Atlas-of-Neurosurgical-Techniques-Spine-and-Peripheral-Nerves

78
Traumaof the LumbarSpine
589
38.lelsrnaRK,Kirsch PT. lelsma LF.et al. Surgical treatment
of thora-
columbarfractures. Surg NeuroI1982;18:156-166
39. LevineAM. Semin Spine Surg 1992
40. CapenerN. The evolution of lateral rhachotomy.J BoneJoint SurgBr
1954;36-B:173-179
41. Larson51,Holst RA. Hemmy DC,Sances A Ir. Lateral extracavitary ap-
proachto traumatic lesions ofthe thoracic and lumbar spine. J Neuro-
surg1976;45:628-637
42. LevineAM. The surgical treatment
of low lumbar fractures. Semin
SpineSurg 1990;2:41-53
43. HanleyIr EN.et al. Semin Spine Surg 1990
44.
An HS.Vaccaro A, Cotler 1M, Un S.Low lumbar burst fractures: com-
parison among body cast, Harrington
rod, Luque rod, and Steffee
plate. Spine 1991;16:5440-5444
45.
Kaneda K. Abumi K, Fujiya M. Burst fractures with neurologic deficits
of the thoracolumbar
spine: results of anterior
decompression
and
stabilization
with anterior instrumentation.
Spine 1984;9:788-795
46.
Olerud S. Karlstrom G. Sjostrom L.Transpedicular
Fixation of thora-
columbar vertebral fractures. Ctin Orthop 1988;227:44-51
47.
Roy-Camille R. SaillantG,MazelC.Platingof thoracic,thoracolumbar.
and lumbar injuries with pedicle screw plates. Orthop Ctin North Am
1986;17:147-159

79
Computer-Assisted Lumbosacral Fusion
LaceyBresnahan and Michael MacMillan
. History
. Anatomy
. Advantages
.
Disadvantages
.
Registration(Pre-operativePlanning)
.
Pathway(Approach)
The lumbosacral or LS-Sl segment can become painful
from a variety of conditions. These conditions include pri-
mary degenerative disease, spondylolysis, spondylolisthesis,
and postlaminectomy syndrome among others.
There are anatomical constraints
in approaching
the
LS-Sl disk both anteriorly and posteriorly. The posterior el-
ements are farthest from the skin surface because of the
lumbar lordosis. The iliac crests border these structures bi-
lateralIy,which makes lateral retraction difficult. FinalIy,the
highlyangled lumbosacral articulation can complicate fixa-
tion techniques.
The anterior approach also has its own unique disadvan-
tages for treatment of lumbosacral disorders. It is now welI
accepted that the direct anterior approach alIows ready ac-
cess to the LS-Sl disk; however, because of body and vascu-
lar anatomy,rigid anterior fixation across the disk is fraught
with complication.Also,if a decompression is required, this
cannot be readily performed through the anterior approach.
Forthese reasons, there is a need for a less invasiveposte-
rior approach that provides fixation, bone grafting, and ac-
cess fordecompression if necessary. This chapter presents a
brief history of this procedure and describes the pertinent
anatomy and the present technique.
. History
The first case of percutaneous lumbosacral fusion was per-
formed in january 1992.The early surgeries were accom-
plished through the use of computed tomographic (CT)
techniques. InitialIy the implants were threaded titanium
screws that provided excelIent mechanical fixation but had
no in-growth or through-growth capabilities. Trials with
both threaded and smooth bone dowels resulted in unac-
590
.
Surgical Technique
Tunnels
Diskectomy
BoneGraft
MeshCylinderImplantation
PosterolateralBoneGrafting
ceptable rates of breakage. In 1998 a thick-walIedmesh
product calIed Pyramesh (Medtronic Sofamor-Danek,Mem-
phis, TN) was introduced
that provided
both mechanical
stability
and biological incorporation.
This product usedin
conjunction with the surgical technique describedherewas
entered into a clinical trial in january 1999.The findings
from this trial to date are discussed here.
. Anatomy
Percutaneous lumbosacral fusion capitalizes on the unique
anatomy of the first sacral segment. The key anatomical
feature is the expanse of bone that extends out fromthe
lateral walI of the SI pedicle and is confluent withthe
sacral ala. This implies that a continuous bony segmentis
present from the SI end plate outwardly (IateralIy)andin-
feriorly (caudalIy) across the pedicle traversing the alaand
exiting through the sacroiliac joint and out the iliaccrest.A
tunnel drilled along this path would alIow a cannulatobe
placed from the gluteal muscles up and into the LS-Sldisk.
The smalIest isthmus along this route occurs wherethe
tunnel crosses the SI pedicle. Several studies haveshown
that this isthmus averages 18 to 20 mm wide, whichpro-
vides ample access to place a mesh cylinder alongthe
pathway.
Currently, this technique is used on patients whosepain
is suspected to arise from the LS-Sl disk and has beenre-
fractory to conservative management. Briefly,the procedure
consistsofthe registration process,creatingthe pathways
to the LS-Sl disk, aggressive diskectomy, percutaneous
computer-guided bone harvesting, implant placement,and,
finalIy, percutaneous
bone grafting in the posterolateral
gutter between LSand S1.

I
I
79
Computer-Assisted
Lumbosacral Fusion
591
. Advantages
. Theideal entry point can be determined for the chosen
pathway.
. Diametersof the implants can be displayed along each
ofthe pathways to ensure that the pathways do not ac-
tuallyintersect.
. Providesintradiskal access without disrupting the
neuralcanalor mobilizinggreatvessels
. Disadvantages
. Requiresthe insertion of pins into iliac crest for registra-
tion purposes (less of an issue if fluoroscopic registra-
tionisavailable)
. Timerequired for diskectomy and bone grafting
. Registration (Pre-operative Planning)
Registrationfor the current computer-assisted
procedure
involvesthe identification
of fixed bony landmarks that
canbe clearly identified on the target anatomy as well as
delineatedon the three-dimensional
model of the surgical
site.Becausethis procedure is percutaneous by definition
there are no accessible bony surfaces. The first step of the
procedure is to embed pins onto the iliac crest (Fig. 79-1).
These specially designed break-off pins are fixed to the il-
iac crest and broken off just beneath the skin's surface.
The four pins are placed under local anesthesia
prior to
surgery. Followingthe placement of the pins the patient is
sent to the CTscanner where contiguous image slices are
made from L5through the coccyx. The completed scan of
the pins in the iliac crest is then transferred to the com-
puter navigation unit (this step is no longer necessary
with the availability
of two-dimensional
fluoroscopic
registration).
The next step is to orientate the patient's configuration
and register it in the surgical space. Adetector that reads
the spatial displacement of light emitting diodes (LED)is
placed approximately
6 feet from the patient. Subse-
quently an array of LEOsis rigidly affixed to it by implant-
ing a threaded pin into the iliac crest and attaching the
LEDarray (Fig. 79-2). With the LEDarray in place. the de-
tector can determine
the exact position of the LEOsand
the patient's pelvis and spine in the surgical space. In or-
der for the computer to detect the exact orientation of the
patient's
pelvis, the positions
of the fiducial pins are
indicated on the iliac crests and correlated
with their
counterparts on the three-dimensional
model. After com-
pleting these steps, the position of the patient's pelvis is
accurately registered
in the surgical space and can be
tracked during the procedure by its attached arc of refer-
ence LEOs.
Figure 79-1
The location
of fiducial
pins. The four
break-off
pins are placed onto the bilateral
iliac crests
and broken off just beneath the skin's surface under lo-
cal anesthesia prior to surgery.

592
Lumbarand Lumbosacral Spine: Anterior Approach
.
Pathway (Approach)
When viewed on plain radiographs, the right and left
pathways crisscross the lumbosacral segment (Fig. 79-3).
On the anteroposterior
view, each tract extends from
above the L5pedicle, across the disk inferiorly to the con-
Figure 79-3
When viewed on plainradiographs, the right and left
pathways crisscross the lumbosacral segment. Eachtract extends
from above the L5pedicle, across the diskinferiorlyto the contralat-
eralS1pedicle,and through the sacroiliacjoint.
Figure 79-2
The registration of pins using the wand.Ade-
tector reads the spatial displacement of the light emitting
diodes.
tralateral Sl pedicle, and through the sacroiliac joint. On
the lateral view, one pathway is quite vertical and parallels
the posterior wall of L5,whereas the other is more hori-
zontal and projects toward the midpoint of the anterior L5
wall.
Computer guidance is obviously helpful in this complex
anatomical region. It allows for the preoperative plans to be
carefully mapped out and reviewed on the three-dimen-
sional cr scan. Atremendous benefit of computer guidance
is that the projected line of the pathway can be identified
even where it extends outside the patient. This means that
the point at which the pathway intersects the skin canbe
found and used as the entry point. Another useful feature is
that the diameters of the implants can be displayed along
each of the pathways to ensure that the pathways do not
actually intersect.
. Surgical Technique
Tunnels
When the entry point has been identified, the skin is in-
cised and blunt dissection is used to palpate the outer
table of the ilium. The drill guide with the attached refer-
ence arc is then tracked and aligned along the respective
pathway. Once the drill guide is lined up, a 2 mm diameter
drill bit is drilled across the ilium, up the sacral ala and
into the L5-S1 disk (Fig. 79-4). This drill bit functions asa
guide pin for the next step of trephining a 7 mm diameter
tunnel along the pathway. Trephining the tunnel rather
than drilling it salvages the bone that can then be used as
a graft. The tunnel can now be converted into a working
portal. To create the working portal, first a large outer

79
Computer-Assisted Lumbosacral Fusion
593
Figure 79-4
A2 mm diameter drill bit isdrilled across the iIIiumup to
the sacralala and into the L5-S1 disk. Thisdrillbit functions as a guide for
the next step of trephination. a 7 mm diameter tunnel along the pathway.
cannula fixed to the outer surface of the ilium is used to
spread and protect the gluteal soft tissues. Then a 7 mm
cannula is inserted into the bony tunnel up to the LS-Sl
disk(Fig.79-5).
Figure 79-5
The trephined
tunnel is converted
into the working
por-
tal. A large outer cannula fixed to the outer surface of the iIIium is used
to spread and protect
the gluteal
soft tissue. Then a 7 mm cannula
is
inserted into the bony tunnel up to the L5-S1 disk.
Figure 79-6
Specializedinstruments are used to dislodge and re-
move disk material through both cannulas.
Diskectomy
Accessto the disk space is provided by the working cannula
(Fig. 79-6). Specialized instruments
are used to dislodge
and remove disk material through both cannulas. It is also
possible to scrape and abrade the end plate in a perimeter
around the cannulas within the disk but this process must
be monitored with fluoroscopy.
Bone Graft
Bone grafting is critical to the procedure and is used in
three separate sites: (1) impacted into the prepared disk
space, (2) compacted into each mesh cylinder, and (3) then
used in a later step for posterolateral graft. Because the il-
iac crests are included in the stereotactic
field it is also
possible to use computer guidance to harvest the bone
graft from the crest. This is accomplished by the use of an-
other trephine and LEDarray, which is again traced by a
detector.
This guided trephine is introduced through a 2 cm inci-
sion over the crest. Following the full introduction and
withdrawal of the trephine the contained bone is pistoned
out. The trephine is then reintroduced at a slightly different
angle and the process is repeated. The crest bone is then
mixed with the bone harvested from the tunnels
and
packed into the mesh cylinders. The mixed bone is also
"muzzle loaded" up the working cannulas and into the pre-
pareddiskspace(Fig.79-7).
Mesh Cylinder Implantation
Toimpact the cylinders across the disk, the body of LSmust
also have tunnels trephined into it. Therefore, the working
cannulas going up to the disk are removed and the trephine
'.1
a.,
.
"
..
1_'
_'__C'II.
..
r-..__
),
,
j, (I
""
r'
0
· 1
'"I
0 h
..
i&
()
b
(\
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19 t
-

594
LumbarandLumbosacralSpine:Anterior Approach
j
{~
Figure 79-7
The prepared disk space is packed with harvested
autologousbone.
is reintroduced up the tunnel. across the disk space, and
intothebodyofLS(boneisalsoobtainedfromthis maneu-
ver). The leading points of the mesh cylinder are bent in-
ward to form a blunt tip, and an impactor is inserted up the
other end. The leading tip of the cylinder is placed against
the outer table of the ilium until it is in the mouth of the
tunnel. The cylinder is then firmly impacted up the path-
way,across the disk, and into the body of LS(Fig. 79-8).
Thisprocedureis repeated on the contralateral side.
Posterolateral
Bone Grafting
The predominant advantage to the posterior approach is
that the posterior elements are available for bone grafting
or even decompression if necessary. Toperform posterolat-
Figure 79-8
Themesh cylinder isfirmly impacted up to the pathway
acrossthe diskand into the body of L5.
eral bone grafting while minimize tissue disruption, we
utilize the cannulas from the Microendoscopic Diskectomy
(MED) system (see Chapter VII.C.6).The area of the lS
transverse process and the sacral ala can be localized using
the StealthStation Guidance System (Medtronic Corpora-
tion, Minneapolis, MN). Again, the drill guide with its
attached reference arc is placed on the skin over the lS
transverse process. When the entry point is identified a 1
cm incision is made, and the drill guide is then directed
down onto the LStransverse process. When the drill guide
is in place, the tract is created by levering the guide and
then removing it. The guide is quickly replaced by the
smallest cannula of the MED system. (Avoid using the
guide pin for the MEDsystem to prevent penetrating too
deeply and contacting the exiting nerve underneath the

...
79
Computer-AssistedLumbosacralFusion
595
Figure 79-9
Transverseprocess fusion is performed
using the METRx system.
transverseprocess.) The larger cannulas are then sequen-
tially introduced
until
the largest
working
cannula
is in
placeand securely fixed (Fig. 79-9). Using only a headlight
andIoupes we peer down the MED cannula and expose the
bone.The L5 transverse
process
is decorticated
with the
drillto expose the bone. The cannula
is then redirected
in-
feriorlytoward the ala. This is usually within
1 cm of the L5
transverse process, and again the soft tissues are removed,
and the ala is decorticated as well. At this point the previ-
ously harvested bone graft is obtained and tamped into the
decorticated areas. The cannula is then withdrawn.
Through a series of small incisionsthe L5-S1 interspace is
decorticated, bone grafted, and rigidly fixated. Then the
posterolateral area is likewisegrafted through minimal inci-
sions accomplishing a 360 degree fusion through a mini-
mally invasiveapproach.

