. At this time, there are no long-term studies that
demonstrate success of this procedure.

AxiaLif: This is another fusion device that has received some
attention, due to its being touted as the “least invasive spine
fusion”. This device is placed across the lowest disc space by
access from the front of the sacrum (a large, triangular bone at
the base of the spine, inserted like a wedge between the two hip
bones). By placing instruments through a small incision near the
rectum towards the spine, the disc is accessed through a series
of cannulas (hollow surgical tubes) and drills. This allows the
disc material to be removed from the disc space. After the disc
material is removed, bone grafting can be placed into the hole
that is created. This disc space is then supported by a tapered
screw placed into the bones. So far, this device has had minimal
post-surgical study and is most likely best done in conjunction
with standard screw and rod fusion techniques.

Flexible Rods:  There has been some recent excitement around
rod and screw systems that are so-called “non-fusion” fusion
devices. This confusing name infers that, although the intent of
the screws and rods is for the bones to not move, these devices
are designed to allow some movement. As was discussed earlier in
this article, fusion is the solid connection of bones that had
previously moved.  The idea of these flexible rods is to provide
“enough” stability to allow the bones to fuse together, but not
enough to change the forces in the spine. This is termed a
“soft-fusion”. At this point, there is no concensus as to how
much or how little support is needed to achieve this goal. It is
known that current screw and rod systems provide enough support
to allow a fusion to occur while providing complete immobility
of the vertebrae. Other than this complete connection, the
amount of support less than complete immobility has not been
defined and at this point is still under investigation.

Disc Replacement: Disc replacement was developed as an
alternative to fusion and is suggested for those discs that have
ruptured, but in which the bone structure is still good. If only
the disc has gone bad, removal of the disc leaves a space that
we normally fill with bone graft to promote fusion in the neck
or lower back. With the development of the disc replacement, the
space that is left from disc removal can be filled with a device
that allows motion, rather than fusion. This is a complete
reversal in the approach to disc removal; from complete
immobility to complete mobility. Disc replacement is intended to
maintain the motion in the spine. This reconstruction of the
spine should maintain the forces across the discs in the spine
to prevent the other discs from deteriorating any more rapidly
than their normal degenerative process. Disc replacement in the
lumbar spine has met with some success in well-selected
patients. It has not been a panacea for all patients with low
back pain or degenerative disc disease. Disc replacement in the
cervical spine has had good success, as most neck fusions are
done for bad discs with the bones being in good condition.

Improved training, including advanced specialty training in
fellowship programs, as well as improved implants, has decreased
most surgical procedure times to 2 hours or less. Historically,
older techniques have been known to take 4-6 hours for the
operation alone. By decreasing operative times, surgeons have
seen decreased complications from the anesthesia, as well as
decreased risks of infection and blood loss.  Most surgeries
under 2 hours will not require a blood transfusion.

A well-informed patient, who understands the benefits and the
risks of their surgery, can fully participate in the choices
that need to be made about their surgery. If you have been told
that you need a spine fusion, ask questions and do your
research. It is appropriate to ask your surgeon about their
experience performing spinal fusions, how many of the fusion
procedures they perform, how long the operation will take and
the likelihood of needing a blood transfusion. Selecting a
well-qualified surgeon can help ensure the best outcome for you
and the success of your spinal fusion.

About the Author: Dr. Jeffrey R. Carlson is a doctor at the
Orthopaedic and Spine Center, a leading provider of Suffolk
orthopedics services such as Suffolk spine surgery, Suffolk knee
surgery, and Suffolk pain management. The Orthopaedic and Spine
Center can be found online at: http://www.osc-ortho.com

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