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INTRODUCTION
TO THORACOSCOPIC SURGERY
Introduction
Developments in scope technology have facilitated the practice of medicine
in the last 10 years and contributed to a renewed interest in endoscopic
surgery.
In 1987, Dubois et al. performed the first laparoscopic cholecystectomies
in France. The modern era of thoracoscopic surgery began in 1990, with
the addition of video monitoring to the standard endoscopic techniques.
Video-assisted thoracic surgery, or VATS, came to refer to the broad spectrum
of diagnostic and therapeutic procedures being performed thoracoscopically.
Posterior percutaneous spinal surgery for the treatment of lumbar disc
herniation has been practiced since the 1960s, with percutaneous intradiscal
chymopapein injection therapy. In the 1980s, Hajikata and Kambin popularized
manual percutaneous discectomy and automated percutaneous discectomy for
contained lumbar disc herniations. Choy and Mathews combined the intradiscal
procedures with laser technology in the late 1980s, and later percutaneous
endoscopic intradiscal and foraminoscopic discectomy techniques during
the 1990s.
Video-assisted thoracoscopic techniques to access the thoracic spine have
been successful and offer advantages over open thoracotomy for the treatment
of thoracic spinal pathology. Operating time and length of hospital stay
can be reduced and patients can return sooner to normal activities of
daily living. Postoperative pulmonary function is also less impaired,
as there is less postoperative pain with smaller incisions. There also
is reduced impairment of shoulder girdle function. Scars from the thoracoscopic
ports are more pleasing cosmetically than the larger scar associated with
an open procedure. Thoracoscopic spinal surgery can be used safely in
a number of diagnostic and therapeutic situations affecting the thoracic
spine.
There is a steep learning curve for these techniques, however, and potential
for problems when interpreting three-dimensional spatial images projected
in two dimensions on a video monitor. There also is a lack of tactile
feedback and need for proficient eye-hand coordination.
Thoracoscopic
anatomy
In most cases, the thoracic cavity is entered via the fifth or sixth
intercostal space in the anterior or mid-axillary line. Before starting
the procedure, it is important to familiar oneself with the local anatomy.
A thoracoscope passed through an anteriorly placed port will give a
panoramic view of the entire thoracic spine and posterior chest cavity.
The view and orientation on the video monitor should not be different
from the view obtained in an open thoracotomy, for the same procedure.
The anterior structures appear at the top of the screen, and the posterior
structures appear at the bottom. If the apical or basal regions of the
chest cavity are to be viewed through either a superior or inferior
port, the anatomy on the video screen will change accordingly. Familiarity
with the normal anatomy from different thoracoscope port positions is
essential for successful surgery.
Once the lung has been collapsed, the spinal column with the ribs should
be well visualized. The sympathetic trunk can be seen coursing over the
heads of the ribs, deep to the parietal pleura (see photo).
The azygos vein runs along the anterior border of the spinal column
on the right side; the descending aorta lies in a similar position on
the left. The ribs can be counted from the apical region down to the
basal areas. The diaphragm can be noted inferiorly and will have to
be retracted inferiorly and laterally to access the inferior thoracic
spine. The disc spaces correspond to the elevated areas of the spinal
column, beneath the parietal pleura. The radicular vessels lie in the
troughs between the discs over the lateral surface of the vertebral
bodies. The rib articulates with the adjacent endplates across a disc
space and overlies the pedicle as it courses posteriorly.
Anesthetic
considerations
The preoperative workup for thoracoscopic procedures is similar to the
workup for an open thoracotomy procedure. Single-lung ventilation is
essential in all thoracoscopic procedures. The presence of lung or chest-wall
pathology may be a contraindication for thoracoscopic spinal surgery.
A history of empyema or pleurodesis again will be a contraindication
for thoracoscopic spinal surgery.
Knowledge of the problems associated with the use of CO2 insufflation
is an essential anesthetic consideration. Although CO2 insufflation
is not routinely utilized in thoracoscopic surgery, it may be used occasionally
to compress air out of the isolated lung at the beginning of the procedure.
