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

57
Anterolateral Graft and Plate Reconstruction
437
(TransthoracicDiskectomy) or Chapter 56 (Transthoracic
Vertebrectomy).
EndPlate Preparation
Regardlessof whether decompression or the patient's pri-
marypathology has caused destabilization, the goal of the
anteriorgraft placement is to help restore normal anatomi-
calalignment and promote stability. The reconstruction
shouldbe carefully tailored to the defect to ensure proper
seatingofthe graft, minimizing the chance of graft pullout
whilemaximizing the patient's alignment and ability to
form a solid fusion.
Removingall of the soft tissue-disk
material and carti-
lage-willenhance the surface area of bone to bone contact
andfacilitatefusion. Therefore, it is important to strip the
bonyend plate of its cartilage. Care must be taken not to re-
movetoo much contiguous cortical bone, for this weakens
theadjacent vertebral bodies, allowing the bone graft to
collapse(telescoping).
Preparingthe site for the graft requires not only stripping
theend plates but also shaping them to accept a relatively
rectangulargraft. Again,care is taken not to violate the cor-
ticalend plates and thereby weaken the construct. At this
time,especially if one is considering eventually placing an
anterolateralinstrumentation
system, the lateral aspect of
thevertebral bodies is shaved with a drill to allow for a
flushseatingofthe plate (Fig.57-1).
Choice of Graft
Choiceofgraft materials is dependant mostly on the nature
ofthepathology being removed as well as the overall lifeex-
pectancyof the patient. In typical cases of benign pathology
(e.g..posttraumatic
burst fractures) or in patients with
pathological fractures who have a relatively long life
expectancy (>2 years), it is important
to perform the
reconstruction using material conducive to the eventual
Figure 57-1
Prepared graft
site. After the decompression,
the sur-
facesare prepared by removing
the cartilaginous
end plates. Note that
the defect has been .squared,"
ensuring
an even distribution
of force
and facilitating
the placement
of the plate. Shown is a corpectomy
de-
fect after the removal ofT12
as the initial bolt (for the instrumentation
system) is being placed.
formation of solid bony arthrodesis. Some surgeons favor
the use of autologous bone sources-devascularized
(rib or
tricortical iliac crest) or vascularized (fibula or rib) grafts.
Others prefer allograft-humerus,
tibia, or femur. Finally,
even metal spacers (titanium mesh cages) can still help to
promote a solid arthrodesis. Aslong as there is no evidence
of infection or local tumor ingrowth, these cages can be
packed with localautologouscancellousbone from the com-
pression fracture or rib from the approach. Alternatively,
they can be filledwith allogeneicbone or bone substitute.
In patients who are being operated on for malignant dis-
ease and who have a significantlyshortened lifeexpectancy,
the goal of the arthrodesis is different. Nosolid bony fusion
is considered requisite. Instead, it is important to givethem
short-term stability. In these patients, the use of auto- or
allograft simply serves as a medium for the remaining ma-
lignant cells to enter. Furthermore, additional adjuvant
therapies (chemotherapy and/or radiation) further weaken
the construct. For these reasons, the patient whose life ex-
pectancy is relativelyshort «
1 year) is typicallyrecon-
structed using polymethyl methacrylate (PMMA).
In the case of osteomyelitis, autogenous bone grafts are fa-
vored. Internal instrumentation
can be placed even in the
setting of pyogenic abscess if debridgement occurs and the
patient is placed on long-term IVantibiotics postoperatively.
Reconstruction
for Benign Disease
Toplace a snugly fitting graft without undue force, the ver-
tebral replacement is sized and placed while the spine is
being distracted. The ligaments and adjacent tissues then
help to hold the graft in place after the tension is released.
Several techniques can be used to help both the reduction
and the distraction. Ifone is using anterolateral instrumenta-
tion to complete the case, the initial screw or bolt placement
may be performed prior to graft replacement and the distrac-
tioncantakeplaceacrossthem (Fig.57-2).Avertebralbody
spreader can be employed, especially when the bone qual-
ity is suboptimal, to limit the pressure directly applied
to the bolts. To limit the manipulation on adjacent levels,
Figure 57-2
Distraction/graft
introduction.
After the posterior
bolts
have been placed (see instruction
later in the chapter),
the bolts are
used to distract
the vertebral
bodies to accept the graft.
Note that the
graft has been shaped to fit the defect.

\
I
438
Thoracic and Thoracolumbar Spine: Antero/Anterolateral
Approach
simply applying force to the patient's back at the site of the
defect can provide sufficient distraction.
As the adjacent vertebral bodies are distracted, the di-
mensions of the graft are measured using a caliper and
depth gauge. The graft is then sized and tamped into the
corpectomy site without excessive force. If desired, small
pieces of local autograft from the initial parts of the proce-
dure (rib and/or vertebral body) can be placed either into
the central portion of the graft or alongside it or both.
When reconstructing
a patient whose bone quality is
suboptimal at adjacent levels (e.g., in the case of adjacent
level metastatic involvement, severe osteoporosis, or previ-
ous irradiation), PMMAmay be used to strengthen the con-
tiguous segment. Secondarily, load sharing can be achieved
as needed by performing posterior instrumentation.
Reconstruction for Malignant Disease
In any case of cancer, synthetic spacers (titanium cages or
methyl methacrylate) provide short-term stability for the
patient who is not expected to create a bony fusion across
this area. A chest tube/PMMA reconstruction is discussed
here. Silastic tubing is cut to the appropriate length based
on the sizeofthe defect-from end plateto endplate.Some
surgeons prefer to recess the tube into the center of the
bodies above and below, drilling into the adjacent vertebrae
so that the rostral and caudal ends of the tube are imbed-
ded into the neighboring vertebral bodies. In this manner,
PMMAinjected into the tubing will fill the adjacent verte-
bral levels and increase their biomechanical strength as
well as helping to prevent dislodgement of the tubing. Oth-
ers favor placing a K-wire superiorly through the end plate
into the midbody above and inferiorly through the cortex
into the body below (Fig.57-3A). The chest tube that strad-
dles these pins is held in place when cemented in with the
PMMA,while minimizing the cortical violation into the ad-
jacent bodies.
Alarge central hole is placed into the midportion ofthe
chest tube to allow the entry of the PMMA.Smallperipheral
holes can also be made to allow air to escape to ease the en-
try of the plastic into the tubing (Fig. 57-38). Care should
be taken not to place any of the holes posterior toward the
thecal sac. The tube is then positioned in the corpectomy
defect, and the PMMAis injected through the central hole
A
B
C
\
\\'1
f
I
D
Figure 57-3
polymethyl
methacrylate
(PMMA) reconstruction
for metastatic
disease. A chest tube reconstruction
is performed
by first sizing the
tubing
to the height of the defect.
(A) Prior to final positioning,
a K-wire is placed into the vertebral
body above and below. (8) Holes are cut into
the tubing
to allow the entry of the PMMA as well as air to escape. (C) PMMA is injected
into the central hole after the chest tube has been posi-
tioned around the K-wires.(D) PMMAfills the corpectomy defect.

57
Anterolateral Graft and Plate Reconstruction
439
to fillthe tubing (Fig. 57-3C). As the PMMAis filling the
tubingit is important that the hardening plastic does not
comeinto contact with the thecal sac because the harden-
ingprocessof PMMAis exothermic. Sterile tongue depres-
sorsora Penfielddissector can help to guide the liquid plas-
tic.Afterthe inside of the tubing is filled, the remaining
substancecan be placed ventrally and laterally to the con-
struct,again ensuring separation from the dorsal dura. As
thematerialhardens, copious amounts of saline are used to
dissipateheat. Finalshaping of the plastic ensures a smooth
transitionfrom the lateral aspect of the surrounding verte-
bralbodiesto the reconstruction, facilitating placement of
ananterolateralplating system (Fig.57-3D).
Instrumentation
Theuse of a Z-Plate II (Medtronic Sofamor-Danek, Mem-
phis,TN)system is outlined here. Although there are spe-
cificnuanceswitheachsystem,manyofthe principlesdis-
cussedherecanbe carried over to other systems.
Aboltisplaced into the posterior/superior
aspect of the
bodyabovethecorpectomy,5 mmventraland 5 mm infe-
riortothe most posterior/superior corner of the body. This
ismirroredinto the body below the reconstruction, 5 mm
rostraland 5 mm anterior to the most inferior/posterior
cornerof the inferior vertebra. These can typically be an-
gledslightlyawayfrom the spinal canal (10 degrees) to help
decreasethe risk of injuring the spinal cord. Aguide helps
toanglethe bolt properly (Fig. 57-4). Apreoperative axial
computedtomographic (CT)scan can be used to indirectly
----------- ;; ::---
r-------
Figure57-4
Angle of bolt placement.
An axial view showing the an-
gleatwhich the posterior
bolt is placed. The trajectory
leads it away
fromthe canal. Care is taken to place the bolt parallel to the adjacent
endplate.
1
Figure 57-5
Plate seating. After the graft
has been placed to fill the
defect, the plate is sized and placed onto the external
shafts. Washers
are laid over the plate and are used as a guide for the screws. A com-
pressive force can then be applied
as a nut is used to secure the plate.
measure the length of the bolts. This can be confirmed with
intraoperative fluoroscopy at the time of placement. Anawl
is used to pierce the cortex and then they are placed with-
out prior tapping. It is across these bolts that a distractive
force can be applied to facilitate placement of the graft.
After the plate is seated across these bolts (Fig. 57-5),
secondary screws are placed more anteriorly, typically with
a slight posterior trajectory (Fig. 57-6A,B). The anterior
screws are placed and angled 10 degrees dorsally and are
typically 5 mm longer than the dorsally placed bolts. After
finaltightening,the boltextendersare removed(Fig.57-7).
Closure
The hardware is cleaned with copious amounts of antibi-
otic-impregnated saline. When incised for operations near
the thoracolumbar junction, the diaphragm is reattached at
its lateral margin, with the crura being sewn directly to the
anterior longitudinal ligament. Any violations in the peri-
toneum should be closed primarily. When entered, the pari-
etal pleura is closed as well, overlying the operative site. Ifa
retropleural exposure was performed, the wound should be
filled with saline to confirm that no occult pleurallacera-
tion took place. When the pleura is entered, a no. 28 French
chest tube is placed and tunneled out through a separate
incision. After the wound is fully closed, the chest tube is
placed onto low wall suctioning. The lung is reinflated un-
der direct visualization.
The intercostal musculature is closed using a running su-
ture. The remainder of the tissue layers are closed with in-
terrupted sutures. Staples or a running suture are used to
close the skin. Asterile dressing is applied. Whether or not
the pleura is entered, a chest x-ray must be performed in
the recovery room.

440
Thoracic and Thoracolumbar Spine: Antero/Anterolateral
Approach
,..... ...
i
~--
~-----
A
1/
V
B
Figure 57-6
Anterior screw placement. (A) Screws are placed more anteriorly through the guides (B) at a 1O-degree posterior angle. Thiscrossing
helps resist screw pullout.
References
1. ErricoTJ. Cooper PRoA new method of thoracic and lumbar body
replacement
for
spinal
tumors:
technical
note.
Neurosurg
1993;32:678-681
Figure 57-7
Finished picture. After the final screw placement and re-
moval of the bolt extensions. the construct is complete.

58
Costotransversectomy
ShaunT. O'Leary,
Aruna Ganju,
Michael J. Rauzzino,
Christopher I. Shaffrey, and
RussP. Nockels
.
Advantages
.
Disadvantages
. Thoracic Diskectomy via Costotransversectomy
SurgicalTechnique
. ThoracicSympathectomy
via Costotransversectomy
SurgicalTechnique
Costotransversectomyemploys a posterolateral approach to
thethoracic spine and provides access to the lateral portion
ofthe vertebral canal and the anterolateral portion of the
thoracicvertebral bodies. With this approach, the spinal
canalmay be decompressed indirectly and a limited ante-
riorfusionmaybe performed.Costotransversectomymay
be utilized in the removal of traumatic! or pathological2
fracturedbone fragments, biopsy or decompression of neo-
plasticmasses,3.4 decompression
of spinal infection, rib
pain,ssympathectomy,6 or removal of soft paracentral her-
niateddisk. It is especially useful in patients who would
poorlytolerate a formal thoracotomy such as elderly pa-
tients or those with significant underlying
pulmonary
pathology.Unlikeanterior approaches to the thoracic spine,
whichare technically difficult and partially limited at the
thoracicinlet and the diaphragm, costotransversectomy al-
lowsforexposureofthe thoracicspinethroughoutitsentire
length.4,7-1tHowever, for laterally placed and soft or mildly
calcifiedthoracic disk herniations, costotransversectomy is
idealbecause it involves more limited dissection than for-
malthoracotomy.The major drawback of costotransversec-
tomyis that the surgeon's view of the anterior canal is
limited,especially immediately anterior to the dura. In ad-
dition,costotransversectomy is less useful in cases where
midlinepathology, such as calcified disks is present. This
chapter focuses on the role of costotransversectomy
in
themanagement of herniated thoracic disks and in sympa-
thectomy.
.
Advantages
.
Bettertolerated than thoracotomy in medicallyfragile
patients
.
Allowsforexposureofthe entire lengthofthe spine
.
Lesspulmonarycomplicationsthan thoracotomy
.
Disadvantages
. Viewof the anterior canal and dura limited
.
Difficultto address anterior midline pathology
.
Thoracic Diskectomy via
Costotransversectomy
Disk herniations occur less commonly in the thoracic spine
than in either the lumbar or the cervical spine. Thoracic
disk herniations account for 0.15%of all disk herniations
and 4%of all disk operations.B.1tThe majority of sympto-
matic thoracic disk herniations arise at T8 or below.B.1tThis
finding is consistent with the theory that the increased
mobility in this area of the thoracic spine makes it more
441

