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CHAPTER 19/SURGICAL APPROACHES TO THE THORACOLUMBAR SPINE / 213
C
FIG. 19-3. (continued).
pedicle are resected, this approach offers better visualization of the anterolateral spinal canal during decompression, although it may be associated with a great deal of
bleeding (1,4,5).
Anterior Anatomy
Anterior approaches to the thoracolumbar junction
require a solid understanding of the associated anatomy
of the chest and abdominal walls, the diaphragm, and the
retroperitoneal contents. Within the chest wall, the ribs
articulate with the spine at the level of the disc space
above (e.g., the 9th rib articulates at the level of the T8-9
disc space) and the transverse process of the same level.
Caudally, the 11th and 12th ribs lack costotransverse
articulations. The ribs are stabilized by a number of
strong ligamentous attachments, particularly the costovertebral and costotransverse ligaments (Fig. 19-5).
The superior costotransverse ligament runs from the inferior aspect of the transverse process to the superior aspect
of the rib below. The medial (capsular) ligament attaches
the posterior neck of the rib to the anterior border of the
FIG. 19-4. Patient positioning in the kneeling
posture on an Andrews table. Note the rolls
allowing for decompression of the abdominal
contents, which decreases intraoperative
blood loss. Alternatively, the patient may be
placed on a posted frame. (From Albert TJ,
Balderston RA, Northrup BE, eds. Surgical
approaches to the spine. Philadelphia: WB
Saunders, 1997, with permission.)
214 /SECTION IV/SURGERY
FIG. 19-5. Ligaments stabilizing the r ibs. A: Axial view. B: Sagittal view. (From Albert TJ, Balderston
RA, Northrup BE, eds. Surgical approaches to the spine. Philadelphia: WB Saunders, 1997, with permission.)
transverse process. The lateral costotransverse ligament
connects the posterior tubercle of the rib to the tip of the
transverse process. The anterior costotransverse (radiate)
ligament connects the head of the rib to its respective vertebral body. The intercostal neurovascular bundle runs
along the inferior surface of the rib in the costal groove.
The endothoracic fascia lies deep to the intercostal muscles. Beneath this lies the pleura, which extends to the
10th rib in the midaxillary line and to T12 or L1 in the
midline posteriorly (6).
The muscles of the anterior abdominal wall represent a
continuation of the layers of the intercostal muscles, with
the external, internal, and innermost intercostals muscles
continuing as the external oblique, internal oblique, and
transversus abdominus muscles, respectively. The transversalis fascia, which lies deep to the transversus aponeurosis, represents the abdominal equivalent of the endothoracic fascia and adheres loosely to the parietal
peritoneum.
The diaphragm attaches anterolaterally to the lo wer six
costal cartilages, lower four ribs, xiphoid process, and the
thoracolumbar vertebral bodies posteriorly. The crura of
the diaphragm insert on the lumbar spine between L1 and
L3, and the aorta passes through the crura at the T12
level. The medial arcuate ligament spans the psoas muscle at L1 or L2, and the lateral arcuate ligament bridges
the quadratus lumborum from the transverse process of
L1 to the 12th rib (Fig. 19-6) (6).
CHAPTER 19/SURGICAL APPROACHES TO THE THORACOLUMBAR SPINE / 215
anterior surface in the lower lumbar region. The sympathetic trunk lies anterior to the psoas along its junction
with the spinal column and may need to be divided (unilaterally) during an anterior approach.
The retroperitoneal space contains the kidneys, adrenal
glands, and the ureters, which course inferomedially
along the ventral aspect of the psoas toward the bladder
between the peritoneum and the psoas fascia. Because the
ureters adhere loosely to the peritoneum, they are usually
safely retracted with the peritoneum and its contents during anterior surgical approaches.
FIG. 19-6. The crura and arcuate ligaments of the diaphragm’s insertion on the posterior abdominal wall.(Modified
from Birch BD, Desai RD, McCormick PC. Surgical approaches to the thoracolumbar spine. Neurosurg Clin 1997;8
(4):471–485.)