80
Anterior Transperitoneal Approach
to the Lumbosacral Junction
Anthony Frempong-Boadu
.
Advantages
.
Disadvantages
.
SurgicalTechnique
.
Decompressive Techniques
Diskectomy
Vertebrectomy
Vertebral Reconstruction
Anterior Instrumentation
Closure
.
Complications
.
Conclusions
Surgicalapproaches to the lumbosacral (LS)junction are
determined by the location of the pathological lesion and
the goalofthe surgical procedure. In particular, approaches
to the LSjunction can be challenging because of the con-
cavity of the LSjunction, the posterior tilt of the sacrum
below the sacral promontory, the relationship of the LS
junction to the pelvis, the iliac wings, the overhang of the
superior
iliac crest. Combined
anterior/posterior
ap-
proaches are often needed to adequately address pathology
in this area ofthe spinal column. The low lumbar spine and
LSjunction are best approached using a direct anterior ap-
proach via either a trans peritoneal or an extra peritoneal
approach. This chapter describes the anterior trans peri-
toneal approach to anterior pathological lesions involving
the LSjunction.
The anterior transperitoneal approach to the LSjunction
has been used extensively in the surgical treatment of de-
generative disk disease, spinal deformities, vertebral os-
teomyelitis, traumatic burst fracture, fracture dislocation,
and tumors of the LSvertebral body. It is best used for ex-
posing anterior pathology of the vertebral bodies, interver-
tebral disks, and nerve roots from L4to the sacrum.I-3 It of-
fers excellent anterior exposure of the thecal sac, and
extensive bilateral
anterior decompression
and LS ve-
rtebral body resection can be performed via this approach.
Direct reconstruction of the anterior load-bearing support
596
structures and stabilization can also be accomplished with
this approach.
The principal disadvantage is that it requires a second
procedure
for decompression
of posterior
pathology
and for placement of posterior supplemental spinal instru-
mentation.
.
Advantages
. Ideal for anterior pathology of the vertebral bodies
.
Excellent exposure of the thecal sac
.
Enablesdirect reconstruction of the anterior load-bearing
structures
.
Disadvantages
.
Requires a second procedure for decompression of pos-
terior pathology and for placing supplemental posterior
instrumentation
.
Riskof vascular complications and sexual dysfunction
.
Riskto bowel/bladder/ureters

. SurgicalTechnique
80
Anterior Transperitoneal Approach
597
Thetransperitoneal approach to the lumbar spine was first de-
scribedfor the treatment
of spondylolisthesis.
In the 1940s
and1950sit was used to perform lumbar interbody fusions as
atreatment for degenerative
disk disease.3-6 Transperitoneal
exposuresprovide excellent visualization of the lower lumbar
vertebralbodies,with optimal exposure of L5-S1.Although
theabdominal viscera can be easily retracted
away from the
spine,the great vessels and the hypogastric nerve plexus must
be carefully mobilized before exposing
the spine. This in-
creasesthe risks of vascular complications
and can cause im-
potencein males.7-9Collaboration with a general or vascular
surgeonmay decrease the frequency of these complications.
Preoperative preparation
includes bowel prep the day be-
foresurgery. The patient is placed supine with the sacral re-
gionelevated by angling the operating
table under the sacral
regionbetween 0 and 40 degrees depending
upon the verte-
bralsegment exposed. This produces hyperlordosis, which fa-
cilitatesexposure of the sacral promontory.
The patient
is
preppedand draped to expose the abdominal
operative field
andthe bone graft site if necessary. A midline, paramidline, or
transverse (Pfannenstiel's)
incision may be used with fluo-
roscopyto identify the level of the spinal lesion (Fig. 80-1).
Theabdominal wall fascia is incised in the midline and the
peritoneum opened
with care to avoid bowel injury (Fig.
80-2).Trendelenburg
position is used to keep the intestines
inthe upper abdomen. The redundant
parts of the sigmoid,
cecum,and small bowel are displaced in the upper portion of
theabdomen and retracted with moist laparotomy sponges to
exposethe lower lumbar and pelvic portion of the posterior
peritoneum.The pelvic portion of the colon and its mesentery
arethen retracted to the left and the ureters are identified. Af-
Figure80-1
Skin incision can be made either in the midline or asa
"pfannenstiel"two fingerwidths abovethe symphysispubis.
Figure 80-2
After transaction of the skin and subcutis, the linea alba
is incised with
a knife in the midline.
1, rectus
abdominis
muscle;
2,
linea alba; 3, umbilicus.
(By permission
from Bauer R, Kerschbaumer
F,
Poisel S, eds. Atlas of Spinal Operations. Stuttgart,
Germany: Thieme;
1993:52, fig. 1.90.)
ter the bowel is mobilized, the aortic bifurcation and sacral
promontory are seen through the posterior peritoneum.
The prevertebral neurovascular structures include the
aorta, vena cava,their collateralvessels,and the hypogastric
nerve plexus. The anatomy of these structures is variable
and knowledge of possible variations is necessary to safely
expose the anterior LSspine.IO-12
L4 to the sacrum can be readily exposed using the
trans peritoneal approach. However, the transperitoneal
approach is best used for exposure of the L5-S1 disk
space.2.3.12Exposure ofthe L4-L5disk space can be limited
by the bifurcation of the great vessels. The L5-S1 disk
space is located several centimeters below the aortic bifur-
cation and can be palpated between the common iliac ves-
sels. The peritoneum is grasped with a toothless forceps
above the aortic bifurcation and opened in the midline
with blunt scissors (Fig. 80-3). The electrocautery should
Figure 80-3
Division of the peritoneum with scissors.1, linea alba;
2, parietal peritoneum; 3, greater omentum. (By permission from
Bauer R, Kerschbaumer F,Poisel S, eds. Atlas of Spinal Operations.
Stuttgart, Germany:Thieme; 1993:52, fig. 1.91.)

598
Lumbar and Lumbosacral Spine:Anterior Approach
not be used when opening the posterior peritoneum
to
prevent damage to the hypogastric plexus and retrograde
ejaculation in males. The incision is continued caudally
following the right common iliac artery to its bifurcation
at the external and internal iliac arteries. The right ureter
is identified and avoided as it crosses under the right ex-
ternal iliac artery. The peritoneal flaps are freed and re-
flected laterally to the common iliac arteries (Fig. 80-4).
The hypogastric plexus is located directly anterior to the
fifth lumbar vertebral body and the LS-S1 disk space (Fig.
80-5). The dissection is continued down to the anterior
longitudinal ligament just medial to the left iliac artery
and vein to avoid injuring the hypogastric plexus. The pre-
vertebral tissues, including the hypogastric plexus, are
then swept from right to left by bluntly dissecting directly
on the anterior surface of the disk. By displacing these
structures en bloc and not dissecting through them, there
is less risk of injuring the hypogastric plexus. The middle
sacral artery is sometimes adherent to the vertebral bod-
ies, and bleeding may occur when it is being mobilized.
Hemorrhage can often be controlled with packing and
pressure. Use the bipolar cautery or vascular clips instead
of the unipolar reduces the risk of hypogastric plexus in-
jury. The iliac vessels are laterally retracted to expose the
LS-S1disk space.
When a large left common iliac vein hinders access to
the body of LS and the sacral promontory,
the vein
should be dissected
free from the left common iliac
artery. Place vessel loops proximally and distally around
the vein with a right angle dissector and retract the vein.
This collapses the vein, allowing mobilization and access
to the vertebral bodies. The left iliac vein can occasion-
ally appear as a flat, white, bloodless ribbon across the
LS-S1 disk space. Brisk hemorrhage
will occur if this
Figure 80-4
The posterior peritoneum is elevated and
opened withscissors.
Figure 80-5
Exposure of the promontory and caudal half of the fifth
lumbar vertebra,
and the upper half of the first sacral vertebra after
transection
of the median sacral artery. The aorta and the common il-
iac artery are secured, and the left and right common
iliac veins are
rectracted.
1, sacrum; 2, abdominal
aorta; 3, common
iliac artery; 4,
medial sacral artery;
5. inferior vena cava; 6, common
iliac vein; 7.
superior hypergastricplexus;V,lumbar vertebra. (Bypermissionfrom
Bauer R, Kerschbaumer
F, Poisel S, eds. Atlas of Spinal Operations.
Stuttgart. Germany: Thieme; 1993:53, fig. 1.94.)

80
AnteriorTransperitonealApproach
599
vesselis not properly identified and mobilized before in-
cising the disk.
. Decompressive Techniques
Diskectomy
Thedisk space is incised with a knife blade (Fig.80-6) on a
longhandle or with an osteotome and removed anterior to
theposterior longitudinal ligament using large curettes and
pituitary rongeurs.
with
care
taken
to preserve
the
endplates (Fig.80-7). It is important to work parallel to the
endplates.especially at LS-S1.Ahigh-speed cutting bur can
alsobe used to perform the diskectomy (Fig. 80-8). In gen-
eral.the posterior longitudinal ligament should be pre-
servedbut it can be resected using small Kerrison rongeurs
alongthe entire width of the spinal canal to ensure ade-
quateofdecompression if necessary.
Vertebrectomy
Theiliacvessels must be identified and controlled as already
described.The end plates and disk spaces above and below
theL5vertebral body must be clearly identified. The L4-LS
diskspace above and the LS-S1 disk space below are in-
cisedwith a knife blade or osteotome and removed using
large curettes and rongeurs. The vertebrectomy
is per-
Rgure80-6
l5-S1 diskectomy.Resectionofthe longitudinalligament
and of the anterior portion of the anulus fibrosus of the lumbosacral
intervertebral disk. 1. sigmoid colon; 2. ascending
colon; 3. aortic
bifurcation;4. right common iliacvessels; 5. left common iliacvessels; 6.
median sacral artery; 7. superior hypogastric plexus; V.lumbar vertebral
body.(Bypermission from Bauer R.Kerschbaumer F.Poisel S. eds. Atlas
ofSpinalOperations. Stuttgart. Germany: Thieme; 1993:270. fig. 6.1.)
formed in a piecemeal fashion using rongeurs and the high-
speed cutting bur. The drill is used to thin the posterior
cortex to an "eggshell" width.
Curettes and
Kerrison
rongeurs are then used to remove the thinned posterior
cortex and posterior longitudinal ligament anteriorly off the
thecal sac. Bleedingduring the vertebrectomy is controlled
using bone wax. Gelfoam. and resection of the cancellous
bone back to the relatively avascular cortical bone. Epidural
bleeding is controlled with Gelfoamand bipolar cautery.
Vertebral Reconstruction
The goal of spinal reconstruction is to restore alignment.
lordosis. and the load bearing and biomechanical properties
of the reconstructed spinal segment so that it performs ade-
quately under physiological loads. Anterior lumbar verte-
bral reconstruction
methods vary depending upon the
pathology being treated. Vertebral body and disk space re-
construction can be performed using structural bone graft
(auto- or allograft)13(Figs. 80-9, 80-10). bone dowels, tita-
nium cages. biological plastics. or Steinmann pins and
methyl methacrylate. In general. reconstruction for trau-
matic fracture, degenerative disease. or infection should be
performed with auto- or allograft bone. either structural or
placed into a titanium cage, to achieve bony fusion of the
affected lumbar vertebral
levels.13.14Reconstruction for
pathological fracture secondary to metastatic cancer can be
performed with Steinmann pins and methyl methacrylate.
titanium cages. or biological plastics.15.16
Anterior Instrumentation
After anterior reconstruction. anterior spinal fixation is gen-
erally not performed because of the location of the iliacves-
sels. With LSvertebrectomy or multilevel anterior lumbar
interbody fusion (AUF).it is usually necessary to perform
posterior supplemental instrumentation
in compression to
obtain immediate stability. increased fusion rates. and main-
tenance of disk height and interpedicular distance while
awaiting development of a physiological fusion mass.17-19
There are new generation LS-S110rdotic cages and titanium
plates that can be placed between the bifurcated iliacves-
sels. These new interbody implants and anterior LS-S1tita-
nium plates combined with bone morphogenic proteins may
obviate the need for posterior supplemental instrumenta-
tion with LSdiskectomy procedures.20-25
Closure
After appropriate
decompression
and reconstruction, a
multilayered closure is performed. Closethe posterior pari-
etal peritoneum using 3-0 Vicryl sutures. Drainage is not
required. Anatomically reposition the bowel loops to pre-
vent bowel torsion. and place the greater omentum over the
intestines. Close the abdominal fascia and anterior parietal
peritoneum
with interrupted
sutures. Each layer of the
abdominal wall musculature
is identified and carefully
reapproximated.
taking care to obliterate potential dead
spaces between layers. The superficial soft tissues are
closed in a standard multilayered anatomical fashion.IO.26
The skin is closed with a running subcuticular stitch. Dry

.
600
LumbarandLumbosacral
Spine:
Anterior
Approach
Figure 80-7
L5-S1 diskectomy.
(A) Removal of the remnants
of the anulus fibrosus at the verebral borders, using a rongeur.
1, sigmoid colon;2,
ascending colon; 3, aortic
bifurcation;
4, right common
iliac vessels; 5,Ieft
common
iliac vessels; 6, median sacral artery;
7, superior hypogastric
plexus; V, lumbar vertebral
body. (8) Debridement
of the adjoining
anterior wall portions
of L5 and S1 by stripping
the periosteum.
(By permission
from Bauer R, Kerschbaumer
F,Poisel S, eds. Atlas of Spinal Operations.
Stuttgart,
Germany: Thieme; 1993:272,
figs. 6.4, 6.5.)
Figure 80-8
L5-S1 diskectomy. Dechondrification of the endplates
next to the off-center spreader. 1, sigmoid colon; 2, ascendingcolon;3,
aortic bifurcation; 4, right common iliac vessels; 5, left common iliac
vessels;6, median sacralartery; 7, superior hypogastric plexus;V,lumbar
vertebral body. (By permission from Bauer R,Kerschbaumer F,Poisel5,
eds.Atlas of Spinal Operations. Stuttgart, Germany: Thieme; 1993:271,
fig. 6.2.)