442
Thoracic and Thoracolumbar Spine: Posterolateral Approach
susceptible to disk herniations caused by degenerative dis-
ease or trauma. Herniated thoracic disks may be located ei-
ther centrally or paracentrally and may be either soft or
caIcified.6.12,13
The signs and symptoms of thoracic disk her-
niation may mimic other pathological processes, and delays
in diagnosis can occur if the index of suspicion is low. Disk
herniations usually present with pain (local or radicular),
sensory loss, lower extremity weakness, gait difficulties,
and bowel/bladder dysfunction.8,14Rarelywill a patient with
a herniated thoracic disk present with Horner's syndrome.IS
Surgicalindications include intractable pain or progressive
myelopathy.16
An early application
of costotransversectomy
in the
management of a herniated thoracic disk was reported by
Hulme in 1960. Hulme focused attention
on the avoid-
ance of spinal cord manipulation
that was required by
the previously employed direct posterior approach. Since
then, numerous reports have shown excellent results us-
ing costotransversectomy
for
thoracic
disk
hernia-
tions.8,I3,14,17-23
SurgicalTechnique
The "classic" operative procedure for the costotransversec-
tomy has been modified so that a surgeon has several
options. The patient may be placed prone, semiprone, or in
a modified lateral decubitus position. The patient may be
intubated with a double-lumen, cuffed endotracheal tube.22
Thisapproach avoids a thoracotomy, but it does not always
avoid a pneumothorax.24 The disk has been approached
from the side with more deficit found on neurological ex-
amination. In cases where the herniations were central and
in the absence of lateralized findings or root pain, the right-
sided approach has been advocated to avoid the risk of in-
jury to the artery of Adamkiewicz, which usually originates
from the left lower intercostal vessels from T8 to L2.8.I3,22
Some authors have recommended
spinal angiogram be-
tween T8and L1 for lateral approaches such as the costo-
transversectomybecause the contents of the neuroforamina
are usually disrupted and, therefore, the terminal artery is
sacrificed,if present.II Other groups have not found this
necessary.2S
The incision may vary from a midline vertical incision or
a midline incisionwith a "r
over the rib to be resected, to a
straight paramedian incision along the lateral border of the
erector spinae muscleswith or without a "hockey stick" ex-
tension (Fig.58-1). Afurther option is a semilunar incision
either midline or paramedian. Variations in incision type
have been introduced to minimize tissue trauma and allow
for better muscle retraction.18The choice of incision is dic-
tated by surgeon preference and the need for postdecom-
pressive instrumentation. If a paramedian incision is cho-
sen, skin, subcutaneous tissue, and fascial flap may be
rotated medially toward the spinous process. Likewise,the
incised trapezius muscle and latissimus dorsi can be rotated
medially. Finally, the erector spinae muscles are dissected
and reflected medially or split transversely to expose the
angle of the ribs. When choosing a midline incision, a stan-
dard subperiosteal dissection is performed and extended to
the tips of the transverse process and proximal ribs. The
c:'5
OJ
OJ
.6
E
:§ ~
::iEa..
Figure 58-1
Variation in incision type. Note: semilunar incision not
pictured.
muscular anatomy is demonstrated in Fig. 58-2. In the up-
per thoracic spine, the trapezius and rhomboid muscles can
be divided. The spine of the scapula is situated at T2-T3and
the tip of the scapula is at n. In the lower thoracic spine
where most herniated disks are encountered, the latissimus
dorsi will be transected. Finally,the serratus posterior infe-
rior will be found near the lowest thoracic vertebrae.26
The ribs to be removed are skeletonized subperiosteally.
Correlation between preoperative radiological studies and
intraoperative radiographs is imperative to ascertain the
correct pathological level. It is important to remember that
entrance into a disk space necessitates exposure of the infe-
rior rib (Le.,entrance into the T8-T9 disk space requires ex-
posure of the ninth rib).27In addition, the heads of the first,
eleventh, and twelfth ribs articulate only with their own
vertebrae.28 An illustration of a thoracic vertebra is seen in
Fig. 58-3. The articulations of interest are the superior and
inferior costal facet and the transverse costal facet. Tradi-
tionally, only one rib would be removed; however, it is now
more common to remove two to three ribs and their associ-
ated transverse processes. The pleura is gently mobilized
and reflected from the underside of the rib and the ventro-
lateral portion of the spine. The ribs of interest are then
transected -5 cm from the rib head.
Removal of the transverse process and dissection of the
costovertebral (radiate) ligaments allow for disarticulation
of the rib (Fig. 58-4). An axial drawing depicting the bony
and ligamentous removal is illustrated in Fig. 58-5. With
this exposure, the lateral vertebral anatomy can be identi-
fied by following the neurovascular bundle under the rib
bed medially to the neural foramen. From here, the lateral
pedicle is identified
and a subperiosteal
dissection of
the upper and lower lateral vertebral bodies is performed.
The foramen is enlarged by partial or complete removal of

58
Costotransversectomy
443
Levator scapulae
m.
Rhomboideus
m.
Trapezius
m.
Latissimus
dorsi m.
Serratus
posterior
inferior m.
Body
Vertebral
Foramen
Superior Articular
Process
Superior
Costal Facet
Inferior Costal Facet
Transverse
Process
Transverse
Costal Facet
Inferior Articular Process
Lamina
Spinous Process
Figure
58-2
Muscular anatomy along the thoracic spine.
Note: erector spinaemusclesnot pictured.
Figure 58-3
Thoracic vertebrae with articulations of interest.

.
444
Thoracic and Thoracolumbar Spine: Posterolateral Approach
Inter-
transverse
ligament
Radiate
ligament
A
Figure58-4
Disarticulation
of the rib head. (A) Intact costotransverse
and costovertebral ligamentous articulations.
(8) Resected rib with transec-
tion of the costotransverse and radiate ligament. (C) Removal of the radiate
ligament and the rib head to expose the disk space.
B
c
Figure58-5
Illustrationofthe bony removalinthe costo-
transversectomy.
The stippled area includes the transverse
process.
rib head. pedicle. and a portion
of the vertebral
body.

58
Costotransversectomy
445
Figure58-6
Lateralview of the bony removal. Note the protruded
diskpressingon the thecal sac.
thecorresponding pedicle to visualize the lateral thecal sac.
Fig.58-6 illustrates the removal of the transverse process
andpedicle with enlargement of the foramen. A protruded
diskis shown compressing on the thecal sac.Once the floor
ofthespinal canal is identified at the upper lateral vertebral
body,more bone may be removed to facilitate the disk re-
moval.A small "gutter" or cavity can be created on either
sideof the disk space by removing the posterior surface of
the upper and lower vertebral bodies prior to diskectomy.
Removal of the pedicle and lateral vertebral body allows for
gentle removal of the disk fragments without
manipulation
of the spinal cord. Fig. 58-7 shows a cadaveric dissection
using a paramedian incision for a"classic" costotransversec-
tomy. Note the neurovascular bundle and its relation to the
disk space and foramen. Fig. 58-8 shows the bony removal
in Fig. 58-7.
After
removal of the herniated disk material,
instru-
mented
or noninstrumented
fusion can be considered
based on the pathological process. The costotransversec-
tomy does not require exposure of the laminar processes;
however, this would be required for instrumentation. Costo-
transversectomy as such does not lead to spinal instability
requiring instrumentation.13
Costotransversectomy
minimizes or avoids many of the
complications
related to thoracotomy,
including
inter-
costal neuralgia,
persistent
pneumothorax,
pulmonary
contusion,
pneumonia,
effusion,
and atelectasis.22 The
lower incidence of pulmonary
complications
makes this
procedure ideal for an elderly or high-risk patient.16.26Vas-
cular-related
complications
are rare. The incidence of
paraplegia secondary to unilateral
disruption
of the tho-
racic segmental vessels is practically
nonexistent.29 Most
vascular injuries,
especially of the major vessels, can be
prevented with careful blunt dissection of the pleura off
the lateral border of the vertebral bodies.29The major dis-
advantage of costotransversectomy is that visualization of
the central spinal canal is not as optimal as with other ap-
proaches, consequently dural tears or spinal cord injury
can occur.16Detailed knowledge of this infrequently
en-
countered anatomy and careful patient selection are criti-
cal to avoid complications.30
Figure 58-7
Lateral view of right-sided
cadav-
eric dissection.
The midline
is uppermost
in the
photograph.
The radiate ligament
(double black
arrows) and rib (large black arrow) are transected
-5
cm. Normally, two rib heads are removed and
blunt dissection
exposes the pleura (single white
arrow)
and the neurovascular
bundle (encircled
by the red vessel loop ). Further bony removal will
enlarge
the
neural
foramen
(double
white
ar-
row), expose the thecal sac (single black arrow),
and the diskspace(18 gaugeneedle).

446
Thoracicand Thoracolumbar Spine: Posterolateral Approach
Headof Rib
lamina
Sympathetic
chain and
ganglion
Rami communicantes
Intercostal nerve
.
ThoracicSympathectomy via
Costotransversectomy
In the late 1800s,surgical sympathectomy was first evalu-
ated as a treatment for hypertension, goiter, and vascular
insufficiency of the extremities. With advances in medicine,
effective pharmacologicaltreatments also became available.
Yet, since the early 1900s, sympathectomy
has been
advocated as a treatment for Raynaud's disease and hyper-
hidrosis.3!
Today, several indications exist for surgical sympathec-
tomy, including causalgia, essential hyperhidrosis, Ray-
naud's disease, and visceral pain syndromes. In all of these
conditions, hyperactivity or hypersensitivity to sympathetic
outflow is postulated to playa role in the pathogenesis. Ac-
cordingly, interruption of this outflow has provided some
relief for those affected.6.32.33
Figure 58-8
Posterolateral
photograph
of the bony removal on a skele-
ton. The removal
is in the shaded
area.
Figure 58-9
Lateral view of the bony removal for thoracic sympathectomy.
Surgical clips on rami and above/below system.
Briefly,the sympathetic nervous system consists ofbilat-
eral ganglionated chains that extend from the skull baseto
the coccyx bone along the anterolateral vertebral body.In
the cervical area, these ganglia are known as the superior,
middle, and inferior ganglia. Similar segmental ganglia are
found in the thoracic, lumbar, and sacral regions. Sympa-
thetic outflow arises from the intermediolateral nucleus of
the cord levels from T1 to L2.The fibers leave the ventral
roots via white rami communicantes and enter the sympa-
thetic ganglia as preganglionic fibers. These fibers travelto
the para- or prevertebral ganglia: postganglionic fibers arise
from these ganglia to innervate end organs.34
Surgical Technique
Regarding the sympathetic denervation of the upper ex-
tremities, many approaches to the lower cervical andupper

58
Costotransversectomy
447
thoracicsympatheticchainhavebeendescribed.Thesein-
cludethesupraclavicular,transaxillary,andtranspleuralap-
proaches.Costotransversectomy via a posterior midline in-
cision provides
ample
opportunity
for
a
bilateral
ganglionectomy.Manyauthors have noted that, for practical
purposes,sympathetic denervation of the upper extremities
needonlyinvolveremoval of the 12 ganglion.6.12.32.33
Forsympathectomy via costotransversectomy, the patient
isplacedin either a sitting or a prone position (as described
previously).Amidline dorsal incision is made over the spin-
ousprocesses of 11 to 13. An intraoperative radiograph is
takenforlocalizationofthe 13 spinousprocess.Forunilat-
eralsympathectomy,once 13 is identified,carefulsubpe-
riostealdissection of the musculature is performed to the
ipsilateraltransverse process of13. This is then removed via
aKerrisonpunch. Directly underneath is the corresponding
rib.Subperiosteal dissection is performed and the 13 rib
headisremoved, with care taken to avoid violation of the
pleura.Tilting of the operating table with elevation of the
ipsilateralside allows for inspection of the posterior medi-
astinum.Dissection anteriorly exposes the lateral aspect of
thevertebral body. Here, the sympathetic chain is identi-
fied.Dissectionis performed superiorly to allow for visual-
References
1. Bohlman HH, Ducker TB. Spine and spinal cord injury. In: Herkowitz
HN. Eismont
FJ, Garfin SR. et ai, eds. The Spine. Philadelphia:
Roth-
man-Simeone:
1999:889-1003
2. Cybulski GR. Stone JL. Opesanmi
O. Spinal cord decompression
via a
modified costotransversectomy
approach
combined
with posterior
instrumentation
for management
of metastatic
neoplasms
of the tho-
racic spine. Surg Neurol1991
;35:280-285
3. Overby MC. Rothman
AS. Anterolateral
decompression
for metastatic
epidural spinal cord tumors.J
Neurosurg
1985:62:344-348
4. Rosenblum B. Phillips E. Klass S. et al. Upper thoracic
disk herniation
secondary to vertebral
metastases.
Surg Neuro11989:31
:473-475
5. TsaiHH. Eastmond
CJ.Modified costotransversectomy
in treatment
of
intractable
costovertebral
pain
in
ankylosing
spondylitis.
Br J
RheumatoI1987:26:66-67
6. Bay JW. Dohn
DE Surgical
sympathectomy.
In: Wilkins
RH. Ren-
gachary
SS. eds.
Neurosurgery.
New
York:
McGraw-Hili;
1996:
3251-3256
7. Birch BD. Rajiv DD. McCormick
Pc. Surgical approaches
to the thora-
columbar spine. Neurosurg
Clin N Am 1997;8:471-485
8. EI-Kalliny M. Tew JM. van Loveren H. Dunsker
S. Surgical approaches
to thoracic disk herniations.
Acta Neurochir
(Wien)
1991 :111:22-32
9. Fidler M. Goedhart
Z. Excision of prolapse
of thoracic
intervertebral
disk: a transthoracic
technique.J
Bone Joint Surg Br 1984:66:518-522
10. Mulier S. Debois V.Thoracic disk herniations:
transthoracic.
lateral. or
posterolateral
approach?
A review. Surg NeuroI1998:49:599-608
11. Stillerman CB. Chen TC, Couldwell
WT. Zhang W. Weiss MH. Experi-
ence in the surgical
management
of 82 symptomatic
herniated
tho-
racic disks and review of the literature.
J Neurosurg
1998;88:623-633
12. Fedder SL.T2-ganglionectomy
via limited
costotransversectomy
for
minor causalgia. Spine 1990;15:269-270
13. Young S. Karr G. O'Laoire SA. Spinal cord compression
due to thoracic
disk herniations:
results
of microsurgical
posterolateral
costotrans-
versectomy. BrJ Neurosurg
1989;3:31-38
14. Ridenour TR. Souheil FH. Hitchon
PW. et al. Herniated
thoracic
disks:
treatment
and outcome.J
Spinal Disord 1993:6:218-224
15. Gelch M. Herniated
thoracic
disk
at Tl- T2 level
associated
with
Horner's syndrome.
J Neurosurg
1978;48: 128-130
16. Stillerman
CB. McCormick
PC. Benzel
EC. Thoracic
diskectomy.
In:
Benzel EC.ed). Spine Surgery:
Techniques.
Complication
Avoidance.
and Management.
New York: Churchill Livingstone:
1999:369-387
17. Bohlman HH. Zdeblick
TA. Anterior
excision
of herniated
thoracic
disks. J Bone Joint Surg Am 1988:70: 1038-1047
ization of the 12 ganglion. The rami communicantes'
con-
nection to the intercostal nerve is noted and divided. Surgi-
cal clips are also placed on the sympathetic
chain both
above and below the ganglion; the ganglion can then be re-
moved.6.12.33
Advantages of the 13 costotransversectomy for T2 gan-
glionectomy include a low risk of pleural injury or Horner's
syndrome. Risksinclude infection,empyema, radicular pain,
and pneumothorax. Aswith any surgical procedure, atten-
tion to detail and review of anatomy decrease the likelihood
of complications.32
Closure
Finally, closure entails meticulous technique to assure he-
mostasis and the absence of a pneumothorax. The surgical
field should be filled with saline and Valsalva's maneuver
should be performed. Pleural defects can be sutured and a
chest tube should be left if a pneumothorax is seen. The in-
cision is closed in layers: paraspinal muscles, lumbodorsal
fascia, and trapezius and latissimus dorsi muscles, over an
external drain.26In the recovery room, a chest x-ray should
be performed to check for pneumothorax.
18. Garrido E. Modified costotransversectomy:
a surgical approach to
ventrally placed lesions in the thoracic spinal canal. Surg Neurol
1980;13:109-113
19.
Lesoin F.Jomin M. Posterolateral
approach
to thoracic
disk herniations
through
tranversoarthropediculectomy.
Surg NeuroI1985:23:375-379
20.
Otani K.Yoshida M. Fujii E. Nakai S. Shibasaki
K.Thoracic disk hernia-
tion: surgical treatment
in 23 patients.
Spine 1988:13:1262-1267
21.
Russell T. Thoracic
intervertebral
disk protrusion:
experience
of 67
cases and review of the literature.
BrJ Neurosurg
1989:3: 153-160
22.
Simpson
JM. Silveri CPoSimeone
FA. et al. Thoracic
disk herniation.
Spine 1993;18:1872-1877
23.
Singounas
EG. Kypriades
EM. Kellerman
AJ. Garvan N. Thoracic
disk
herniation.
Analysis
of 14 cases
and
review
of the literature.
Acta
Neurochir
(Wien) 1992:116:49-52
24.
Borges
L. Surgical
approaches
to the
thoracic
and
thoracolumbar
spine for decompression
and stabilization.
In: Schmidek
HH. Sweet
WHo eds. Operative
Neurosurgical
Techniques:
Indications.
Methods.
and Results. Philadelphia:
WB Saunders:
1995:1887-1893
25.
Sekhar L.Jannetta
P. Thoracic
disk herniation:
operative
approaches
and results. Neurosurgery
1983:12:303-305
26.
Johnson
RM. Murphy
MJ. Southwick
WOo Surgical approaches
to the
thoracic
spine. In: Herkowitz
HN. Eismont
FJ.Garfin SR. et al. eds. The
Spine. Philadelphia:
Rothman-Simeone:
1999:1537-1557
27.
Ahlgren BD. Herkowitz
HN. A modified
posterolateral
approach
to the
thoracic
spine.J
Spinal Disord 1995:8:69-75
28.
Rogers MA. Crockard
HA. Surgical treatment
of the symptomatic
her-
niated thoracic
disk. Clin Orthop
1994:300:70-78
29.
Stambough
JL. Simeone
FA.Vascular
complications
in spine surgery.
In:
Herkowitz
HN. Eismont
FJ. Garfin
SR. et al. eds.
The Spine.
Philadelphia:
Rothman-Simeone;
1999:1711-1724
30.
Fessler
RG. Sturgill M. Review: complications
of surgery
for thoracic
disk disease. Surg NeuroI1998:49:609-618
31.
Greenwood
B.The origins of sympathectomy.
Med Hist 1967:11 :165-169
32.
Dohn DF. Sava GM. Sympathectomy
for vascular
syndromes
and hy-
perhidrosis
of
the
upper
extremities.
Clin
Neurosurg
1978;25:637-650
33.
Wilkinson
HA. Surgery
for hyperhidrosis
and sympathetically
medi-
ated
pain syndromes.
In: Schmidek
HH. Sweet
WHo eds. Operative
Neurosurgical
Techniques:
Indications.
Methods. and Results. Philadel-
phia: WB Saunders;
1995:1573-1584
34.
Truex RC.Carpenter
MB. Human Neuroanatomy.
Baltimore:
Williams
& Wilkins:
1969:216-235