Vascular structures encountered in the anterior
approach include the aorta, diaphragmatic arteries, celiac
trunk, superior renal artery, and the left renal artery on
the left and the inferior vena cava on the right. The aorta
is essentially tethered to the spine by the segmental arteries, which run toward their respective foramina. The
artery of Adamkiewicz usually arises from the aorta in
the lower thoracic or upper lumbar level along the left
side (3).
The ilioinguinal and iliohypogastric nerves course
inferolaterally over the quadratus. The genitofemoral
nerve emerges from the body of the psoas, lying on its
Surgical Technique
The spine is usually approached from the left side,
since it is much easier to mobilize the aorta than the vena
cava. The patient should be positioned in the lateral position with the area of interest over the break in the table.
An axillary roll and sufficient padding should be used to
prevent neurovascular compression injuries (Fig. 19-7).
The patient may be rolled slightly posteriorly by 45° to
60° (1,3,5).
At our institution, we prefer the transpleural retroperitoneal approach. The incision is made over the rib one or
two levels proximal to the level of spinal pathology. The
incision extends anteroinferiorly from just lateral to the
paravertebral musculature over the rib (10th, 11th or
12th), tow ard the anterior superior iliac spine. The subcutaneous tissue and musculature are divided with electrocautery to help control bleeding. The periosteum of the
rib is then dissected free, taking care to preserve the intercostal neurov ascular bundle inferior to the rib . After stripping the periosteum from the rib to within 1 or 2 cm of
the costotransverse joint, the rib is resected using rib cut-
FIG. 19-7. Patient positioning for the
anterior approach to the thoracolumbar spine. The level of interest should
be placed over the break in the table
and the incision should be made over
the rib two levels above the level of
interest in the midaxillary line. (From
Albert TJ, Balderston RA, Northrup
BE, eds. Surgical approaches to the
spine. Philadelphia: WB Saunders,
1997, with permission.)
216 /SECTION IV/SURGERY
ters and is saved for possible future bone grafting (Fig.
19-8). The pleura is then incised (3–5).
The diaphragm may be released from its lateral insertions in the thoracoabdominal wall (Fig. 19-9). The peritoneum is then gently mobilized away from the posterior
abdominal wall with blunt dissection. Dissection of the
diaphragm then proceeds medially, elevating the medial
and lateral arcuate ligaments from the underlying musculature. The medial attachment of the lateral arcuate ligament and the lateral attachment of the medial arcuate ligament are divided at their insertion on the L1 transverse
process, taking care to retain sufficient tissue to permit
reattachment of the diaphragm. Finally, the left cr us of
the diaphragm is divided approximately 2 cm from the
vertebral body, allo wing communication between the thoracic and abdominal cavities (1,4–6).
The lung is then retracted medially along with the
diaphragm and peritoneum. The intercostal and lumbar
vessels should be ligated close to the aorta to mobilize the
great vessels (3). Elevation of the psoas muscle laterally
to the pedicles allows for adequate exposure of lumbar
segments. Occasionally, the sympathetic chain, which
lies along the anterior spine, may need to be transected
during this approach. If this is done, the patient should be
told that the foot on the side of the sympathetectomy will
become warmer (5). The periosteum of the v ertebral body
is incised and dissected away. Care is taken not to cauter-
FIG. 19-9. Line of incision to detach the diaphragm from the
posterior and lateral abdominal wall. One should leave a cuff
of approximately 1 cm for reattachment. (From Albert TJ,
Balderston RA, Northrup BE, eds. Surgical approaches to
the spine. Philadelphia: WB Saunders, 1997, with permission.)
FIG. 19-8. Removal of the rib 1 to 2 cm distal to the costotransverse joint. (From Albert TJ, Balderston RA, Northrup
BE, eds. Surgical approaches to the spine. Philadelphia: WB
Saunders, 1997, with permission.)
ize blood vessels around the intervertebral foramen. Once
exposed, decompression and stabilization may be performed (Fig. 19-10).
