Egypt Neuro Spine

Last Update: December 2011

Minimally Invasive Spinal Approaches (MISA)

The Theory:

“It is not difficult to change, but if you have the idea that it
is, then it will become difficult” Osho.

It has not been that easy to change what we have learnt and the
conventional methods we have used for years and switch to minimally invasive
methods. The biggest obstacle before us has always been the things we have
thought to be correct. Despite all, we have relentlessly continued with our
studies. We needed to engage in evidencebased medicine in order to be included
in textbooks on conventional treatment methods;however, initially we confined
ourselves only to publications based on personal observation and breakthroughs.
Randomized double-blinded studies have been conducted throughout the years.
While on one hand, MISA has begun to be used in many centers.

As Albert Einstein once said, “Whether you can observe a
thing or not depends on the theory which you use. It is the theory which
decides what can be observed.” We have reflected our theory on our
observations.

We claim that even the seemingly most complex spine complications
can be solved by using the methods offered by MISA. Decompression is not
sufficient and we have to engage in cellular treatment which would provide
regeneration. The first condition to these treatments is to intervene in the patient
without harming normal tissues. And intervention without harming normal tissues
is possible with MISA which is proved to be an effective method today.

We will continue to prepare ground for informative minimally
invasive believes.!

Minimally Invasive Spinal Approaches (MISA)

A WAY OF THINKING

To me, MISA is a believe, a faith, and a different way of thinking
rather than another method of treatment. I found these methods the most
suitable addition in spine management for patients care. The complications of
classic spinal surgeries are many and sometimes handicaping. If we can find a
way or the other that can solve the patient problem with minimal drawback, it
will be excellent. This is what MISA provide.

 

Minimally Invasive Spinal Surgery:

A Historical Perspective:

Since the 1930s, the relationship between disc herniation and
sciatica has been well recognized. Since that time, intraoperative tools have
been developed to facilitate surgical approaches and treatment of disc disease.
Pool used a modified illuminated otoscope to perform myeloscopic examinations
of the dorsal nerve roots in cases of disc herniations.In 1955, Malis used the
operating microscope and bipolar coagulation in facilitating his surgical
approach. With the introduction of the operating microscope, Yasargil and
Caspar both described the minimally invasive concept of microdiscectomy. During
the same period, biochemical advances in the treatment of disc herniations were
also developed. In 1964, Smith was able to dissolve the nucleus pulposus in a
rabbit model via percutaneous enzymatic applications; this technique was later
successfully applied in humans. In 1975, Hijikata described the first
percutaneous discectomy, which later evolved into automated discectomies. In
addition to automated techniques, adjuvant treatments of discogenic disruption
have included the use of lasers and thermal heating probes. In 1984, Ascher and
Heppner used an Nd-YAG laser to heat the nucleus pulposus in attempts to shrink
the disc and relieve the symptoms of nerve compression. Since the 1990s, with
the application of video imaging to standard endoscopy, minimally invasive
endoscopic and thoracoscopic procedures have gained rapid use and have
diversified in their clinical applications. In this report, we review the
historical perspectives and the concept of minimally invasive spinal techniques
as they are used in different portions of the spinal column.

The concept of minimally invasive spinal surgery embodies the goal
of achieving clinical outcomes comparable to those of conventional open
surgery, while minimizing the risk of iatrogenic injury that may be incurred
during the exposure process. The development of microscopy, laser technology,
endoscopy, and video and image guidance systems provided the foundation on
which minimally invasive spinal surgery is based. Minimally invasive treatments
have been undertaken in all areas of the spinal axis since the 20th century.
Lumbar disc disease has been treated using chemonucleolysis, percutaneous
discectomy, laser discectomy, intradiscal thermoablation, and minimally
invasive microdiscectomy techniques. The initial use of thoracoscopy for
thoracic discs and tumor biopsies has expanded to include deformity correction,
sympathectomy, vertebrectomy with reconstruction and instrumentation, and
resection of paraspinal neurogenic tumors. Laparoscopic techniques, such as
those used for appendectomy or cholecystectomy by general surgeons, have
evolved into procedures performed by spinal surgeons for anterior lumbar
discectomy and fusion. Image-guided systems have been adapted to facilitate
pedicle screw placement with increased accuracy. Over the past decade,
minimally invasive treatment of cervical spinal disorders has become feasible
by applying technologies similar to those developed for the thoracic and lumbar
spine. Endoscope-assisted transoral surgery, cervical laminectomy, discectomy,
and foraminotomy all represent the continual evolution of minimally invasive
spinal surgery. Further improvement in optics and imaging resources,
development of biological agents, and introduction of instrumentation systems
designed for minimally invasive procedures will inevitably lead to further
applications in minimally invasive spine surgery.