59
Thoracic Laminectomy
Anantha Kishan and Mitchell R.Gropper
.
Indications
.
Contraindications
.
Advantages
.
Disadvantages
.
SurgicalTechnique
Closure
Laminectomy is the most common neurosurgical procedure
performed and was first described Alban G.Smith in 1828.1
It is the exposure of choice for the majority of spinal condi-
tions. A decade later Key described the management of a
thoracic disk herniation with this approach. Loguewas the
first to look at the outcomes of patients with thoracic disk
herniations and found poorer than expected outcomes. In
1971 Morgan et al demonstrated
similart results with
laminectomy for incomplete spinal cord injuries.2Questions
as to the efficacy of laminectomy arose as our understand-
ingof the pathophysiology of spinal cord compression syn-
dromes, blood flow, and spinal biomechanics grew, and
from 1958 onward the literature focused on alternative
approachesto thoracic compressive pathology.3
We must keep in mind the anatomical features of the
thoracicspine so that we may minimize morbidity. The tho-
racicvertebrae differ from the rest of the spine as they have
costal articulations. The spinal canal in the thoracic region
is small and circular, the pedicles do not diverge and the
laminae are short, thick, broad and overlap one another.4
These specific bony features limit the amount of room to
work in, thus necessitating even more cautious dissection.
There is also a varibility in blood supply from the radicu-
lar and parenchymal distributions
creating a watershed
zone from T4 to T9 so that the surgeon must be keenly
aware of the number ofvessels taken during dissection and
the systemic blood pressure throughout the case.
Despite
all of these issues and
concerns,
thoracic
laminectomy has remained a mainstay for a large number
of afflictions. Radiculopathy,in and of itself, is a rare indica-
tion for surgery. Radiculomyelopathy from thoracic disk
herniation and thoracic spondylosis is the usual surgical
indicator, with tumors and infection accounting for the ma-
jority of the rest,5.6
448
The chapters in this subsection
focus on dorsal ap-
proaches to the thoracic spine, with occasional mentionof
lateral extension of these approaches to allow discussionof
a particular problem. They also focus on specific anatomical
points to highlight complication avoidance.
.
Indications
.
Thoracic canal stenosis/spondylosis
.
Bonyneoplasms involving posterior elements of spine
.
Dorsal epidural tumors
.
Intradural extramedullary tumors
.
Intradural intramedullary tumors
.
Vascular malformations
.
Syringomyelia
.
Epidural abscess
.
Epidural hematoma
.
Epidural neurostimulator placement
.
Trauma spine injuries
.
Contraindications
.
Centraldiskherniation
.
Ventralepiduraltumors
.
Severeanteriorand middlecolumnfailure(trauma)

. Advantages
59
Thoracic Laminectomy
449
. Lessoverlying muscle and soft tissue compared with
cervicaland lumbar spine
. Well-knownand widely used techniques
. Noneed for "access"surgeon
. Lowerrisk of postoperative instability compared with
cervicaland lumbar procedures due to rib cage support
. Lessmorbidity than thoracotomy
. Disadvantages
. Canbe difficult to localize correct level intraoperatively
. Riskofspinal cord injury
. Difficulto access ventral pathology
. Limitedworking space within spinal canal
. Notidealfor pure radiculopathy
. SurgicalTechnique
Thepatient is positioned prone on chest rolles or an ad-
justableframe with the arms supported on arm rests on ei-
therside(Fig.59- t). Satisfactory positioning is essential to
avoidpressure points, abdominal compression, and stretch-
ingof nerves. Abdominal compression will lead to inade-
quatevenous return and engorgement of the epidural ve-
nous plexus.
Excessive intraoperative
bleeding
may
necessitateoveruse of electrocautery devices and subse-
quentneural injury and neuropathic pain syndromes.
Theskin incision extends in the midline from one level
aboveto one level below the extent of the lesion. Surface
landmarksthat help to mark the incision are the C7spinous
process,the superior scapular angle corresponding to 13,
andthe inferior scapular tip corresponding to T7(Fig.59-2).
Anintraoperative x-ray with a marker, or a preoperative
scratchlocalizationwill aid confirming the level.Ascertaining
theappropriate level is paramount in the preoperative set-
ting.Manypatients will present with 11or 13 ribs thus con-
fusingthe neurosurgeon and neuroradiologist. Intraoperative
radiographsmay not cover all of the ribs, and the surgeon
mustbe prepared to count both up from the bottom rib and
downfromthe top rib to determine the appropriate level.
(
)
I
(
,/
I T3
I T7
\
Figure 59-2
Surface landmarks for the lower cervical and thoracic
region.
The skin and subcutaneous tissue are incised down to the
deep fascia.Adequate injection of the deep dermal layer with
epinepherine allows avoidance of electrocautery until the
fascial layer is to be opened. Local anesthetics are not
required unless the patient is awake as in cases of dorsal col-
umn stimulator placement and biopsy. Significant devascu-
larization ofthe skin layer in the thoracic spine may disallow
healing in an area where the blood flow is already marginal.
The paraspinal
muscles
are then
separated
subpe-
riosteally from the spinous processes on either side using
electrocautery.The muscles encountered are the aponeurotic
Figure 59-1
Positioningfor dorsal thoracic ap-
proaches.

450
ThoracicandThoracolumbarSpine:PosteriorApproach
origin of the trapezius, the rhomboideus muscles in the up-
per thoracic spine, and the latissimus dorsi in the lower
thoracic spine. Next,the intrinsic dorsal muscles consisting
of the erector spinae group superficially (iliocostalis, longis-
simus, spinalis thoracis, spinalis cervicis) and the deep
transversospinal group are separated subperiosteally from
the spinous processes and laminae.7 Alarge peroisteal ele-
vator is used on either side of the spinous processes to sep-
arate the muscles from the bone. It is important to stay in
the subperiosteal plane to avoid troublesome bleeding. The
presence of ribs on either side narrows the paraspinal re-
gion necessitating properly angled self-retaining retractors.
Placement of retractors on the rib heads and the use of
Gelpi-type retractors should be avoided because tearing of
the tissues deep to the ribs and lateral to the pars interar-
ticlaris may lead to pleural injury and pneumothorax.
The facet joints are exposed bilaterally without stripping
their capsules. Care is taken to avoid injury to the neurovas-
cular bundle, which lies at the level of the isthmus between
the zygapophyseal articulation and the base of the trans-
verse process and runs along the inferior aspect of the ribs.
The spinous processes of the laminae are removed using
Leksellrongeurs, and laminectomy may be continued with
the same instrument or a high-speed bur to make lateral
troughs on either side of the lamina (Fig. 59-3). The
thinned-out laminae are removed using a fine 1 mm Kerri-
son ronguer. The ligamentum flavum is then cut sharply
Figure 59-3
Cutting of lateral gutters with a high-speed air dril. This
may also be done with a footed drillor rongeurs.
taking care to avoid injury to the dura (Fig. 59-4). The
spinal canal is now open with the dural tube exposed(Fig.
59-5). Further operative technique depends on the nature
of the lesion.
Laminectomy is combined with unilateral facetectomy
and pedicle resection to gain access to the lateral thoracic
spinal canal if necessary (Fig. 59-6). If the stability ofthe
spine is compromised by tumor, trauma, or bilateral facet
removal,posteriorinstrumentationisperformed.Bonegraft
is also used to fillthe lateral gutters bridging the dorsalsur-
faces of the transverse processes. Posterior instrumentation
provides a very rigid construct in the thoracic spine dueto
the costosternal and costovertebral articulations.
Closure
Hemostasis is ensured and the dura is closed in a watertight
manner. Valsalva's maneuvers and reverse Trendelenburg
maybe utilizedto checkforcerebrospinalfluid(CSF)leak-
age if the dura has been violated. Proper closure of the dor-
sal fasciais essentialbecauselimitedamountsoftissueare
present above this layer should a CSFleak become a prob-
lem. An epidural drain is left in place if necessaryand
brought out through a separate skin incision. Drains should
be avoided if the dura has been violated; they may promote
leaks. The subcutaneous
tissue and skin are brought to-
gether taking care to obliterate any potential dead space.
Figure 59-4
After cuts havebeen made in the laminae,the ligamen-
tum flavum isincisedand the posterior elementsare removed.

59
ThoracicLaminectomy
451
Figure59-5
Thelaminectomycompleted.
References
1.
Lawrence F. B: Surgical approaches
to the thoracic
and thoracolumbar
spine for decompression
and stabilisation.
In: Schmidek
HH. Sweet
WHo eds. Operative
Neurosurgical
Techniques.
Vol 2. Philadelphia:
WB Saunders;
1995: 1887-1893
2.
Morgan TH, Wharton
GW, Austin GN. The results
of laminectomy
in
patients
with incomplete
spinal cord injury. Paraplegia
1971 :9:14-23
3.
Stillerman
CB. Weiss MH. Management
of thoracic
disk disease.
In:
Clinical
Neurosurgery.
Vol
38.
Baltimore:
Williams
& Wilkins;
1992:325-352
Figure59-6
Removalofthe joint complex. pedicle, and transverse
processallowsincreasedlateralexposure ofthe thecal sac.
4.
The axial skeleton.
In: Williams
PL, Warwick
R. Dyson M. Bannister
LH. eds. Gray's
Anatomy.
37th
ed. London:
Churchill
Livingstone:
1989:315-337
5.
Barnett GH. Hardy RW. Little jR, et al. Thoracic spinal canal stenosis.j
Neurosurg
1987;66:338-344
6.
Yamamoto
I. Matsumae
M. Ikeda A. et al. Thoracic spinal stenosis: ex-
perience
with seven cases.j
Neurosurg
1988;68:37-40
7.
Thoracic
spine.
In: Louis R. ed. Surgery
of the Spine.
New York:
Springer-Verlag;
1983:175-248

60
Thoracic Laminoplasty
Mitchell R. Gropper and Anantha Kishan
.
Indications
.
Advantage
.
Disadvantage
.
SurgicalTechnique
Expansion
Laminoplasty
Closure
Multilevel laminectomy in the developing spine of children
is known to cause long-term complications of spinal col-
umn deformity.1.2Cadaverstudies have shown that removal
of the posterior elements of the thoracic spine allows a
greater degree of flexion. extension. and axial rotation.3
Kyphosis.scoliosis.and combined spinal deformity can oc-
cur in the thoracic spine following loss of tension band sta-
bility. It is well accepted that total reconstruction of the
posterior spinal arch is essential after spinal canal surgery
in children.3Yasuokaet al found spinal deformity occurring
in 36% of patients below 25 years of age after thoracic
laminectomy.!
The term laminotomy was used by some authors to de-
scribe the replacement of the posterior elements of the
spine in the normal position after completion of surgery.2,4.5
The term laminoplastyisnow used to include all procedures
wherein the laminae of the spine are replaced and expan-
sion laminoplasty is used whenever the spinal canal dimen-
sion is altered. Even in adults it may be preferable to per-
form an arch reconstruction to reestablish the normal
anatomy and avoiddeformity.
This chapter focuseson procedures that first giveaccess to
the thoracic spinal cord and nerve roots and second allow
reconstruction with or without expansion of the neural arch.
.
Indications
. Epidural tumors
.
Intradural tumors-intramedullary
and extramedullary
.
Vascular malformations
.
Congenital spinal lesions
.
Arachnoid cyst
452
. Enterogenous cyst
.
Diastematomyelia
.
Syringomyelia
.
Thoracic canal stenosis
.
Advantage
.
Prevention of spinal deformity
.
Disadvantage
. Increased operative time
.
Surgical Technique
Surgery is once again performed in the prone position tak-
ing care to avoid pressure points. abdominal compression,
or stretching of nerves. The midline skin incision is marked
using the surface landmarks as described for laminectomy.
The paraspinal muscles are then separated subperiosteally
fromthe spinousprocessesand laminaetakingcaretopre-
serve the supraspinous and interspinous
ligaments. The
facet joints are exposed on either side without disturbing
the capsule of the joints.
Laminoplasty can now be performed in different ways.G-ID
The interspinous ligament is cut at the upper and lower
ends ofthe proposeddecompression.Careis takentopre-
serve the ligamentum flavum at these sites. Ahigh-speed
drill is used to makea narrow gutter on either sideofthe
midlinejust medialto the facetjoints (Fig.60-1). Thedrill

60
Thoracic Laminoplasty
453
Figure 60-2
Thecuts are made with a lateralto medialorientation.
Figure 60-1
A high-speed
drill with a small bur is used to make cuts
inthe laminae. The smallest possible bur should be used to avoid too
muchbone loss.
isused in a brushlike manner, gradually shaving off the
outer cortex of bone along the length of the laminoplasty.
Theinner cortex is also carefully drilled, exposing the liga-
mentflavum on both sides. The drilling should be done in
ananteromedial direction to obtain the shortest depth of
thelaminar groove (Fig.60-2). The spinous process is now
heldto lift the lamina outward and the ligamentum flavum
iscut on either side using scissors or a fine scalpel blade,
takingcare to avoid injury to the dural tube or epidural ve-
nousplexus (Fig.60-3). The laminae and spinous processes
are removed en bloc with the underlying ligamentum
tlavumexposing the spinal canal and the dural tube.
Another method of performing the laminoplasty is to
separatethe lower margin of the most caudal lamina from
theligamentum flavum and to use the footplate of a high-
speed drill just medial to the facet joint and underlying
pedicle(Fig. 60-4). The groove is extended across all the
laminaeto be opened using the footplate. The same process
isthen repeated on the other side. When using this maneu-
verthe cuts should proceed in a caudal-rostral fashion due
tothe shingling of the laminae as described in Chapter 59.
Thelaminae are then lifted off the dural tube using sharp
dissection to divide the attachment
of the ligamentum
tlavumcompletely.
Figure 60-3
Incisionofthe ligamentumflavumisdone on onlyone
side unless the structures must be removed to perform intradural
surgery.
,....,
- ...
./
J
"
l..
,I
/