80
AnteriorTransperitonealApproach
601
A
/
B
Figure80-9
L5-S1 anterior
interbody
fusion with bone graft. (A) The trimmed,
pressure-resistant
graft is driven into the maximally
expanded
space.(B) The remaining space is packed with autologous cancellous bone. The anulus fibrosus prevents excessive penetration.
(By permission from
BauerR,Kerschbaumer F,Poisel S, eds. Atlas of Spinal Operations.
Stuttgart,
Germany: Thieme; 1993:273,
figs. 6.6, 6.7.)
Figure80-10
L5-S1 anterior Interbody fusion with bone graft. 1,
bodyof fifth lumbar vertebra; 2, anulusfibrosus;3, sacrum(FirstSacral
Vertebra).(Bypermissionfrom BauerR,KerschbaumerF,PoiselS,eds.
Atlasof SpinalOperations. Stuttgart, Germany:Thieme; 1993:274, fig.
6.8([left]).)
sterile dressings
are placed. The patient
should
receive con-
tinuous
neurovascular
monitoring
in the intensive
care unit.
.
Complications
Vascular and bowel injuries are possible with the transperi-
toneal LS approach. Furthermore,
because one or more
major anterior abdominal wall muscles are divided. wound
dehiscence. herniation. and hematoma can also occur. It is
also associated with sterility
in males secondary to retro-
grade ejaculation
caused by damage to the superior hy-
pogastric plexus.
The superior hypogastric plexus is located directly ante-
rior to the fifth lumbar vertebral body and the LS-S1 disk
space and carries sympathetic
autonomic fibers. During
ejaculation,
it causes the smooth muscle of the seminal
vesicles to contract as the bladder neck closes.It is respon-
sible for sperm transport
from the testes to the seminal

602
LumbarandLumbosacralSpine:AnteriorApproach
..
vesicles via the vas deferens. Thus damage to the superior
hypogastric plexus can result in sterility through loss of
normal sperm transport or secondary to retrograde ejacula-
tion caused by failure of seminal vesicle contraction during
ejaculation. There is a 0.44%reported incidence of retro-
grade ejaculation with anterior approaches to the LSjunc-
tion. Impotence can also occur if the parasympathetic fibers
responsible for penile erection-arising
from the S2-S4 seg-
ments and carried in the inferior hypogastric plexus-are
damaged during the resection of extensive sacral lesions.
7-9,27-29
These complications are best avoided by limiting the
use ofthe electrocautery when incising the posterior peri-
toneum and by using careful blunt dissection when expos-
ing the LS-Sl disk space.7.27-30
The surgeon should be prepared for vascular anomaly,
and vascular instruments should always be available when
performing transperitoneal
approaches.IO.31-33If injury to
one of the great vessels occurs, compression above and be-
low the injury or placing temporary vascular clamps will
reduce hemorrhage while the defect is being repaired.34
Avoidexcessive traction on diseased calcified arteries-of-
ten found in elderly patients-to
prevent fracture of an ath-
erosclerotic
plaque
and
possible
arterial
thrombosis.
Also, because venous structures are mobilized, the inci-
dence of postoperative deep venous thrombosis is signifi-
cant and all patients should have perioperative prophylactic
anticoagulation. Care must be taken throughout the proce-
dure to avoid compressing the iliac arteries or veins for pro-
longed periods to further avoid vessel thrombosis.
References
1.
Birch BD, Desai RD. McCormick
Pc. Surgical approaches
to the thora-
columbar spine. Neurosurg
Clin N Am 1997;8:471-485
2.
Burke PJ.Anterior
lumbar
interbody
fusion. Radiol Technol 2001 ;72:
423-430
3.
Freebody D. Bendall
R. Taylor RD. Anterior
transperitoneallumbar
fusion.J Bone Joint Surg Br 1971 ;53:617-627
4.
Hodgson AR.Stock FE. Anterior
spinal fusion: a preliminary
commu-
nication on the radical treatment
of Pott's disease
and Pott's paraple-
gia. BrJ Surg 1956;44:266-275
5.
Kondo S. Hamano K. Kamijo M. et al. Transperitoneal
approach
to the
lower
lumbar
and the
lumbosacral
vertebra
for the treatment
of
tuberculous
spondylitis.
Bull Osaka Med Sch 1964;10:79-88
6.
Raugstad TS. Harbo K. Oogberg A. et al. Anterior
interbody
fusion of
the lumbar spine. Acta Orthop Scand 1982;53:561-565
7.
Christensen
FB, Bunger CEoRetrograde
ejaculation
after
retroperi-
toneallower
lumbar
interbody
fusion.
Int Orthop
1997;21 :176-180
8.
Flynn JC. Price CT.Sexual complications
of anterior
fusion of the lum-
bar spine. Spine 1984;9:489-492
9.
Tiusanen
H. Seitsalo S. Osterman
K, et al. Retrograde
ejaculation
after
anterior
interbody
lumbar fusion. Eur Spine J 1995;4:339-342
10.
Barone
GW. Pait TG. Eidt JF. et al. "General
surgical
pearls"
for the
anterior
exposure
of vertebral
fractures.
Am Surg 2001 ;67:939-942
11.
McCormack
B. Maher D. Fessler R. Anterior approaches
to the lumbar
spine. In: Sonntag
V.ed. Principles
of Spinal Surgery.
New York: Mc-
Graw-Hili;
1996:1293-1306
12.
Watkins
RG. Surgical
Approaches
to the Spine. New York: Springer-
Verlag; 1983
13.
Wetzel
FT, Hoffman
MA. Arcieri RR. Freeze-dried
fibular
allograft
in
anterior
spinal
surgery:
cervical
and lumbar
applications.
Yale J Bioi
Med 1993;66:263-275
Ureteral injury or delayed ureteral fibrosismayoccur
from manipulation or traction. For this reason, if ureteral
mobilization is necessary, include a generous portion ofthe
periureteric
tissue to avoid compromising blood sup-
ply.28.35.36
Bladder injury can also occur. Familiaritywiththe
location and blood supply of both the ureter and the blad-
der are key to avoiding injury to these structures.28.35,37
The peritoneum should be repaired during closureasde-
scribed to avoid the possibility of visceral herniation and
strangulation. All bowel perforations must be immediately
oversewn, usually with the help of a general surgeon.
Accurate meticulous closure of all traversed abdominal
wall muscle layers must also be accomplished to avoid
wound dehiscence, hematomas, and abdominal incisional
hernias.10.26
. Conclusions
Surgical decision making regarding
approaches to the
spine depends upon the location of the pathology, the
need for thecal sac decompression,
and the presence of
spinal deformity. The transperitoneal approach providesex-
cellent anterior exposure of the LSjunction. This approach
offers a safe and effective means of treating anterior com-
pressive lesions of the LSjunction. It allows for direct de-
compression of the LSjunction, placement of interbody
grafts under compression, and the ability to correct sagit-
tal plane deformities.
14.
Wolfla CEoMaiman
DJ.Coufal FJ. et al. Retroperitoneal
lateral lumbar
interbody
fusion
with
titanium
threaded
fusion
cages. J Neurosurg
2002;96:50-55
15.
Cooper PRoErrico TJ. Martin
R. et al. A systematic
approach
to spinal
reconstruction
after anterior
decompression
for neoplastic
disease of
the thoracic
and lumbar
spine. Neurosurgery
1993;32:1-8
16.
Lozes G. Fawaz A. Devos P. et al. Operative
treatment
of thoraco-
lumbar
metastases.
using
methylmetacrylate
and Kempfs
rods for
vertebral
replacement
and
stabilization:
report
of 15 cases. Acta
Neurochir
(Wien) 1987;84:118-123
17.
Bozkus H. Chamberlain
RH. Perez Garza LE,et al. Biomechanical
com-
parison
of anterolateral
plate,
lateral
plate. and pedicle
screws-rods
for enhancing
anterolateral
lumbar
interbody
cage
stabilization.
Spine 2004;29:635-641
18.
Brodke DS. Gollogly S. Bachus KN. et al. Anterior
thoracolumbar
in-
strumentation:
stiffness
and load sharing
characteristics
of plate and
rod systems. Spine 2003;28:1794-1801
19.
Faro FD.White KK,Ahn JS. et al. Biomechanical
analysis of anterior in-
strumentation
for lumbar
corpectomy.
Spine 2003 ;28:E468-E471
20.
Hu ZM. Peel SA, Sandor
GK, et al. The osteoinductive
activity of bone
morphogenetic
protein
(BMP) purified
by repeated
extracts of bovine
bone. Growth Factors 2004;22:29-33
21.
Magin MN. Delling G. Improved
lumbar vertebral
interbody
fusion us-
ing rhOP-1 : a comparison
of autogenous
bone graft. bovine hydroxylap-
atite (Biol-Oss). and BMP-7 (rhOP-1) in sheep. Spine 2001 ;26:469-478
22.
Muschik
M. Schlenzka
D. Ritsila V. et al. Experimental
anterior spine
fusion using bovine bone morphogenetic
protein:
a study in rabbits.J
Orthop Sci 2000;5:165-170
23. Sandhu HS,Khan SN.Suh DY.et al. Demineralized bone matrix. bone
morphogenetic
proteins. and animal models of spine fusion: an
overview. Eur SpineJ 2001; 10(Suppl2):5122-5131

80
AnteriorTransperitonealApproach
603
24. Xu W. Chen A.Feng X. et al. Anterior
lumbar
intervertebral
fusion
with artificial bone in place of autologous
bone. J Huazhong
Univ Sci
Technolog Med Sci 2003;23:300-301
25. ZlotolowDA.VaccaroAR. Salamon ML.et al. The role of human bone
morphogenetic
proteins
in spinal
fusion.
J Am Acad Orthop
Surg
2000:8:3-9
26. Honig MP. Mason RA. Giron F.Wound
complications
of the retroperi-
toneal approach
to the
aorta
and
iliac vessels. J Vasc Surg
1992: 15:28-34
Tl. BirchN. Shaw M.Retrograde ejaculation after anterior lumbar inter-
body fusion. Spine 2004:29:
106-107
28. Johnson RM. McGuire EJ.Urogenital complications of anterior ap-
oroaches to the lumbar
spine. Clin Orthop
1981 ;154: 114-118
29. Sasso RC, Kenneth
Burkus J.LeHuec Jc. Retrograde
ejaculation
after
anterior lumbar
interbody
fusion:
trans peritoneal
versus
retroperi-
toneal exposure. Spine 2003:28:1023-1026
30. LiebermanIH,Willsher PC.Litwin DE,et al. Transperitoneallaparo-
scopic exposure
for lumbar
interbody
fusion. Spine 2000;25:509-515
31. BakerJK.Reardon PRoReardon MJ,et al. Vascular injury in anterior
lumbar
surgery. Spine 1993:18:2227-2230
32.
Ebraheim
NA. Xu R, Farooq A, et al. The quantitative
anatomy
of the
iliac vessels
and their
relation
to anterior
lumbosacral
approach.
J Spinal
Disord
1996:9:414-417
33.
Kulkarni
SS. Lowery
GL, Ross
RE, et al. Arterial
complications
follow-
ing anterior
lumbar
interbody
fusion: report of eight cases. Eur Spine
J 2003;12:48-56
34.
Woolsey RM.Aortic laceration
after anterior
spinal fusion. Surg Neurol
1986;25:267-268
35.
Faraj AA. Webb JK, Lemberger
RJ. Urinary bladder
dysfunction
follow-
ing anterior
lumbosacral
spine fusion: case report
and review
of the
literature.
Eur SpineJ 1996;5:121-124
36.
Isiklar ZU. Lindsey RW. Coburn M. Ureteral injury after anterior
lum-
bar interbody
fusion: a case report. Spine 1996;21 :2379-2382
37.
Chan FL.Chow SP.Retroperitoneal fibrosis after anterior spinal fusion.
Clin RadioI1983;34:331-335

..
81
Anterolateral Retroperitoneal Approach
to the LumbosacralSpine
H. Louis Harkey III,
Timothy
M. Wiebe,
and Michael
P. Schenk
.
Indications
.
Contraindications
.
Advantages
.
Disadvantages
.
Radiological Evaluation
.
Preoperative Planning
.
Surgical Technique
Anesthesia and Positioning
Incision
Approach
.
Lumbar Sympathectomy
Indications
Approach
.
Diskectomy and Fusion
Approach
.
Vertebrectomy and Fusion
Approach
.
Plate Stabilization
Approach
Closure
.
Postoperative Care
The anterolateral retroperitoneal approach enables visual-
ization of all lumbar vertebrae and access to the lumbar
sympathetic chain (Fig. 81-1). It is practical for anterior
pathology ranging from L2to L4,whereas an approach to LS
or below may be complicated by the iliacvessels. Retroperi-
toneal dissection may avoid complications of entering the
pleural and peritoneal cavities. Ageneral surgeon may lend
experience with mobilization of the great vessels and han-
dling of the abdominal contents.
Adorsalapproach has advantages forstabilization.including
load sharing and instrumentation of all three spinal columns,
while avoidingmany of the complications associated with an
anterolateral approach. Emergingdata suggest that both ante-
riorand posteriorapproaches are ofcomparablesafety.
604

Vertebral body
81
Anterolateral RetroperitonealApproach
605
Anterior longitudinal
ligament
Superior facet
Spinous process
Posterior longitudinal
ligament
A
Figure81-1
(A) Axial image.(B) Lateralview.Anatomicalrelationshipsinthe anterolateralretroperitonealapproach.
. Indications
. Sympathectomy
. Decompression(tumor, trauma, and degenerative disease)
. Stabilization
. Contraindications
. Morbidobesity
. Calcificationof the great vessels
. Preclusivemetastatic disease
. Priorabdominal surgery/infection
. Priorirradiation of the surgical path
. Retroperitonealfibrosis
. Advantages
. Enablesvisualizationofalllumbarvertebrae
. Accesstothe lumbarsympatheticchain
. Allowsforventraldecompression
. Disadvantages
. Accessto LSobstructed by iliac vessels
. Right-sidedapproach limited by the liver
. Potentialfor complications to the abdominal viscera
. Rostraland caudal extent of the lumbar dissection may
be limited
B
.
Radiological
Evaluation
Investigative studies are case specific. The delineation of
soft tissues with magnetic resonance imaging (MRI) se-
quences is useful to visualize and characterize virtually all
spinal pathology. Plain spinal radiographs may identify
preclusive vascular calcification of the great vessels and de-
lineate gross tumor, bone density, alignment, and stability,
as well as landmarks to guide dissection. Plain spinal com-
puted tomography (cr) clarifies the status of bone and liga-
mentous elements with regard to stability and thecal com-
pression and also provides a template for measuring screws
and bolts to be used for instrumentation.
Myelography de-
lineates significant neural impingement and may comple-
ment cr. Selective spinal angiography may delineate tumor
vascularity for preoperative embolization.
Intraoperative roentgen studies should be prearranged for
noninstrumented cases,whereas a fluoroscopicoperatingtable
and (-arm augment instrumentation procedures by enabling
visualization of spinal levels and instrumentation. Similarin-
formation maybe gained from image-guidedsurgicalsystems,
which have the advantage ofassisting in the selectionofscrew
trajectory. Intraoperative microscopyand a high-speed pneu-
matic drillmake thecal compressionsaferand more precise.
Somatosensory evoked potential monitoring quantifies
the integrity of the central neuraxis and may indicate
changes coincident or subsequent to surgical manipulation.
.
Preoperative
Planning
Prior to elective spinal surgery patients should be nutritionally
optimized
and counseled
for smoking cessation. Autologous
blood banking should be offered when available, whereas a

