| As you know, back problems affect most of us significantly and cause more lost work days than any illness except the common cold. Estimates of numbers of surgeries for disc problems run around 200,000 per year, with about 20% being fusion procedures. To put this in perspective, a brief overview of degenerative surgical spinal disease and operations for it, is in order.
The spine is composed of repetitive stacked assemblies of three joints
(an intervertebral disc and two facet joints) which allows for both stability
and motion. Most problems are caused by one of three mechanisms:
1) pressure on the nervous tissue by parts of discs which are protruding
where they are not supposed to be.
2) general deterioration of the stabilizing structures of the joints,
causing stimulation of the microscopic pain nerves during normal activities.
3) pressure on the major nerves from reactive soft and bony tissue formation which inhibits the nerve's blood supply.
Frequently, combinations of these abnormalities exist simultaneously.
The first category, protruding discs, is treated surgically by partial
removal of the disc.
The second category of painful, worn out joints, is surgically treated
by fusion procedures; that is, bridging across the joint with solid bone,
causing all of its motion to stop and thereby diminishing mechanical stimulation of the pain receptors.
The third type, pressure or entrapment of major nerves by degenerative
bone and soft tissue, is relieved by surgical removal of the offending tissue.
This type of surgery, which is commonly referred to by surgeons as "decompression" is at the present time not amenable to an ENDOSCOPIC approach. Both advances in technology along with increasing surgical experience could eventually change this for some cases. The fact that these problems typically involve entrapment by bone and are located posteriorly (toward the back) in the spinal canal, makes them not as easily treated from an anterior endoscopic approach as from the posterior approach which is not so conducive for endoscopic assisted surgery.
Discectomy procedures and fusion procedures are very different in terms
of order of magnitude of surgery, and they present different sets of issues
as far as the advantages of performing them laparoscopically are concerned.
Let's look at anterior endoscopic discectomy for protruding discs first.
To put this procedure in context, we need to look at the advantages it has
over other techniques. Because of the position of the nerve elements in
the spinal canal in relation to the disc, in most cases an anterior approach
is ideal. This has not generally been popular, however, because of the technical difficulty of getting the great blood vessels and bowel safely out of the way to expose the spine itself. First of all, most spinal surgeons in the
United States, historically, have not been familiar with an anterior approach.
However, within the last decade, this is less true. Secondly, the approach
itself involves a rather big incision and good visualization in order to
safely expose the spine. Thirdly, there are quite a few possible complications
from the anterior approach which are related in great part to the experience
of the surgical technicians performing it. With the development of laparoscopic
and endoscopic retroperitoneal instrumentation surgery and a growing number
of surgeons skilled in these techniques, we have eliminated the problem
of a large incision and the complications from the approach will be minimized.
We have seen from endoscopic surgery in other fields of Surgery such as
General Surgery, that rather complicated cases can be safely and routinely
performed in this way.
To date, one group of Spine Surgeons in Southern California, who have
been interested in this approach, has been doing it since 1991 and has recently
published their early results on 21 patients. Another group in New Jersey
has also reported on 10 cases. The experience with the initial group of
patients has been favorable, indicating that this technique is most likely
as effective as any of the other procedures in common use. The procedure
is performed on an outpatient setting and the estimated cost is approximately
one-half of the standard laminectomy type of procedure. Postoperative rehabilitation has also been faster than the usual type of open disc removal procedure. Since one is operating through the disc itself as opposed to through the spinal canal where the nerve tissue is contained, there would appear to
be less chance of scarring of the nerves from an anterior approach. So,
in relation to the standard laminectomy procedure, it has definite at least
theoretical advantages.
On the other hand, we have other minimally invasive procedures to remove
disc material which are also successful. These include percutaneous automated
nucleotomy, percutaneous laser discectomy, chemonucleolysis, and arthroscopically assisted percutaneous discectomy. All of these procedures are done from the posterolateral approach through incisions of negligible size and have a success rate of approximately 60-85%, depending on the degree of selectivity in picking the patients for the procedure. At the present time, these procedures are somewhat limited because of their posterolateral approach in getting access to the part of the disc which is causing the difficulty. Technical improvements in these procedures continue to occur, which will undoubtedly result in higher success rates. Nevertheless, the anatomic advantage of the direct anterior approach to the disc, which one has with endoscopic anterior surgery, may turn out to make this approach the most useful and applicable. In the near future, our ability to negotiate within the spinal
canal itself would appear to be much simpler from the direct anterior approach
that endoscopy provides.
Now let's take a look at spinal fusions. Despite the fact that this is
such a common operation and has been around for many decades, many aspects
of the procedure are poorly understood. The reasons for this are multiple,
but some of the principal ones are that fusions are done in large part for
pain control and our understanding of the complex pain mediation systems
is very primitive. Secondly, there is a myriad of different ways one can
perform a fusion procedure, and the success rate can vary greatly, according
to the meticulousness of the surgeon and the selection process of the patients
who are to undergo the procedure. Thirdly, because we are dealing with human
beings and their subjective complaints of pain, it has been almost impossible
to obtain studies which truly control all the variables. A general rule
in surgery is, if there are a lot of different ways to perform a given operation, it is because either they all work quite well or none of them works very well. Spinal fusions fall more into the latter group. Nevertheless, they
are the only available technique that can alleviate many of the back pain
syndromes that do not respond to non-surgical care.