A CO2 flow rate of 1.5 to 2.0 L/minimum to a maximum pressure of 10
to 12 mm Hg maybe used when necessary to achieve maximal collapse of
the ipsilateral lung. Higher pressures in the thoracic cavity may lead
to mediastinal tamponade.
Double lumen tubes are commonly used to allow isolation of the lung
on the operative side and ventilation of the opposite lung. Alternatively,
an endobronchial tube may be used to isolate the lung. This technique
is used in young children where double lumen tubes cannot be utilized.
Postoperatively, epidural analgesia and intercostal nerve blocks are
not necessary due to reduced levels of pain, as compared to open thoracotomy.
Equipment
and instrumentation
The basic equipment required for thoracoscopic procedures include endoscopes
(zero- and 30- degree angles), xenon-light source, camera, monitors, video
recorders and CO2 insufflators.
The most commonly used telescope is the rigid-quartz lens system, with
fiber-light bundles incorporated into the shaft. The most popular are
the 10mm-diameter, zero-degree, end-viewing scopes, and the 30-degree,
angled scopes.
Light sources are high-intensity, metal halide or xenon lamps. They
operate in the range of 5600 to 6000 kelvin.
The telescopes are connected to a camera. Three-chip camera technology
now transmits truer images to the video screen. Video monitors vary
from 13 inches to 21 inches. A VCR is used for recording (S-VHS). CO2
insufflators are standard equipment in endoscopic procedures, although
not usually used in thoracoscopic procedures.
Thoracoscopic
instrumentation
These instruments can be divided into those required for soft tissue
access used in all standard endoscopic techniques with minor modifications,
and the longer spinal instruments.
Soft thoracic ports, as opposed to the hard ports, were developed to
reduce the postoperative, intercostal, neuralgic pain. To overcome the
limitations of straight instruments due to the rigid chest cavity, some
laparoscopic instruments were shortened and curved instruments were
developed.
In addition to the trocars for chest wall access, graspers, scissors,
retractors, endoscopic staplers, monopolar and bipolar cautery are available
for use with thoracoscopic procedures. Spinal instruments in the chest
are merely extended versions of the standard spinal instruments. Any
instrument, provided it is long enough, can be used, as no CO2 insufflation
is utilized with thoracoscopic spinal surgery. A standard thoracotomy
set should be available in the operating room in case of emergencies.
Patient
positioning and port placement
Patients are in the lateral decubitus position, as they are for open thoracotomy.
The patient is positioned over the "break" or the "kidney rest," so that
flexion of the table can open the intercostal spaces and facilitate entry
into the chest cavity.
Two video monitors are placed on either side of the head when working
on the mid- to upper- thoracic spine: one monitor for the surgeon and
one for the assistant. When the lower thoracic spine or the lumbar spine
is to be accessed, the monitors are placed at the foot end. The whole
chest wall is prepared and draped as for open thoracotomy; thus, if the
need arises, immediate thoracotomy can be performed.
The anesthesiologist is asked to collapse the lung during the preparation
and draping of the patient. The initial port is placed around the sixth
intercostal space in the anterior axillary line, depending on the level
of the spine to be accessed.
A
10 mm-incision is made in the chosen space, the dissection carried down
to the parietal pleura. The pleural space is entered using a kelly clamp,
a finger is placed through this opening to lyse any lung adhesions before
introducing the trocar. The scope is placed via this port and should provide
a panoramic view of the spinal column.
Subsequent port placements are done under direct vision. The access ports
should be placed in the anterior axillary line on either side of the projected
target. The ports are placed such that they are not too close to the target,
thus allowing a panoramic view of the region of the target. These ports
should not be placed too close together, or the instruments will tend
to duel with each other within the chest cavity. The number of ports and
their location will depend on the procedure and the level of the pathology.
Typically, one can start with a zero-degree, angled scope and switch to
a 30-degree scope when working on the spine. Additional working ports
maybe be placed posteriorly as required, and also one directly over the
site of the pathology for drilling.