606
Lumbarand LumbosacralSpine:AnterolateralApproach
red blood cell saver used intraoperatively may prevent
exposure to blood products. For patients who will require
an orthosis, it may be more convenient to have it prepared
preoperatively. Ureteral stenting should be considered for
ureteral identification in cases of related malignancy or
fibrosis.
. SurgicalTechnique
Anesthesia and Positioning
Following induction, a nasogastric tube is placed for gas-
tric decompression.
Minimal vascular access includes
peripheral venous and arterial catheterization;
with case
selective central venous access for fluid administration
and invasive monitoring.
Anti-embolus
stockings and
pneumatic compression devices are applied to the lower
extremities. An indwelling urinary catheter will decom-
press the bladder and provide a measure of fluid status
and renal perfusion.
Undergeneral anesthesia the patient is positioned right lat-
eral decubitus with the flank over the division in the operat-
ing table. A right axillary roll is positioned after which the
right arm is placed on an arm rest and padded at the cubital
and carpal prominences. The left arm is supported by pillows
parallelto the right arm. The hips are positioned on a deflat-
able beanbag. Pillows are placed between the legs to cover
the medial tibial and malleolar prominences, and the right
fibular and lateral malleolar prominences are also padded.
The thighs are belted or taped to secure the patient to the
table.Arestraint mayalso be placed acrossthe deltoid region.
In stable patients slight table flexion at the flank reduces
the angle of the costal margin with the iliac crest, and left
hip flexion reduces tension of the psoas muscle. For many
surgeonsanatomical orientation is enhanced by positioning
the patient in an orthogonal anatomical plane. For the an-
terolateral approach the patient should ultimately be posi-
tioned in the true lateral plane, which can be verified by the
alignment of the pedicles and spinous processes on an an-
teroposterior roentgen view.
The anterolateral approach may be modified with the
patient supine and the left flank elevated (paramedian ap-
proach); or rarely performed from the right side for sympa-
thectomy and for cases with marked left-sided scoliosis.
The left-sidedapproach avoids the liver and minimizes han-
dling of the inferiorvena cava.
The skin isshaved and draped from the left costal margin
to a point below the left iliac crest, which may be taken for
grafting. The intended incision is marked and hashed, fol-
lowed with sterile preparation and draping, including the
placement of an occlusive iodine-impregnated
drape over
the operative region.
In noninfected cases administration of perioperative in-
travenous antibiotics for gram-positive coverage (cefazolin
25 mg/kg) should commence just prior to incision and
continue 24 hours postoperatively. Consider vancomycin
15 mg/kg for patients with allergic contraindications to
cefazolin. Infected patients should begin antibiotics after
cultures have been obtained. Someauthors advocate preop-
erative initiation
of a methylprednisolone
protocol for
spinal cord injury in noninfected patients with intact neu-
rologicalfunction and severe spinal cord compromise.
Incision
The incision may be localized with fluoroscopy or image
guidance. Empiricallythe operating surgeon stands anterior
to the patient and begins the flank incision at the posterior
axillary line. To expose L1-L2 the incision begins above and
two levels rostral to the desired level of exposure andter-
minates at the lateral border of the rectus sheath abovethe
midpoint between the costal margin and the umbilicus.To
expose L2-L5 an incisionbegins in the posterioraxillary
line equidistant between the costal margin and the superior
iliac crest, and terminates at the lateral border of the rectus
sheath. The incision for exposure
of L2-L3 extends between
the costal margin and the umbilicus; L3-L4 toward the
umbilicus; and L4-L5above the midpoint between the um-
bilicus and the pubic symphysis (Fig. 81-2). Toexposethe
lumbosacraljunction an incision begins slightlysuperolateral
to the anterior superior iliacspine and continues rostraland
parallel to the iliaccrest and inguinal ligament to a terminus
at the lateral border of the rectus sheath.
Approach
A muscle-splitting
approach
involves division of the
abdominal skeletal musculature along anatomical planes.
Figure 81-2
Incisional considerations
for the operative level. Incision
A for L2-L3 lesions, incision B for L3-L4 lesions, and incision C for
L4-L5 lesions.

81
Anterolateral Retroperitoneal Approach
607
Dissection plane
Figure 81-3
Retroperitoneal
approach utilizing
a dissection
plane for access to the anterolateral
lumbar spine.
Followingskin incision a Kellyclamp is used for dissection
throughthe anatomical plane of the external and internal
obliquesand through the transversus abdominis muscles-
thelatterofwhich may be inapparent (Fig.81-3). Anatomical
dissectionof the internal obliques limits exposure rendering
thisapproach most suitable for biopsy. drainage. and lim-
ited sympathectomy. Preservation of anatomical muscle
planesreduces pain and promotes healing.
Theflank approach involves linear electrocautery dissec-
tionthrough the anatomical planes of the external oblique
andthe transversus abdominis muscles (Fig. 81-4). In con-
trastto the muscle splitting approach the intervening inter-
nalobliques are transected against their anatomical plane
tofacilitateexposure.
The transversalis
fascia should be opened
laterally
where the peritoneum
is thickest and least likely to be
adherent. The peritoneum
is usually transparent
gray.
and if a peritoneal opening is encountered
it should be
closedwith absorbable suture prior to proceeding. Blunt
dissection of the retroperitoneal
plane between the renal
fascia ventrally
and
the
quadratus
lumborum/psoas
musclegroup posteriorly leads to the vertebral column
(Fig.81-5). The inferior pole of the left kidney is re-
tracted medially using a Deaver retractor padded with a
lap sponge. and longitudinal
retraction
may be aug-
mented with a Buckwalter retractor. The genitofemoral
nerve exits the body of the psoas muscle medially near
the level of L3and should be protected during lateral re-
traction of the psoas muscle to avoid dysesthesia of the
anterior thigh and inguinal region. Identification
of the
ureter may be confirmed by preoperative stenting and by
Kelly's sign of visible ureteral peristalsis following appli-
cation of gentle pressure. The ureter is gently elevated
and retracted medially with the retroperitoneal
fat pad
when possible.
Exposure of the rostral lumbar spine may be augmented
by costal resection two levels above the desired vertebral
body. ResectionofT11 and 12 ribs would expose the inferior
body of L1.Division of the diaphragmatic crus from the an-
terior longitudinal ligament and subsequently of the arcu-
ate ligament from the transverse process of L1facilitates
exposure ofthe caudal extent ofT12. Diaphragmatic dissec-
tion should commence at the periphery, -2 cm from the
lateral margin. to prevent injury to the phrenic nerve. which
originates medially.
The lumbosacral junction lies below the iliac bifurcation.
The hypogastric plexus overlies the middle sacral vessels in
the interiliac space. and these structures may be mobilized
by fascial dissection medial to the left common iliacvessels.
Further exposure of the lumbosacral junction may require
proximal ligation and division of branches of the internal il-
iac vessels for mobilization and distraction to the contralat-
eral side over a vertebral body.
Subsequent steps are described in the remaining sections.

...
Figure81-4
Incision and dissection of musculature
in the retroperitoneal
approach.
/
/'
608
/
/
f"t
.....
Figure 81-5
Retraction enables identification of
relevant retroperitoneal structures.

. LumbarSympathectomy
81
Anterolateral RetroperitonealApproach
609
Indications
. Causalgia/reflex sympathetic
dystrophy
. Pain-central and phantom hyperhidrosis
. Vascularinsufficiency
. Postfrostbitesyndrome
Approach
Amuscle-splitting
approach
for focal exposure
or a stan-
dard flank incision may be used. Alternatively
an oblique
flankincisionabove the anterior superior iliac crest is con-
tinued toward the tip of the twelfth
rib. A right-sided
ap-
proachmay be indicated
for right-sided
pathology.
Followingthe standard approach
the sympathetic
chain is
identifiedalong the lateral vertebral margin by its pale yellow
hueand by its ganglionic swellings. The psoas muscle may be
elevated bluntly from its attachments
to the vertebral
end
platesand anulus using a Cobb periosteal elevator and bipolar
cautery to facilitate exposure. Intervening
lumbar veins may
bedivided, particularly on the right side where the right sym-
patheticchain lies dorsal to the inferior vena cava.
Forsympathectomy the chain is elevated with a blunt hook,
clipped,and divided. Proximal lower extremity symptomatol-
ogymay require sympathectomy
as high as T12. Division at
U-L2 may lead to retrograde ejaculation. L2-L3 is divided for
general lower extremity
sympathectomy,
and inclusion of L4
mayyield a more complete result. Intervening
rami commu-
nicantes should be divided to abolish communication
from
intermediate ganglia and contralateral circuits.
/
Figure81-6
.
Diskectomy and Fusion
Approach
Followingthe standard approach the concave vertebral bod-
ies may be discriminated visually and manually from the
convex intervertebral disks. The prominence of the lum-
bosacral junction serves as a landmark. A20 gauge spinal
needle fashioned as a bayonet may safely mark the disk of
interest for radiographic confirmation.
Diskexposure begins with psoas mobilization and retrac-
tion, which may occasionally require division of the psoas
muscle. Segmental lumbar arterial branches arise at the
midvertebral
level. The radiculomedullary
artery
of
Adamkiewicz (RA)is known to have a variable distribution
and a tendency to arise from the left thoracolumbar region.
As it nears the neural foramen collateral vascular supply to
the RAdiminishes, and for that reason segmental lumbar
arteries are divided in the midline. The anterior thora-
columbar spinal cord receives collateral vascular supply,
and surgical division of a single segmental lumbar artery at
the level of the neural foramen is not known to cause spinal
cord infarction. Routine preoperative angiography to evalu-
ate the RAis not indicated; nor should the occurrence of the
RAin the surgical path warrant the abortion of an indicated
thoracolumbar procedure.
The fifth lumbar vein occasionally enters the common
iliac vein as the ascending iliolumbar vein, and it may be
ligated and divided as it crosses the L4-LSdisk level on the
left (Fig.81-6). The aorta is elevated medially.
The neural foramen is gently probed with a blunt right-
angled nerve hookand decompressedas necessary by removal
,
/
\
j

...
610
LumbarandLumbosacralSpine:AnterolateralApproach
ofthe anterior margin with an angled Kerrisonrongeur. The
anterior longitudinal ligament is dissected lateromedially
from the anterior vertebral body and intervertebral disk
with a Cobb periosteal elevator. A window is sharply ex-
cised from the lateral anulus, and diskectomy proceeds to
the margins of the posterior longitudinal ligament with a
pituitary rongeur. The posterior longitudinal ligament may
be sharply incised and elevated with a blunt probe, then re-
moved with angled Kerrison rongeurs for thecal decom-
pression. The cartilaginous end plates of the disk spa~e are
sharply curetted and fashioned or slotted with a high-speed
pneumatic drill bit for acceptance of a graft.
.
Vertebrectomy
and Fusion
Approach
Vertebrectomy and instrumentation require vertebral expo-
sure rostral and caudal to the level of pathology. The stan-
dard approach should be followed to anatomical levels
flanking the level of interest and then proceed toward the
region of pathology. The disks flanking the pathological ver-
tebral level are grossly resected. Vertebrectomy proceeds
from a lateral trajectory with an osteotome followed by
curettage to salvage bone for grafting. In cases where verte-
bral bone is unsuitable for graft, such as infection or malig-
nancy,vertebrectomy is performed with a high-speed driII
a'nda diamond bur. The anterior and contralateral margins
of the vertebral body remain as barriers to the great vessels.
Fineposterior bone dissection is performed with Kerrison
rongeursand curettage. The posterior longitudinal ligament
maybe excised for thecal decompression.
Flankingcartilaginous end plates are curetted and fash-
ioned prior to fusion. Hemorrhage from bone surfaces along
the fusion interface is stayed with thrombin-impregnated
Gelfoam.Bonewax is deleterious to bone fusion and should
be avoided. Physiological graft may include autologous
costal struts and humeral or tibial allograft. Titanium cages
can be fashioned to conform to end plate margins and
packedwith autologous bone. Distraction pins may be used
to place the graft under compression with caution when
distracting below calcifiedvessels, which may rupture.
For fusion with polymethyl methacrylate a large-bore
chest tube can be excised and countersunk into the flanking
vertebral bodies along its longitudinal axis. After the dura
has been protected a port is incised in the wall of the chest
tube. Rapid-setting polymethyl methacrylate
is injected
into the chest tube through a large-bore catheter. The field
is subsequently irrigated copiously to disperse heat.
.
PlateStabilization
Approach
Asan adjunct to interbody fusion plate stabilization requires
lateral exposure of vertebral bodies rostral and caudal to
the level of pathology. Following the standard approach
segmental lumbar arterial branches are identified at the
midvertebrallevelsofthe vertebrato beplatedandarelig-
ated and divided in the midline. Division of segmental
branches rostral and caudal to the level of fusion willpre-
vent vascular compression and avulsion during placement
of instrumentation.
Rarely the psoas muscle may require
incision for lateral exposure. Following lateromedial sub-
periosteal dissection the lateral vertebral margins maybe
contoured with a high-speed driII and cutting bur to create
flush apposition with the plates.
The nuances of plate stabilization vary with the system
employed. Generally, lateral plates are affixed with screws
in the midcoronal plane of the vertebrae rostral and caudal
to the level of fusion. Accurate screw placement is vitalto
avoid neurovascular injury and should be confirmed with
an intraoperative roentgen study. Cable and rod systemsare
more commonly used for degenerative and multisegmental
conditions.
Closure
Following irrigation with antibiotic solution hemostasisis
confirmed. Diaphragmatic openings may enlarge with time
and predispose to diaphragmatic hernia. and for that rea-
son they should be sutured closed. Peritoneal openings
may be closed with a running suture. Drainage of the
perivertebral space is usually not required. Musclesare
closed in layers with interrupted resorbable sutures stag-
gered through the aponeuroses. The dermis is closedwith
buried interrupted resorbable suture, and a running subcu-
ticular skin closure is reinforced with sterile adhesiveprior
to dressing application.
.
Postoperative Care
In cases of fusion/instrumentation biplanar radiographsare
obtained while the patient is supine in the recovery room.
Extubation proceeds in the early postoperative period.
Patient-controlled anesthesia may augment early mobiliza-
tion. Intravenous fluid maintenance continues until oralin-
take is advanced on the first postoperative day, coincident
with returning signs of bowel function. Intermittent naso-
gastric suction may reduce nausea in the early postoperative
period, however, the nasogastric tube should be removedas
soon as possible to prevent sinus infection. The urinary
catheter should be removed by the first postoperative day,
and signs of urinary retention should be sought and treated
with intermittent urinary catheterization.
External rigid orthosis is indicated for patients undergo-
ing bone fusion of the lumbar spine. Thoracolumbosacral
orthosis (TLSO)with a hip extension orthosis providescom-
fortable immobilization of the lumbar spine and augments
lumbar bone fusion. The orthosis should be applied while
the patient is supine, and subsequent lateral radiographsof
the lumbar spine should be compared with the patient
supine and standing. Ifthere is no radiographic instability
the patient should be aggressively mobilized with assisted
ambulation. External electrical bone stimulation mayaug-
ment bone fusion in the early postoperative period. The

