Definition
Anterior cervical decompression
and fusion is removal of disc and/or bone through an approach through
the front of the neck and then filling the cavity formed with bone from
the hip and possibly placing screws and plates to hold the whole
construct into place. The typical
patient presents with either arm symptoms such as pain, weakness,
numbness or pins and needles, or else symptoms and signs of spinal cord
dysfunction, termed myelopathy.
Myelopathy can manifest in a number of
ways, including generalized stiffness, difficulty walking, loss of fine
motor control in the hands etc etc. Compression of nerves or
spinal cord is typically caused by disc material or bony spurs.
A disc protrusion per se may not
cause symptoms. If the annulus is acutely torn, neck pain may result, but
the management is usually not operative. If the disc pushes on a nerve,
as shown in the previous scans, then symptoms down one or
occasionally both arms may result. The symptoms can include
pain,
numbness, “pins and needles”,
and weakness.
Anatomy
The anatomy of a typical
intervertebral disc as shown below:
(Below): The
intervertebral disc lies in front of the spinal nerves and is situated
between the vertebral bodies. It carries 80% of the load through that
level and is the
shock absorber
for the spine. The lowermost discs (C56
and C67) are most prone to wear and tear and potential rupture.
Note that there is an
outer shell, called the
annulus fibrosis and an inner core called the
nucleus pulposus.
The annulus is the consistency of a pencil eraser, whereas the nucleus is
gel-like and, as we get older, dehydrates and becomes like crabmeat. The
discs act as shock absorbers and flexing the spine loads the disc. A
tear in the outer annulus can consequently cause severe back pain.
Patients will often be able to remember a time when they lifted poorly
or twisted their back and had severe back pain prior to getting the leg
pain. Once an annular tear occurs, it may heal, or it may allow nucleus
to come out of the centre of the disc, into the spinal canal, where it
may compress nerves. This is usually called one of a number of terms,
including “disc
prolapse”, “ruptured disc”, “slipped
disc”, “extruded disc” etc etc. All these terms essentially mean the same thing.
Once nerves are compressed, surgery may be complicated. It is important
to know that the prolapsed disc cannot be pushed back into place and
nothing but time will heal the annular tear. Thus, in general, any
surgery is aimed at improving the leg pain, not the back pain.
Reason For Operation
Cervical disc protrusions are not
usually operated upon early, but there are some clear situations when a
surgeon may recommend early surgery. If there is evidence of
severe weakness, early surgery may be
offered. If the pain in the arm is so severe that narcotic analgesia is
not controlling the pain, early surgery may again be an option. If there
is spinal cord compression typically early
surgery is also offered.
If a patient has pain,
but it is not too severe, then typically conservative management is
initiated. It must be remembered that the vast proportion of patients
will settle with time and as long as improvements are noted at 6 weeks,
there is minimal or no weakness, and the pain is not excruciating and is
livable with oral analgesia, then waiting and continuing with
conservative therapy is a good option.
If weakness occurs and
is not improving, surgery is usually offered. Similarly, if symptoms are
not improving at 6 weeks then surgery is an option.
In most cases, when
managing arm leg pain, surgery is a
treatment option that speeds up the rate of recovery, remembering
that most cases will get better by themselves. Again, specific
recommendations are tailored to the patient. In the vast number of
cases, the goal is control of pain, and an intervention that achieves
this and is less invasive than surgery is a reasonable option.
The main reason this form of surgery is performed is
to try and reduce the risk of deterioration in spinal cord function.
At
the extreme end, bad myelopathy patients are wheelchair bound. Coupled
with this, even patients with little in the way of symptoms are
more at
risk of spinal cord injury. This is because the space for the spinal
cord is reduced and an accident as trivial as a minor car accident can
transiently narrow this space via ligamentous buckling, injuring the
cord. Consequently, this surgery is primarily performed as a
prophylactic procedure to stop deterioration in the future.
Technique
The operation is preformed under
general anesthesia and as shown above a cut is made in front of the
neck. The food and wind pipe are shifted over and the operation is
performed between these and the blood vessels to the brain. The disc is
removed in entirety, and after the spinal cord and nerves have pressure
from them removed, graft is placed into the cavity.
This can
typically be:
1. bone from
the hip (autograft). Painful
2. Bone bank
bone (allograft). From cadavers with a small risk of disease
transmission
3. A Plastic
cage made of PEEK, filled with bone graft substitute or BMP, to enhance
fusion (much more common now).
A plate and screws may be placed
over this to keep the graft in place. The operation takes
1-3 hours and
after surgery a collar is in place for 6 weeks.
A cervical plate is shown below:
Risks
The greatest risk is
injury to one or more nerves and this is typically 1-2%.
There is a risk of death, quadriplegia or severe spinal cord injury. The risks of
infection, bleeding etc. etc. are similar to those for a laminectomy as
are the risks of general complications. There are other risks particular
to this operation. Temporary or permanent swallowing problems or
hoarseness of voice can occur. They are common temporarily but not so
permanently The hip graft site is more likely to get infected. The
combined risks are about 5-10%.
The
small but real risks from surgery are the reason why all patients with
disc protrusions do not immediately have surgery.
Expectations
In uncomplicated cases
the likelihood of good/excellent relief of
arm pain is 80-90%. Numbness is slow to recovery and may persist.
Weakness also may take 6-12 weeks to return to normal. Pins and needles
usually starts to improve immediately.
If the surgery was for
myelopathy, as a rule:
Recovery
The hip graft site, if harvested, is quite
sore for after surgery and is the
main slowdown to mobilization. Some pain on swallowing is not uncommon.
Some pain at the back of the neck is not uncommon and
is due to stretching. Most patients spend 1 night in
hospital and mobilize and
go home the next day.
A collar is worn for 6 weeks. At
this time repeat x-rays are done, which if satisfactory, lead to
discontinuation of the collar.
Non-Surgical Options
Despite the length discussion about surgery,
most patients get better without surgery.
Conservative therapy
comprises
·
Analgesia with NSAIDs (e.g. Mobic,
Voltaren or Celebrex)
·
Analgesia with other medications such as
Tramadol
·
Avoidance of neck flexion at computer
screens etc. for long periods
·
Physiotherapy (traction may help)
·
Hydrotherapy (particularly if back pain
is a problem)
· Cessation
of smoking
·
Possibly acupuncture
·
Hydrotherapy (particularly if back pain
is a problem)
·
Perineural steroid and local anesthetic
injections
This is not the case for myelopathy
secondary to spinal cord compression, in which there are no
conservative options
except observation (which we try and avoid) or surgery.
Other
Points
Anterior cervical surgery is being supplanted by
artificial disc surgery. It still plays a role in trauma, deformity and
in the management of older patients with cervical disc disease.
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