Anterior approach to spine surgery
The anterior approach to the spine has been around
since the 1950’s. Originally, the surgery involved
a large abdominal incision in which the surgeon would
cut through the abdominal muscles and the peritoneal
cavity to gain access to the spine. The peritoneal
cavity contains the patient’s intestines. This
would require long recovery times due to the large
dissection of the abdomen and muscles to get access
to the spine.
Today, however, the anterior approach to lumbar spine
fusion (or other spine surgery, such as the artificial
disc) can be done with a minimally invasive approach,
involving the following steps:
-
A relatively small incision (around 3-5 inches)
is made for a single level fusion surgery (see Figure
3).
This incision is normally 4 to 5 inches below the
belly button and usually is low enough to be covered
by the patient’s pants, especially
if a lower lumbar disc level (such as L5-S1) is
being fused.
-
A retroperitoneal (behind the peritoneum—the
membrane that lines the abdomen) muscle sparing
approach is typically done, which means that the
front abdominal muscles are gently moved to the side
and not cut and the peritoneal cavity is not entered.
-
The peritoneal cavity is moved to the side so
that it is out of the way to allow for access to
the midline spinal column. The anatomy of the abdomen
is really a “bag within a bag” and
the inner bag that holds the intestines is not
entered.
-
Directly in front of the vertebral bodies of the
spine are large blood vessels that bring blood
back and forth to the legs. Depending on
the level of the disc, some of these vessels may
need to be gently retracted to allow for access
to the disc space. Because of the risks and special
skills involved with manipulating blood vessels,
a vascular surgeon or general surgeon is required
to assist with the anterior approaches to help
gain exposure to the disc.
Once the disc space is exposed (see Figure
4),
the degenerated disc itself is removed, and disc material
that is bulging on the nerve roots can carefully
be eliminated. At this point, the disc space
can be restored to its native height, which will
decompress the nerve roots indirectly in the foramen
space, and also help regain any lordosis of the spine.
A structural bone graft, cage, total disc replacement,
or other device would then be placed into the empty
disc space.
Potential risks and complications unique to the
anterior approach
As with all surgical procedures, the anterior approach
to spine fusion carries with it a few risks and potential
complications that are unique to this surgical approach.
-
Blood vessel injury. The incidence
of injury to the large blood vessels is very small,
typically being around 1-2%. To minimize
this risk, a vascular surgeon (or general surgeon
with the appropriate skills and training) should
be involved in the surgery to manipulate the large
blood vessels to help the spine surgeon gain access
to the front of the spine.
-
Retrograde ejaculation. For male patients,
a rare complication (< 1%) from the anterior
approach to spine surgery is retrograde ejaculation.
At the lower end of the lumbar spine, there is
a group of small nerves which can lie over the
lowest disc space (L5-S1). These nerves help control
a valve needed to express semen, and instead the
semen goes up into the bladder after ejaculation.
The nerves do not have any effect on erectile function,
which is controlled separately by a different set
of nerves. In the majority of patients who
experience this complication, the condition resolves
by itself within 3 to 6 months, but if necessary,
an urologist can be consulted to help with fertility. If
the retrograde ejaculation becomes permanent, the
patient may be unable to have children (without
medical intervention from a fertility expert) but
will otherwise have normal sexual function.
The other risks and potential complications associated
with the anterior approach to spine surgery are similar
problems that one would encounter with a posterior
spinal surgery, such as infection, and are not unique
to the anterior approach. Infection is very rare.
There is an excellent blood supply to the area.
Non-unions can occur, but done properly one should
expect a 90-95% fusion rate for patients. Pain
relief in patients with degenerative disc disease varies,
but it has been reported to be effective for pain relief
in between 60% - 90% of patients.
By: Mark Mikles, MD and
Jeffrey A. Goldstein, MD
October 22, 2004
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