Lumbar Spine

Chemonucleolysis

Chymopapain was discovered and isolated by Jansen and Balls in 1941
from the latex of the fruit of Carica papaya. By depolymerizing the
proteoglycan and glycoprotein macromolecules of the nucleus pulposus,
chymopapain can reduce the water content of the extracellular matrix of the
nucleus pulposus and cause reductions in intervertebral disc height and bulge.
In addition to reducing intradisc pressure, chymopapain may also have an
antiinflammatory role in the nerve root itself. Watts proposed that chymopapain
interacts with the sensory fibers of the anulus to produce a total or partial
neurectomy effect.

The first clinical treatment of sciatica by using chymopapain was
applied by Smith in 1964. In the following three decades, chemonucleolysis was
actively used to treat disc disease; however, controversial issues surrounding
its safety and efficacy, arose despite the fact that it has the approval of the
US Food and Drug Administration. Overall, the efficacy of chemonucleolysis was
noted to be between 74 and 77% in several reports. The largest series was
reported by Nordby and Javid; they published a 14-year study of 3000 patients
and noted a success rate ranging between 82 and 87.2%. Other published outcome
reports were inconclusive, however, and brought into question the safety and
efficacy of chymopapain. Anaphylactic reactions to this substance can result in
death. An inadvertent intrathecal chymopapain injection can cause hemiparesis
and paraplegia, raised intracranial pressure, meningitis, and hemorrhage.

A review of the literature nevertheless does reveal data supporting
the continued use of chemonucleolysis for the treatment of lumbar disc
herniations. Proper patient selection is crucial for success. Chemonucleolysis
should be reserved for patients with radicular symptoms caused by a soft
herniated disc as demonstrated by imaging studies. Patients older than 60 years
of age may lack sufficient mucoprotein for hydrolysis and tend to respond
poorly to this procedure. Absolute contraindications to chemonucleolysis
include allergic reactions to papain, history of discitis, cauda equina
syndrome, pregnancy, arachnoiditis, migrated discs, and canal stenosis.

Percutaneous Lumbar Discectomy

In 1975, Hijikata first described a percutaneous nucleotomy
technique involving a partial resection of the disc material via a
posterolateral approach. The procedure was performed using local anesthesia. In
1983, Kambin and Gellman performed a dorsolateral discectomy by inserting a
Craig cannula and a small forceps into the disc space. In 1985, Onik and
colleagues introduced a nucleotome for PLD. In 1986, Kambin and Sampson
initiated the use of fluoroscopy for percutaneous discectomy. Instruments
similar to those developed for ophthalmologists to remove the vitreous humor of
the eye were redesigned for use in percutaneous discectomies; some flexibility
was provided to approach the L5–S1 and L4–5 levels.

Patient selection for percutaneous discectomy is similar to that
used in patients undergoing chymopapain treatment. Similarly, the procedure of
percutaneous discectomy is most ideal for contained disc fragments, with the
size of the protrusion being an important factor in obtaining successful
outcomes. In addition, patients with narrowed disc spaces are also poor
candidates for percutaneous discectomy. Automated PLD can be a treatment option
for patients with single-level disc disease. It is not indicated for patients
with a history of previous chemonucleolysis, surgical discectomy, progressive
neurological deficits, sequestered disc fragments, spinal stenosis, or
spondylolisthesis. Success rates reported in the literature range from 77.5 to
87% and the complication rate is 1%. To date, however, there have been no
prospective randomized controlled studies to validate the long-term outcomes of
PLD.