Thoracoscopic
discectomy
Large central or calcific disc herniations requiring an antero-lateral
thoracotomy approach can be accessed thoracoscopically. The patient is
in the lateral decubitus position. A right-sided approach is preferred,
unless the pathology dictates otherwise. The patient's pelvis and shoulders
are taped to the table. The axillary lines and sites for port placement
are marked on the patient. The chest is prepared and draped, as for a
thoracotomy. The initial port is placed in the anterior axillary line.
The intercostal space selected will depend on the level of the disc herniation.
The ipsilateral lung is collapsed. A 10 mm-incision is made in the skin
down to the intercostal muscle layer. A kelly clamp is used to separate
the muscles down to the parietal pleura. The clamp is pushed gently into
the pleural cavity after ascertaining that the ipsilateral lung is collapsed
and opened.
A finger is next passed into the pleural cavity and any lung adhesions
lysed. A soft thoracoport is placed into the chest cavity and, the zero-degree
scope is passed into the cavity. A panoramic view of the chest cavity
is obtained.
At
this point, the remaining ports are placed under direct vision. Typically,
three ports are used: two in the anterior axillary line on either side
of the target, and a third inferiorly in the posterior axillary line.
The disc space to be operated on is identified by counting the ribs from
the apex downward within the cavity; the highest rib that can be visualized
from within the chest cavity is the second rib. Once a level is identified,
a long, spinal needle is passed percutaneously into the disc space under
direct vision, and a cross-table, A-P x-ray is obtained to confirm the
level.
Once the level is identified, the parietal pleura over the disc space
and corresponding rib are opened with the bovie, hooked to one of the
dissecting instruments. The intercostal vessels over the adjacent bodies
are identified, clipped and divided. The periosteum of the rib is scraped
off protecting the neurovascular bundle, and the rib is divided three
centimeters distal to its head, using a high-speed drill or an osteotome
and mallet. The head of the rib is separated from its attachment to the
vertebral body and adjacent endplates, and the rib removed in one piece.
Next, the soft tissue overlying the pedicle is coagulated with the bipolar,
thus identifying the lateral surface of the pedicle. The kerrison punch
is used to remove the pedicle from rostral to caudal, identifying the
lateral surface of the dura. At this point, the margins of the endplate,
adjacent to the identified disc space, is removed with the kerrison punch,
exposing the disc and the posterior longitudinal ligament, and finally
the ventral epidural space. The disc is gently freed from the dura decompressing
the cord.
A
fourth port may be necessary, directly over the disc space for drilling.
A drill can be used to create a trough behind the disc space to facilitate
this process. Hemostasis is achieved with thrombin-soaked gel foam and
bipolar coagulation. The piece of rib removed earlier can be used in the
vertebral-body trough to achieve a fusion. A chest tube is placed via
one of the ports and guided to the appropriate position in the chest cavity,
as needed. The ports are closed after achieving hemostasis and injecting
0.5 percent marcaine in the wound, with subcuticular sutures.
Contraindications
to thoracoscopic spinal surgery
All patients considered for thoracoscopic spinal surgery should be evaluated
for previous and present pulmonary and chest wall pathology. Patients
with a history of previous thoracotomy, empyema and pleurodesis on the
ipsilateral side run a significantly higher risk of lung injury and
should be excluded. Some relative contraindications are previous ipsilateral
thoracoscopy, severe COPD and under five years of age.
Problems and complications
Common problems encountered with thoracoscopic surgery include trocar-site
bleeding and, as a result, bleeding on the endoscopic lens. This can
be prevented by atraumatic placement of the ports, staying above the
lower rib, away from the neurovascular bundle, and by adequate coagulation
of the trocar-site bleeding when encountered. Fogging of the lens is
encountered because of the difference in the ambient and intrathoracic
temperatures. It can be reduced by cleaning the lens frequently with
a defogger (Fred) and keeping the scope in a warm, saline bath.
Duelling instruments occurs when ports are placed too close together.