81
Anterolateral RetroperitonealApproach
611
patient is advised to avoid smoking
for the duration
of the
recoveryperiod.
Stability of the lumbar
fusion segment is evaluated
3monthspostoperatively with lateral flexion/extension
ra-
diographsof the lumbar spine. If the spine appears stable
Suggested Readings
1. Bauer R. Kerschbaumer
F. Poisel S. Atlas of Spinal
Operations.
Stuttgart:GeorgThieme 1993;64-66:270-302
2. BauerR.KerschbaumerF.Poisel S.Operative Approaches in Orthopedic
SurgeryandTraumatology. Stuttgart: GeorgThieme 1987:41-63
3. BenzelEC.Biomechanicsof Spine Stabilization.
New York: McGraw-
Hill 1995
4. ColtonCt. Hall AJ.Atlas of Orthopedic
Surgical Approaches. Oxford:
Heinemann1991:112-113
external orthoses may be discontinued or retained as nec-
essary for patient comfort. Subsequent radiographs are at-
tained at 6 months and 1 year postoperatively to evaluate
bone fusion and to guide recommendations for progressive
physical exertion.
S.
Hoppenfeld
S. deBoer P. Surgical exposures in orthopedics.
The
Anatomic Approach. New York: Lippencott 1994:2:227-245
6.
Orner CE. Spinner. Van Beek At. Management of Peripheral Nerve
Problems. 2 ed. Philadelphia: Saunders 1998
7.
Spetzler RF.Op Tech Neurosurg 1:3: 127-133.1998
8.
Wmter RB.Lonstein JW. Denis F.et al. Atlas of Spine Surgery. Philadel-
phia: Saunders 1995: 368-377

82
Approach to the Lumbar Spine
RichardK.Osenbach
.
Indications
.
Advantages
.
Disadvantages
.
Objective
.
Surgical Technique
Anesthesia and Positioning
Radiological Evaluation
Operative Exposure
.
Conclusions
The pathological conditions that affect the lumbar spine are
diverse, yet among the most common problems encoun-
tered in the practice of neurosurgery. Many of these disor-
ders can be managed surgically using anyone of a variety of
surgical approaches and techniques. However, no approach
would seem more useful or versatile than the posterior
midline approach to the lumbar spine. Indeed, the posterior
midline exposure of the lumbar spine is one of, if not the
most, widely utilized approaches in neurosurgery in general
and the field of spinal surgery in particular. Consequently, it
is incumbent upon anyone who operates on this segment of
the vertebral column to be intimately familiar with the
practical regional surgical anatomy that is pertinent
to
accomplishing a safe and efficient exposure of this area.
This chapter reviews the muscular and osseous anatomy
ofthe lumbar spine along with the surgical exposure of the
dorsal spine.The chapters that follow outline more specific
techniques
and
procedures,
namely,
decompressive
laminectomy, hemilaminectomy, foraminotomy, and mi-
crodiskectomy.
.
Indications
.
Herniated lumbar disk
.
Lateralrecess stenosis due to spondylosis
.
Facetsynovialcysts
.
Central canal stenosis
612
.
Intervertebral diskitis, vertebral body osteomyelitis,or
spinal epidural abscess
.
Correction of spondylolysis/spondylolisthesis
.
Posterolateral intertransverse fusion
.
Iliaccrest bone graft harvest
.
Posterior lumbar interbody fusion
.
Pedicle screw fixation
.
Vertebral fractures
.
Epidural and intradural neoplasms
.
Advantages
.
Well-known technique
.
Versatile and can be used to address most pathologyof
the lumbar spine
.
Largespinal canal and low risk of spinal cord injury
.
Ease of localization of appropriate spinal level
.
Disadvantages
. Deepsofttissueand musculardissection
.
Riskofiatrogenicspinalinstability
. Restrictedaccesstoventralpathology

. Objective
82
Approachto the lumbar Spine
613
Thegoalof the posterior midline approach to the lumbar
spineisexposure of the posterior elements including the
laminae,zygapophyseal
joints,
and transverse
processes.
Removal ofthe lamina allows easy access to the dorsolateral
portionofthe thecal sac, exiting nerve roots, and interverte-
braldisk.Further removal of variable portions of the medial
facetandpedicles provides additional access to the inter-
vertebralforamen as well as ventral to the thecal sac in-
cluding accessto the vertebral body proper.
Theextent of the exposure and degree of bony removal
willobviouslydepend upon the goal of the operation. Exci-
sionof a herniated disk generally can be easily achieved
throughasmall hemilaminotomy. On the other hand, a pos-
teriorlumbar interbody fusion using a threaded cage usu-
allyrequiresan extensive if not complete facetectomy along
withresectionof the medial aspect of the pedicles to gain
adequate exposure of the intervertebral disk without injury
tothe neural elements.
. Surgical Technique
Anesthesia and Positioning
Mostoperations on the lumbar spine are performed
under
general endotracheal
anesthesia.
However,
for relatively
shortprocedures such as microdiskectomy, it has become
morecommon to utilize regional anesthetic techniques
suchasa spinal epidural block or in some instances even lo-
calanesthesia supplemented
with intravenous
sedation.
Just as proper positioning
is central to safety and success
forcranialprocedures, such is also the case for operations
onthespine.The posterior midline approach to the lumbar
spine is most easily accomplished with the patient
in
thedirect prone position. The patient may be positioned:
(1) using a spinal
frame
or table
in which
the
legs are
approximately parallel
to the spine, or (2) using a knee-
chest type of frame in which the hips and knees are flexed
to 90 degrees and a major portion of the body weight is
supported by the knees (Fig. 82-1).
For a straightforward,
...
-- ~
.
;?"-;~
. .
,,\
- }..
I
1
Figure 82-1
The patient
is positioned
using a knee-chest
frame,
whichallows the knees to support
a significant portion of the body
weightbykeepingthem flexedat 90 degrees.
uncomplicated posterior approach, the author prefers a
padded radiolucent spinal frame that sits atop the standard
surgical bed in a modified knee-chest position. However,
the choice of the frame or other positioning device is not so
important as is the attention to detail once the patient is
placed in the prone position.
Several important points must be borne in mind regard-
ing proper positioning because improper positioning cannot
only make the surgical procedure more difficult but can
also result in additional morbidity unrelated to the proce-
dure itself. One of the most critical points is avoiding any
significant pressure on the abdomen that can produce ele-
vated pressure in the epidural venous system and result in
vexing bleeding during surgery. The chest should be prop-
erly supported
to ensure adequate ventilation. Proper
positioning of the face requires collaboration between the
surgeon and anesthesiologist.
I prefer the face to point
straight to the floor with the head supported on a soft,
padded foam doughnut. Alternatively, the head can be
placed in a padded horseshoe headrest or immobilized in a
Mayfield pin headholder. Regardless of the method, pres-
sure on the orbits must be avoided to prevent corneal abra-
sions or visual loss. The neck should be maintained in a
roughly neutral position and should approximately parallel
the contour of the upper thoracic spine.
The upper extremities
should be positioned with the
shoulder abducted and elbow flexed 90 degrees and sup-
ported by adequate foam padding. Excessive abduction or
flexion of the shoulder should be avoided because this can
result in a stretch injury of the brachial plexus. The position
of the legs is also important in terms of ease of access to the
spinal canal. Flexionof the hip reduces the amount of lordo-
sis, increases the interspinous and interlaminar distances,
and facilitates access to the spinal canal. In contrast, de-
pending on the goal of surgery, lordosis can be maintained
by extending and elevating the hips. Flexion of the knee re-
duces the degree of stretch on the sciatic nerve. Although it
is customary to place a safety strap across the buttock or
upper thighs to stabilize the pelvis, a strap made too tight
for a long procedure can result in a pressure palsy of the sci-
atic nerve. The feet should be elevated to facilitate venous
drainage. Finally,pressure points such as the anterior iliac
crest should be adequately padded to prevent a neuropraxia
of the lateral femoral cutaneous nerve.
Radiological Evaluation
Accurate intraoperative localization begins with a careful
preoperative review of the radiographic studies. In this re-
gard, I routinely obtain an anteroposterior (AP)and lateral
plain radiograph of the area of interest to exclude aberrant
anatomy such as an altered number of rib-bearing thoracic
vertebra and lumbarized or sacralized segments caudally.
Indeed, it is the responsibility of the surgeon to recognize
any variations and operate on the correct level. In the lum-
bar spine (particularly for a single-level lumbar diskec-
tomy), the level is initially approximated from the plain
x-rays realizing that the intercrestal line usually passes
through the L4-L5interspace (Fig.82-2). Alternatively, af-
ter prepping the skin,a sterile 18gauge spinal needle can be
inserted and the position confirmed with a lateral x-ray.

614
LumbarandLumbosacralSpine:PosteriorApproach
The lumbodorsal fascia can now be identified by its inter-
digitating fibers. As one proceeds more caudally and en-
counters the segment overlying L5-Sl, this becomes even
more apparent and can be a helpful landmark in the very
obese patient in whom precise localization can be problem-
atic. The fascia is extremely robust in this region. beingre-
inforced by the aponeuroses of the latissimus dorsi and
posterior serratus inferior muscles (Fig.82-3). The fasciais
opened in the midline using either a fresh scalpel or the
electrocautery.
Alternatively. the fascia may be opened
slightly off the midline. The latter technique may providea
slightly better cuff of fascia on either side to facilitate
closure.
The next step in exposing the dorsal spine involves
dissection of the paraspinous
musculature. The lumbar
paraspinous muscles are arranged into superficial and deep
layers. In addition to the lumbodorsal fascia. which en-
velopes the underlying deep muscles. the superficial layeris
primarily composed of the erector spinae muscles. The
latter consist of the spinalis. longissimus. and iliocostalis
in a medial to lateral direction (Fig. 82-4). The deep
layer of muscles includes the multifidus. rotatores. and
intertranversarii.
Although there are many techniques for performing a
subperiosteal dissection of the paraspinous musculature,
there are several themes that should be common to any
technique. namely. safety. efficiency. and minimal blood
loss. The fascial attachment
to the spinous process is
divided just off the midline to introduce a periosteal eleva-
tor at the most dorsal. superior margin of the spinous
process.Themusclesare stripped fromsuperficialto deep
until the laminar surface is encountered. The laminar at-
tachments can then be swept from medial to lateral. Inser-
tion of a gauze sponge can facilitate the periosteal dissec-
tion. especially the medial to lateral dissection to expose
the facets (Fig.82-5). Although considerable force is some-
times required in heavily muscled patients to accomplish
the exposure. all movements must be precisely controlled.
Excessivedownward force should be avoided to prevent in-
jury to the neural elements or creation of a dural tear and
cerebrospinal fluid ((SF) leak. This can sometimes occurin
patients with occult spinal dysraphism and is also a poten-
tial pitfall in patients with posterior element fractures.
Additionally. in some patients. the interlaminar space can
/'
Figure 82-2
The intercrestalline usuallypasses through the L4-L5
interspace. which is approximated
by careful preoperative
review of
the anteroposterior
and lateral plain x-rays.
The tract can then be marked by injecting sterile methylene
blue. Fora single-level lumbar diskectomy. a 3 to 4 em inci-
sion is highlighted using an indelible marker that will not
come offduring prepping. It is certainly possible to perform
microdiskectomy through a smaller incision. However. the
incision should at least be sufficiently large to accommo-
date whichever self-retaining retractor is used to prevent
the device from stretching and damaging the skin edges.
Indeed. this can result in poor wound healing and occasion-
allysuperficialwound dehiscence.
Oncethe superficial exposure is made. an intraoperative
x-ray is obtained with a towel clip on the exposed spinous
process to confirm the operative level. Alternatively. one
canuse (-arm fluoroscopy if available for localization. How-
ever.regardless of the method utilized. the surgeon must al-
ways be confident that the level is correct. Anysignificant
deviation from the expected pathological findings based on
the preoperative imaging should prompt an immediate re-
assessment of the level. Ifthere is any question. the surgeon
should reexamine the imaging studies and obtain another
confirmatoryintraoperative x-ray.
Operative Exposure
The proposed skin incision and underlying subcutaneous
tis-
sues are infiltrated with a 50: 50 mixture of 1%lidocaine with
1:200.000 epinephrine and 0.5% bupivacaine. Injection of lo-
cal anesthetic
with epinephrine
reduces bleeding and limits
the need for cautery in the subcutaneous
tissues. The skin is
sharply incised and extended into the subcutaneous
tissues.
Hemostasis
is achieved
at each step of the procedure
as
necessary
using bipolar electrocautery.
although
excessive
cauterization
with charring of tissues
should
be avoided.
Dissection
of the subcutaneous
tissues
can be completed
with either the scalpel or the monopolar electrocautery.
The
subcutaneous
tissues are then retracted using a self-retaining
Weitlander
retractor. Once again. care should be exercised to
avoid damage to the skin edges with the retractor.
Figure 82-3
Cross-sectionalaxialanatomy of the L5-S1 region.

82
Approach to the lumbar Spine
615
\
beratherwide, in which case caution must be exercised to
avoidinadvertent penetration into the spinal canal. The ex-
tentofthe lateral dissection will be determined by the op-
eration.Fora simple hemilaminectomy and diskectomy, a
unilateralexposure that extends just to the facet joint is
)
/
Figure 82-4
Anatomicallocationofthe deep paraspinalmuscula-
ture inthe L5-S1region.
customarily adequate. On the other hand, a posterolateral
fusion requires a wide bilateral exposure that completely
exposes the facet joint and the transverse processes, which
lie more laterally and deep. There are numerous
self-
retaining
retraction
systems
that
can be utilized
for
B
A
Figure82-5
(A)The paraspinal muscles are stripped superficialto deep from their attachment locations on the periosteum. (8) The laminar
attachmentsare sweptfrom medialto lateralto exposethe facet.