.
454
Thoracic and Thoracolumbar Spine: Posterior Approach
Figure 60-4
Useof a footed drill should proceed in a caudal to ros-
tral fashion.
Expansion Laminoplasty
In situations with thoracic canal stenosis due to any cause,
an expansion laminoplasty may be performed to increase
the dimensions of the spinal canal. Although there seems to
be an endlessly growing number of techniques, we present
two of the more common of those described.
A simple open-book laminoplasty can be done in the
same manner as in the cervical spine. After exposing
the spinous processes and laminae, grooves are made on
the lateral aspects of the laminae and along the midline us-
ing a high-speed drill.The ligament fIavum is cut at the up-
per and lower ends of the larninoplasty and the midline cut
is taken through the underlying ligament (Fig. 60-5). The
bone chips from the resected spinous processes are then
placed over the lateral grooves and the split laminae are
folded over the grafted bone laterally and held in place by
suturing the ligament fIavum to the paraspinal muscles.
Autograft may be harvested as necessary from the iliac
crest to augment local bone. Thistype of laminoplasty may
be performed
using a bur as originally described
by
Kurokawa in 1982 or with a threadwire T-saw as described
by Tomita et al in 1998.6The addition of a posterolateral
...
IT" ~
.
i
Figure 60-5
In an open-book laminoplasty, the lateral cuts arenot
taken through the inner cortex and there is a midline cut that canbe
madewith awire sawor air drill.
fusion was described by Miyazaki et al and modified by
Shikata et aF; however, the use of custom-made hydroxya-
patite spacers between the spinous processes has also been
described.s
A second method, also used in the cervical spine, is the
open-door laminoplasty. In this technique, a single lateral
trough is made on one side while a complete cut through
the other side is done according to the surgeon's preference.
There is no need to remove the spinous processes in thisdis-
section. Ascalpel or small Kerrison rongeur can be usedto
cut through the ligamentum
fIavum along the deeper
groove. Gentle pressure
is applied
along the spinous
processes to the opposite side to expand the opening inan
open-doorfashion(Fig.60-6). Careis taken to ensurethat
adhesions to the dura, if present, are separated with a Pen-
field dissector. Nonabsorbable sutures are passed through
the bases of the spinous processes. Bone graft is placed
along the trough on the hinged side after decortication.The
spinous processes are secured into the facet capsulesateach
level, thereby expanding the spinal canal. This expansive
open-door laminoplasty was devised by Hirabayashiet alfor
management of ossification of the posterior longitudinallig-
ament causing cervicalspondylotic myelopathy.9

60
ThoracicLaminoplasty
455
Figure60-6
An open-door
laminoplasty
is performed
by pushing
the laminae laterally
and suturing
them segmentally
to the paraspinal
musclesor joint capsules.
Closure
Atthe end of the procedure. holes are drilled in the spinous
processes of the adjacent vertebrae at both ends of the
laminoplasty.Holes are also drilled in the laminae on both
References
1. Yasuoka S. Peterson
H. MacCarty C. Incidence
of spinal column
defor-
mity after multilevel
laminectomy
in children
and adults. J Neurosurg
1982;57:441-445
2.
Raimondi AJ. Gutierrez
FA. Di Rocco C. Laminotomy
and total recon-
struction
ofthe
posterior
spinal arch for spinal canal surgery in child-
hood.J Neurosurg
1976;45:555-560
3. White AA III. Hirsh C. The significance
of the vertebral
posterior
ele-
ments in the mechanics of the thoracic spine. Clin Orthop 1971;81 :2-14
4.
Cochrane DD. Steinbok
P. Laminotomy:
a technical
note. Childs Nerv
Syst 1992;8:226-228
5. Abbott R. Feldstein
N. Wisoff JH. et al. Osteoplastic
laminotomy
in
children. Pediatr Neurosurg
1992;18:153-156
6. Tomita K. Kawahara
N. Toribatake
Y. Heller JG. Expansive
midline
T-saw laminoplasty
(modified
spinous process-splitting)
for the man-
agement of cervical myelopathy.
Spine 1998;23:32-37
~
"
-
~\
,
,
.
,
.~J
'""
.~4A~
.
~y
..~
.
'~\
"
J
I
/r
.......---
Figure 60-7
Suturing the laminae back into position after intradural
surgery iscompleted.
sides. In cases in which the laminae had been removed such
as pediatric spinal cord tumors, the laminae may be sutured
back to the joint capsules prior to muscle closure (Fig.
60-7). The paravertebral muscles are then brought together
using 2-0 Dexon sutures. with special attention being paid
to a good closure of the dorsal fascia. The subcutaneous tis-
sue and skin are then brought together and closed. Adrain
may be left in the wound outside the replaced laminae and
brought out through a separate stab wound if deemed nec-
essary.
7.
Shikata J. Yamamuro
T. Shimizu
K. et al. Combined
laminoplasty
and
posterolateral
fusion for spinal canal surgery
in children and adoles-
cents. Clin Orthop
1990;259:92-99
8.
Nakano K. Harata S. Suets una F.Araki T.ltohj.
Spinous process: split-
ting laminoplasty
using hydroxyapatite
spinous process spacer. Spine
1992;17(3
Suppl):S41-S43
9.
Hiroabayashi
K. Watanabe
K. Wakano
K. et al. Expansive
open-door
laminoplasty
for
cervical
spinal
stenotic
myelopathy.
Spine
1983;8:693-699
10.
Goel
A. Deogaonkar
M. Thoracic
laminoplasty
using
spinous
processes:
technical
note.
Neurol
Med
Chir
(Tokyo)
1996:36:
659-661

61
18
Thoracic Epidural Abscess
Milind Deogonkhar and Mitchell R. Gropper
.
Advantages
.
Disadvantages
.
Etiologyand Pathogenesis
.
Pathophysiologyand ClinicalManifestations
.
Investigationsand Imaging
Theincidence of spinal epidural abscess has steadily in-
creased over the last 3 decades. This increase, from 0.18
casesper 10,000 admissions to 2.8 cases per 10,000 admis-
sions, could be a reflection of greater recognition and im-
proved imaging.] Increased
use of spinal instrumentation,
intravenous
drug abuse, immunodeficiecy
disorders, and an
aging population may also have contributed
to this increase.
The uniqueness
of spinal epidural
abscess
lies in its vari-
able presentation, often overshadowed by seemingly more
acute
medical
illnesses,
and
its
rapid
onset
of often-
irreversible neurological deficits. Thoracic epidural abscesses
account for 25 to 50%of all spinal abscesses.2.3 The relatively
small epidural space in the thoracic region results in rapid
and,
at times
catastrophic,
development
of neurological
deficits. Magnetic resonance imaging (MRI) is the single most
useful imaging technique used in diagnosis of thoracic spinal
abscesses. Computed tomographic (CT)scanwith or without
myelography may also be helpful.The treatment of choice is
immediate surgicaldecompressionand debridement.
.
Advantages
.
Most instances can be treated with simple laminectomy
and drainage.
.
Rapidintervention canhalt or reverse neurologicaldecline.
.
Recently, many cases can be treated with an extended
course of antibiotics.
.
Disadvantages
.
Certain patients with delayeddiagnosis/treatment are
proneto permanentneurologicaldeficit.
I
I
l
456
.
Management
.
Surgical Technique
Approaches
.
Outcome
. Ventrallesionscanbe moredifficultto drain.
.
Spinalinstabilitymayoccur requiringplacementofin-
strumentationinthe faceofinfection.
.
Etiology and Pathogenesis
Twomajor etiological mechnisms
of thoracic epidural
abscesses consist of spread from adjecent vertbral os-
teomyelitis and hematogenous spread. Vertebral osteomyli-
tis accounts for 5 to 45%of cases.4Skin and soft tissue
remain the major sources of infection in hematogenous
spread.Urinarytract infections,dental procedures,andar-
teriovenous fistula infections also act as sources in a small
number of patients.s Trauma, lumber puncture, and spinal
surgery account for 5 to 8%of all spinal epidural abscesses.
Thesourceof infectiondictates locationof the abscess.In
intravenous drug users and upper extremity infections the
thoracic spine is more often involved. Hematogenous
spread occurs through the spinal epidural venous plexus
(Fig. 61-1). Thrombosis
of these veins at the level of abscess
and venous engorgement
above and below the abscess is
commonly seen.6
Staphylococcus
aureus
is the
most
common
organism
causing epidural abscesses. It accounts for almost 60%
of infections. Streptococci, gram-negative organisms, fungi,
and
Mycobacterium
tuberculosis
are
other
causative
organisms.7,8
The location of an abscess in the epidural space is dic-
tated by the anatomy of the canal in the thoracic region. The
dorsal portion of the canal, with its relatively larger volume
and poorly vascularized
epidural
fat, make it the prime site
for these infections to localize. The location of abscesses can
roughly be divided into four groups (Fig.61-2A-C):

61
ThoracicEpiduralAbscess
457
Figure61-1
segment.
The venous drainage of a typical thoracic vertebral
A
(
1.
Anterior symmetrical
2.
Anterior asymmetrical
3.
Posterior (dorsal)
4.
Circumferential
Dorsal predilection of thoracic epidural abscesses was
challenged by a recent MRI-basedstudy that found ventral
location to be the commonest (50%),then circumferential
(36%),and dorsal (14%).9
The male to female incidence is -1.5:1. Medical comor-
bidity such as diabetes. chronic renal failure, alcoholism.
immunosupression,
and
malignancies
predispose
to
epidural spread. In 50 to 80%of patients at least one of
these risk factors is present. In 95%of cases the inciting or-
ganism can be identified by blood cultures.
B
Figure 61-2
Typical locations of epidural abscesses (dorsal not
shown)(A)Ventral.(8) Ventrolateral.(C)Circumferential.

458
ThoracicandThoracolumbarSpine:PosteriorApproach
.
Pathophysiology and Clinical
Manifestations
Mechanisms by which thoracic epidural abscessesproduce
neurological deficits have been a matter of debate for many
years. The catastrophic nature of neurological involvment,
which is often disproportionate
to the size of the abscess
and extent of cord compression, has led to speculations
about
vascular
mechanisms.
Mechnical
compression
alone is not an adequateexplanation. Studiesin a rabbit model
and autopsiedpatients haveshown the following mechanisms
. Venous compression
and thrombosis
.
Thrombophlebitis
of epidural
space and spinal cord
. Venous infarction
and edema
.
Hypoxiasecondaryto rostral venousdrainageobstruc-
tion and venous stasis
.
Arterial thrombosis
This explains the rapidity of onset and often irreversibil-
ity of neurological deficits. It seems prudent to conclude
that vascular and compressive factors act in combination to
produce the full clinical picture.
High variability
in the clinical picture often poses diag-
nostic difficulties. The majority of the patients are febrile on
presentation and have signs of systemic infection. They of-
ten have more obvious and acute medical problems. Classic
clinical evolution of thoracic epidural abscessestakes place
through four clinical stages:
1.
Focalspinal pain and tenderness
2.
Radicularpain
3.
Weakness
4.
Paralysis
The latent period
between
onset of pain and neurological
deficit
varies in each patient.
The time taken for progression
from
pain to weakness
groups
these abscesses into acute
and chronic.
The acute group
has rapid
onset and complete
paralysis
and is often accompanied
by high fever, tachycar-
dia, and leukocytosis.
Chronic
patients
have less pain and
slowly
progressive
paraparesis.
The chronic
group also car-
ries a better
prognosis
for neurological
recovery.
Some in-
vestigators
have classified
patients
with
symptoms
lasting
less than 2 weeks as acute and those with
symptoms
lasting
more
than
2 weeks
as chronic.
Ascending
neurological
deficits
in a previously
paraplegic
patient
could be a signof
developing
epidural
abscess.
.
Investigations
and Imaging
Leukocytosis
and elevated erythrocyte
sedimentation
rate are
noted in the acute phase. Lumbar puncture
is no longer neces-
sary to make a diagnosis of thoracic epidural abscess. It carries
the risk of neurological
deterioration
if performed
below a
block or it carries the possibility
of traversing
the abscessand
transmitting
the infection
to the subarachnoid
space. The
possibility
of isolating
the
infective
organism
from
cere-
brospinal
fluid
(CSF) is as low as 5 to 15%.On the other hand,
blood cultures are positive for infective organisms in 40 to 95%
of cases.The best yield is from the operative specimens, which
are positive for infective organisms in 80 to 100%of cases.
MRI is the investigation
of choice (Fig. 61-3A,B).lt
shows
the full extent
of the abscess,
bone, soft tissue, and spinal
..
A
&:11 _
..~-
-;;:--_ -
_
_
--&I B
Figure 61-3
Magnetic resonance image of spondylodiskitis. (A) Note enhancement of the disk and symmetric destruction of the end plates. (8) Axial
image demonstrating
extent of ventral extension with thecal sac compression.