Careful planning and spacing of the ports using the "baseball-diamond
principle" will eliminate this problem. Evaluate patients preoperatively
for intrathoracic pathology to avoid problems during surgery. Paralytic
hemidiaphragm should be recognized prior to surgery, to avoid placing
the initial trocar through the diaphragm. Preoperative chest x-rays
will help to localize the level of the dome of the diaphragm. Identify
and localize the level of the pathology by counting the ribs from the
apex down with the scope and subsequently obtaining intraoperative cross-table
x-rays with a percutaneously placed needle in the disc space.
Epidural bleeding, when it occurs, can be dealt with using bipolar coagulation,
tamponaded by packing with thrombin-soaked gel foam and endo-avitene.
Dural tears are difficult to control thoracoscopically. Small tears
may be packed with gel foam, layered with fibrin glue and fat graft.
Larger tears, however, may have to be dealt with by converting to an
open thoracotomy.
Injury to the spinal cord is avoided by removing the head and neck of
the rib and the underlying pedicle to identify the dural tube at the
outset, before embarking on disc removal. Use of SSEP monitoring in
all patients, with or without preoperative spinal cord compression,
is recommended.
Finally, injury to large arteries and veins in the thoracic cavity,
should they occur, can be tamponaded initially with a four-inch by four-inch
sponge and, if unable to control, open the chest to arrest the bleeding.
Always work with an experienced thoracic surgeon who will be available
in an emergency. A standard thoracotomy set should be in the room and
immediately available.
Thoracic tumors
The ideal tumors for endoscopic transthoracic resection are those located
paravertebrally, with or without an extension through the foramen into
the spinal canal (dumbell tumors - Schwannoma, Neurofibroma).
Resection of such tumors is indicated to prevent spinal cord compression,
malignant transformation and for tissue diagnosis. In the past, these
tumors required a thoracotomy for their removal. Dr. Perin has utilized
thoracoscopic techniques to remove such tumors. When there is a tumor
component within the spinal canal, as occurs in a dumbell schwannoma,
he combines a posterior hemilaminectomy to resect the intra-spinal component
and release the tumor from all neural elements.
Next,
a thoracoscopy is performed utilizing three or four two-centimeter ports
to remove the remaining tumor in the chest cavity, which has already been
released via the posterior approach described. The larger tumors removed
are placed in a specimen pouch (cinch bags), morselized and removed gradually
before they are of a sufficient size to be pulled out of the chest via
one of the ports. This approach reduces postoperative pain, shortens hospital
stay and reduces impairment of chest wall and shoulder girdle muscles
that would occur after open thoracotomy approaches.
Thoracoscopy also is suited for the treatment of metastatic tumors to
the thoracic spine, requiring open thoracotomy. These tumors can be removed
endoscopically, decompressing the spinal cord, followed by stabilization.
The bone graft or metallic cage can be placed in the vertebrectomy defect
and a plate placed endoscopically, or via a subsequent operation, posteriorly.
Biopsy
of spinal lesions/osteomyelitis
In most instances, infections and tumors of the thoracic spine can be
biopsied and treated endoscopically with minimal postoperative pain and
disability, as opposed to open techniques. Disc space infections and osteomyelitis
can be treated endoscopically by debriding the dead and infected material
followed by the placement of bone graft and instrumentation where appropriate,
without resorting to a thoracotomy.
Anterior
release in scoliosis surgery
In young patients with a rigid scoliosis, an anterior release followed
by posterior reduction with instrumentation and fusion is advised. The
anterior release is usually done by opening the chest widely (thoracotomy).
Dr. Perin has performed this anterior release and interbody bone grafting
using thoracoscopic techniques successfully, thus reducing the postoperative
pain and shoulder girdle muscle disability.
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Laparoscopic
lumbar interbody fusion
Anterior
lumbar interbody fusions at L5-S1 and L 4-5 can be performed when indicated
using minimally invasive techniques, resulting in reduced post-operative
pain and disability. The access to the anterior lumbar disc spaces is
achieved by the laparoscopic surgeon, the discectomy followed by the placement
of cages or bone dowels with fusion is achieved by the neurosurgeon. Patients
with discogenic back pain and instability, with anterolisthesis of grade
1 or less are suitable candidates for this technique.
