What is Spinal Fusion?
The spine is made up of a series of bones
called "vertebrae"; between each vertebra are strong connective tissues which
hold one vertebra to the next, and acts as a cushion between the vertebrae. The
disc allows for movements of the vertebrae and lets people bend and rotate their
neck and back. The type and degree of motion varies between the different levels
of the spine: cervical (neck), thoracic (chest) or lumbar (low back). The
cervical spine is a highly mobile region that permits movement in all
directions. The thoracic spine is much more rigid due to the presence of ribs
and is designed to protect the heart and lungs. The lumbar spine allows mostly
forward and backward bending movements (flexion and extension).
Indications for spinal
fusion and stabilization
- degenerative segmental instability and
Failed-back-Syndrome
- postoperative segmental instability
- Spondylolisthesis (vera or
degenerative)
- after Spondylitis/Spondylodiscitis
- after spinal or spinal cord tumors
Fusion is a surgical technique in which
one or more of the vertebrae of the spine are united together ("fused") so
that motion no longer occurs between them. The concept of fusion is similar
to that of welding in industry. Spinal fusion surgery, however, does not
weld the vertebrae during surgery. Rather, bone grafts are placed around the
spine during surgery. The body then heals the grafts over several months -
similar to healing a fracture - which joins, or "welds," the vertebrae
together.
When Is Fusion Needed?
There are many potential reasons for a surgeon
to consider fusing the vertebrae. These include: treatment of a fractured
(broken) vertebra; correction of deformity (spinal curves or slippages);
elimination of pain from painful motion; treatment of instability; and treatment
of some cervical disc herniations. One of the less controversial reasons to do
spinal fusion is vertebral fracture. Although not all spinal fractures need
surgery, some fractures - particularly those associated with spinal cord or
nerve injury - generally require fusion as part of the surgical treatment.
Certain types of spinal deformity, such as scoliosis, are commonly treated with
spinal fusion. Scoliosis is an "S" shaped curvature of the spine that sometimes
occurs in children and adolescents. Fusion is indicated for very large curves or
for smaller curves that are getting worse. Sometimes a hairline fracture allows
vertebrae to slip forward on top of each other. This condition is called
spondylolisthesis (see North American Spine Society patient education brochure
on Adult Isthmic Spondylolisthesis), and can be treated by fusion surgery.
Another condition that is treated by fusion surgery is actual or potential
instability. Instability refers to abnormal or excessive motion between two or
more vertebrae. It is commonly believed that instability can either be a source
of back or neck pain or cause potential irritation or damage to adjacent nerves.
Although there is some disagreement on the precise definition of instability,
many surgeons agree that definite instability of one or more segments of the
spine is an indication for fusion. Cervical disc herniations that require
surgery usually need not only removal of the herniated disc (discectomy), but
also fusion.
With this procedure, the disc is removed through an incision in the
front of the neck (anteriorly) and a small piece of bone is inserted in place of
the disc. Although disc removal is commonly combined with fusion in the neck,
this is not generally true in the low back (lumbar spine). Spinal fusion is
sometimes considered in the treatment of a painful spinal condition without
clear instability. A major obstacle to the successful treatment of spine pain by
fusion is the difficulty in accurately identifying the source of a patient's
pain. The theory is that pain can originate from painful spinal motion, and
fusing the vertebrae together to eliminate the motion will get rid of the pain.
Unfortunately, current techniques to precisely identify which of the many
structures in the spine could be the source of a patient's back or neck pain are
not perfect. Because it can be so hard to locate the source of pain, treatment
of back or neck pain alone by spinal fusion is somewhat controversial. Fusion
under these conditions is usually viewed as a last resort and should be
considered only after other conservative (nonsurgical) measures have failed.
How Is Fusion Done?