Percutaneous Laser-Assisted Discectomy

The development of laser light amplification by stimulated emission
of radiation dates back to 1958 and was accomplished by Arthur L. Schawlow and
Charles H. Townes. Since then, numerous applications of laser technology in
medicine have been reported in the specialties of ophthalmology, plastic
surgery, urology, vascular surgery, general surgery, gynecology, neurosurgery,
and orthopedics. Laser-assisted discectomy evolved from percutaneous discectomy
techniques. After percutaneous placement of a single needle in the disc space,
laser energy is passed through a fiber, which is coupled to the needle, into
the disc space. The laser energy is transmitted in short bursts to avoid
excessive heating of adjacent tissue. In 1984, Ascher and Heppner used carbon
dioxide and Nd lasers to treat lumbar disc disease. Their method involved
measuring intradisc pressure before and after laser discectomy by using a
saline manometer. These authors postulated that the removal of even a small
volume of tissue from the disc caused a corresponding decrease in intradisc
pressure, thus relieving back pain and inflammation. In 1990, Yonezawa, et al.,
used an Nd–YAG laser to transmit energy through a double-lumen needle with a
bare quartz fiber; their tip-type pressure transducer was similarly able to
record intradisc pressure. The use of a KTP laser for lumbar disc ablation was
introduced in 1992. Recent advances have allowed the development of side-firing
probes, which provide better directional control and visualization. The
side-firing laser probe reduces the risk of injury to anterior structures such
as the vena cava, aorta, and iliac vessels. Yeung recommended injecting discs
with indocyanine green to act as a chromophore, thus maximizing delivery and
minimizing the chance of injury to adjacent structures. The holmium– YAG system
involves a unique pulsed laser that enables the adjustment of pulse width and
frequency to cause disc cavitation and reduce intradisc pressure while
minimizing injury to adjacent structures.

Overall, the combined results of several series demonstrated a 70
to 80% rate of long-lasting pain relief. The only reported complication was one
case of discitis in a series of 333 procedures, which was described by Choy, et
al. Other possible complications of laser-assisted discectomy can include
perforation of the aorta, vena cava, iliac vessels, or abdominal organs, and
cauda equina syndrome. To date, however, there are no reported prospective
controlled studies involving percutaneous laser discectomy. As such, the results
of percutaneous laser discectomy for back and leg pain due to disc protrusions
are still inconclusive. The largest experience in the literature, reported by
Choy, et al. documented a 78.4% success rate with a 26-month period follow up.
Yeung reported an 84% rate of good or excellent results with the KTP/532
device. On the other hand, Sherk and associates observed no differences between
treated and control groups in an analysis of responses to pain questionnaires
or the presence of physical signs.

Yeung and colleagues published a recent retrospective review of 307
consecutive patients with lumbar disc herniation who were treated by
posterolateral endoscopic laser discectomy. These authors showed satisfactory
results in 89.3% of patients. The rate of response to the questionnaire was
91%. The responses indicated that 90.7% of the respondents were satisfied with
their surgical outcomes and would undergo the same endoscopic procedure again
if faced with a similar herniation in the future. Poor outcomes occurred in
10.7% of the primary group and in 9.7% of the group responding to the
questionnaire. The combined major and minor complication rate was 3.5%.

Arthroscopic Microdiscectomy

Kambin and Hijikata and their colleagues independently developed
mechanical tools for percutaneous nucleotomy. Refinements of the method
involved the use of an automated system. The instruments were designed to
remove disc material from the center of the disc and to decrease the amount of
nucleus pulposus posterolaterally. Subsequent developments led to the design of
a 2.7-mm glass arthroscope combined with a videodiscoscope with a single
working portal. The introduction of arthroscopic illumination and magnification
allowed identification of the triangular working zone. The triangular working
zone has been identified as a safe zone in the posterolateral anulus, which
allows safe passage of instruments with minimal risk to the exiting nerve.
Placement of the needle is confirmed with the aid of an intraoperative
fluoroscope. Within the triangle, there is generally room for introduction of
the coaxial instruments. The initial open procedure in which a tube is
introduced posterolaterally was slowly replaced by a completely percutaneous
operation in which a modified discoscope, working portals, and special
instruments are used.

The mechanism of pain relief after arthroscopic microdiscectomy and
central nucleotomy is controversial, but the theory involves the reduction in
intradisc pressure, removal of inflammatory agents, and reduction of tension on
the nerve root. Additionally, the arthroscopic approach provides the
opportunity to inspect the anulus, spinal nerve, and foramina. All intraanular,
subligamentous, and extraligamentous herniations are accessible via the
arthroscopic microdiscectomy procedure. Nevertheless, sequestrated and migrated
disc fragments cannot be safely removed using the arthroscopic microdiscectomy
method.