There are two essentially different types of fusions that are commonly
done at the present time. These types are interbody fusions and posterolateral
fusions. Interbody fusions involve bridging the bone between the vertebra
by replacing the disc material with either bone or, more recently, metallic
devices that are filled with bone. A posterolateral fusion involves placing
bone along the side of the spine, bridging the bony rings together. The
posterolateral procedure is technically less demanding and has less potential
for complications. The interbody fusions are usually performed by the more
experienced and specialized spine surgeons and have the theoretical advantage
of restoring the abnormalities of the spine to a more normal position, and
because the fusion itself is centered at the center of motion of the spine,
confer a greater rigidity to the fusion. Myself and others are convinced
that in some of the pain syndromes, this rigidity is necessary to obtain
an optimally good result.
There are basically two types of interbody fusion: the posterior approach
and the anterior approach. The difficulties with the posterior approach
are related to having to deal with the nerve tissue which is between the
surgeon and the disc, where he would like to perform the fusion. As with
our discussion of discectomy, the anterior approach is ideal in that the
spinal exposure is better and in the region in which the surgeon wants to
perform the fusion, and the nerve roots are spared from retraction and scarring.
Because of the frequent failure rates of the fusions becoming solid by
the simpler techniques, within the last 15 years, an evolution of additional
metallic fixation devices has been developed, whose goal is to hold the
spine still, which allows the body to more readily form a fusion. Initial
attempts at this were done with distraction rods which were not very effective
in the lumbar spine, and then pedicle fixation systems were developed and
are still evolving and have been found to be effective if properly utilized.
The newest approach to instrumentation in the lumbar spine has been an interbody fixation technique using bullet-shaped, threaded, hollow fusion cages. These have been found to hold the vertebra as still as the screw and rod versions, and they sit in the interbody space right at the center of motion of the spine. These fusion cages have completed FDA Clinical trials and the early
results seem to be favorable and they are recessed for general use.
About four years ago, my associates and I at the St. Mary's Spine Center
in San Francisco, obtained a research grant in order to develop a laparoscopic
percutaneous fusion procedure. Our original plan was to utilize donor bone
augmented with bone morphogenic protein placed within the disc space to
cause the fusion to take.
We began performing the procedure in pigs in order to develop the approach
and instrumentation. Shortly after this, development of the fusion cages
provided an ideal internal fixation device that could be passed through
a tube into the disc space, with minimal need for visualization and exposure.
Over a couple of years, specific instrumentation for insertion of the cages
laparoscopically was developed in prototype until we were able to perform
the procedure reliably in the porcine model. We performed the first human
instrumented laparoscopic spinal fusion in the world in September 1993,
and since then the procedure has also been performed all over the worlds
and FDA will likely soon approve this technique for general use. Obviously,
it is too soon to give objective data in regard to clinical results. However,
our impression is that once the learning curve is mastered, the procedure
has significant advantages over other fusion techniques because of diminished
hospitalization, diminished patient discomfort, diminished medical expense,
and an expected high fusion rate. The specifics of the procedure are important
here as some levels in the spine are more technically difficult to do that
others.
There has been a study comparing the medical expense of open and laparoscopic techniques for procedures commonly done in general surgery. Laparoscopic techniques showed significant cost savings. We believe this will be the same result in endoscopic spine surgery, especially after the instrumentation, technique, and surgical expertise are further refined. Advancements in fiber optic visualization and remote instrumentation will certainly broaden the applications for the procedure, as our capacity to manipulate tissue through small holes from remote sites safely increases. Thus, less and less normal tissue will have to be violated in order to correct the areas of abnormality which are much smaller than the currently used exposures.
Quicktime Movies:
The technique for laparascopic spine fusion surgery , which will be illustrated in the videotape, is basically as follows: A special insufflation needle is placed through the umbilicus into the peritoneal cavity and air is insufflated into the peritoneum. This creates a space so that the abdominal cavity can be clearly visualized with the laparoscope. A 1 cm incision is made and the laparoscope is inserted through a trochar and the abdominal cavity visualized. Under direct visualization, two more 1 cm incisions are made for retractors and operating instruments on either side opposite the level to be fused. Under direct, and I must say extremely clear, visualization, dissection
is carried out at the bottom of the abdominal cavity overlying the spine,
to expose the anterior aspect of the discs. An electrical cutting device
makes an incision on one side of the disc and alignment is checked with
a mobile fluoroscope machine. A 13-l7 mm incision is made directly over
the disc to be operated on, and the operating trochar is placed under visualization into the abdominal cavity. Through the incision made in the disc, a series of increasingly larger spacers are used in order to restore the height of the degenerated disc back to its original size. This distraction force causes compression on the intervertebral space which will anchor the fusion cage in place and also internally fix the vertebra on either side. After the
disc is distracted by the spacers to the desirable height, an incision is
made on the other side of the disc and the operating trochar tube placed
over the incision anchored in the bone of the vertebra above and below.
Reamer drills are then used to drill out the disc material and a portion
of the vertebra above and below. A tapping device is used to tap the intervertebral space before the fusion cage is placed. The fusion cage is packed with bone taken from the drill reamings or from the anterior or posterior pelvis, at the surgeon's discretion, and screwed into position inside the intervertebral space. Attention is then directed back to the other side of the disc. The spacer is removed, and in a similar fashion, another fusion cage is placed on that side. More bone is placed within the fusion cage and this essentially completes the procedure. The small incisions are closed and the patient is expected to ambulate the day following the procedure. Discharge is expected two to four days after the procedure. |