61
ThoracicEpiduralAbscess
459
cordinvolvement.AspinalepiduralabscessonT1-weighted
images appears as an isodense extradural mass. On T2-
weightedimages it appears to be completely silhouetted by
the high densities of the (SF. Gadolinium enhancement on
Tt-weighted images should show a homogeneous or cap-
sule-enhancinglesion. Plain radiographs show the bony de-
structionassociated with spondylodiskitis. CTmyelograms,
though sensitive, are invasive and may not show the full
extentofthe lesion and status of the cord.
. Management
Themanagement of thoracic epidural abscesses is dictated
bythe anatomi,cal peculiarities of the region, which include
anarrowspinal canal, a meager blood supply and the pres-
enceof the rib cage, which confers stability. Traditionally,
emergencyoperative decompression has been the treatment
ofchoice.In more recent times, however, patients have been
managedwith antibiotics and external bracing. This is rec-
ommendedonly in patients with minimal or no neurological
deficitswho can have frequent and vigilant neurological at-
tentionand rapid access to MRI.Some studies also recom-
mendnonoperative therapy in patients who are poor surgi-
calriskswith multilevel extensive abscesses and profound
neurologicaldeficits for more than 3 days.
Antimicrobial therapy should be started immediately if
thepatient is septic and in all patients after the appropriate
culturesare obtained. Empirical antibiotics should include
first-line antistaphylococcal agents. Synthetic penicillins
orcephalosporins are appropriate choices. Four to 6 weeks
ofintravenousantibiotics are recommended in all patients.
Alongercourse is recommended in cases with poor clinical
response, systemic infections, or infections caused by
organisms like tuberculosis, methicillin-resistant
Staph-
ylococcusaureus, or actinomycosis. Patients who are im-
munosupressed or of advanced age need longer courses of
antibiotics.
Externalbracing is helpful in relieving pain and promot-
ing bony healing. It also minimizes spinal deformity.
Orthosesare used for a minimum of 6 weeks. A thora-
columbosacralorthosis (TLSO)is used for mid- to lower
thoracicspine stabilization.
Theuse of steroids is controversial. Though steroids are
oftenused in patients with overt signs of spinal cord com-
pression,they are more useful as a preoperative adjunct.
Surgical management
of thoracic epidural
abscesses
includedrainage and debridement.
Stabilization of the
spineisused whenever necessary. Indications for emergent
decompression include progressive neurological deficit,
sepsis with a large epidural mass, significant bony in-
volvementwith deformity, and osseous destruction without
bacteriologicaldiagnosis. Delayed surgical intervention is
consideredwhen medical management fails.
. SurgicalTechnique
Regardlessof the surgical approach, the basic principles of
thesurgery remain the same. They include adequate expo-
sureand complete resection of the infective material and
involved soft tissue and bone. Antibiotics are administered
only after intraoperative cultures are obtained. Adequate
excision is indicated by healthy bleeding from the bone and
soft tissue. Attempts to correct the spinal instability or de-
formity are undertaken during the same procedure or they
may be staged. Instrumentation and harvested bone grafts
are used when indicated. The wound is primarily closed af-
ter thorough irrigation with antibiotic solution. An external
drain usually helps in draining the residual infection.
Approaches
Surgical approaches to the thoracic spine can be divided
into ventral, dorsal, and dorsolateral approaches. They can
either be used alone or in combination; either at the same
time or in staged procedures. The surgical approach is de-
termined by the pathological process, its location,evidence
of spinal cord compression, instability, and the patient's
medical condition. This chapter discusses dorsal and dorso-
lateral approaches.
Dorsal surgical approaches to thoracic spine include
laminectomy, trans pedicular decompression
and costo-
transversectomy (Fig.61-4 A,B).
Laminectomy
Laminectomy (Fig. 61-4A), which is a midline surgical ap-
proach, is used exclusivelyfor dorsally situated abscesses. It
is not useful for isolated ventral abscesses. Laminectomy is
performed through a standard midline thoracic incision
(Fig. 61-5). The paraspinal muscles are often edematous
and inflamed. The stripping of paras pinal muscles exposes
laminae, which could be destroyed, exposing the thecal sac,
which calls for extra caution. Removal of the lamina
exposes the dorsal thecal sac and overlying infected mater-
ial. The purulent
material
and the granulation
tissue
are scraped off the dura, taking care not to perforate it.
Healthy bleeding from the dural surface marks adequate
debridement.
TranspedicularApproach
The transpedicular
approach and costotransversectomy
(Fig. 61-4B) provide more lateral exposure. These ap-
proaches confer an advantage of avoiding the surgicalmor-
bidity of ventral approaches and at the same time provide
good access to the ventrolateral aspect of the spinal cord.In
effect they provide a safe way to decompress the ventrolat-
eral region but one that is less complete and less reliable.
They also minimally destabilizes the spine.
The exposure for the transpedicular approach isachieved
through a standard midline incision (Fig. 61-5). Laminec-
tomy is optional but is often performed to get a good expo-
sure. The ipsilateral
facet joint and pedicle are then
removed with a drill while protecting the spinal cord with
handheld, malleable retractors. This exposes the lateral
thecal sac and exiting nerve root. The nerve root can
often be sacrificed to provide additional ventral exposure or
to carry out partial vertebrectomy. Bilateral transpedicular
approaches can be performed for bilateral decompression.

460
ThoracicandThoracolumbarSpine:PosteriorApproach
I
A
an.
B
Figure 61-4
Classic approaches to the thoracic spine showing degree of thecal sac exposure. (A) Laminectomy. (B) Transpedicular approachand
costotransversectomy.
Figure 61-5
Skin incisions for dorsal and dorsolateral
exposures.
The midline excision can be converted to a hockey stick incision and
will be used for midline pathology or in cases in which bilateral decom-
pression
is needed.
The curved paramedian
incision can be used for
lateral extracavitary
exposure or costotransversectomy.
Neither inci-
sion precludes posterior instrumentation.
Figure 61-6
The rib head is removed for the lateral extracavitaryap-
proach or the costotransversectomy.
Care should be taken to protect
the pleura during its removal. Notethe neurovascular bundle,which
can be usedto findthe neuralforamen.

Costotransversectomy
61
ThoracicEpiduralAbscess
461
Costotransversectomy is performed
through
a midline
or paramedian incision (Fig. 61-5). It is identical to the
transpedicular approach except that the rib head and
transverse process are removed (Fig. 61-6). The addi-
tionalexcision of a rib head and transverse process gives a
wide lateral and ventrolateral
access.
Partial verte-
brectomyis technically more feasible and safe with this
approach.
LateralExtracavitaryApproach
Thelateral extracavitary approach is a dorsolateral
ap-
proachthat was first described by Potts in 1900. It pro-
videsgood visualization and decompression
of the ven-
tral thecal sac through
a dorsolateral
incision.
This
approachdoes not violate the chest cavity and has less
surgicalmorbidity than ventral approaches.
Dorsal in-
strumentation can be performed during this approach.
Thepatient is placed in the prone position and either a
hockeystick or paramedian incision can be used. Amid-
lineincision is also used when circumferential
decom-
pressionis planned. The hockey stick incision is a midline
incisioncurved 45 degrees off midline for 6 to 8 cm in
the lower portion. A paramedian
incision centered over
thelateral aspect of the paraspinal muscles can be used if
midlineexposure is not needed (Fig. 61-5). A plane is
then developed
between
the
superficial
and
deep
paraspinalmuscles. A myocutaneous flap is thus lifted off
toexpose the lateral paraspinal muscle and rib cage. The
paraspinal muscles are mobilized off the underlying rib
andtransverse process. One or more ribs are then excised
alongwith their ligamentous attachments without violat-
ingthe pleura. The transverse
process is also removed.
Theneurovascular bundle is isolated and used as a guide
tothe vertebral foramen. The pleura and the intercostal
musclesare bluntly dissected away from the vertebral
body(Fig. 61-7). The pedicle and the lateral vertebral
bodycanthen be drilled to expose the ventrolateral as-
pectof thecal sac. The radicular artery is located in this
regionand care is taken not to damage it. A thorough
evacuationand debridement of infected material is done.
Onlayand interbody bone grafts are used for stabiliza-
tion,which can further be reinforced by dorsal instru-
mentation. Pleural tears are repaired
if present. Chest
tubesare used as necessary. Layered closure is performed
inthe usual fashion.
Placement of bone graft and spinal instrumentation
duringthe primary procedure is still controversial. Place-
mentof hardware in an infected surgical bed had been
stronglydiscouraged in years past, and a small number of
surgeons still defer it to a staged procedure.
In recent
Figure 61-7
Exposure afforded by the lateral extracavitary approach.
studies, however, no increases in complication rates were
reported in instrumented
fusion performed during the
primary
procedure.
The fusion
rate
approaches
99%
and no additional
complications
were reported
in this
study. Vascularized autologous
grafts are superior
to
nonvascularized
grafts. Vascularized rib is most com-
monly used due to its accessibility and high content of
bone morphogenic protein.
. Outcome
The prognosis in patients with thoracic epidural abcesses
has improved dramatically with the evolution of antibi-
otics and newer surgical approaches. The mortality rate,
which was as high as 30 to 80%in older studies, has re-
cently been reported as low as 2 to 9%.The neurological
outcome depends primarily on the degree of cord function
and duration of symptoms before drainage and decom-
pression. Patients who are paralyzed for less than 36 hours
make excellent recovery after surgical decompression. The
chance of recovery significantly decrease after 72 hours.
The degree of thecal sac compression and age of the pa-
tient have a significant independent association in deter-
mining the outcome. Patients older than 60 with more
than 50%canal compromise have poor neurological recov-
ery. In general, one third of patients are left with major
neurological deficits and only 40%achieve full functional
recovery.

References
462
ThoracicandThoracolumbarSpine:PosteriorApproach
1. DannerRL.HartmanBJ.Updateof spinal epidural abscess: 35 cases
and review of literature. RevInfect Dis 1987;9:265-274
2. BakerAS.Ojemann RG.Swartz MN.Richardson EPJr. Spinal epidural
abscess. N EnglJ Med 1975:293:464-468
3.
CareyME. Infection
of the spine and the spinal cord. In: Youmans JR.
ed. Neurological Surgery. 4th ed. Philadelphia:
WB Saunders:
1996:3270-3304
4.
Carragee E. Pyogenic
vertebral
osteomyelitis.
J Bone Joint Surg Am
1997:79:874-880
S. Hlavin ML. Kaminski
HJ. Ross JL. et al. Spinal epidural
abscess:
a ten
year perspective.
Neurosurgery
1990:27: 177-184
6.
Morikawa M. Sato S. Numaguchi Y. et al. Spinal epidural venous
plexus:
its MR enhancement
patterns
and their clinical significance.
Rad Med 1990:14:221-227
7. Feldenzer
JA. McKeever PE.Schaberg
DR. et al. Experimental
spinal
epidural
abscess:
a pathophysiological
model in rabbit. Neurosurgery
1987:20:859-867
8.
Heusner AP.Nontuberculous spinal epidural infections. NEngljMed
1948:239:845-854
9.
Eichbaum E. Martz P. McCormick B.Spinal infections. In: BenzelEC.
Stillerman
CB.eds. Thoracic Spine. St. Louis: Quality Medical Publish-
ers: 1999:577-598

62
ThoracicExtensionOsteotomy
MitchellR.Gropper
. Indications
. Advantages
. Disadvantages
. HistoricalPerspective
. Objective
. SurgicalTechnique
Sagittalplane imbalance occurs in a variety of settings and
carrieswithita cumbersometreatment algorithm.Preven-
tionthrough early recognition and adequate medical treat-
mentshould be the mainstay; however,alItoo often patients
presentwith deformity that requires surgical intervention.
Progressiveneurological deficit is an obvious indication
forcorrectivesurgery. Pain, however, is a more common in-
dicationfor surgical management. Careful consideration,
therefore,must be given to the biomechanical causes of
the deformity, the psychosocial and physical makeup of
the patient, his or her prior management, the morbidity
associated with the chosen surgical approach, and the
costof the procedure prior to embarking on deformity
correction.
Inthe face of pain and sagittal imbalance, patient expec-
tationsmust be clearly elucidated prior to discussing surgi-
calapproach.Toooften. patients expect complete resolution
ofpain from an operation. Because there are no random-
ized,controlIed trials as to the outcome of spinal fusion as it
relates to pain, patients
must understand
that
repeat
surgeryor surgery for deformity correction carries a higher
rateofpseudarthrosis. This may require revision or salvage
surgery in the future. Only after patient and physician
expectations are aligned should surgical approaches be
reviewed.
. Indications
. Kyphosis
. Ankylosing spondylitis
.
Marie-StriimpelI spondylitis
.
Posttraumatic kyphosis
Anesthesia and Positioning
Incision
Bone Exposure
Osteotomy
Osteoclasis and Instrumentation
Closure
.
PostoperativeCare
.
Postsurgical kyphosis
.
Tuberculosis
.
Congenital thoracic kyphosis
. Scoliosis
.
Flat-back syndrome
.
Advantages
. Enables correction of midline sagittal imbalance
.
Mayarrest progressing neurological deficits
.
Disadvantages
. Significantbloodlosscanoccur.
.
Painand paresthesiasresultwhen nerverootsaresacri-
ficed.
.
HistoricalPerspective
The original description of the posterior approach for cor-
rection of sagittal imbalance was described in 1945 by
Smith-Peterson et al.l Since then the majority of clinical re-
ports have centered around the management of kyphosis in
ankylosing spondylitis. These procedures generalIy included
anterior procedures combined with removal of the poste-
rior elements.2-6
In 1946 LaChapelIe7described a two-staged procedure
that involved the posterior decompression followed by an
463

464
Thoracicand Thoracolumbar Spine: Posterior Approach
anterior wedge osteotomy. This procedure, as well as that
described by Hodgsonin 1965,8involvedthe anterior wedge
to avoid osteoclasis and the potential for stretching neural
elements.
Heinig9and Thomasen 10both describe posterior proce-
dures that allow removal of portions of the vertebral body
and subsequent controlled collapse. These procedures avoid
the added morbidity of the anterior approach. Avoidanceof
distraction and spinal cord stretch is another advantage.
Adequate enlargement of the neural foramen is paramount
to these approaches.
. Objective
Tocorrectsagittalimbalancethroughcontrolledcompres-
sionofboththe posteriorand middlecolumns
.
SurgicalTechnique
Anesthesia
and Positioning
General anesthesia is employed on a standard operating
room table. Longchest rolls should be used (Fig.62- t). The
table is then flexed with the maximal area of deformity cen-
ter at the break point. The kneeling position should be
avoided because this will disallow osteoclasis through ele-
vation of the lower body. The Phalen table may be used as
long as it can be removed if osteoclasis is required. The
arms may be put at the patient's side or above on arm
boards depending upon the surgeon's preference.
Ifthe patient has severe kyphosis or arthrosis at the hips
and knees (Le.,ankylosing spondylitis) adaptations must be
made. Bolsters and rolls should be used at the iliac crests
and thighs to disallow collapse of the kyphotic segment
while performing the osteotomy. Again,care must be taken
to provideaccess to the legs for osteoclasis.
Incision
The skin incision should be made with instrumentation
in
mind. Holdingthe alignment after osteoclasis is paramount,
and instrumentation
is required. The surgeon must decide
on short-segment
instrumentation
or a longer construct.
Longer constructs will be required when there is a signifi-
cant amount of instability and loads are to be displaced
over multiple segments. Exposure of no fewer than three
and generally no more than eight segments is required.
Bone Exposure
Exposure of the posterior elements must take in mindthe
subsequent instrumented
fusion. As previously stated the
levels of exposure depend upon the surgeon's preferenceas
to short- or long-segment fixation. Lateral exposure should
include the entire transverse process. Care must be takento
avoid excessive blood loss from the intercostal vessels.All
soft tissue should be removed from the bone to allowland-
mark identification for the osteotomy (Fig.62-2).
Osteotomy
The osteotomy will be done at the site of maximum defor-
mity. If the Heinig eggshell procedure is to be performed,
then the pedicles of the affected level will be used to re-
move the majority of the vertebral body. The pedicle can
most easily be found by removing the lower half of the infe-
rior articular process or by widening the laminectomy if
this has been the cause of the kyphosis (Figs. 62-2,62-3).
After identification of the pedicle a high-speed air drillor
a pedicle sound can be used to traverse to the vertebral
body. Localbone can be saved by utilizing a trap on the suc-
tion tubing. Ifthe cortex of the pedicle is breached during
this portion of the procedure, care must be taken to protect
the nerve roots.
Asuggestion to the surgeon is to sacrifice the nerve roots
by ligating them as well as the intercostal vessels with silk
sutures (Fig. 62-4). Leaving the sutures uncut will allow
light traction to be applied to the roots and thecal sac.This
allows increased exposure of the posterior aspect of the
vertebral body. Although this maneuver will produce some
numbness and minimal motor loss, it may produce neuro-
pathic pain that can be distressing to the patient and hinder
a good outcome. Another suggestion is the use of cryother-
apy to the proximal end of the cut nerve root. This should
lessen the chance of denervation pain.
1'J.'-
r£;
.
Figure 62-1
The positioning for thoracic os-
teotomy. Notethat the maximalarea ofsagittalplane
deformity should be placed at the break pointinthe
table. The table should be flexed to conformto the
patient's habitus. Extra padding should be usedto
avoidpressurenecrosis.