Kambin reported an 87% successful outcome rate with arthroscopic
microdiscectomy. Others reported similar successes withthis procedure. Mayer
and Brock, in a paper on a prospective randomized control trial, achieved
favorable outcomes with minimal complications. The reported complications in
the literature included discitis, instrument breakage, and psoas hematomas; no
neurovascular complications arising from posterolateral access to the
intervertebral discs of the lumbar spine have been encountered. Proper patient
selection makes arthroscopic microdiscectomy an attractive option as a sameday
surgical procedure. Negligible blood loss, avoidance of general anesthesia, and
minimization of scar tissue can all contribute to desirable outcomes.

Lumbar MED

Because of familiarity, better long-term outcome studies, and the
ability to address concomitant pathological bone and ligament conditions,
microsurgical discectomy has been recognized as the surgery of choice for
treating lumbar disc herniations by many surgeons when compared with other
percutaneous procedures. In an attempt to achieve the same desirable outcomes
as those provided by the microsurgical discectomy technique, by using a
minimally invasive muscle splitting approach, a tubular retractor system for
microdiscectomy was first developed in 1994. The system consists of a series of
concentric dilators and thin-walled tubular retractors of variable length; its
basic concept is the foundation on which several contemporary approaches to
minimally invasive spinal fusion are based. The spine is accessed via serial
dilation of the cleavage plane between the muscle fascicles. The midline
supporting the musculoligamentous structures are left intact using this
technique. In 1997, the MED system was introduced. Since then, the MED
procedure has become the most popular and successful of the minimally invasive
procedures. The steep learning curve associated with the use of the endoscope
for MED procedures initially deterred many surgeons from widespread acceptance
of the technique. The lack of depth perception and stereoscopic visualization
associated with the use of the endoscope compounded the steep learning curve of
the procedure. The next generation of the MED system, called the METRx
(Medtronic Sofamor Danek, Minneapolis, MN), provided increased working space
and better illumination. Surgery can now be performed using the operating
microscope, loupes, an endoscope, or a combination of techniques, depending on
the preference of the surgeon. Essentially, one can follow the same method as
the open microdiscectomy. Currently, over 6000 MED procedures have been
performed at more than 500 institutions. Using this procedure, surgeons can now
also treat free-fragment disc herniations as well as canal stenosis, conditions
that were previously unaddressed by other percutaneous procedures. At several
centers this procedure is performed as a routine outpatient procedure without
general anesthesia.

Lumbar Fusion

Laparoscopic Anterior LIF

Prior to the 1980s, laparoscopic procedures were mainly used in the
fields of gynecology and urology. The transition into general surgery began in
the 1980s when the first laparoscopic appendectomy was performed in Germany. In
1987, the first human laparoscopic cholecystectomy was performed in France. The
widespread acceptance of this minimally invasive approach can best be
appreciated by noting that within only 3 years after its introduction, more
than 90% of all cholecystectomies were being performed laparoscopically. The
significant advantages of transperitoneal laparoscopic surgical treatment
include marked reductions in postoperative pain, early hospital discharges, and
reduced incidences of postoperative ileus.

Anterior lumbar fusion was initially described by Burns in 1933 for
the treatment of spondylolisthesis. In 1991, Obenchain first described the
laparoscopic approach to the lumbar spine for discectomy. In 1995, Mathews, et
al., and Zucherman, et al., described the technique in detail and published
preliminary outcome data for laparoscopic anterior lumbar fusion. In 1999,
Regan and associates published a prospective study in which open and
laparoscopic methods of anterior lumbar fusion were compared. They demonstrated
that patients who underwent the laparoscopic procedure had a shorter hospital
stay and reduced blood loss, but an increased operative time. Operative time
shortened in patients who underwent the laparoscopic procedure as surgeons’
experiences increased. Operative complications were comparable in both groups,
with an occurrence of 4.2% in those in whom the open approach was used and 4.9%
in those in whom the laparoscopic approach was used. Overall, the
device-related rate of repeated surgery was higher in the laparoscopy group
(4.7% compared with 2.3%), primarily as a result of intraoperative disc
herniation. Conversion to an open procedure in patients who initially were
treated laparoscopically was 10%.Authors of a more recent study did not favor
the video- assisted laparoscopic approach. Escobar, et al., published a
comparative analysis focusing on the complications of four techniques—a
transperitoneal video assisted procedure with insufflation; a retroperitoneal
endoscopic video-assisted procedure; minilaparotomy retroperitoneal surgery;
and a traditional oblique muscle-splitting retroperitoneal surgery—for anterior
LIF in 135 patients. The study revealed that the highest incidence of
complications occurred in video-assisted laparoscopic approaches. Complications
are primarily related to surgical exposure of the anterior spine, which can
include damage to important vascular structures, the sympathetic plexus, or the
abdominal viscera.