Closure begins with reattachment of the diaphragm to
the psoas, L1 transverse process, quadratus, and the cuff
of tissue remaining along the anterior and lateral chest
wall from which it was initially dissected. A chest tube
and retroperitoneal drain are inserted, and the abdominal
and chest walls are then closed in layers.
A retropleural retroperitoneal approach may also be
used to expose the thoracolumbar spine (1,5,6). This
approach is similar to the one described previously, with
the incision made along the rib, two levels above the
spinal pathology, from the paraspinal muscles to the
midaxillary line. The rib that crosses the midaxillary line
on the lateral chest radiograph should be resected. The rib
is dissected subperiosteally and removed, taking care not
to damage the underlying pleura. The endothoracic fascia, which lies deep to the rib periosteum, may then be
incised with scissors in line with the incision. The parietal
pleura is then carefully freed from this fascial layer by
blunt dissection with either a finger or a sponge on forceps beginning anteriorly and progressing posteriorly.
CHAPTER 19/SURGICAL APPROACHES TO THE THORACOLUMBAR SPINE / 217
FIG. 19-10. Axial section demonstrating the anterior retroperitoneal exposure of the thoracolumbar
spine. The lungs and abdominal contents are retracted medially, providing excellent exposure. (From
Albert TJ, Balderston RA, Northrup BE, eds. Surgical approaches to the spine. Philadelphia: WB Saunders, 1997, with permission.)
The abdominal muscles are divided and the peritoneum is carefully mobilized. The costal cartilage may
then be divided allowing the peritoneum and abdominal
contents to be swept laterally from the undersurface of
the diaphragm. The diaphragm is then incised, leaving a 1
cm cuff of tissue for reattachment. The vertebral column
is then approached as described earlier. The diaphragm is
reattached, and if the pleura was violated during the
approach, a chest tube should be placed at the time of closure.
Complications associated with the anterior approach
include vascular and visceral injuries, chyle leak, dural
tears, neurologic injury, and hernias (1,5). At our institution, somatosensory evoked potentials (SEP) and motor
evoked potentials (MEP) are routinely used. Blood loss is
best controlled by carefully cauterizing or ligating small
bleeding vessels during the approach. Bone wax or
Gelfoam pledgets may be used for dissection adjacent to
the neural elements; as monopolar electrocautery should
be avoided here, only bipolar cautery should be used. A
thorough knowledge of anatomy is the key to identifying
and ligating blood vessels (especially veins) during this
approach.
A dural tear may occur during decompression. Anterior dural tears are difficult to repair, and may be treated
alternatively by application of Gelfoam. Direct suturing
of the tear or application of fat or muscle patches may
also be tried. Additionally, placement of a subarachnoid
drain may be considered if closure cannot be obtained.
As mentioned previously, the sympathetic chain is
often sacrificed or injured during the anterior approach
with no long-term effects. Patients must be forewarned,
however, that a temperature difference between the limbs
may be experienced, with the leg on the sympathectomized side feeling warmer.
Finally, because the diaphragm is incised for this
approach, care must be taken to securely reattach it to the
chest wall to avoid herniation of abdominal contents into
the thoracic cavity. Postoperative pulmonary toilet must
be employed, and close attention should be paid to chest
tube protocol if one is used.
COMBINED ANTERIOR AND POSTERIOR
APPROACH
Occasionally, the degree and complexity of pathology
is best treated with a combined anterior and posterior
approach. This is most often used for tumorous or traumatic injuries resulting in three-column instability and
neural compression. The sequence of the surgical
approach—anterior followed by posterior, posterior followed by anterior, or simultaneous—depends upon the
pathology and the patient, and should therefore be determined on a case-by-case basis (7).