...
616
Lumbar and Lumbosacral Spine: Posterior Approach
f.
A .
.7
-
~ . /-
(
I
\
,L
,,'I
t
\
I
I B
Figure 82-7
(A) In the lower lumbar spine each vertebra
articulates
with its neighbor
rostrally
and caudually through
the disk and the facet joint.
(B) Normal anatomy of the lumbosacral
spine.
maintaining the exposure. The ideal system is one that is
simple to use, maintains a low profile so as to be unobtru-
sive and preserve lines of site to the surgical field. provides
a variety of retractor blades, and is radiolucent so as not to
interfere with the useof intraoperative imaging.
Once dissection and retraction
of paraspinous muscles
are complete. the surgeon has a full view of the posterior
spine (Fig. 82-6). The spinous processes become progres-
sively larger in the lumbar spine. Although
the spinous
processes in the thoracic spine point inferiorly,
this be-
comes less apparent in the lumbar spine. Indeed at the
lower lumbar levels, the spinous processes point directly
posteriorly. Eachvertebra articulates with its neighbor ros-
trally and caudally through the intervertebral
disk and the
facet joints (Fig. 82-7). Each facet consists of the inferior
articular process of the vertebra above and the superior ar-
ticular processof the vertebra below. The inferior processis
situated medially with the superior processlaterally. An im-
portant structure is the pars interarticularis. a portion of the
lamina that provides the bony connection
between the
superior and inferior
articular
processes of an individual
vertebra. The transverse processesproject laterally from the
level of the superior articular facet.
The
important
ligamentous
structures
include
the
supraspinous and interspinous ligaments. the ligamentum
fIavum. the facet capsule. and the intertransverse ligament.
The iliolumbar ligaments run from the transverse processes
of LSto the iliac crestsand help stabilize this area.
The sacrum is composed of fused remnants of segmental
bony elements. The dorsal surface is irregular owing to the
presence of irregular crests overlying the fused spinous,
articular.
and transverse
processes. On either
side of
the sacrum are four pairs of foramina for the passageof the
\
Figure 82-6
After dissection and retraction
of the paraspinal mus.
cles a full view of the dorsal
aspect
of the lumbar
spine is available.
dorsal rami of the sacral nerve roots. Caution
must beexer-
cised when exposing the sacrum to avoid passage into these
openings
with
resultant
bleeding
or cerebrospinal
fluid
leakage.
'. /

. Conclusions
82
Approachto the LumbarSpine
617
Although the posterior
midline
approach to the lumbar
spineseems simple. failure to understand
variations
in
localanatomy and failure to adhere to meticulous surgical
Suggested Readings
1. Kramer DL,Booth RE,Albert Tj, et al. Posterior lumbar approach. In:
Albert Tj, Balderston
RA, Northrup
BE.eds. Surgical Approaches
to the
Spine. Philadelphia:
WB Saunders;
1997:173-192
2. Long D. McAfee PC. eds. Atlas of Spinal Surgery. Baltimore:
Williams
&Wilkins; 1992:2-22
techniques
can result in significant
morbidity
from the soft
tissue
exposure
alone. However,
the surgeon
who has a
grasp of the anatomy and adheres to strict principles
of
proper surgical technique will usually be rewarded with a
successfuloutcome.
3.
Mclain
R. Surgical approaches to the lumbar
spine. In: Frymoyer jW,
ed. The Adult Spine:
Principles
and Practice.
2nd ed. Philadelphia:
Lippincott-Raven;
1997:1723-1744
4.
Watkins RG.Posterior surgical approaches to the lumbar spine. In:
Andersson G. McNeill TW. eds. Lumbar Spinal Stenosis. St. Louis:
Mosby; 1992:31-45

83
Lumbar Laminectomy
Richard K.Osenbach
. Advantages
.
Disadvantages
.
SurgicalTechnique
RemovalofSpinousProcessesand lamina
Closure
.
Complications
Bilateral lumbar laminectomy is most commonly performed
to achieve decompression of neural elements that reside in
a stenotic spinal canal in patients with degenerative spinal
stenosis who present with neurogenic claudication. The fact
is, some degree of laminectomy is usually required to con-
duct many of the various procedures that are performed on
the lumbar spine. For example, a standard open lumbar
microdiskectomy usually requires at least a small hemi-
laminotomy (discussed in Chapter 84) for removal of the
prolapsed disk material. In contrast, procedures such as de-
compression for degenerative spinal stenosis, posterior
lumbar interbody fusion, the trans pedicular approach for
decompression of a burst fracture, and certain cases requir-
ing instrumentation (e.g., pedicle screw fixation, threaded
interbody cages, ete.) require a more radical bilateral expo-
sure to properly decompress the neural structures. In the
case
of
classic
degenerative
lumbar
spinal
stenosis,
laminectomy
alone
is often
not
sufficient
to achieve
adequate
decompression
of the
thecal
sac and nerve
roots because the compression
is frequently multifactorial
(Table 83-1).
In many instances,
the laminectomy mustbe
supplemented
by one or more of the following: partial face-
tectomy,
foraminotomy
(Chapter
85), and diskectomy
(Chapter
86). Occasionally,
the decompression
results in
spinal instability
necessitating
the incorporation ofa bony
arthrodesis
and instrumentation.
In any case, the extentof
the decompression
required
is dictated by the locationand
extent
of pathology
in an individual
case. This chapter de-
scribes
the
technique
of bilateral
lumbar
laminectomy
along with the pitfalls to be avoided, with emphasis onthe
relevance of this procedure
to the treatment
of degenerative
spinal stenosis.I-S
Table 83-1
Anatomical Factors Contributing to Lumbar Spinal Stenosis
Congenitally short pedicles
Facet joint hypertrophy (usually the superior facet)
Disk space narrowing with upward migration of superior articular process into neural foramen
Acute herniated disk superimposed
on already narrowed canal
Chronic calcified disk
Disk margin osteophyte
Thickening of ligamentum flavum
Synovial cyst formation
Degenerative spondylolisthesis
618

. Advantages
. Familiarapproach
. Directaccess to posterior pathology
. Disadvantages
. Laminectomyalone is often not sufficient
to achieve ad-
equatedecompression
of the thecal sac and nerve roots.
. Canpotentially result in spinal instability
. SurgicalTechnique
Thebasictenets of patient positioning and intraoperative
localizationhavebeen outlined in Chapter 1 and will not be
repeated.However,one point regarding positioning bears
reiteration.It is extremely important that the patient be
positionedsuch that the abdomen hangs free. Indeed,
83
Lumbar Laminectomy
619
pressure on the abdomen will increase the pressure within
the epidural venous plexus and likely lead to annoying ve-
nous bleeding throughout the procedure.
A midline incision is marked based on the radiographic
studies that demonstrate the pathology to be addressed. The
incision is made and the dissection proceeds in exactly the
same fashion described previously(see Chapter 82).The fas-
cia is opened over the spinal segment to be exposed and a
subperiosteal dissection isperformed to gainexposure of the
dorsal aspect of the spine. Once the laminae have been
cleared at the appropriate levels,a self-retaining retractor is
inserted to maintain lateral retraction of the paraspinous
musculature. The exposure required for a straightforward
laminectomy need only be taken as farlaterallyas the axis of
the facetjoints. However,further lateral exposuremaybe re-
quired if a fusion or insertion ofinstrumentation isplanned.If
further lateral exposure is required, one can identifythe base
of the superior articular process and dissect the tissue offof
its inferior and lateral surface, which will lead to the base of
the transverse process. The dissection should not go beyond
the tip of the transverse process to avoid injury to the neu-
rovascular structures in the intertransverse space (Fig.83-1).
Figure 83-1
Theexposed anatomy ofthe intertransversespace.
The dissection should not go beyond the tip of the transverse
processto avoidinjury.

620
Lumbarand LumbosacralSpine:PosteriorApproach
Removalof SpinousProcessesandLamina
After completing the exposure, one is ready to proceed
with the laminectomy. The spinous processes are first
removed at the levels to be decompressed. This is easily ac-
complished using a large rongeur or a Horsley bone cutter
(Fig.83-2). One must avoid biting too deep; otherwise the
posterior apex ofthe spinal canal can be entered, potentially
producing a dural injury with cerebrospinal fluid ((SF) leak-
age or even injury to elements of the cauda equina. The liga-
mentum flavum is then detached from the inferior aspect of
the lamina (Fig. 83-3). The author has found that a broad,
flat dental instrument is ideal for this maneuver; an Adson
periosteal elevator or a small curette works equally well.
Alarge Leksellrongeur is used for the initial phase of the
laminectomy. The lower blade should be inserted just be-
neath the leading inferior edge of the lamina -30 degrees
from the vertical or 60 degrees to the long axis of the spine
(Fig. 83-4). Maintaining the instrument at this angle will
help prevent insertion of the lower blade too deep into the
spinal canal. Removal of each side is performed in turn and
additional ligamentum flavum is removed as necessary. As
the pedicle is approached, the lamina tends to become
thicker and substitution of a narrower instrument facilitates
t
Figure 83-2
A rongeur is used to remove the spinous processofthe
levels to be decompressed.
I
I
Figure 83-3
A small curette is used to detach the ligamen-
tum flavum from the inferior aspect of the lamina.

f
Figure 83-4
To prevent insertion of the lower blade too
deep into the spinal canal the lower blade of the Kerrison
rongeur should be inserted just beneath the leading inferior
edge of the lamina at- 30 degreesfrom vertical or 60 degrees
from the spine.
--
-r
I
~
I
I,
Figure83-5
A scalpel is used to remove the ligamen-
tum flavum from the bone while the underlying dura is
protected with adural elevator.

622
Lumbarand LumbosacralSpine:PosteriorApproach
bone removal. In most cases, it is desirable to first create
a trough in the center of the lamina. This facilitates removal
of the more lateral portions of the lamina on each side
using a series of Kerrison rongeurs. In many patients, the
ligamentum flavum can be removed along with the bone by
first separating the ligamentum from the dura. However,
this must be done with extreme care as the ligamentum is
not uncommonly adherent to the underlying dura. Indeed,
taking a bite of lamina and ligamentum with a dull Kerri-
son rongeur and pulling on ligamentum that has not been
completely separated from the dura will more often than
not lead to a dural tear and CSFleak. Consequently, this
technique, although
useful if performed
carefully, can
lead to complications when performed in haste. Assuming
the ligamentum is to be removed separately, this can be
accomplished by sharp dissection using a scalpel while
protecting
the underlying
dura with
a dural elevator
(Fig.83-5).
The preceding bone removal will produce a central de-
compression. In patients with severe spinal stenosis, this of-
ten may not be adequate and further lateral decompression
with undercutting of the facet is required. This is most eas-
ily accomplished using 45 degree Kerrison punches (2, 3,
and 4 mm). The plane between the ligamentum flavum and
the dura should be clearly identified before inserting the
footplate of the instrument to avoid dural tears and injury
to the nerve roots (Fig. 83-6). If possible, the epidural fat
should be preserved, although there is often a paucity of
fat in patients with very severe stenosis. Ifepidural bleed-
ing occurs, it should be controlled with warm irrigation,
hemostatic agents (Gelfoam, thrombin, Surgicel, etc.)and
gentle tamponade. However, one should avoid leavinglarge
amounts of hemostatic agent lest the stenosis be re-created.
Bipolarcautery may be used cautiously if a specific bleeding
point can be clearly identified.
Laminectomy performed with high-speed drills has be-
come a popular technique. Indeed, careful use of a drillin
experienced hands can greatly facilitate the operation. Con-
versely, improper use of such an instrument can result in
significant morbidity such as dural tears and injury to the
cauda equina. There are two basic methods of removing
bone using a high-speed drill. The first is to progressively
thin the lamina to the thickness of an eggshell using a large
cutting bit and then removing the remaining bone in the
standard fashion already described (Fig. 83-7). The other
and perhaps riskier technique involves en bloc removalof
the lamina using a footplate inserted beneath the edgeof
the lamina (Fig.83-8). This technique is not only more dan-
gerous but is probably ill advised in patients with signifi-
cant canalstenosis.Inanyevent,this techniqueshouldonly
be performed by individuals who are intimately experi-
enced with the use of such instruments and only then after
extensive practice in the laboratory on cadaveric spines.
Closure
Prior to closure, the self-retaining retractors are loosened
and meticulous hemostasis is performed. In the author's
Rgure 83-6
The footplate of the Kerrison punch
is inserted between the ligamentum flavum and
the dura to avoid dural tears and injury to the
nerve roots.

I
83
LumbarLaminectomy
623
)
~-
.
Figure 83-8
The lamina is removed as a whole by inserting
the foot-
plate beneath the edge of the lamina.
,
Figure83-7
The lamina
is thinned
to the
thickness
of an eggshell
using a large cutting
bit. The bone is then carefully
removed
using
the standard fashion.
experience, proper attention
to hemostasis
will almost
always obviate the need for a drain. However, in selected
cases in which an extensive dissection has been performed,
an epidural drain left in place for 24 hours may be quite
reasonable. One should try to avoid an epidural drain at all
costs if a dural tear and CSFleak have occurred.
The paraspinous muscles are reapproximated with inter-
rupted absorbable sutures such as O-Vicryl,although tying
the sutures excessively tight should be avoided. Rather,
bleeding points should be controlled using bipolar cautery.
The lumbodorsal fascia should be carefully and accurately
closed with an absorbable suture. The author's preference is
to use interrupted sutures ofO-Vicryl; a continuous suture
is also acceptable provided the knots are carefully secured.
The subcutaneous tissues should be closed with absorbable
suture. The sutures through the deep subcutaneous tissues
can incorporate the fascia to eliminate any potential dead
space. The skin is closed with a running suture of nylon or
can be reapproximated with surgical staples, or even a run-
ning subcuticular suture.
.
Complications
Complications following lumbar laminectomy alone are
mostly related to infection,CSFleakage,and postlaminectomy
spondylolisthesis.Neuralinjury is rare and can almost univer-
sally be avoided by attention to proper surgical technique.