62
ThoracicExtensionOsteotomy
465
Stout, variable-angled
pituitary rongeurs are required
to remove bone. No attempt
should be made to breach
the anterior cortex of the body. This will lead to vascular
injury that cannot be controlled. Bleeding from severely
osteoporotic bone, as in ankylosing spondylitis, is brisk
andessentially uncontrollable. This portion of the proce-
dure should be done as swiftly as possible to minimize
risk.
Theremoval of the transverse processes and rib heads is
notessential but will allow for less compression of the nerve
roots if they are spared. Their removal will also afford a
better trajectory for removal of the lateral aspect of the
vertebralbody (Figs. 62-4, 62-5). The osteotomy can easily
Figure62-3
Bywidening the laminectomy one canfeel the medial
borderof the pedicle, which canalso befound below and slightly ros-
tral to the inferior articular process. The pedicle should be used to
guidethe surgeonto the vertebral body.
Figure 62-2
The surface bony exposure for osteotomy.
The neurovascular
bundle
can be used to identify
the
neural foramen.
Bipolar cautery
should be used if there is
bleeding
from
aggressive
dissection
of the intercostal
artery
and vein; this will allow as much protection
of the
pleura as possible. The pedicles can be found in line with
the transverse
processes and below the inferior
articular
process.
be taken through the vertebral body ending at each end
plate (Fig. 62-5). Bilateral decompression and removal of
all posterior elements
allow adequate
mobilization
for
osteoclasis.
Another
technique
for the osteotomy
is to take it
through the disk space (Fig. 62-6). This approach is the
same as that described elsewhere in the text as a costo-
transversectomy. For osteoclasis, however, the removal of
the lower pedicle, transverse process, rib heads, and bony
end plates must be done to allow room for both nerve
roots to occupy a single neuroforamen. Sacrificing the su-
perior nerve root, as already described, will make this ma-
neuver safer.
Figure 62-4
Ligationof the nerve roots will allow increased expo-
sure of the vertebral body. The intercostal vesselsshould be ligated
with silk sutures; electrocautery may allow rebleeding, which must be
avoided.

466
Thoracicand Thoracolumbar Spine: Posterior Approach
-
."~
.,"'"
~,
.
,,"
t!
.
'
'".. '---
\'
",""
-
-,
I
"r;;'"
..
/
I
Figure 62-5
The osteotomy
has been performed
by removing the
majority of the bone of a single vertebral segment. Removal is taken to
the superior and inferior end plates. As in Figure 62-4. the laminec-
tomy has been completed
and the transverse
processes and rib heads
have been removed bilaterally to allow adequate
mobilization for os-
teoclasis. Note the exposure afforded by using the nerve roots for light
retraction of the thecal sac.
Osteoclasis and Instrumentation
Osteoclasis is a controlled fracture that allows remodeling
of a deformed bony structure. In the spine. osteoclasis
should be done with the instrumentation
in place. For se-
verely osteoporotic bone the surgeon should consider the
use ofa long-segment hook-rod construct to allow distribu-
tion of loads over many segments. This will avoid undue
Figure 62-6
The osteotomy mayalsobe done by removing a disk
and the adjacent end plates.
stress application to weak bone; a strategy that subse-
quently leads to construct failure.
Often the surgeon wishes to use short-segment fixation
as in trauma and tumor. Shorter constructs can distribute
loads nearly as well as hook-rod devices through the useof
a rigid cantilever beam fixation (Le.. pedicle screws).A
novel approach for porotic bone has been to fillthe segment
with polymethyl methacrylate or hydroxyapatite cement
prior to screw insertion (Fig. 62-7). This can increase pull-
out strength as high as 149 to 296% in some series. thus
making it possible to use these devices even in ankylosing
spondylitis.n-13
The longitudinal member (rod. or plate) should not be
applied until after osteoclasis. If the case has been done
on a standard operating room table, then it should be
done with the table flexed at the point of maximal defor-
mity(Fig.62-t). Atthispoint.the anesthesiologistcanlevel
the table and the segment will fracture allowing closureof
the osteotomy (Fig. 62-8). Removal of extra bolsters will
also promote fracture. Lifting the legs and hips is some-
times required in cases of severe kyphosis.The rodscan
then
be applied
to hold the correction
(Fig. 62-9).
Crosslinking the construct is required based on the degree
of instability created.
Closure
The wound closure should be done over large, closed
drainage devices. Slow bleeding from the various bone
edges should be expected. The use of epidural analgesia is
encouraged if the dura has not been violated; however,
monitoring of cardiopulmonary function is necessary ifthe
decompression is in proximity to the T4 level. Closure is
performed in the standard fashion.
Figure 62-7
The injection of polymethyl methacrylate
(PMMA)can
increase
pullout strength
of pedicle screws in osteoporotic
bone.
PMMAis injected through the pedicle until increased resistance is met.
Ifthe anterior cortex has been breached then sterile barium should be
mixed into the PMMAand fluouroscopic guidance should be used.

62
ThoracicExtensionOsteotomy
467
Figure 62-8
The table is leveled and the bolsters have been removed to flatten the patient. The surgeon must watch carefully as the osteotomy
closes(osteoclasIs). Occasionally two assistants may be needed to lift the legs off the table to promote fracture.
.
PostoperativeCare
Patients must be watched for hemodynamicinstabilityin
the postoperative setting. Cases of fracture of severely calci-
fied aortas have been described not only in trauma but in
deformity correction as well. Early mobilization should be
encouraged. The use of external orthoses is dependent upon
individual preferences.
Figure62-9
long constructs will be required to distribute loads over
manysegments indeformity correction. Ifassistants are used to lift
the legs. they will need to do so until the longitudinal
members
have
beensecured.
References
1. Smith-Peterson
MN. Larson CB.Aufranc
OE. Osteotomy
of the spine
for correction
of flexion
deformity
in rheumatoid
arthritis.
j Bone
Joint Surg Am 1945;27:1-11
2.
Goel MK.Vertebral osteotomy
for correction
of rigid flexion deformity
ofthe spine.J Bone joint Surg Am 1968;50:287-293
3.
Hammerberg
KW. Kyphosis.
In: Bridwell
KH. DeWald
RL. eds. The
Textbook of Spinal Surgery. Philadelphia:
jB Lippincott;
1991 :501-524
4.
Hebert JJ. Vertebral
osteotomy
for kyphosis.
especially
in Marie-
Striimpell arthritis. j Bone joint Surg Am 1959;41 :291-320
5.
Kostuik jP. Maurais
GR. Richardson
Wj. Okajima Y.Combined
single
staged
anterior
and posterior
osteotomy
for correction
of iatrogenis
lumbar
kyphosis. Spine 1988;13:257-266
6.
Louw jA. Spinal
tuberculosis
with
neurological
deficit:
treatment
with
anterior
vascularised
rib grafts.
posterior
osteotomies
and
fusion. j Bone joint Surg Br 1990;72:686-693
7.
La Chapelle
EH. Osteotomy
of the
lumbar
spine
for correction
of
kyphosis
in a case of ankylosing
spondyloarthritis.
j Bone joint
Surg
Am 1946;28:851-858

468
ThoracicandThoracolumbarSpine:PosteriorApproach
8. Hodgson AR. Correction of fixed spinal curves: a preliminary
commu-
nication. J Bone Joint Surg Am1965:47: 1221-1227
9.
Heinig CF. Eggshell procedure.
In: Luque E, ed. Segmental
Spinal In-
strumentation.
NJ: Slack: 1984;221-234
10.
Thomasen
E. Vertebral osteotomy
for correction
of kyphosis
in anky-
losing spondylitis. Clin Orthop 1985;194:142-152
11. LotzJC,Hu55,Chiu DF,YuM.Colliou O.Poser RD.Carbonated apatite
cement
augmentation
of pedicle
screw fixation
in the lumbar
spine.
Spine 1997:22:2716-2723
a
12.
Yerby
SA, Toh E. Mclain
RF. Revision of failed pedicle screws using hy-
droxyapatite
cement:
a biomechanical
analysis. Spine 1998:23:
1657-1661
13. Pfeifer BA. Krag MH.Johnson C.Repair of failed transpedicle screw
fixation:
a biomechanical
study comparing
polymethylmethacrylate,
milled
bone.
and
matchstick
bone
reconstruction.
Spine 1994:19:
350-353

---
63
Diagnosis and Management of Thoracic
DiskHerniation and the Transpedicular
Decompression for Thoracic Disk Herniation
EhudMendel,
Bernard H. Guiot,
Robert E. Isaacs,
Laurence D. Rhines,
Richard G. Fessler, and Oran Aaronson
.
Advantages and Disadvantages
.
Advantages
.
Disadvantages
.
Radiological Evaluation
.
Therapeutic Management
.
The Transpedicular Approach
Thoracicdisk herniation is an uncommon event. A peak
incidenceis noted in the fourth decade, estimated between
7 and 15%.1.2Symptomatic thoracic disks constitute be-
tween0.15and 1%of patients requiring disk operations and
are estimated to occur in 1 in every million patients per
year.3-9Seventy-five percent of protruded disks occur below
T8and present most commonly with pain. Sensory and mo-
tordisturbances are also common. Indeed, 90%of patients
withthoracic disk herniations have spinal cord involvement
atthe time of diagnosis.
. Advantagesand Disadvantages
Historically, the management of this disorder has been
problematic. Due to the relative rarity of thoracic disk dis-
easeand the nonstereotypical presentation, establishing the
correctdiagnosis and selecting the appropriate therapeutic
option present a challenge. In addition, the procedures
for decompression are numerous. Selection of the "best"
surgicalapproach is controversial. Several operative tech-
niqueshave evolved for the treatment of herniated thoracic
disks, including the transthoracic,lO-24 lateral extracavi-
tary,8.14.15.23.24
transpedicular,23-27transfacet pedicle-sparing
approaches,27and, lately, the thoracoscopic approach. There
Historical
Considerations
.
SurgicalTechnique
.
Discussion
.
Summary
.
Acknowledgments
is a learningcurve in this latest techniquerequiring
additional training for even the most experienced spine
surgeon.
These approaches to the thoracic spine allow surgeons to
safely remove herniated disks, including those with central
osteophytes and intradural fragments. They evolved in re-
sponse to the disappointing results of laminectomy when
used to decompress ventrally situated lesions. Due to its
relatively
high incidence
of spinal
cord injury,19.28-31
laminectomy has essentially been abandoned. Indeed, a
posterior approach for removal of an anterior lesion entails
significant spinal cord manipulation. This trauma causes
mechanical injury to the cord and may alter blood flow,re-
sulting in vascular insufficiency.There are also biomechani-
cal disadvantages to laminectomy. Breig and others have
shown that posterior decompression for ventral disease is
ineffective in diminishing either the compressiveforcesact-
ing on the anterior surface of the cord or the axial tension
on the posterior surface.32-35Flexiondeformities following
the removal of posterior elements mayalso result in neuro-
logical dysfunction.
This chapter presents various management options for
the treatment
of thoracic disk herniation and considers
those anatomical and biomechanical features that are im-
portant in the operative management of thoracic disk her-
niation using a transpedicular approach.
469

470
ThoracicandThoracolumbarSpine:PosteriorApproach
.
Advantages
. Lessinvasivethan thoracotomy
.
Reducedoperating time and blood loss
.
Shorter hospitalization and recovery
.
Doesnot require an access surgeon
. Applicableto all levels of the spine
.
Disadvantages
. Limitedaccessto ventralmidlinepathology
. Difficulto evaluatethe extentofdecompression
. Notoptimalforintraduralpathology
. Extensiveproceduresmayresultininstability.
. Radiological Evaluation
Complete radiological evaluation should include thoracic
and lumbar spine x-rays, magnetic resonance
imaging
(MR[),and possibly computed tomographic (CT)scan after
myelography. Lumbar and thoracic x-rays are necessary to
determine the number and appearance of the vertebrae in
both the lumbar and the thoracic spine. These are also nec-
essary for absolute identification of the surgical level intra-
operatively. MR[is an excellent screening procedure and
can be used in place of a myelogram/CTfor absolute identi-
fication of the pathological level.This requires the ability to
count to the herniated disk from either C2or the sacrum in
the sagittal plane. Disks can then be assessed in terms of
size and location. The herniated disk is classified as lateral if
it projects beyond the margin of the thecal sac. Otherwise,
it is deemed to be a central herniation. The degree of cord
compression is documented and an intradural disk frag-
ment must be ruled out. This has been reported to occurin
up to 12%of cases.14.23.36.37
MRIis very sensitive in the identification of thoracicdisk
protrusions
but has a relatively high false-positive rate
(14.5%),making clinical correlation potentially more diffi-
cult.38.39[n addition, radiological findings do not always
correlate with the severity of the neurological dysfunction.
Therefore, if there is any question regarding the significance
of the disk herniation, or if there is any doubt regardingthe
exact level of disk herniation, it is important to performa
thoracic myelogram and postmyelography CT.This should
include both sagittal and coronal reconstructions. Fortho-
racic disk disease at or below T8, selective spinal angiogra-
phy might be considered to define the location of the major
radicular medullary artery (ofAdamkiewicz).
.
TherapeuticManagement
Adiagnosticalgorithmfor thoracicdisk herniation is out-
lined in Fig. 63-1. [n brief, patients require plain x-raysand
MRIto establish the correct diagnosis. The decision to oper-
ate is made on the basis of the patient's clinical status.
Asymptomatic patients or patients with localized axialpain
who are not myelopathic rarely need surgery. Rather,con-
servative modes of treatment, including bracing, steroidal
and nonsteroidal
antiinflammatory
drugs, and physical
therapy are recommended.
[n selected patients, surgery
may be indicated when radicular pain proves to be refrac-
tory to maximum medical therapy. [n general, documenta-
tion of a protruding
disk herniation
in a myelopathic
patient is an absolute indication for operative intervention.
Atherapeutic algorithm is presented in Fig.63-2.

63
Thoracic Disk Herniation
471
Surgery considered
1
Thoracic myelogram CT
1
Confirmation of significant neurocompression
/
Pathology correlates with clinical picture~
I d..
·
1
I Hard centrnl disk
on latera
IS-
Extradural
I
I Soft/hard lateral disk
Centrolateral disk
Extradural
Transpedicular
costotransversectomy
Transfacet pedicle sparing
Costotransversectomy
Lateral extracavitary
Intradural disk
Lateral
extracavitary
Lateral extracavitary
Transthoracic
Figure63-1
Diagnostic algorithm for thoracic disk herniations.

472
Thoracic and Thoracolumbar Spine: Posterior Approach
/
Chief Complaint
I Back/radicular pain
I
Plain radiograph
Calcification
Spondylosis
~onsurgicalcare
Disk protrusion
Thoracic
myelogram/CT
I
Surgical care
I
I ~onsurgical care
I
Figure 63-2
Therapeuticalgorithm for thoracic disk herniations.
. The Transpedicular Approach
Historical Considerations
The trans pedicular approach. used for the surgical treat-
ment of thoracic herniated disks, was first described in
1978 by Patterson et al.27Three cases of thoracic disk herni-
ation presenting with signs of spinal cord compression
were reported. These patients were approached through a
midline incision.The entire pedicle and facet were removed
to achieve decompression, after which complete laminec-
tomy was performed at that level.
In 1993 LeRoux, et aps treated 20 consecutive patients
for
symptomatic
thoracic
disk
herniation
with
a
trans pedicular approach. All patients were significantly
I Paraparesis/urinary dysfunction
I
Further
evaluation
for other
etiologies
Tumor
Infection
Syrinx
AVM
Appropriate evaluation
and care
improved and eight patients were asymptomatic. Inhis
comment response to Le Roux's paper, Patterson26re-
ported that. since 1983 he had operated on 31 patients
utilizing the trans pedicular approach without complica-
tions. Most of these patients had spinal cord compression,
but several had only pain. The outcome in patients with
pain alone was not as satisfactory for Patterson asforLe
Rouxet al.
.
SurgicalTechnique
The transpedicular approach allows anterolateral access to
the thecal sac by removing some of the facet joint and
the pedicle ipsilateral to the lesion (Fig. 63-3). The patient

r
63
Thoracic DiskHerniation
473
isplacedin a prone position on radiolucent chest rolls.
Securingthe patient with tape allows the table to be rolled
awayfrom the surgeon during disk removal. Tilting the
patient15to 20 degrees away from the surgeon maximizes
visualization and minimizes manipulation
of the spinal
cord.
Ananteroposterior (AP)and lateral fluoroscopic image is
used to identify the involved disk space. This localizing
x-rayisobtained before making the incision. Amidline in-
cision,-5 cm long is made over the disk space. The mus-
cleson the side of either or both the herniation and maxi-
malradicular symptoms are reflected laterally over the
posteriorelements from the spinous process to the trans-
verseprocess, thereby exposing the appropriate pedicle,
Facet joi nt
Nerve root
---------
Figure 63-3
The transpendicular approach: the site of
pediculectomyisshown.
facet, and disk space (Fig. 63-4). After identification of the
correct facet, the microscope is brought into the operative
field, and the center of the pedicle, caudal to the herniated
disk, is drilled with a high-speed cutting bur (Fig. 63-5).
The extent of the pediculectomy can be determined by in-
traoperative AP fluoroscopy prior to and during drilling.
This view will also demonstrate where the disk space is in
relationship to the facet. Adiamond bur is used as the dura
is approached. An attempt should be made to preserve as
much of the pedicle and facet as possible. If necessary, the
pedicle can be removed to the caudal portion of the verte-
bral body, providing exposure to the lateral area of the
vertebra as well as the lateral disk space. Atrough is then
created
in the underlying
disk space (Fig. 63-6). The
Pedicle
Figure 63-4
Superior view of the bound-
aries of the pediclelectomy
and facetectomy
and the disk space in the relationship
to the
pedicle/facet complex.