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Spine and spinal cord injury
Acute spinal cord injury following motor vehicle accidents or falls afflicts
a substantial number of young, active adults. Early, aggressive treatment
using pharmacological agents to reduce the effects of secondary injuries
after the initial trauma helps improve long-term outcomes. In addition,
early surgery to relieve ongoing pressure on the spinal cord and stabilization
of the spine, when it is unstable, allows for maximal recovery of function.
Dr. Perin has successfully treated several hundred patients acutely and
sub-acutely, depending on their time of presentation, with phamacological
agents and surgery. This early, aggressive treatment achieves excellent,
long-term recovery of function, making a quick transition to rehabilitation
possible.
Vertebroplasty
Percutaneous trans-pedicular injection of bone cement(methyl methcrylate)
into the vetebral body. Patients with osteoporotic fractures, tumors such
as hemangiomas, myelomas and metastatic tumors with intractable pain not
relieved by conservative treatments, without neural compression in the
thoracic and lumbar spine will be candidates for this procedure. This
technique is especially useful in elderly patients with intractable pain
related to osteoporotic fractures not responding to standard treatments.
This is a relatively safe yet very effective technique and affords immediate
relief of pain.
Spine
and spinal cord tumors
Both primary and secondary tumors of the spine can lead to pain and neurological
deficits. Early diagnosis and appropriate treatment can allow patients
a cure in most cases. At St. Luke's-Roosevelt Hospital Center, a variety
of primary and secondary tumors of the spine have been treated with excellent
results. Patients undergo appropriate staging of tumors with MRI, CT scans,
bone scans and angiography.
In vascular tumors, preoperative embolization is used to reduce the
vascularity of the tumor. Aggressive surgical intervention is used with
physiologic monitoring of the motor and sensory evoked potentials to
minimize injury to the spinal cord. Gross, total removal of a visible
tumor can be achieved in a large number of patients. Patients undergo
stabilization of the spine with titanium implants. These implants are
placed with computer image guidance to improve accuracy and the reduce
risk of neural injury.
Spinal cord tumors initially present with pain, followed by neurological
symptoms. These tumors are usually benign and slow growing. The common
adult tumor is an ependymoma and in most instances can be removed completely
to achieve a cure. Many of these tumors have been treated successfully
at St. Luke's-Roosevelt Hospital Center with intra-operative motor and
sensory-evoked potential monitoring.
Degenerative
disorders of the cervical and lumbar spine
(disc herniation, stenosis, pondylolysis, pondylolisthesis)
Most adults experience neck and lower-back pain at some time in their
lives. Cervical and lumbar disc herniations account for the majority of
these complaints. Most of these patients are treated conservatively with
anti-inflammatory medications and physical therapy. Patients who do not
respond to these treatments are investigated with MRI, CT scans, etc.,
and are considered for surgical treatment. Patients with neurological
deficits are considered for surgical intervention earlier.
Spinal
instrumentation
Instability in the spine can follow trauma, destruction by a tumor or
be caused by congenital disorders or degenerative, inflammatory and infective
processes. These patients require stabilization after undergoing treatment
for the primary pathology. Dr. Perin and his team have successfully treated
several hundreds of patients with instability from the occipito-cervical
through the cervical, thoracic lumbar and sacral regions. All patients
undergo monitoring of motor and sensory-evoked potentials during instrumentation
to reduce risk of injury to the spinal cord. Pedicle screws in the thoracic
and lumbar spine are placed utilizing stealth computer image guidance
to reduce the risk of nerve-root injury and achieve superior results.
Spine
teaching programs (research)
The spinal cord injury laboratory at St. Luke's-Roosevelt Hospital Center
carries out research activities in spinal cord injury in animal models.
Several pharmacological agents are used to reduce the secondary cascade
of events that normally occurs after a spinal cord injury, and thus
improves outcomes. Dr. Perin's team also is involved with many clinical
studies in the spine using bone-growth factors to improve bone fusion.
They also participate in a national study to evaluate outcomes after
lumbar discectomy.