An anterior, followed by a posterior, procedure is useful in situations where the use of anterior instrumentation
is contraindicated, or w hen anterior instrumentation alone
may not adequately stabilize the spine, but the coronal
218 /SECTION IV/SURGERY
alignment of the spine is satisfactory. In these instances,
an anterior decompression and fusion is followed by a
posterior stabilization procedure. For deformity surgery,
the anterior approach is generally done to decompress
and release a kyphotic deformity with the use of structural graft for fusion. Additional correction may be
attempted by the posterior procedure.
A posterior, followed by an anterior, procedure may be
indicated in patients with significantly displaced fracture
dislocations. The initial posterior procedure restores
realignment of the spine in the coronal and sagittal
planes. In patients with loss of anterior column support,
an anterior procedure may be necessary. Finally, the posterior reduction and decompression may not adequately
decompress the spinal canal, in which case an anterior
procedure should also be performed.
The inherent instability of injuries requiring combined
anterior and posterior procedures increases the risk of complications. Careful electrophysiological monitoring can help
avoid intraoperative neurologic injuries. Blood loss is
increased in these combined procedures due to the extended
operative time needed. An operating table which allows
axial rotation of the patient’s body without the need for repositioning can help decrease the potential for complications
by reducing procedure time as well as a v oiding any potential
injuries which may occur from patient movement (7).
REFERENCES
1. Kostuik JP. Surgical approaches to the thoracic and thoracolumbar
spine. In: Frymoyer JW, Ducker TB, Hadler NM, et al., eds. The adult
spine: principles and practice, 2nd ed. Philadelphia: Lippincott-Raven,
1997:1437–1470.
2. Kramer DL, Booth RE, Albert TJ, et al. Posterior lumbar approach. In:
Albert TJ, Balderston RA, Northr up BE, eds. Surgical approaches to
the spine. Philadelphia: WB Saunders, 1997:173–192.
3. Hoppenfeld S, de Boer P. The spine. In: Hoppenfeld S, de Boer P, eds.
Surgical exposures in orthopaedics: the anatomic approach, 2nd ed.
Philadelphia: JB Lippincott Co, 1994: 215–301.
4. Adams PR, Cotler HB. Alternative anterior lumbar exposures. In:
Albert TJ, Balderston RA, Northr up BE, eds. Surgical approaches to
the spine. Philadelphia: WB Saunders, 1997:157–172.
5. Emery SE. Anterior retroperitoneal lumbar exposures. In: Albert TJ,
Balderston RA, Northrup BE, eds. Surgical approaches to the spine.
Philadelphia: WB Saunders, 1997:145–156.
6. Birch BD, Desai RD, McCormack PC. Surgical approaches to the thoracolumbar spine. Neurosurg Clin North Am 1997;8:471–485.
7. Vaccaro AR. Combined anterior and posterior surgery for fractures of
the thoracolumbar spine. Instr Course Lect 1999;48:443–449.
CHAPTER 20
Surgical Approaches to the Lumbar Spine: Anterior and Posterior
Anthony P. Dwyer
This chapter discusses the surgical anatomy of the anterior and posterior approaches to the lumbar spine, including the advantages, disadvantages, risks, and complications of each approach. It does not discuss specific
anatomic detail, which can be revie w ed in man y e xcellent
surgical anatomy textbooks (1–5).
Surgical anatomy consists of surface anatomy, radiologic anatomy, and the surgical approach anatomy (4,6).
There must be an understanding of the principle of the
internervous plane and the steps to expand the approach
of surgical dissection (7). Such anatomic knowledge
helps the surgeon anticipate the complications of each
approach and assists in potential disaster planning, such
as injury to a major vessel, the spinal cord, nerves, or viscera.
Finally, it is important to remember the principles of all
surgical approaches (4).
1. Each surgical layer must expose the margins of the
wound.
2. Exposure of each surgical layer must be completed
before the next layer is exposed.
These principles avoid a conical e xposure, w hereby the
exposure is narrow with deeper dissection.
The decision to use the anterior or posterior approach to
the lumbar spine is based on the site of the pathology and
the best approach to that pathology afforded by each. It is
also important to know and understand the vital structures
that are encountered with each approach. Each pathology
must be considered, as well as its location. Such pathologies include: coronal or sagittal deformity, neurologic
compression, infection, primary and metastatic tumors,
nonunion, and instability of the spinal column.