..
474
Thoracicand ThoracolumbarSpine:PosteriorApproach
Nerve
root
Drilled
pedicle
Herniated
lateral
thoracic
disk
Drilled
facet
Figure
63-5
After drilling
part of the pedicle/facet,
the dorsal portion
of the foramen is entered. The lateral margins of the anulus are identified.
extruded disk is pushed into the cavity by using downcut-
ting (Epstein) curettes (Fig. 63-7) and removed using
curettage or forceps (Fig.63-8). Thismaneuver enables ex-
tirpation of the disk across the midline to the contralateral
side while minimizing the possibility of trauma to the adja-
cent neural structures. Ifa calcified disk is encountered, it
canbe managedbycreatinga troughinthe underlyingver-
tebral body with a high-speed drill. The disk can then be
pushed into the cavity by using a downcutting curette ina
similar fashion.
Pituitary
forceps
Trough
Nerve root
Figure 63-6
Atrough iscreated in the underlying disk.
L

63
Thoracic DiskHerniation
475
- .
-"
Herniated disk
Nerve root
Trough
Microangle curette
Figure63-7
The underlying disk isthen deliveredand pushedinto the cavity by usinga microangle curette.
Figure63-8
Removalof diskfrom insidethe createdtrough.
. Discussion
In their original report Patterson and Arbit described a
trans pedicular approach. which required the removal of the
entire pedicle and facet to achieve decompression before
continuing with complete laminectomy at that level,27This
aggressive facetectomy creates a potential source of insta-
bility. Therefore. the procedure has been modified some-
what to preserve as much of the pedicle and facet as possi-
ble. and laminectomy is not routinely performed. With this
modification. fusion or stabilization with the transpedicular
approach is usually not required because the integrity ofthe
spine/rib cage complex. and the anterior longitudinal and
posterior ligaments are left intact.
Neurological outcome with the transpedicular approach
for appropriately selected cases has been reported to be
equivalent to the transthoracic and lateral extracavitary ap-
proaches.5.9.10.13.18.21.24.38.39
The transthoracic
and lateral
extra-
cavitary approaches. however. give superior exposure for
calcified. central disk herniations.8.9.13.14.18.19.21.24.41
There is
one report
of a delayed compression fracture after a
transpedicular approach.23These limitations have led many
surgeons to consider the anterior approach to manage hard
disk herniations. intradural disks. and kyphosis associated
with thoracic disk disease.

~
I
476
ThoracicandThoracolumbarSpine:PosteriorApproach
It has been pointed out that "the outcome in patients
with pain alone has not been entirely satisfactory."26 The
reason for this may be related to the loss of mechanical in-
tegrity by disruption of the facet-pedicle and disk. It should
be noted that large studies using a more extensive approach
in conjunction with fusion do not report this problem of lo-
calized pain.8.23.24.40
One method to improve the problem of
localized back pain and possibly to improve mechanical in-
tegrity is the transfacet pedicle-sparing approach proposed
by Stillerman et al.3! Like the transpedicular approach, the
transfacet pedicle-sparing approach allows removal of the
thoracic disk through the posterolateral
approach. It has
also been used for calcified cenral-Iateral and soft central-
thoracic disks at alllevels.3!
. Summary
The trans pedicular
approach
utilizes
a posterior
and
slightly lateral trajectory for resection of thoracic disk dis-
ease.It can be used for the treatment of most soft disk her-
niations in symptomatic cases,for lateral soft and calcified
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all levels. This technique
may be used for the treatment of
myelopathy,
radiculopathy,
and back pain. The transpedicu-
lar approach
is safe and can be performed
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without the hazards and complications associated with
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lating and sectioning
neurovascular
bundles. Furthermore,
it can be performed
in much less time than the other pro-
cedures.
In deciding
upon a specific operative
approach,
the surgeon's
familiarity with the approach is crucial.
Other considerations such as the patient's age,the location
(central or lateral) and characteristics
of the disk (i.e.,
soft or calcified), the need for anterior interbody fusion,
and the presence of dural attachment or invasionarealso
important.
.
Acknowledgments
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and the University of Florida, Department of Neurosurgery,
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40.
Horowitz
MB. Moossy JJ.Julian T. et al. Thoracic diskectomy
using
video assisted thoracoscopy. Spine 1994;19: 1082-1086
41.
Lesoin F.Rosseaux M, Autricque A. et al. Thoracic disk herniations:
evolution
in the approach
and indications.
Acta Neurochir
(Wien)
1986;80:30-34

64
Spinal Arteriovenous Malformations
Edward H. Oldfield
.
Indications
.
Objectives
.
Normal Vascular Anatomy of the Spinal
Cord(Fig. 64-1 )
Preoperative Planning
Surgical Technique
. Dural AVFs (Fig. 64-2)
Pathophysiology/Objectives
Therapeutic Options
Surgical Technique
.
Intradural AVMs
.
AVMs of the Spinal Cord
.
Indications
Current techniques
of diagnosis and treatment
permit
early detection, exact anatomical definition, and successful
treatment of most patients with spinal arteriovenous mal-
formations (AVMs).Before treatment of spinal AVMsis rec-
ommended, the natural history of patients
with these
lesions must be weighed against the risks of therapy. For
the most common type of AVM,the spinal dural arteriove-
nous fistula (AVF),outcome is predictable once symptoms
appear. Within a few months or years of the onset of symp-
toms other than pain most patients are disabled and many
are confined to bed or a wheelchair or are unable to walk
without assistance. Because the treatment of these lesions
is safe and is almost universally effective, all patients diag-
nosed with spinal dural AVFneed treatment. In contrast,
the intradural AVMshave a less predictable natural history.
Furthermore,
because treatment
of these AVMs is less
likely to permanently obliterate the AVMand is associated
with risks of paraplegia or quadriplegia, the decision to
478
Pathophysiology
Therapeutic Options
Operative Technique
.
Intradural AVFs (Perimedullary
AVFs)
Pathophysiology/Objectives
Therapeutic Options
.
Cavernous Angiomas
Pathophysiology/Objectives
Indications
Surgical Technique
.
Summary
treat and whether to treat with surgeryor embolicocclu-
sion requires consideration of the specific circumstancesof
each patient.
.
Objectives
For all types of spinal AVMssuccessful treatment requires
(1)diagnosisofthe AVMbeforeirreversiblecordinjuryoc-
curs, (2) determination
of the site and type of AVMand
identification of the vascular anatomy of the AVMand of
the vessels supplying the spinal cord in the vicinity ofthe
AVM,(3) linking the goals of surgery with the mechanismof
spinal cord injury, which differs in the different types of
spinal vascular malformations. and (4) successful execution
of the planned surgery. Ideally, treatment should perma-
nently obliterate the nidus of the AVFor the AVMwithout
damaging the spinal cord and without compromising the
blood supply to, or from, the spinal cord (Table64- t).

Table64-1
ClassificationofSpinalVascularAbnormalities
64
Spinal ArteriovenousMalformations
479
Dural arteriovenous
fistulas
(AVFs)
Intradural arteriovenous
malformations
(AVMs)
,.
AVMs of the spinal cord
a. Juvenile AVMs
b. Glomus AVMs
2. Intradural
(perimedullary)
AVFs
Cavernous angiomas
Thereare three major types of vascular abnormalities
of the spinal
cord:dural AVFs,intradural AVMs,and cavernous angiomas. These
three major types of lesions, which appear to be distinct biological
entities because they have distinct mechanisms
of origin, anatomi-
caldistribution, pathophysiology,
and epidemiology, are distin-
guished bythe location and type of vascular nidus of the lesion.
DuralAVFsare imbedded
in the dura of the proximal portion of the
nerveroot sleeve and the adjacent spinal dura, whereas the nidus
ofthe intradural AVMsand the cavernous angiomas lies within, or
onthe surface of, the spinal cord. The intradural AVMsare further
classifiedinto three subtypes: juvenile and glomus AVMs,in which
anAVMlieswithin cord parenchyma,
and AVFs,in which a direct ar-
terialto venous transition occurs (usually on the surface of the
spinalcord) without an intervening glomus of abnormal vessels.
~ ,
Ant.Spk)al
artery
I
\~
. ~
Medullary
artery
Duralartery
Medullary vein
, ,
,
Medullary
artery
'"
Dural artery
Radicular artery
. Normal Vascular Anatomy of the Spinal
Cord(Fig.64-1 )
Preoperative Planning
Selective spinal arteriography is required to determine pre-
operatively which type of spinal AVMaffects the patient
(Table 64- t), to demonstrate the precise site of the arteri-
ovenous nidus, to assess the operabilityofthe malformation,
and to aid in its safe obliteration by demonstrating the pre-
cise anatomy of the vessels supplying and draining the AVM
and the normal cord vasculature in the involved region of
the spinal cord. With the high-flow intradural AVMs,high-
resolution digital imaging with rapid sequencing permits
the nidus ofAVMsand the site of the AVshunt ofAVFs(peri-
medullary AVFs)to be distinctly demonstrated before early
opacification of the veins begins to obscure it. Byusing this
technique some of the lesions of the spinal cord that have
previously been considered to be AVMsusing standard arte-
riography are shown to be perimedullary AVFs.
Intravenous steroids are administered just before and
continued
during surgery or embolization.
To prevent
propagation of venous thrombosis ofthe intrathecal spinal
Coronal venous plexus
Figure
64-1
At each segmental
level the
spinal ramus of each intercostal
artery (or its
equivilant in the cervical and lumbar levels)
divides, after entering the intervertebral fora-
men and penetrating
the outer surface of the
dura, into radicular arteries, which supply the
anterior or posterior nerve roots, and adural
artery, which provides arterial blood to the
spinal dura
and the
nerve root sleeve. At
some levels the intervertebral
portion ofthe
spinal ramus of the intercostal
artery is also
the origin of a medullary artery, which pene-
trates
the dura adjacent
to the nerve root
ganglion, ascends, and joins the anterior, or a
posterior,
spinal artery to supply the spinal
cord. The major conduit for arterialbloodto
the spinal cord below the midthoracic level is
the artery ofAdamkiewicz,whicharisesfrom
an intercostal
artery between T6 and L3.The
anterior
spinal artery supplies the anterior
two thirds of the cross-sectional
area of the
spinal cord, including the corticospinal tracts.
The posterior
spinal arteries, two plexiform
channels
running along the posterolateral
surface
of the cord, perfuse the posterior
third of the spinal cord. The spinal cord is
drained by radialveins,whichcarrythe blood
to the surface to the coronal venous plexus, a
plexiform network of interconnecting
veins in
the pia, or sulcal veins. These are drained by
medullary veins, which penetrate
the dura
adjacent to, but slightly separate
from, the
dural penetration
of the nerve roots to join
the epidural venous plexus. The medullary
veins, like the medullary arteries, have a spo-
radic occurrence
along the long axis of the
spine. (From Oldfield" with permission.)
- I

480
ThoracicandThoracolumbarSpine:PosteriorApproach
veins when embolization is used to occlude spinal AVMs,
intravenous heparin is used during the procedure and is in-
fused for 24 to 48 hours afterward (1000 units/hour). With
the intradural AVMsand AVFs,preoperative embolization
with particles of polyvinyl alcohol (PVA),performed during
arteriography 1 to 2 days before surgery reduces the blood
flowthrough the lesion and facilitates manipulation of the
vesselsduring surgery.
Surgical Technique
Anesthesia,
Positioning, and Monitoring
A midline vertical incision permits a wide laminectomy
centered over the lesion and includes one lamina above and
below the superior and inferior margins ofthe lesion.Thepa-
tient isplaced in the prone position under general anesthesia.
Dural AVF
'1
Coronal
venous
plexus
With high cervical lesions the surgery may be performedin
the prone or the sitting position. Intraoperative
somatosen-
sory monitoring
may be helpful with certain intramedullary
lesions. However, the neurological function of many patients
is impaired and the necessary waveforms cannot be detected,
and in other patients, particularly patients with dural AVFs,it
is unnecessary. In certain intradural lesions induced hypoten-
sion may be helpful but is generally unnecessary.
The operating
microscope
and appropriate
microsurgical
instrumentation
and technique
are required
for the in-
tradural portion of the surgery for all spinal AVMs.
.
DuralAVFs(Fig. 64-2)
This type comprises most spinal AVMs.These lesionsaffect
adults and cause the gradual onset and progressionof
myelopathy, usually affecting only the lower extremities.
Figure 64-2
Dural arteriovenous
fistulas (AVFs)aresup-
plied by a dural artery
and drained
by a medullary vein,
which carries the arterialized
blood retrograde
to the nor-
mal direction
of venous drainage
to the coronal venous
plexus, which
becomes
elongated,
tortuous,
and dilated
by the reception of arterial blood. Becauseof the valveless
nature of the intradural
venous system, the increased ve-
nous pressure within
the coronal
venous plexus is trans-
mitted
to the
radial
veins
and to the
spinal
cord and
causes myelopathy.
Almost
all dural AVFs can be perma-
nently obliterated
by identifying
the site of intradural pen-
etration
of the arterialized
vein draining
the dural AVF(al-
most always next to the dural penetration
of the nerve
root), coagulating
a segment
of it with
bipolar forceps,
and sharply dividing
it. (From Oldfield'l
with permission.)
I,I
"'-
--
.....
I"
\
l
L
\,
....l
},"---
"".
. .'