There are many surgical approaches and methods
to fuse the spine, and they all involve placement of a bone graft between the
vertebrae. The spine may be approached and the graft placed either from the back
(posterior approach), from the front (anterior approach) or by a combination of
both. In the neck, the anterior approach is more common; lumbar and thoracic
fusion is usually performed posteriorly. The ultimate goal of fusion is to
obtain a solid union between two or more vertebrae. Fusion may or may not
involve use of supplemental hardware (instrumentation) such as plates, screws
and cages. Instrumentation is sometimes used to correct a deformity, but usually
is just used as an internal splint to hold the vertebrae together to while the
bone grafts heal. Whether or not hardware is used, it is important that bone or
bone substitutes be used to get the vertebrae to fuse together. The bone may be
taken either from another bone in the patient (autograft) or from a bone bank
(allograft). Fusion using bone taken from the patient has a long history of use
and results in predictable healing. Autograft is currently the "gold standard"
source of bone for a fusion. Allograft (bone bank) bone may be used as an
alternative to the patient's own bone. Although healing and fusion is not as
predictable as with the patient's own bone, allograft does not require a
separate incision to take the patient's own bone for grafting, and therefore is
associated with less pain. Smoking, medications you are taking for other
conditions, and your overall health can affect the rate of healing and fusion,
too. Currently, there is promising research being done involving the use of
synthetic bone as a substitute for either autograft or allograft. It is likely
that synthetic bone substitutes will eventually replace the routine use of
autograft or allograft bone. With some of the newer "minimally invasive"
surgical techniques currently available, fusion may sometimes be done through
smaller incisions. The indications for minimally invasive surgery (MIS) are
identical to those for traditional large incision surgery; however, it is
important to realize that a smaller incision does not necessarily mean less risk
involved in the surgery.
How Long Will It Take To Recover?
The immediate discomfort following spinal
fusion is generally greater than with other types of spinal surgeries.
Fortunately, there are excellent methods of postoperative pain control
available, including oral pain medications and intravenous injections. Another
option is a patient-controlled postoperative pain control pump. With this
technique, the patient presses a button that delivers a predetermined amount of
narcotic pain medication through an intravenous line. This device is frequently
used for the first few days following surgery. Recovery following fusion surgery
is generally longer than for other types of spinal surgery. Patients generally
stay in the hospital for three or four days, but a longer stay after more
extensive surgery is not uncommon. A short stay in a rehabilitation unit after
release from the hospital is often recommended for patients who had extensive
surgery, or for elderly or debilitated patients. It also takes longer to return
to a normal active lifestyle after spinal fusion than many other types of
surgery. This is because you must wait until your surgeon sees evidence of bone
healing. The fusion process varies in each patient as the body heals and
incorporates the bone graft to solidly fuse the vertebrae together. The healing
process after fusion surgery is very similar to that after a bone fracture. In
general, the earliest evidence of bone healing is not apparent on X-ray until at
least six weeks following surgery. During this time, the patient's activity is
generally restricted. Substantial bone healing does not usually take place until
three or four months after surgery. At that time activities may be increased,
although continued evidence of bone healing and remodeling may continue for up
to a year after surgery. The length of time required you must be off of work
will depend upon both the type of surgery and the kind of job you have. It can
vary anywhere from approximately 4-6 weeks for a single level fusion in a young,
healthy patient with a sedentary job to as much as 4-6 months for more extensive
surgery in an older patient with a more physically demanding occupation. In
addition to some restrictions in activity, a brace is sometimes used for the
early post-operative period. There are many types of braces that might be used.
Some are very restrictive and are designed to severely limit motion, while
others are intended mainly for comfort and to provide some support. The decision
to use a brace or not, and the optimal type of brace, depends upon your
surgeon's preference and other factors related to the type of surgery. Following
spinal fusion surgery, a postoperative rehabilitation program may be recommended
by your surgeon. The rehabilitation program may include back strengthening
exercises and possibly a cardiovascular (aerobic) conditioning program, and a
comprehensive program custom-designed for the patient's work environment in
order to safely get the patient back to work . The decision to proceed with a
postoperative rehabilitation program depends upon many factors. These include
factors related to the surgery (such as the type and extent of the surgery) as
well as factors related to the patient (age, health and anticipated activity
level.) Active rehabilitation may begin as early as 4 weeks postoperatively for
a young patient with a single level fusion.
What Can I Expect in the Long Run?