The surgical management of these pathologies must be
easily and safely attainable with the selective surgical
approach.
There are general indications, contraindications, and
specific risks for each approach. Ideally the lumbar spine
should be approached from the left side because the arterial structures are more resistant to surgical trauma than
are venous structures, but a right-sided retroperitoneal
approach can be used if it there has been a previous leftsided approach, which may produce significant scarring
and fibrosis. Other examples of conditions that might
alter the choice of surgical approach include: excessive
subcutaneous fibrosis following burns or radiation therapy that prevent a safe posterior approach to the lumbar
spine, or the potential for an anterior approach to the lumbar spine to cause retrograde ejaculation from damage to
the hypogastric plexus (8).
Each surgical approach has its own adv antages and disadvantages, and at times both must be used in a single
stage (9). For e xample, the anterior approach may require
the presence of a general or vascular surgeon, but the
reduced surgical trauma associated with the minimized
muscular cutting of the new approaches may result in a
shorter hospital stay and quicker rehabilitation. On the
other hand, the posterior approach is more common and
routine, but is associated with more surgical trauma from
ischemia and denervation of the muscles. In addition, the
prone position may be associated with cardiopulmonary
problems in the older patient, injury to the peripheral
nerves, and ophthalmic complications.
ANTERIOR SURGICAL APPRO A CH T O THE
LUMBAR SPINE
This discussion covers the retroperitoneal approach to
the lumbar spine, as popularized by Hodgson and others
(10–12). Both the antero-lateral approach (with the
patient in the lateral or semilateral position), and the
direct anterior midline approach (via the rectus abdomi-
219
220 /SECTION IV/SURGERY
nus muscle and the transversalis fascia muscle, with the
patient in the supine position) are discussed. This section
does not cover the transperitoneal approach to the lumbar
spine, because this is generally used only for exposure of
the lumbosacral junction and is discussed in a separate
section.
The retroperitoneal approach to the lumbar spine has
the advantage of being readily expanded to provide
access to the anterior and middle columns of the lumbar
spine. Also, it allows ready access to the vertebral bodies,
the annulus and intervertebral disc, the anterior aspects of
the transverse process and lateral pedicle, the neural foramen, and the anterial epidural space.
It is useful for surgical access for vertebral body and
disc space infection, primary and secondary tumors,
decompression of the vertebral canal from anterior
pathology, correction of lumbar deformity, reconstruction
of the anterior column, and stabilization and fusion of a
symptomatic unstable segment.
DIRECT ANTERIOR APPRO A CH
Surface and Radiologic Anatomy
The surface landmarks for the anterior approach to the
lumbar spine consist of the iliac crest, anterior superior
iliac spine, pubic symphysis, the coastal margin and the
umbilicus (6).
In a thin patient the lumbar sacral junction and the
aorta can be readily palpable through the midline.
The surface anatomic landmarks need to be compared
with a careful study of the antero-posterior (AP) and lateral views of the lumbar spine, noting the relationship
between anatomic landmarks and X-ra y anatomy in order
to properly plan the skin incision and surgical approach.
Usually the intercristal line on top of the iliac crest
passes through the L4-5 disc, but this varies among individuals and may be altered with lumbosacral anomalies
such as sacralization of the fifth lumbar vertebrae or lumbarization of the sacrum.
Inadvertent operating at the wrong level of the lumbar
spine may be prevented by “signing your site” and confirming the specific level with intraoperative X-rays.
Patient Position
tion with the upper extremities partially abducted. Compression stockings to the lower extremities should be
used and an indwelling urinary catheter inserted.