Retroperitoneal Lumbar Fusion

The retroperitoneal approach to the lumbar spine was first described
by Iwahara in 1963 and is now being increasingly used for treatment of
spondylolisthesis, degenerative disc disease, internal disc derangement, and
instability, as well as for repeated operations. Endoscopic approaches to the
retroperitoneal space, known as “retroperitoneoscopies” were
initially described by urological surgeons in the 1990s. Gaur and McDougall and
coworkers first used balloon dissection of the retroperitoneal space to enable
laparoscopic visualization of the surrounding anatomy. This eventually gave
rise to applications for treatment of lumbar disease. The balloon-assisted
endoscopic retroperitoneal gasless procedure is a minimally invasive
retroperitoneal approach to the anterior lumbar spine. A gasless
retroperitoneal approach has additionally advantages. This procedure is similar
to an open spinal procedure and conventional instruments may be implemented.
Trocars with valves are not required and complications associated with carbon
dioxide insufflation are avoided. Advances in interbody cage technology and
artificial discs have generated a great deal of interest in anterior lumbar
fusion. Minimal access techniques of treating the anterior lumbar spine will be
important in optimizing clinical outcomes, in addition to preserving posterior
load-bearing elements.

Minimally Invasive Posterior and Transforaminal LIFs

The concept of LIF, as initially described by Cloward in 1951,
offers several advantages over traditional posterolateral arthrodesis,
including a rich blood supply from the cancellous fusion bed, a load-bearing
force occurring through the fusion bed, the ability to distract the disc space
and neuroforamina, and the ability to restore segmental lordosis. Traditional
open posterior LIF procedures have been reported to yield successful outcomes
in approximately 80% of patients with fusion rates near 90%. Since 2000,
minimally invasive posterior LIF procedures have been performed to reduce
iatrogenic injury, which can be incurred during the exposure process of the
open procedure. Long-term follow-up data are lacking, but retrospective reviews
of minimally invasive posterior LIF performed with the aid of the microscope,
premachined bone graft or cages, a virtual fluoroscope, and a percutaneous
pedicle screw system were reported to yield clinical improvement more than 1
year postoperatively, which is comparable to the outcomes of an open
procedure.Transforaminal LIF, a unilateral posterior approach for achieving an
interbody arthrodesis, has gained recent popularity. The disc interspace is
accessed by performing a unilateral facetectomy. Retraction of the nerve root
is kept to a minimum, allowing for safer placement of the interbody graft. The
METRx system can be used for exposure of the disc space and completion of the
facetectomy. Placement of a premachined bone graft or cage supplemented with
BMP can obviate the need for local harvesting of an autograft. Supplemental
percutaneous pedicle fixation is added for completion of the transforaminal LIF
procedure.

The unilateral transforaminal LIF approach for interbody fusion
offers several advantages over the posterior LIF procedure. Retraction of the
nerve root and dura mater is minimized, because of the lateral entry point, and
this reduces the risk of neural injury. This lateral entrance into the disc
space also makes revision surgeries less difficult, because there is less need
to mobilize nerve roots that may be surrounded by epidural scar tissue. A
potential disadvantage of unilateral transforaminal LIF is that direct nerve
root decompression can only be performed unilaterally. With the increasing use
of the tubular retractor system, however, bilateral foraminal decompression can
be achieved via a unilateral approach, as previously described.

