Considerations for a cervical disc replacement
surgery
There are a number of factors that are important in
considering cervical disc replacement vs. a traditional
decompression and fusion surgery. Perhaps
the most important consideration is that longer term
studies and follow-up will be needed to fully understand
the potential risks and benefits of cervical disc replacement. At
present, most of the information on the discs remains
theoretical.
Indications for an artificial cervical disc
The
indications for a cervical disc replacement are generally
the same as for a cervical discectomy and fusion. A
person must have a symptomatic cervical disc, which
may be causing arm pain, arm weakness or numbness with
some degree of neck pain. These
symptoms may due to a herniated disc and/or osteophytes
compressing adjacent nerves or the spinal cord. This
condition typically occurs at cervical spine levels
C4-5, C5-6, or C6-7.
Prior to being admitted into a clinical trial, the
candidate must usually meet strict defined entrance
criteria, which at least include:
-
Undergo a trial of non-operative treatment for
at least 4 to 6 weeks, usually consisting of anti-inflammatory
medication and physical therapies
-
Have had no prior neck surgery
-
Must be deemed a good surgical candidate
At this time in US clinical trials only single-level
cervical disease is being treated. In Europe
multilevel disease is being addressed. Multilevel disease
will hopefully be cleared for clinical trials in the
United States in the near future.
Surgical procedure for cervical disc replacement
The
standard surgical procedure for a disc replacement
is an anterior (from the front) approach to the cervical
spine. This surgical approach is the same
as that presently used for a discectomy and fusion
operation. The affected disc is completely removed
including any impinging disc fragments or osteophytes
(bone spurs). The disc space is distracted (jacked
up) to its prior normal disc height to help decompress
(relieve pressure) on the nerves. This is important
because when a disc becomes worn out, it will typically
shrink in its height, which can also contribute to
the pinching on the nerves in the neck. See
figure
7.
At this point, using x-rays or fluoroscopy, the artificial
disc device is implanted into the prepared disc space.
Postoperatively, the patient typically can go home
within 24 to 48 hours with minimal activity limitations.
Potential risks and complications
The potential complications with an artificial device
are at least similar to an anterior cervical discectomy
and fusion and may include:
Although these complications can be severe, they are
very rare occurrences.
In addition, the artificial disc does theoretically
have some of the same potential complications associated
with total hip and knee arthroplasty. An arthroplasty
is a mechanical device and by the laws of physics will
wear out over long periods of time. That time
period remains to be defined for total disc replacement. In
addition, small particle debris may react with the
body. Laboratory and animal studies for some
of the devices have shown that after simulating ten
years of wear, only minimal disc wear occurs and the
materials appear to be well tolerated over time.
Potential benefits of a cervical artificial disc
vs. a fusion
Unlike a fusion procedure, the artificial
disc surgery does not have the potential complications
associated with taking a bone graft from the hip
nor the theoretical risk of infection transmission
from using a cadaveric bone graft. Clearly
the issue of bone graft healing is eliminated. The
disc replacement also should reduce the chances for
adjacent segment disease (versus a fusion), since
the artificial disc should allow for more normal
neck motion and absorb some of the daily stresses
of the neck. The length and type of activity restrictions
following surgery are also much less with disc replacement.
By: Mark Mikles, MD and
Jeffrey A. Goldstein, MD
April 12, 2004
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