Incision
There are four choices for the skin incision:
1. Horizontal paramedian
2. Vertical paramedian (Fig. 20-1)
3. Pfannenstiel or horizontal incision above the pubic
symphysis
4. Oblique
The horizontal and vertical paramedian incisions are
most commonly used. The Pfannenstiel incision may be
used for cosmetic reasons and the oblique incision is
rarely used for the direct anterior approach because the
anatomy is the same as in the antero-lateral approach.
The level of a transverse incision depends on the specific level of pathology. As mentioned, the surface and
radiologic anatomy need to be cor related with each other
to make sure that the intercristal line does indeed go
through the L4-5 disc. With that determined, the L3-4
disc generally is at the lev el of the umbilicus, and the L5S1 disc is usually halfway between the umbilicus and
pubic symphysis.
Access to more than two lumbar le vels usuall y requires
the use of a vertical paramedian decision, with the length
determined by the specific number of levels required.
Access is through the rectus-abdominus muscle to the
posterior rectus sheath above the arcuate line, or b y mobilization of the rectus laterally. Incision of the anterior rectus sheath in line with the skin incision or it can be
enlarged by making a vertical incision at both its medial
and lateral margins as described by Henderson (8) and
Fraser (13,14). The specif ics of this are described in the
following.
Incision
bone
graft
Incision L4-L5 disc
For the direct anterior approach to the lumbar spine,
the patient is positioned in the supine position with a
padded support under the prominence of the sacrum and
the lumbar spine centered over the break in a radiolucent
operating table to allow for adjustment in the degree of
extension of the lumbar spine. The direct anterior
approach is ideal for an average-sized patient but a large
patient may require the antero-lateral approach to allow
the abdominal contents to convenientl y fall a wa y from the
lumbar spine. The head and neck are in the neutral posi-
Incision L5-S1 disc
FIG. 20-1. Vertical paramedian incisions. (Modified from
Henderson, RJ. Anterior approach for lumbar fusions and
associated morbidity. In: Spine care. St. Louis: Mosby,
1995:1112–1134, with permission.)
CHAPTER 20/SURGICAL APPROACHES TO THE LUMBAR SPINE / 221
Surgical Anatomy
The key muscle in the direct anterior approach is the
rectus abdominus with its anterior and posterior sheaths
above the arcuate line. Division of the anterior rectus
sheath exposes the rectus muscle (Fig. 20-2). The underlying transversalis fascia is defined and carefully incised
to gain entry into the retroperitoneal space. The peritoneal fat is gently freed with a finger from the transversalis fascia. The freed peritoneum, with its contents, is
retracted medially (Fig. 20-3). The psoas is encountered
posteriorly and medially with the genitofemoral nerve
located on its surface and the sympathetic trunk located
medially.
The ureter is identified by its peristaltic movements
and accompanying blood vessels. The ureter usually stays
with the posterior peritoneum as it is moved forward. The
major blood vessels are identified: the aorta and common
iliac and iliac arteries anteriorly and to the left of the corresponding veins.
The left iliolumbar vein may have several different
configurations and should be doubly ligated before it is
incised and mobilized (Fig. 20-4) (2).
The presence of the hypogastric plexus coming off the
aorta can be at risk of damage as it courses over the anterior aspect of the lumbosacral disc (Fig. 20-5). Electrocautery should not be used in this area in males in order
to avoid damage to the hypogastric plexus, which could
result in retrograde ejaculation.
Contraindications and Disadvantages of the Anterior
Approach
Contraindications to the direct anterior approach to the
lower lumbar spine include the presence of pathology in
Linea alba
Peritoneum
Inferior
vena cava
FIG. 20-3. Direct retroperitoneal approach. (Modified from
Nakano N, Nakano T. Anterior extraperitoneal lumbar discectomy without fusion. In: The lumbar spine. Philadelphia:
WB Saunders, 1990:987–989, with permission.)
Rectus abdominis
Abdominal
aorta
the posterior column, and situations where the anatomy
does not allow safe access to the anterior and middle
columns. This includes low bifurcation of the aorta that
may prevent safe access to the L5-S1 or L4-5 disc or the
presence of significant retroperitoneal scarring from previous surgeries.