624
LumbarandLumbosacralSpine:PosteriorApproach
The incidence of wound infection in a clean, uncomplicated,
noninstrumented laminectomy should not exceed 2 to 3%.
The risk of wound infection can be reduced by the use of a
single dose of a prophylactic antibiotic directed against skin
flora. This antibiotic should be chosen based on the infec-
tions encountered and drug sensitivities for an individual
institution. Other measures that can reduce infectious com-
plications include achievement of meticulous hemostasis
and gentle handling of tissues.
Dural injury with (SF leakage has been reported to occur
in as high as 15%of cases of lumbar laminectomy.Duraltears
are better avoided than repaired and the measures to avoid
dural tears have already been outlined. Ifa clean tear occurs
in the dorsolateral dura, every attempt should be made to
perform a primary repair. Ifthe tear is irregular and wide, a
graft can be utilized. Ifthe tear is ventral, repair will be ex-
tremely difficult if not impossible and attempts at primary
repair mayonly serve to enlarge the defect. In such cases,the
References
1.
Kramer
DL. Booth RE. Albert T]. et al. Posterior
lumbar
approach.
In:
Albert T], Balderston
RA.Northrup
BE. eds. Surgical Approaches
to the
Spine. Philadelphia:
WB Saunders;
1997:173-192
2.
Long D. McAfee PC. eds. Atlas of Spinal Surgery.
Baltimore:
Williams
& Wilkins;
1992:2-22
3.
Watkins
RG. Posterior
surgical
approaches
to the lumbar
spine. In:
Andersson
G. McNeill TW. eds. Lumbar
Spinal
Stenosis.
St. Louis:
Mosby; 1992:31-45
dural opening
should be covered with a layer of Gelfoam.
Alternatively,
a piece of fascia can be used and secured in
place using fibrin glue. In the latter cases, a lumbar subarach-
noid drain will provide (SF diversion while the defect heals
and will lessen the chances of (SF cutaneous
fistula.
The incidence of iatrogenic postlaminectomy
spondylolis-
thesis has been reported to run between 4 and 15%.6The risk
of a slip depends on several factors, including the number of
levels operated.
the extent
of the decompression,
whether
partial or complete
facetectomies
have been performed, and
the presence of increased or decreased joint mobility preop-
eratively, patient
age, and degree of spondylosis.
Theoreti-
cally, a complete unilateral facetecto my can be safelyper-
formed
as long as the
contralateral
joint
is intact. The
presence of preoperative
hypermobility
is generally taken as
an indication for fusion. Older individuals with markedly de-
generated
motion segments
are far less likely to develop a
subsequent
slip as compared
with younger patients.
4.
McLain R. Surgical approaches
to the lumbar
spine. In: Frymoyer jW.
ed. The Adult Spine:
Principles
and Practice.
2nd ed. Philadelphia:
Lippincott-Raven;
1997:1723-1744
5.
Torrens M]. Lumbar laminectomy.
In: Torrens M]. Dickson RA.eds. Oper-
ative Spinal Surgery. Edinburgh:
Churchill
Livingstone;
1991:119-124
6.
Shenkin
HA. Hash
CJ. Spondylolisthesis
after
multiple
bilateral
laminectomies
and facetectomies
for lumbar
spondylosis:
follow-up
review.]
Neurosurg
1979;50:45-47

84
Hemilaminectomy
RichardK.Osenbach
. Advantages
. Disadvantages
. SurigicalTechnique
Preparationand Positioning
Closure
Uniiaterallaminectomy!laminotomyor hemilaminectomy!
hemilaminotomyis performed in a manner quite similar to
thatdescribedforbilateral lumbar laminectomy.1.2The ma-
jordifferenceisthat the dissection is limited to one side of
theinterspinousligament.Restricting the exposure to a sin-
glesideenablesone to limit the size of the initial skin inci-
sion.The primary indication for hemilaminectomy
or
hemilaminotomyis to create an exposure that will allow
foraminotomy
or removalof a herniated disk or both.
. Advantages
. Smallerskin incision
. Unilateralmuscle dissection
. Disadvantages
. Lateralexposure and bony removal may lead to postop-
erativepainor instability.
. SurigicalTechnique
Preparationand Positioning
Mostprocedures are performed
under general anesthesia,
althoughit has recently
become
increasingly
popular
to
employregional anesthetic
techniques,
thereby
avoiding
the potentially undesirable
side effects of a general
anes-
thetic.The standard position
is to have the patient
prone,
supportedon a standard spinal frame or chest rolls. Again, it
cannotbe overemphasized
that the abdomen
should hang
freetoavoidincreased pressure in the epidural veins and
vexingbleeding during the procedure.
Alternatively,
some
surgeons prefer and are more comfortable with the lateral
decubitus position. This position obviously avoids any pres-
sure on the abdomen. However, this position can be awk-
ward for those not accustomed to operating in this position.
Once the patient is properly positioned,
prepped, and
draped, lateral fluoroscopy is used to locate the appropriate
level to minimize the length of the incision required.
Asmall midline incision is marked, centered over the in-
terlaminar space of interest. The incision is made sharply
and the initial dissection through the subcutaneous tissues
proceeds in a manner identical to that described previously
(Chapter 82). A brief word of caution is offered regarding
the size of the incision. Although a small incision obviously
is pleasing to the patient, one should not make the incision
so small that it cannot accommodate the self-retaining re-
tractors without stretching and contusing the skin edges.
Indeed, the author has observed several cases of skin dehis-
cence and wound infection related to retractor trauma
caused by failure to make a large enough skin incision. In
the author's opinion, this is a preventable complication and
should never occur with proper technique and tissue
handling.
Next, the lumbodorsal fascia is incised in the midline over
a distance between the spinous processes immediately
above and below the level of pathology (Fig.84-1). Alterna-
tively, the incision in the fascia can be made just off the
midline to provide a better cuff of fascia for closure. The
paraspinous muscles are then detached from the spinous
processes and swept laterally to expose the laminae overly-
ing the herniated disk, or other pathology such as lateral
recess stenosis or a synovial cyst.Thisdissection can be per-
formed with the electrocautery or using a periosteal eleva-
tor (Fig.84-2). The latter tends to create more bleeding and
therefore the author prefers to use the electrocautery for
this purpose. Regardless of the technique, caution must be
exercised to avoid violation ofthe spinal canal. Fora unilat-
eral dissection, the spinous processes are not removed and
it is not only possible but also prudent to preserve the inter-
spinous ligaments. The paraspinous muscles are retracted
625

626
Lumbar and Lumbosacral Spine: Posterior Approach
Figure 84-1
A midline incision over a distance be.
tween the spinousprocessdirectly above and belowthe
level of pathology is made to retract the lumbodorsal
fascia.
laterally and held out of the way using any of a variety ofre-
traction devices. The author's preference is to use a Gelpe-
Myerding retractor that has a toothed blade to hold the
muscles laterally and a spike that is anchored medially in
the interspinous ligament (Fig.84-3). Alternatively,a Taylor
retractor can be inserted lateral to the facet joint and willbe
just as effective.
Once the exposure of the laminae and interlaminar space
has been completed, fluoroscopy is again used to reconfirm
the level before proceeding with bone removal. The inter-
laminar space is now clearly defined along with the inferior
edge of the rostral lamina and the inferior edge of the
caudal lamina. The ligamentum superior fIavum is detached
from the inferior surface of the lamina above using a fine
curette (Fig. 84-4). In some patients, the lamina may over-
lap significantly and there is essentially no interlaminar
space. In those cases, a portion of the inferior lamina may
need to be removed with a high-speed drill to gain accessto
the ligamentum fIavum. The most inferior edge of the
hemilamina is easily removed with the Leksellrongeur.The
ligamentum fIavum is detached more cephalad as necessary
and the hemilaminectomy is completed with 45 degree an-
gled Kerrisonpunches (Fig.84-5). The rostral extent of bone
removal required to expose the disk will vary from one
individual to another and also from one spinal level to an-
other. Forexample. the L5-S1 disk space lies approximately
Figure 84-2
The paraspinal
muscles are detached
from the spinous
process to expose the laminae overlying the herniated disk.
, Ift,,,-
",,C6 -
r
'f;
,
"
( pi
/' \
....'/
..
0
'--./
t
'1

84
Hemilaminectomy
627
---
I
__1
Figure84-3
Theparaspinal muscles are retracted laterally using a Gelpe-Myerding retractor that is anchored in the interspinous ligament.
atthelevelof the interlaminar space. Indeed, some individ-
ualshave an extremely large LS-S1 interlaminar
space
makingbone removal either unnecessary or minimal. How-
ever,as one progresses cephalad, the disk space becomes
morecephalad in relation to the interlaminar space, and
therefore,exposurerequiresproportionatelymorebonere-
moval.Some bone from the medial aspect of the facet or the
pars interarticularis may need to be removed to achieve ad-
equate lateral exposure. This is especially important with a
large disk herniation to mobilize and retract the nerve root
v
--
A
'-' '--
B
Figure84-4
(A) Afinecurette is used to detach the ligamentum flavumfrom the inferiorsurface ofthe lamina. (8) Surgicaldepiction of the
processofseparatingthe ligamentumflavumfromthe epiduralspace.

-
628
Lumbar and Lumbosacral Spine: Posterior Approach
Figure 84-5
AKerrisonpunch isused at a 45 degree angle to com-
pletethe hemilaminectomy.
without undue pressure. Although the facet can be under-
cut to improve lateral exposure, the facet capsule should be
preserved. Disruption of the facet capsule can lead to signif-
icant, sometimes disabling, postoperative back pain. How-
ever, if the facet capsule and facet joint are damaged, it is
often better to perform a complete medial facetectomy be-
cause this is less likely to cause significant postoperative
,/
-....
I
r
back pain than is leaving a damaged unstable joint. Aslong
as the contralateral facet is intact, unilateral facetectomy
should theoretically not result in spinal instability. Also,a
portion of the pars interarticularis should be preserved to
maintain stability of the motion segment. Once the bonere-
moval is complete, a small amount of bone wax applied
with a PenfieldinstrumentwiIIeasilycontrolbleedingfrom
the bone.
To expose the nerve root and underlying disk, the liga-
mentum fIavum must be removed. This task can be accom-
plished in several ways and is performed by the author in
the following manner. Using loupe magnification and a
headlight (the operating microscope can also be used),
the ligamentum
flavum is grasped with a fine-toothed
forceps and incised longitudinally using a no. 15 blade on
a long handle (Fig. 84-6). The opening is made at an angle
to avoid incising the ligament obliquely. A Penfield no.4 is
then used to further separate the fibers and gently "pop"
into the epidural space. At this point. the fibers of the lig-
amentum flavum can be rather easily split longitudinally
to enlarge the opening. A small cottonoid is inserted into
the epidural space to protect the dura and a generous
window of ligament is excised. Additional ligament can
then be removed using Kerrison rongeurs. Extreme medial
removal of ligament is not advised because this is most
often not necessary and placement
of the footplate of
the
Kerrison
medially
has been
known
to produce
dural tears
outside
the extent
of the bony opening.
Indeed, these may sometimes
go unnoticed
at surgery
and only become apparent
when the patient
returns
postoperatively with (SF drainage from the incisionor
\
'II
Jlj
II
Figure 84-6
The ligamentum flavum is secured with a
toothed forceps and the ligamentum flavumisincised lon-
gitudinallyusinga no. 15 blade.

84
Hemilaminectomy
629
complainingof postural headaches and is discovered to
havea pseudomeningocele.
Closure
Closureof the incision is straightforward. Prior to closure,
Valsalva'smaneuver to 40 cm H20 is performed
and the ex-
poseddura is inspected for any leakage of (SF. None being
References
1. Kempe L. Lumbar radiculoneuropathy:
herniated
intervertebral
disk.
In: Kempe
L, ed.
Operative
Neurosurgery.
Vol
2. Berlin:
5pringer-
Verlag;
1970:266-276
seen, the self-retaining retractor is removed and any bleed-
ing points on the muscle are controlled with the bipolar
cautery. Asingle suture is usually sufficient to reapproxi-
mate the paraspinal muscles and eliminate any potential
dead space. The fascia is then carefully reapproximated
with interrupted absorbable sutures. The subcutaneous tis-
sues and skin are closed in a standard fashion based on the
surgeon's preference.
2.
Hitchon
P, Traynelis
V. Lumbar
hemilaminectomy
for excision
of a
herniated
disk. In: Rengechary
55, Wilkins
RH, eds. Neurosurgical
Operative
Atlas. Voll
Baltimore:
Williams & Wilkins;
1991 :135-140

85
Foraminotomy
RichardK.Osenbach
.
Advantages
.
Disadvantages
.
Objectives
. Anatomy
Boundaries of the Intervertebral Foramen
.
SurgicalTechnique
Foraminotomy is an important procedure in spinal surgery.
It is most commonly performed to treat foraminal stenosis
caused by nerve root compression from the superior articu-
lar process and pedicle or from a foraminal disk hernia-
tion.I-5 Less commonly, nerve root compression
results
from an osteophyte originating from the posterior aspect of
the vertebral body (Fig.85-1).
. Advantages
.
Can directly address cause of foraminal
compression
. Preservationofmotionsegmentstability
.
Disadvantages
. Notapplicableas a sole approachto more diffuse
pathology
.
Objectives
The goals of foraminotomy, decompression of the exiting
nerve root and preservation of motion segment stability,
can usually be accomplished by removal of part of the pedi-
cle and the undersurface of the superior articular process
from the vertebra below without violating the integrity of
the facet joint proper. Although partial or complete medial
facetectomy is occasionallynecessary, decompression of the
630
-
root can be accomplished
in the majority of cases by simple
bone removal without
entering the joint.
. Anatomy
Boundaries of the Intervertebral
Foramen
Superior: cephald pedicle
Inferior: caudal pedicle
Roof:superior articular facet
Floor: posterior vertebral body and intervertebral disk
The key to foraminotomy is an understanding
of the
anatomy of this region (Fig.85-2). The superior boundaryof
the intervertebral foramen is the caudal surface of the supe-
rior pedicle whereas the inferior boundary is formed by
the cephalad surface of the inferior pedicle. The floor ofthe
foramen consists of the posterior border of the cephalad
vertebral body, the intervertebral disk, and perhaps the up-
permost portion of the posterior aspect of the more caudal
vertebral body.The roof is formed primarily by the superior
articular process and pars interarticularis of the caudal seg-
ment. In the lumbar spine, the exiting spinal nerve traverses
the upper portion of the foramen, passing beneath its corre-
sponding pedicle; in other words, the LSnerve root will pass
beneath the LSpedicle and exit through the LS-S1foramen.
The sinuvertebral nerve and its corresponding artery also
pass through the foramen just inferior to the spinal nerve.
There are also several veins that traverse the foramen. The
dorsal root ganglion lies in the distal portion of the foramen.