Thoracic Spine

Video-Assisted Thoracoscopic Surgery

The history of thoracoscopy dates back to 1910, when Jacobaeus
performed the first thoracoscopic and laparoscopic procedure. In 1990, the
introduction of video imaging to standard endoscopy marked the modern era of
thoracoscopic surgery. A description of video-assisted thoracic surgery was
first reported in 1993 by Mack, et al. Video-assisted thoracic surgery has
since played a major role in the treatment of thoracic disc herniations and
spinal deformities requiring anterior release, as well as in corpectomies for
the treatment of vertebral body tumors. Several published reports have
demonstrated the efficacy of video-assisted thoracoscopic surgery for the
excision of thoracic disc herniations. Thoracoscopic spine surgery has also
made treatment of hyperhidrosis possible in a minimally invasive way. Picetti,
et al., performed corrective surgery with the aid of a thoracoscope in 50
patients with thoracic scoliosis. Endoscopic instrumentation was successfully
performed in all patients. Curve corrections averaged 50.2%, and this rate
improved to 68.6% in the last 10 cases. The preoperative axial rotation (as
measured using a scoliometer) averaged 16°; this was corrected to 5°.
Postoperative pain was reduced as was the duration of postoperative analgesic
use in patients treated thorascopically, compared with patients treated with
formal open procedures.

In the trauma series reported by Khoo and associates 371 patients
with fractures of the thoracic and thoracolumbar spine (T3–L3) were treated
with a thoracoscope-assisted procedure. Seventy-three percent of the fractures
were located at the thoracolumbar junction. In 49% of the patients,
mobilization of the diaphragm was performed thorascopically to expose the
fracture site. The severe complication rate was low (1.3%), with one case each
of aortic injury, splenic contusion, neurological deterioration, cerebrospinal
fluid leak, and severe wound infection. Compared with a group of 30 patients
who were treated with open thoracotomy, patients treated thoracoscopically required
42% less narcotic agents for pain treatment after the operation.A special fan
retractor is used to retract the diaphragm. Minimal dissection of the diaphragm
was performed to expose the thoracolumbar junction. C: Thoracoscope-assisted
screw fixation. D: Final construct after thoracoscope-assisted thoracolumbar
fixation.

A thoracoscopic approach can only access the anterior and
anterolateral aspects of the vertebrae and spinal canal. It cannot adequately
expose the posterior elements, the contralateral pedicle, or the transverse
process. Thoracoscopic surgery, like endoscopic surgery, will require a steep
learning curve, but it has the advantages of reducing postthoracotomy pain
syndromes and exposure-related morbidity.

Cervical Spine

 

Cervical Microendoscopic Discectomy

In selected patients with laterally herniated disc fragments,
isolated foraminal narrowing, multilevel foraminal narrowing without central
stenosis, or continued nerve root symptoms after anterior cervical discectomy
and fusion, a posterior cervical approach will be necessary. Although the
anterior approach to the cervical spine has become increasingly popular, the
posterior cervical discectomy technique, as described by Scoville and
associates is quite effective in relieving radicular pain and avoids the need
for a fusion. The disadvantage of the standard posterior approach, however, is
significant paraspinous muscle dissection, postoperative axial neck pain,
potential instability, and subsequent deformity.

By applying the MED system to the lumbar area, the disadvantages of
the posterior cervical exposure process can be minimized by avoiding the need
for a midline muscle dissection. Dilators are sequentially inserted through the
posterior neck musculature and docked at the junction of the lamina and the
lateral mass. An intraoperative fluoroscope is used to confirm the level and
correct placement of the tube. The microsurgical procedure is performed through
the tubular retractor, as it is during an open procedure.Roh, et al., performed
posterior cervical foraminotomies by using either the MED system or
conventional open techniques in four cadaveric specimens. They were able to
demonstrate greater decompression by using the MED procedure and showed the
possibility of minimally invasive cervical foraminal decompression and
discectomy. Adamson stated that excellent or good results were obtained in 97%
of his patients treated by cervical MED for unilateral cervical radicular
syndromes due to foraminal stenosis or disc herniations. No serious
complications were reported.

Minimally Invasive Cervical Laminoplasty

Expansile laminoplasty has been successfully used to treat cervical
myelopathy that is attributable to canal stenosis; however, detachment of the
posterior cervical muscles is thought to contribute to postoperative axial neck
pain and kyphosis. Minimizing the amount of muscular dissection might reduce
the likelihood of these sequelae. Wang and associates assessed the feasibility
of a minimally invasive laminoplasty technique by applying it to cadaveric
spines. A 22-mm tubular dilator port was used to access lamina–facet junctions
from C-2 to C-7 through bilateral stab incisionsmade at C4–5 and C5–6. Troughs
at the lamina–facet junctions were drilled bilaterally and the contiguous
laminae were lifted en bloc from one side. Ten-millimeter rib allograft spacers
were inserted to maintain a gap on the open side. These researchers found that
exposure of six cervical levels can be accomplished by creating two small
incisions on each side. The diameter of the midsagittal spinal canal was
increased by a mean of 38% and the area of the spinal canal was increased by an
average of 43% at the level of C-5.