Disadvantages include the technical challenges of dissecting and manipulating major arteries and veins;
namely, the iliolumbar vein, vena cava, common iliac
vein, and accompanying arteries.
As indicated, the arterial structures are more resistant
to manipulation than veins, so the approach to and the
Posterior lamina
of sheath of
rectus abdominis
Arcuate line
FIG. 20-2. Rectus abdominis. (Modified from Nakano N,
Nakano T. Anterior extraperitoneal lumbar discectomy without fusion. In: The lumbar spine. Philadelphia:WB Saunders,
1990:987–989, with permission.)
Truncus
sympatheticus
Lumbar artery
and vein (ligated)
L4 - L5
disc
Iliolumbar vein
(ligated)
FIG. 20-4. Retroperitoneal str uctures at the L4-5 disc level.
(Modified from Henderson, RJ. Anterior approach for lumbar
fusions and associated morbidity. In: Spine care. St. Louis:
Mosby, 1995:1112–1134, with permission.)
222 /SECTION IV/SURGERY
Aorta
Vena Cava
L5-S1
disc
Truncus sympatheticus
Ureter
Superior
hypogastric plexus
dissection of the lower lumbar spine should be done from
the left. This approach also minimizes the potential damage to hypogastric ple xus over the lumbosacral disc, minimizes the risk of injury to the ureter and the genitofemoral nerve and other nerves that lie within and on
the psoas muscle.
The surgeon should be aware that anterior and lateral
vertebral osteophytes can cause adherence of venous
structures to the spine and make their dissection and
manipulation difficult and dangerous because of the
potential of injuring one of the veins. The assistance of an
experienced vascular surgeon is invaluable to minimize
this occurrence and help manage it if it occurs.
FIG. 20-5. Hypogastric plexus, vessels, and ureter.
(Modified from Henderson, RJ. Anterior approach
for lumbar fusions and associated morbidity. In:
Spine care. St. Louis: Mosby, 1995:1112–1134,
with permission.)
Once the patient is properly positioned, a beanbag is
inflated to provide support. The bean bag must not come
higher than the umbilicus anteriorly and the spinous
process posteriorly in order to avoid limitation of the surgical exposure. The patient is secured with strapping
around the shoulders and over the greater trochanter, to
stabilize the patient when the table is rotated.
It is very important to keep the posterior cortex on the
vertebra in a direct vertical alignment when decompressing the spine anteriorly in order to avoid disorientation
and potential neural injury by penetration through the
posterior cortical wall into the anterior epidural space of
the vertebral canal.
ANTEROLATERAL APPROACH
Indications for the anterolateral approach are similar to
those for the direct anterior approach. It is particularly
helpful in the obese patient, where the lateral decubitus
position permits the viscera and abdominal wall to fall
out of the way.
Patient Position
The patient is positioned in the decubitus position with
the left side up over a beanbag on a radiolucent operating
table. The patient must be positioned o v er the break in the
table so that flexion of the table will permit lateral flexion of the patient. This lateral flexion increases the interval among the costal margin, iliac crest, and pubic symphysis to facilitate exposure. An auxiliary role is placed
under the dependent axilla and the upper arm is placed in
a relaxed neutral position over a pillow or armboard. The
hips and knees are flexed and padded to protect the
peripheral nerves, particularly the lateral popliteal nerve
at the knee. Flexion of the hips relaxes the psoas muscle,
which aids in its dissection from the lateral aspect of the
lumbar bodies and the transverse process.
Incision
As with the direct anterior approach to the lumbar
spine, the incisions for the antero-lateral approach to the
lower lumbar spine depend on which levels require exposure (Fig. 20-6). Usually the lateral edge of the incision is
CaudadCephalad
L3-4 L4-5 L5-S1
FIG. 20-6. Variation in oblique incision for specific lumbar
level.(Modified from Watkins RG.Surgical approaches to the
spine. In: The lumbar spine. Philadelphia: WB Saunders,
1996:1263–1271, with permission.)