85
Foraminotomy
631
c
A
Figure85-1
(A) Stenosis secondary to facet hypertrophy.
(8) Nerve root compression
secondary
to herniated disk. (e) Foraminal stenosis sec-
ondaryto foraminal osteophyle.
.
SurgicalTechnique
Figure85-2
Illustration depicting the anatomy of the foramen with
a pathological process.
The exposure required for foraminotomy is identical to that
described in the previous chapters and will therefore not be
repeated. A hemilaminectomy is performed and the liga-
mentum flavum removed to enter the epidural space. Small
Kerrison punches are used to remove the lateral portion of
the ligamentum and extend the dissection as far laterally as
possible. When gaining lateral exposure, the punches must
be used very carefully to avoid injury to the nerve root. The
root should be visualized at all times. A Penfield no. 4 dis-
sector is ideal for probing and verifying the plane between
the lateral dura of the root sleeve and the lateralligamen-
turn to be removed. Once the ligamentum has been re-
moved, it should be possible to visualize the nerve root
winding around the pedicle and the site of compression
within the foramen. The foramen can be probed to assess
the extent of narrowing and root compression.
After the anatomy has been assessed. the next step is to
remove the undersurface of the superior articular facet.
This maneuver can be accomplished in several ways. Per-
haps the easiest is to use small angled Kerrison punches
with a thin footplate. The footplate is inserted under the

632
Lumbar and Lumbosacral Spine: Posterior Approach
A
c
B
lip of the superior articular process, and the lower portion
of this structure is removed (Fig. 85-2). Keep in mind that
the nerve root should be visualized at all times and care
must be exercised not to traumatize
the nerve during the
process of bone removal. A second method is to create a
new foramen using small osteotomes. An osteotome is
used to remove the inferior
one half to two thirds of the
Figure
85-3
(A) An osteotome
is used
to remove the inferior one
half to two thirds of the superior
articular
process. (8) A high-speed
drill can also be used to remove
the bone. (C) As bone is progres-
sively removed
and compression
on the nerve root lessens, one can
actually
observe the root to migrate
laterally
and the tension on the
root to decrease.
superior articular
process and then gradually thin the
pedicle until the nerve root has been adequately decom-
pressed (Fig. 85-3A). This technique involves removing
thin slivers of bone; if one attempts to remove large por-
tions, it is easy to fracture the zygapophyseal joint or the
pedicle. It is important
that fragments of bone not be
driven into the nerve root or left in the foramen to cause

85
Foraminotomy
633
residualcompression.Yeta third methodof bone removal
isby the use of a high-speed drill (Fig. 85-38).
If one
electsto use a drill, it is critical that the nerve root and
thecalsac be protected at all times. This can be done by
havingthe assistant gently retract the root medially.An
appropriatecutting bur is then carefully inserted into the
foramenand both the pedicle and superior
articular
processesare drilled away until sufficient space has been
createdforthe exitingnerve root.Asbone is progressively
removedand there is less compression on the nerve root,
onecan actually observe the root to migrate laterally
and the tension on the root to lessen (Fig. 85-3C).
Oncedecompression of the nerve root has been com-
pleted,the foramen is again probed to assess the adequacy
ofthedecompression (Fig. 85-4). If the foramen has been
satisfactorilyenlarged, the probe should pass easily out
intothe paravertebral muscles. Once the procedure has
beencompleted,closureproceeds ina fashionidenticalto
thatdescribedforhemilaminectomy.
References
1. KramerDL.Booth RE.Albert Tj, et al. Posterior lumbar approach. In:
Albert Tj. Balderston
RA. Northrup
BE.eds. Surgical Approaches
to the
Spine. Philadelphia:
WB Saunders:
1997:173-192
2. LongD. McAfee PC, eds. Atlas of Spinal Surgery. Baltimore:
Williams
&Wilkins: 1992:2-22
3. Watkins RG.Posterior surgical approaches
to the lumbar spine. In: An-
dersson G. McNeill TW, eds. Lumbar Spinal Stenosis. St. Louis: Mosby;
1992:31-45
~
Figure 85-4
After decompression
of the foramen, the foramen is
probed with a Penfield no. 4 instrument.
4.
Mclain
R. Surgical approaches
to the lumbar
spine. In: Frymoyer jW.
ed. The Adult Spine:
Principles
and Practice.
2nd ed. Philadelphia:
Lippincott-Raven;
1997:1723-1744
5.
Torrens
Mj. Lumbar
laminectomy.
In: Torrens
Mj. Dickson
RA. eds.
Operative
Spinal
Surgery.
Edinburgh:
Churchill
Livingstone:
1991:
119-124

86
Microdiskectomy
RichardK.Osenbach
.
Advantages
.
Disadvantages
.
SurgicalTechnique
Positioning
Incision
Dissection
Closure
Removalof a lumbar disk remains the most common proce-
dure performed by neurosurgeons. In fact, the prolapsed
lumbar disk is the most common cause of nerve root com-
pression and radiculopathy. Although the basic goal of the
procedure remains the same; namely, removal of disk that
is compressing the nerve root, the technique for accom-
plishing this task has significantly evolved over the years.
Largeincisions and bilateral exposures for removal of a uni-
lateral disk protrusion have largely been supplanted
by
smaller, less invasive procedures, and microdiskectomy has
become the norm rather than the exception.I-3Indeed, min-
imallyinvasive techniques such as percutaneous automated
diskectomyand microendoscopic diskectomy have been in-
troduced as potential techniques that with further develop-
ment and refinement may one day become the norm, thus
replacingstandard open microdiskectomy. Notwithstanding
the technical advances in this area, open lumbar mi-
crodiskectomystill remains the gold standard against which
other techniques must be compared. This chapter describes
the technique of open lumbar microdiskectomy along with
the potentialcomplications.
Before proceeding further, a comment regarding ter-
minology is necessary. The terms microdiskectomy and
634
microsurgical lumbar diskectomy must be differentiated
from the specific technique designated
as microlumbar
diskectomy (MLD), a procedure
introduced
in 1977 by
Williams.3 The two former terms refer only to the use of
microsurgical instrumentation
for removal of a lumbar
disk. These terms do not define any specific surgical para-
meters and otherwise
impose no restraint
on the tech-
nique employed by the individual surgeon. On the other
hand, MLDis an exact and totally microsurgical technique
that is designed specifically for initial "soft" disk hernia-
tions in patients with otherwise
normal lumbar spinal
canal as depicted on computed tomography (CT) or
magnetic resonance imaging (MRI).The technical parame-
ters that define this unique procedure
are designed to
eliminate the most common tissue morbidities
that are
observed
in patients
following
"failed back surgery"
(Table 86-1). Therefore, it has been maintained that even
the slightest deviation from this technique does not rep-
resent true MLDand consequently does not produce simi-
lar long-term
results. Because most neurosurgeons
do
not perform
a true MLD, we will subsequently
refer
to the procedure
being described
simply as a lumbar
microdiskectomy (LM).

86
Microdiskectomy
635
Table86-1
Technical Parameters to Eliminate Tissue
Morbidities
of Failed Back Surgery
Minimalradiographicallylocalizedmidline skin incision
NomLiscieincisionor musclesuturing
Absoluteminimal removal of lamina and ligamentum flavum
Completepreservationof epidural fat
Constantvisualizationof the nerveroot
Noannularincision
Nocurettageof intervetebral disk
Noelectrocoagulationin epidural space
Noforeignsubstancesleft in the spinalcanal
. Advantages
. (ammon
procedure
. Minimaltissue disruption
. Disadvantages
. Limitedapplication
. Potentialfor nerve root injury
. SurgicalTechnique
Positioning
Thestandard position for LMiswith the patient prone, sup-
portedby a standard spinal frame (the author prefers the
Wilsonframe). The abdomen is allowed to hang free to re-
ducethe intra-abdominal pressure and thus the pressure
withinthe epidural venous plexus. After the lumbar region
hasbeen prepared with antiseptic solution and draped, the
(-arm fluoroscope (which has been sterilely draped) is used
to obtaina lateral view of the spine to mark the correct
level.
Incision
Amidline skin incision is marked several centimeters in
lengthand then infiltrated with local anesthetic containing
epinephrine.This reduces bleeding in the subcutaneous tis-
suesand minimizes the amount of cauterization required.
Theincision is made through the skin and is carried down
throughthe subcutaneous tissues until the fascia is encoun-
tered.
The lumbodorsal fascia is incised in the midline over a
distance between
the spinous
processes
immediately
aboveand below the level of pathology. Alternatively, the
incision in the fascia can be made just off the midline,
whichsometime provides a better cuff of fascia for closure.
Theparaspinal muscles are then detached from the spinous
processes and reflected laterally in a manner
identical
to that described in Chapter 84. Retraction of the
paraspinous muscle is maintained using a self-retaining
retractor
or the surgeon's preference.
Care should
be
taken not to damage the facet or the facet capsule with the
retractor.
Dissection
The interlaminar
space and adjacent laminae
should
now be readily visible. Before proceeding with any bone
removal, the level is again confirmed with fluoroscopy.
The ligamentum
flavum is detached from the inferior
surface of the lamina above using a fine curette, and a
hemilaminotomy
is performed. The rostral extent of the
hemilaminecotomy
required will vary from one spinal
level to another. For example, the L5-S1 disk space lies
approximately
at the level of the interlaminar
space.
However, as one progresses cephalad, the disk space be-
comes more cephalad
in relation
to the interlaminar
space and, therefore, exposure requires proportionately
more bone removal.
Some bone from the medial aspect of the facet or the pars
interarticularis
may need to be removed to achieve ade-
quate lateral exposure to the underlying disk. This is espe-
cially important with large disk herniations to mobilize and
retract the nerve root without undue pressure. From here
on, magnification and additional illumination are utilized.
This can be accomplished with the operating microscope or
using surgicalloupes and a headlight.
Next, the ligamentum flavum is removed to gain access
to the epidural space. The ligamentum flavum is incised
longitudinally in the direction of its fibers using a no. 15
blade. The opening must be made at an angle so as not to
cut obliquely through the ligament. A Penfield no. 4 dis-
sector is then employed using a gentle sliding motion to
further
separate
the fibers and gently "pop" into the
epidural space. At this point, the fibers of the ligamentum
flavum can be rather easily split longitudinally to enlarge
the opening. It is now possible to insert a small cottonoid
into the epidural space to displace the thecal sac and pro-
tect the dura. In cases in which there is an extremely large
disk protrusion that pushes the neural elements dorsally
against the ligamentum flavum, this may not be feasible.A
generous
window
of ligament
is excised. Additional
ligament can then be removed laterally using Kerrison
rongeurs to get lateral to the nerve root. It should be re-
membered that the ligamentum constitutes a portion of
the medial wall of the facet joint capsule and therefore as
the ligamentum is removed caution must be exercised not
to open the facet capsule. Extreme medial removal of liga-
ment is not advised because this is not necessary and
placement
of the footplate
of the Kerrison medially
has been known to produce dural tears outside the extent
of the bony opening. Indeed, these may sometimes
go
unnoticed
at
surgery
and
only
become
apparent
when
the patient
returns
postoperatively
with
cere-
brospinal fluid (CSF)drainage from the incision or com-
plaining of postural headaches and is discovered to have a
pseudomeningocele.

636
Lumbarand Lumbosacral Spine: Posterior Approach
-
Figure 86-1
The epidural space is explored to identify the nerve root.
Once the ligamentum fIavum has been removed, the
epidural space is explored with the purpose of identifying
the nerve root (Fig. 86-1). The root is usually seen as a
white tubular structure with minute vasculature visible on
the surface. The nerve root may be displaced either later-
allyor medially by disk herniations and it is crucial that it
be unequivocally identified prior to attempting removal of
any disk material. The epidural fat overlying the thecal sac
and nerve root can be gently separated and teased out of
the way using a Penfield dissector. Epidural veins should
be individually coagulated with bipolar cautery on a low
setting and sharply divided with microscissors. However,
excessive use of the cautery in the epidural space should
be discouraged. Using a blunt dissector, the lateral gutter
of the spinal canal is palpated as far cephalad as possible.
Bybeginning cephalad. one can avoid inadvertent
entry
into the axilla of a laterally displaced and stretched nerve
root. The nerve root is then gently retracted medially and
is maintained in this position using a nerve root retractor.
This maneuver will expose the underlying disk herniation.
If a free fragment of disk material is identified it is re-
moved. Ifno free fragments are seen, the posterior longi-
tudinalligament
and anulus are then incised in a cruciate
fashion and the interspace
is entered.
Disk material
will often extrude spontaneously
and this is removed
(Figs. 86-2 and 86-3). Anydisk material that is free in the
interspace is also removed. Additional disk material may
be freed up by scraping the vertebral end plates with a va-
riety of curettes. The author is not convinced that this adds
any protection against recurrent disk herniation and does
not perform
this as a routine practice. Moreover, it is
also this author's opinion that patients in whom the end
plates have been aggressively and excessive scraped suffer
significantly more postoperative back pain than patients in
whom this technique is not practiced. At this point, the
spinal canal is explored looking for any additional free
fragments of disk material. Exploration is also performed
Figure 86-2
The nerve root isretracted mediallyto expose the her-
niated disk.Theposterior longitudinalligament and anulusare incised
and the diskinterspace isexposed.

86
Microdiskectomy
637
Figure86-3
Thedisk material isremoved to sufficiently decompress
theneuralelements.
References
1. KempeL.Lumbarradiculoneuropathy:herniatedintervertebraldisk.
In: KempeL. ed. Operative Neurosurgery.Vol 2. Berlin: 5pringer-
Verlag;1970:266-276
2. HitchonP.TraynelisV.Lumbarhemilaminectomy for excision of a
herniateddisk. In: Rengechary55.Wilkins RH.eds.Neurosurgical
in the neural foramen above and below the nerve root.
This must be done with extreme vigilance in order not to
push an occult fragment of disk material further out into
the foramen.
At this point, a Valsalva's maneuver is performed and
the thecal sac and nerve root are carefully inspected for
evidence of a (SF leak. The author then places 40 mg of
Depo-Medrol over the nerve root. Placement of a fat graft
over the nerve root is a standard practice of many surgeons.
However, the utility of this and whether this truly prevents
epidural fibrosis and subsequent recurrent pain is of some
question.
Closure
The wound is then closed in a fashion identical to that de-
scribed in the previous chapters.
Operative
Atlas. Vol 1. Baltimore:
Williams
& Wilkins;
1991:
135-140
3.
Williams
RW. Microlumbar
diskectomy:
a conservative
surgical
approach
to the virgin herniated
lumbar
disk. 5pine 1978;3:175-182