Minimally Invasive Cervical Lateral Mass Screw Fixation

Although not without its limitations, cervical instrumentation can
also be accomplished via a minimally invasive approach. A “novel”
surgical technique of lateral mass screw fixation through a special tunnel
retractor has recently been described. The procedure is performed while the
patient is in the prone position by using tubular retractors, which are
introduced two or three levels below the pathological region, at an angle used
for placement of the lateral mass screws. Dorsal elevation of the retractor system
will provide room for placement of the rod. This technique can be applied to
three contiguous cervical levels.

Vertebroplasty and Kyphoplasty

Developed in France in the late 1980s, minimally invasive
vertebroplasty involves the percutaneous injection of PMMA into a fractured
vertebral body. Although this does not reexpand a collapsed vertebra, it
reinforces and stabilizes the fracture, which seems to alleviate pain. The
procedure was first used to treat aggressive vertebral hemangiomas and was later
applied to other lesions that weaken the vertebral body, including osteolytic
metastases, and osteoporotic vertebral collapse. Although the European
experience with vertebroplasty in the setting of spinal metastases and myeloma
is more extensive, indications for treatment in North America are currently
heavily weighted toward osteoporotic bone disease. Percutaneous balloon
kyphoplasty is a recent modification of the vertebroplasty method and involves
inflation of a balloon within a collapsed vertebral body, to restore height and
reduce kyphotic deformity, followed by stabilization with PMMA. The risk of
cement extravasation is theoretically reduced because the balloon creates a
void within the vertebral body into which cement can be injected under relatively
low pressure. Nevertheless, vertebroplasty still has been known to be
successful for the treatment of compression fracture of the spine.In addition
to PMMA and bone mineral cement, several alternative biological materials have
been used in attempts to augment compromised vertebral bodies. The efficacy of
osteoinductive growth factors (transforming growth factor–β, BMP-2, and BMP-7)
in enhancing arthrodesis is currently being studied in patients undergoing
spinal instrumentation.

Intradiscal Electrothermal Therapy

Saal and Saal hypothesized that thermal energy might play a role in
the treatment of internal disc disruption and thus chronic low-back pain.
Intradisc electrothermal coagulation is a therapeutic innovation specifically
designed to treat discogenic pain. The most commonly used electrosurgery unit,
the Ellman Surgitron IEC, produces ultrahigh- frequency radio-wave energy,
which is delivered through modified monopolar and bipolar tools. The energy is
filtered back to the electrosurgery unit without causing adjacent tissue
damage. In the normal intervertebral disc, sensory nerves do not penetrate
beyond the outer one third of the anulus fibrosis; in degenerative disc
disease, however, neoneuralization can occur, resulting in new nerve fibers that
contribute to a painful sensation. The diagnosis of this condition is based
largely on the patient’s medical history and on radiological findings.
Discograms, although controversial, are often used as additional confirmatory
tests.

Intradiscal electrothermal therapy delivers targeted thermal energy
designed to shrink collagen fibrils, cauterize granulation tissue, and
coagulate nerve tissue in the posterior anulus fibrosus. Intradiscal
electrothermal coagulation requires percutaneously threading a flexible heating
electrode into the disc, such that the electrode passes circumferentially
around the inner surface of the disc. Direct application of thermal energy to
the intervertebral disc is thought to reduce discogenic pain either by thermal
coagulation of nociceptors or by increasing the stability of the disc via
contraction of collagen Type I fibers.

Saal and Saal recently developed a novel resistive heating catheter
that can be introduced into the anulus and navigated through the nucleus and
around the inner wall of the anulus. Personnel at Oratec Interventions, Inc.,
compared 36 patients treated with IDET with those treated conservatively for
chronic discogenic back pain. To be eligible for the study, patients were
required to satisfy criteria for internal disc disruption, as characterized by
the International Association for the Study of Pain, that is, pathological
findings on a discogram and evidence of a Grade III anular tear on a CT scan.
The results of that study indicated that 60% of the selected patients
experienced profound reductions in pain.

