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Surgical
procedure (anterior cervical decompression)
Surgical approach
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The
skin incision is about one inch, horizontal and can be made
on the left or right hand side of the neck
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The thin platysma muscle
is then split in line with the skin incision and the plane
between the sternocleidomastoid muscle and the strap muscles
is then entered
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Next,
a plane between the trachea/esophagus and the carotid sheath
can be entered
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A thin fascial layer (flat layers of fibrous tissue)
covers the spine (pre-vertebral fascia) which can easily
be dissected away from the disc space
Disc removal
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A needle is inserted into
the disc space and an x-ray is done to confirm that the surgeon
is at the correct level of the spine
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After correct disc space has
been identified on x-ray, the disc is removed by first cutting
the outer annulus fibrosis (fibrous ring around the disc) then
removing the nucleus pulposus (soft inner core of the disc)
Dissection
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Dissection
is carried out from the front to back to a ligament called
the posterior longitudinal ligament. Often this ligament is gently
removed to allow access to the spinal canal to remove any osteophytes
(bonespurs) or disc material that may have extruded through the
ligament.
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The
dissection is often performed using an operating microscope
to aid with visualization of the canal.
Surgical procedure (anterior cervical
fusion)
To achieve a fusion, a bone graft is used to connect
two bones together. The patient’s own bone will grow into
the bone graft and incorporate the graft bone as its own. This
process creates one continuous bone surface and eliminates motion
at the fused joint. A small piece of bone is used to fuse a disc
space.
There are different
ways to get a bone graft:
Autograft bone (patient’s own bone)
is taken from the iliac crest (hip). The principal disadvantage
with using autograft bone is that another incision needs to be made
over the hip to get the bone graft.
Chances of complication increases with
the size of the bone graft. The bone graft is an important part
of the procedure. Many patients find the site the graft is taken
from to be more painful than the cervical surgery itself.
Allograft bone (donor bone from a cadaver) eliminates
the need to take bone from the patient. Basically, the donor bone
graft acts as a calcium scaffolding into which the patient’s
own bone grows. There are no living cells in the bone graft, so there
is no chance of a graft rejection. This process, called “creeping
substitution”, is slower than
an autograft bone fusion. In one-level fusions, it yields equivalent
fusion rates as autograft bone. If more than one level is fused,
it does not heal as well as autograft bone. To enhance the healing
rate – especially if more than one level is fused – many
surgeons combine allograft with anterior plating of the spine.
If plating plus allograft bone is used for a multi-level fusion,
the fusion rate is equivalent to autograft bone.
Bone graft substitutes
An
anterior fusion can also be achieved by using one of the newer
bone graft substitutes. Although no current products are FDA
approved specifically for this indication, there are many products
that can either mimic the structure of bone (osteoconductive products)
or start the fusion process biochemically (osteoinductive). The
anterior disc space lends itself well to a bone graft substitute
since it is a relatively easy site to obtain a fusion (i.e. there
is not a lot of stress in the cervical spine). Currently, there
are no bone graft substitutes that are structural, so they usually
have to be combined with a titanium cervical cage which gives the
disc space structural support.
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