64
SpinalArteriovenousMalformations
481
Becausetheyareroutinelysusceptibleto safeand curative
treatment if they are diagnosed early, before irreversible
cordinjury has occurred, prompt treatment of them is al-
ways indicated.
Pathophysiology/Objectives
Theabsenceofvalves in the intrathecal veins permits trans-
missionof the high venous pressure to the spinal cord, re-
ducingthe arterial perfusion pressure of the spinal cord and
causingmyelopathy.The goals of treatment, (1) elimination
ofthe transmission of venous hypertension to the spinal
cordand (2) permanent obliteration of the AVF,should be
accomplishedearly before significant and permanent neu-
rologicaldeficitsare present.1.2
TherapeuticOptions
Theoptions for treatment of dural AVFsinclude surgery to
interruptthe vein draining the AVFas it penetrates the in-
nerlayerof dura (Fig. 64-2), embolic occlusion during ar-
teriography,and surgery after embolization. Embolic oc-
clusionwith particulate materials, such as PVA,does not
permanently obliterate the nidus of the dural fistula be-
causerecanalization and return of flow through the AVF
andinto the veins of the spinal cord usually occur within
a few months.3 It is not used
alone
for treatment.
Althoughthe use of one of the polymerizing glues for em-
bolizationmay be more likely to provide lasting occlusion,
it usually does not provide permanent
occlusion of the
AVFbecause it is commonly associated with either incom-
plete occlusion at the outset or early recanalization
of
the fistula.4 For these reasons, I manage these lesions
surgically.
PatientswithRapidlyProgressiveMyelopathy
Specialcircumstances may dictate which of the approaches,
orwhichcombination of them, should be used in individual
patients.Most patients with spinal AVMsand the Foix-Ala-
joininesyndrome have dural AVFsassociated with marginal
arterialperfusion of the spinal cord. These patients need
immediateelimination of the transmission of venous hy-
pertension to the spinal cord. This can be accomplished
most rapidly by embolic interruption
of the dural AVF
duringarteriography, permitting immediate reduction in
venouscongestion of the cord until surgery can be per-
formed.5
SurgicalTechnique
Simpleinterruption of the vein that carries blood from the
duralAVFto the coronalvenousplexuscuresalmostallpa-
tientsby eliminating venous hypertension and by inducing
retrogradethrombosis and permanent fibrotic obliteration
ofthe dural AVEThe lamina ofthe neural arches one level
aboveand below the AVFare removed widely. The spinal
duraisthen opened in the midline, the arachnoid is sepa-
ratedfrom the underlying vessels, and the dura and arach-
noid are retracted laterally with dural sutures. Correlation
of the vascular anatomy as seen on the preoperative arteri-
ography with that seen intraoperatively permits accurate
identification
of the site of dural penetration
of the
medullary vein carrying arterial blood.The site of intradural
penetration of the arterialized vein draining the dural AV
fistula is identified adjacent to the site of dural penetration
of the nerve root.6Thisvessel iscoagulated with bipolar for-
ceps and divided as it enters the dura. This simple proce-
dure provides effective, permanent therapy for almost all
patients? (Fig.64-2).
DuralAVFswith IntraduralandExtraduralVenousDrainage
In rare patients the venous drainage from the fistula is by
two routes, intradurally into the medullary vein and ex-
tradurally into the epidural veins.? To permanently elimi-
nate the dural AVFin these patients, the nidus ofthe fistula
in the dura must either be excised or occluded embolically
during arteriography. Surgical excision is performed after
interruption of the intradural vein draining the AVF(already
described), the bone overlying the intervertebral foramen is
removed with rongeurs or by drilling, and dissection ex-
poses the AVFimbedded in the dural covering of the nerve
root and the adjacent spinal dura. The portion of the dura
that contains the AVFis excised, a fat graft is placed over
the duraldefect,the siteofthe graftissealedwith a biologi-
cal glue, and the cerebrospinal fluid is drained externally
via a lumbar drain for 3 to 5 days.
.
Intradural AVMs
Because the intradural AVMsare high-flow lesions that con-
sistently receive blood from vessels which also supply the
spinal cord, their treatment is associated with higher risks
than is treatment of spinal dural AVFsor cavernous an-
giomas of the spinal cord. When arteriography reveals that
the anatomy would allow complete excision of an intradural
AVMor AVFwith limited risk, surgery alone or surgery after
embolization should be considered. Many lesions can be
identified by arteriography (or during surgery) as being as-
sociated with unacceptable risks with persistent attempts
at complete excision; for these lesions embolization is
recommended.
.
AVMs of the Spinal Cord
In the AVMSof the spinal cord (the juvenile and glomus
types of AVMs),the nidus ofthe AVMis within the spinal
cord (Figs. 64-3 and 64-4). One of the feeding vessels of
these AVMs is almost always an enlarged
medullary
artery that also supplies the spinal cord. Because most of
these AVMs are in the ventral aspect of the cord, they
are usually supplied by the anterior spinal artery. Juvenile
type AVMs(Fig. 64-3) of the spinal cord usually become

482
Thoracic and Thoracolumbar Spine: Posterior Approach
-
"
,
(
Figure 64-3
The juvenile type of intramedullary
arteriovenous
mal-
formation
(AVM) is fed by enlarged medullary
arteries via dilated ante-
rior and posterior spinal arteries. The nidus of the AVM is extensive, of-
ten filling the spinal canal, and usually contains neural tissue within
the
interstices
of the vessels of the AVM. Most of these lesions cannot
be
safely excised. (From Oldfield"
with permission.)
symptomatic in children and young adults. The glomus
type AVMis a localized nidus of smaller blood vessels
confined to a short segment of cord that generally pre-
sents in adults (Fig. 64-4A). Glomus type lesions often
have only a single feeding vessel and may have slow tran-
sit time of contrast.
Pathophysiology
Intradural spinal AVMscause myelopathy by repeated hem-
orrhage in about half of the affected patients and in the re-
maining half by causing (1) venous hypertension. (2) pro-
gressive ischemia by vascular steal from the normal arterial
perfusion of the spinal cord, or (3) compression and distor-
tion of the spinal cord by the distended vessels or by an
associated venous or arterial aneurysm.!
/'
(
'1"
~\
j
)
J
(
.....
A
Figure 64-4
(A) The nidus of the glomus type of intramedullary spinal
arteriovenous
malformation
(AVM) is a tightly
packed nidus of blood
vesselsconfined to a limited segment of the spinalcord.Becausethese
AVMs are usually in the anterior
half of the cord, they are usuallysup-
plied by the anterior spinal artery. Those in the posterior aspect ofthe
spinal cord, as the one depicted
here. usually are supplied by the ante-
rior and posterior
spinal arteries
and may be susceptible
to excision.
Therapeutic Options
The goal of therapy for intradural vascular malformations
is completeand permanent obliterationof the AVMwhile
preserving the blood supply to the spinal cord.Froma practi-
cal standpoint. however. the feasibility of this goal,and
whether it can be best accomplished with surgery alone,

64
SpinalArteriovenousMalformations
483
a
b
Posterior
spinalartery
Veins draining
AVM
c
d
(
B
Figure64-4 (Continued) (B)Afterseparating the arachnoidfromthe AVM,(a,b)a diamond knifeisused to incisethe piaat the edge ofthe nidus.
Toobtain the exposure neccesary for excision of the deep portion of the AVMthe pial incision is extended
a few millimeters rostrally and caudally,
usuallyinthe midline. The superficial feeding vessels (c.d) are interrupted sharply after they have been coagulated with the bipolar forceps. Bygentle
retractionwith a microsucker, with the tip on a small cottonoid and the suction on low setting, dissection with the tips of the bipolar forceps inthe
glioticplane between the malformation
and the spinal cord. This is performed by elevation of the malformation while working from from one pole
upwardordownward.to expose, coagulate,and interruptthe vesselsenteringand leavingthe malformationventrally,the nidusofthe malformation
isdissectedfromthe surrounding cord. Asthe marginsofthe malformationare dissected bipolar coagulation isused to graduallyshrinkthe AVM
andrender it less susceptible to rupture during manipulation.
Progressive shrinking of the AVMby cogulation also reduces turgidity in the nidus as
thedissection procedes. Generally, at least one of the major draining veins is preserved patent until dissection around the periphery of the malfor-
mationhas been completed and all arterial feeding vessels have been occluded (d). although when the AVMis occluded by presurgical embolization
thismaynot be necessary. (From Oldfield" with permission.)
embolization,or surgery after embolization, depends on the
type,size, and location of the specific malformation under
consideration. In vascular malformations
with adverse
riskfactors(large size, location in the thoracic or lumbar seg-
mentsofthe spinal cord, involvement of the ventral portion
ofthespinal cord, extensive involvement of the spinal cord)
preservationof neurological function and avoidance of iatro-
genic disability often mandate less definitive treatment
whetherthe therapeutic approach issurgery or embolization.
JuvenileAVMs
Unfortunately, these AVM.sfill the spinal canal and contain
cord tissue within the interstices of the AVM(Fig. 64-3)
and, therefore, are not amenable to excision. Because they
are supplied by vessels that also contribute blood supply to
the spinal cord and they frequently cannot be safely and
permanently occluded with embolization, the optimal ap-
proach for these AVMsis usually repeated embolization

484
Thoracic and Thoracolumbar Spine: Posterior Approach
with PYA.Embolic therapy reduces blood flow and may
diminish the incidence of hemorrhage but usually does not
provide curative treatment, and the interval of efficay is
variable.
GlomusAVMs
Totalexcision is occasionally possible with glomus AVMs,
particularly posterior
lesions or those
in the cervical
segments of the spinal cord where collateral flow in the
anterior spinal artery can arise inferiorly or superiorly
(Fig.64-48). However, surgical excision is hazardous with
the more common ventral lesions in the thoracic and lum-
bar segments, where collateral blood supply to the spinal
cord is limited.
If the juvenile or glomus AVMoccupies a considerable
portion of the parenchyma of the ventral half of the spinal
cord, it is usually impossible to remove it without eliciting
unacceptable
neurological deficits and surgical excision
is not attempted.
Reduction of flow in these lesions by
repeated embolization with particulates (PVA)diminishes
the incidence
of subsequent
hemorrhage,
reduces the
degree of vascular steal, venous congestion, and associ-
ated ischemia of the cord, and usually provides neur-
ological stability for several months or years.8 However,
these benefits are temporary because reestablishment
of
flow to preexisting
levels usually occurs within
6 to
12 months.
Operative Technique
The technique for excision of a posterior glomus-type
AVMof the spinal cord is illustrated
in Fig. 64-48. The
dura is opened in the midline using care to keep the
arachnoid intact so that tearing of the large, fragile under-
lying vessels is avoided. This is particularly important in
patients
with
previous
subarachnoid
hemorrhage
in
whom the arachnoid may adhere to the underlying ves-
sels of the malformation. In patients with recent hemor-
rhage, surgery is postponed until the blood products have
been absorbed from the subarachnoid
space. The arach-
noid is removed from the surface of the underlying mal-
formation. Sutures retract the dura and arachnoid later-
ally. Correlation of the vascular anatomy as seen on the
preoperative
arteriography
with that seen intraopera-
tively is then performed, (1) so that all medullary arteries,
particularly the artery of Adamkiewicz and the anterior
spinal artery, are preserved during dissection and (2) to
aid the identification
and early interruption
of major
feeding arteries as they enter the malformation. In lesions
that have received preoperative particulate embolization,
the particles in the arteries to the AVMaccumulate at the
margin of the nidus and can be used to help identify ves-
sels carrying blood to the AVM.Throughout the intradural
dissection
meticulous
hemostasis
is essential
because
blood-stained pia obscures the anatomical details. Liberal
irrigation
during
bipolar
coagulation
is essential
to
prevent coagulatedvesselwallsfromadheringtothetips
of the forceps. Largerfeeding vessels may requireliga-
tures or clips,but essentially all vesselscanbe managed
with simple bipolar coagulation and interruption. Plansto
completely excise or obliterate
the malformation may
have to be abandoned intraoperatively if it becomesevi-
dent that the risk of cord infarction is high with continued
attempts at complete removal. Awatertight dural closure
is performed. Postoperativespinal arteriographyisused
routinely 7 to 10 days after surgery and at 1 year postop-
eratively to assess the success of complete and lasting
obliteration of the AVM.
. Intradural
AVFs
(perimedullary
AVFs)
These are simple AVFsin the pia with a direct shunt froman
artery to a vein, frequently with an aneurysm or venous
varix at or near the transition from artery to vein.Theyare
predominantly anterior lesions affecting the caudalregion
of the spinal cord where
they are supplied
by the anterior
spinal artery, but they occasionally occupy a dorsolateral
position and are supplied predominantly by a posterior
spinal artery9.10(Fig. 64-5).
Pathophysiology/Objectives
These lesions cause myelopathy by venous congestion,
vascular steal, or compression of the spinal cord by the
aneurysmal dilatation of the distal arterial or proximalve-
nous element. The goal of treatment is interruption ofthe
abnormal communication precisely between the arterial
and venous elements, distal to the last arterial collateral
branch to the spinal cord. This may be achieved bysurgery
(bipolar coagulation and interruption,
or ligation), em-
bolization,
surgery following embolization
with PYA,oraf-
ter intraluminal
placement
of a coil or a detachable balloon.
Therapeutic Options
These
lesions
can be categorized
into three
groups: (1)
small fistulas supplied by a long, thin anterior spinal
artery; (2) larger fistulas fed by an enlarged spinalartery;
and (3) giant fistulas supplied by an enormously enlarged
spinal artery.1OSurgical intervention is typically reserved
for posterior or posterolateral
lesions and for circum-
stances in which embolization is inherently dangerous.For
example, in lesions supplied only by a very long anterior
spinal artery of small caliber, embolization may not besafe
or effective and surgical intervention
may entail lower
risks. Patients with large fistulas and a greatly enlarged
anterior spinal artery can be treated with embolic occlu-
sion with solid materials,
by balloon occlusion, with
surgery, or with a combination
of embolic and surgical
approaches.

64
SpinalArteriovenousMalformations
485
I'
Figure64-5
Intradural
arteriovenous
fistula (AVF) in the pia (perimedullary
AVF). Medullary
arteries provide the arterial supply, in this instance via
aposterior spinal artery. Intradural AVFs often have associated arterial or venous aneurysms at the junction
of the arterial and venous elements.
Note
thedilatation of the vein just distal to the AV shunt. The site of arterial to venous transition
is identified
and, after bipolar coagulation
of a 4 to 6 mm
segmentof the distal portion
of the artery(s)
to the AVF, the AV shunt is interrupted
on the distal portion
of the arterial
side of the fistula,
beyond
the lastarterial branch to the spinal cord. In some instances a small clip or ligature is required,
but most feeders can be managed by bipolar coagula-
tion and sharp interruption
alone. If an aneurysm
or varix is the site of convergence
of the feeding vessels, it is excised. Many of these lesions are not
assimple asthat illustrated
here because these lesions can have more than one simple fistula in the same region of the pia and the tortuosity
and di-
latationof the venous drainage often obscure the site of the AVF beneath a nest of blood vessels. (From Oldfield11 with permission.)
. Cavernous Angiomas
Cavernousangiomas of the spinal cord are histologically
identicalto those that occur in the brain, They may occur
multiplyat more than one level of the spinal cord, or may
ariseinassociation with intracranial cavernous angiomas,
especiallywhen they are associated with familial cavernous
angiomatosis,
Pathophysiology/Objectives
Althoughcavernous angiomas of the spinal cord are low-
flowlesions,the pathogenesisofmyelopathyis usuallyvia
hematomyelia.They usually are diagnosed after they cause
progressive,stuttering myelopathy by a cycle of repeated
small intramedullary
hemorrhages. Symptomatic lesions
typically demonstrate a hemosiderin-stained glioticcapsule
at surgery and/or a hemosiderin ring on magnetic reso-
nanceimaging(MRI)(Fig.64-6), whichindicatespriorhe-
morrhage. Symptomatic cavernous angiomas tend to first
cause symptoms in early adulthood and middle age (third
to sixth decades),
Indications
Small cavernous angiomas may remain clinically silent
throughout life and become evident only at postmortem ex-
amination. Recommendations for treatment must consider
the patient's symptoms, the presence ofa neurological deficit
or progression of myelopathy, and the projected risks of
"-
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I
I
AVFistula
.
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.-- ";
I \"
,
"f
/
t.
I
I
'-
,.,
-) ,
\
'J
"'"
""'-
.--'..
I
I ./
!n..
I
I
,,,J {O"?:-+N
I
-
-
-
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