Saal and Saal showed that the IDET-treated study group (58
patients) reported a statistically significant improvement in visual analog
pain scores and in bodily pain on the SF-36 Health Survey scores after 2 years
of followup review. The IDET-treated group demonstrated improvement in physical
function, as noted by statistically significant improvements in the amount of
time the sitting position was tolerable and in the physical function SF-36
scores. Additionally, there were improvements in all SF- 36 subscales
concerning quality of life.

The use of high-frequency radio waves has proved to be efficacious
in minimally invasive spine surgery. The studies have evoked some optimism for
the use of IDET in the treatment of discogenic pain in properly selected
patients; this may help avoid or delay a spinal fusion in some patients.

Image-Guided Surgery

Since its introduction, transpedicular screw fixation has been
extensively used in various spinal disorders to promote fusion and
stabilization. Screw misplacement can lead to undesirable neurovascular
complications. Pedicle screw placement in patients with deformities carries an
even greater risk of serious complications. Weinstein and coworkers reported
perforation of the cortex due to pedicle screws in close to 20% of these cases.
To increase the accuracy of screw placement, various methods have been used to
target the pedicle more effectively with respect to the trajectory and the
depth of screw placement.

Image-guided systems are widely used in intracranial surgery and
have been adapted to assist with screw placement since the mid-1990s. The use
of image-guided systems for pedicle screw placement has improved the accuracy
of the placement. The system relies on precise localization of the pedicles by
using CT scanning. Furthermore, by replacing direct visualization with
radiographic visualization, it has enabled a reduction in sugical exposure,
duration, and blood loss. Foley, et al., described “virtual fluoroscopy”
and its successful use in various spinal procedures including pedicle screw
insertion, interbody cage placement, odontoid screw insertion, and atlantoaxial
transarticular screw fixation.

Nolte and associates described the principles of computer- assisted
pedicle screw fixation. An infrared camera (Optotrak; Northern Digital,
Waterloo, ON, Canada) was used to track specific instruments (pedicle probe,
awl, and space pointer) that were equipped with light-emitting diodes. The
dynamic reference was fixed to the spinous process of the vertebra to receive
instrumentation. Normal bone landmarks and their correlations with images
confirmed the calibration accuracy. Using that computerized system, Nolte, et
al., reported a pedicle screw misplacement rate of 4.3% under clinical
conditions. In contrast, Choi, et al. reported the use of computer-assisted
fluoroscopic targeting for pedicle screw fixation. The authors compared the
accuracy of pedicle screw placement accompanied by the fluoroscopy-guided
system with the image-guided system and observed no significant differences.

The recent development of isocentric C-arm fluoroscopy, in which CT
images are generated with the aid of an intraoperative fluoroscope, may offer
another means of three-dimensional navigation by using a two-dimensional
intraoperative imaging source. With increasing familiarity, image-guided
surgery will be a very useful adjunct to the further development of minimally
invasive surgery.

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Emerging Technologies in Spinal Motion Preservation:

A New Paradigm in Spinal Care:

“By 2011, motion
preservation technologies will achieve revenues of US$ 5.1 billion and account
for 50% of the market” Motion preservation is the hottest topic around in
spinal specialists – a sector forecast to achieve 16% growth per year till
2011. The concept of motion preservation in the spine is an intriguing one and
the array of non-fusion technologies being introduced to the market offer a
great deal of promise for spinal surgery patients.

However, despite the fact that some of these technologies have been
in use in Europe and other international markets for many years, the clinical
outcomes data available are extremely limited in proportion to the tens of
thousands of procedures performed. While this has apparently not inhibited
international growth, regulatory clearance criteria in the US are by far the
most rigorous in the world. As such, the paucity of well-designed studies to
prove the safety and effectiveness of artificial discs may hinder growth in the
US.

Despite the lack of evidence, patient demand has not been dampened.
A recent industry study of 461 prospective spine fusion patients, found that
49% would rather wait for a motion preserving implant than undergo a fusion
procedure. A further 26% are still weighing the pros and cons of the two
surgeries. Only 26% opted for the fusion procedure. Of course, owing to the
many contradictions for total disc replacement, not all patients will be
suitable candidates for the procedure. What has become clear is that for
optimal results, patient selection is critical with poor selection too often
resulting in poor outcome. For certain segments of the patient population,
traditional fusion will remain the appropriate therapy.