Although fusion can be a very good treatment
for some spinal conditions, it does not return your spine to "normal." The
normal spine has some degree of motion between vertebrae. Fusion surgery
eliminates the ability to move between the fused vertebrae, which can put added
strain on the vertebrae above and below the fusion. Fortunately, once a fusion
has healed it rarely, if ever, breaks down. However, it does place more stress
on the vertebrae next to the fusion. This has some potential to accelerate
degeneration of those segments, but this risk varies between individuals. Many
surgeons therefore recommend that spinal fusion patients avoid repetitive
strenuous activities that involve combined lifting and twisting maneuvers to
minimize the stress on the areas around the fusion. The decision whether or not
to undergo spinal fusion is complex and involves many factors related to the
condition being treated, the age and health of the patient, and the patient's
anticipated level of function following surgery. This decision must therefore be
made carefully and should be discussed thoroughly with your surgeon
Surgery of
Cervical Instability & Instrumentation
There are several operations that may be
used to treat
cervical disc disease. The selection of which operation and
the determination of when to perform the operation depend on many factors,
which obviously differ for each patient and doctor combination. However,
some general factors include the kind of disc disease you have (herniated
disc or bone spurs), whether there is pressure on the spinal cord or spinal
nerve, the presence of one or more areas of disease within the cervical
spine, and if the spine is dislocated in addition to pressure on the cord or
nerves. Other factors are determined by your age, how long you have had the
disease, other medical problems, previous operations on the neck, and so on.
The particular combination of these and other factors will determine the
choice of surgical treatment.
Anterior Cervical Disectomy & Fusion
This operation is performed on the neck to
relieve pressure on one or more nerve roots, or on the spinal cord. The
procedure is performed from the front, or anterior, approach.
Discectomy means to remove the disc. Surgery for anterior cervical
discectomy is performed with the patient under general anesthesia
lying on his or her back. The surgeon may place a traction device to pull on
the neck. During the course of the operation x-rays may be obtained to
assist the surgeon in the surgery. The surgeon will make an incision in the
front of your neck; if only one disc is to be removed it will typically be a
small horizontal incision in the crease of the skin. If the operation is to
be more extensive, the incision may be oblique (slanted) or longer. The soft
tissues within the neck are separated to allow the surgeon to reach the
front of the spine, following which the intervertebral disc and bone spurs
are removed. An operating microscope may be used to better display the area
while part of the disc is removed with forceps. Other instruments such as a
drill or bone-cutting instruments may be used to enlarge the disc space.
This will help the surgeon to relieve any pressure on the nerve or spinal
cord due to bone spurs or the ruptured (herniated) disc. Sometimes the space
between the vertebrae is refilled with a small piece of bone (fusion).
The bone may be yours (for example, from your hip bone) or it may be taken
from a bone bank. In time, the vertebrae may fuse, or join together. In
addition to the piece of bone, some surgeons may place a metal plate at the
fusion site to strengthen it.The neck incision is closed in several layers.
Skin suture material may need to be removed or the surgeon may use absorbing
sutures and strips of tape which you can later remove by yourself.
Historically and statistically, there are
few surgical risks with anterior cervical discectomy; however, some risk is
unavoidable and the unexpected may occur resulting in complications.
Although every precaution will be taken to avoid complications, common risks
possible with surgery are: infection, excessive bleeding (hemorrhage) and an
adverse reaction to anesthesia.
Other risks possible with anterior cervical
discectomy include: stroke; injury to the recurrent laryngeal nerve, which
causes hoarseness and may or may not be permanent; and injury to the
involved nerve root(s) or the spinal cord, both of which can cause varying
types and degrees of paralysis. The process of informed consent is designed
to make you familiar and comfortable with the reasonable expectations and
foreseeable risks. Your surgeon and anesthesiologist will discuss these with
you and assist you in your decision-making.
Cervical Corpectomy
This operation is an extension of the
discectomy procedure. Also using an anterior approach, the surgeon removes a
part of the vertebral body to relieve pressure on the spinal cord. One or
more vertebral bodies may be removed including the adjoining discs. The
incision is generally longer. The space between the vertebrae is filled
using a piece of bone (fusion) and maybe a metal plate. Because more bone is
removed, the recovery process for the fusion to heal and the neck to become
stable again is usually longer than with anterior cervical discectomy.
Cervical Laminectomy and Discectomy
This operation is performed through a
vertical incision in the back of the neck, generally in the middle. Through
this opening the surgeon will use an instrument (a retractor) to pull aside
the strong muscles of the neck and expose the arch of bone (lamina) that
forms the spinal canal. A drill and bone cutting instruments are used to
remove the bone around the spinal cord (laminotomy) or the bone around the
nerve opening (foraminotomy). Once the nerve is located, it is moved gently
aside and an incision is made on the outside covering of the disc through
which the disc material is then removed.
See also:
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