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

I
87
Far-LateralMicrodiskectomy
639
. Advantages
. Objective
Midline
. Easyconversion to bilateral decompression
. Lateralrecess stenosis addressed
. Accessto central HNP as well
Paramedian
. Minimalmuscle stripping
. Facetjoint preserved
. Gangliondirectly visualized
Endoscopic
. localanesthesia possible
. "Micro"incision
Three surgical approaches to the treatment
of far-lateral
disk herniation are described.
.
SurgicalTechnique
Anesthesia
and Positioning
. Disadvantages
Dexamethasone (10 mg) and prophylacticantibiotics are ad-
ministered prior to induction ofgeneral. endotracheal anes-
thesia. The patient is positioned on an Andrewstable or any
spinal table that reverses lumbar lordosis.The incisionis in-
filtrated with 0.25%Marcaine with 1:200.000 epinephrine,
and the skin is prepped in standard fashion.Preoperativelo-
calization with portable x-ray is useful to limit incision
length above U-L5where palpation of bony landmarks may
be difficult. In obese patients. it is critical.Allpatients come
to the operatingroom(OR)with plainanteroposterior(AP)
and lateral x-rays to plan a minimal incision accurately,and
to anticipate any deviation from normal osseous anatomy.
Midline
. Potentially destabilizing
. Largestincision/muscle
retraction
. Maymiss far-lateral
fragment
Paramedian
. Difficultconversion to midline approach
. Inability to treat "double" HNP.central and lateral
. Lateralrecess stenosis not addressed
Endoscopic
. Incomplete decompression
of disk space
. Technically difficult
. Highlyspecialized
equipment/training
required
Incision and Approach: Midline
The 4 em incision is placed slightly more cephalad to the disk
space than for a standard microdiskectomy.
Unilateral subpe-
riosteal dissection of muscles with cautery or a Cobb dissector
should be performed
somewhat
more lateral to ensure three
fourths ofthe
facet joint is visualized. Portable x-ray is done
to confirm the correct level. A self-retaining retractor is placed
with the blade resting on the facet joint. the hook in the inter-
spinous ligament or spinous process of the superior vertebral
body. The operating microscope with a 350 mm lens provides
an excellent working distance and is brought into the field at
the time of bone drilling or immediately
thereafter.
Figure 87-1
Midline approach. Extent of bone removal re-
quired for far-lateral HNPusing midline approach. Note the un-
dercutting of the facetjoint.

.
640
Lumbarand Lumbosacral Spine: Posterior Approach
Apartial (one half to two thirds) hemilaminotomy of the
superior laminae, one fourth hemilaminotomy of the infe-
rior laminae,and medial (less than one half) facetectomy is
performed with use of a high-speed drill and no. 4 Kerrison
rongeur (Fig.87-1). Removing the medial half of the supe-
rior articulating process of the vertebra below helps to fully
open the root foramen. Occasionally it is necessary to drill
the most superior aspect of the pedicle of the lower verte-
bra to visualize the lateral margin of the disk. Undermining
the facet joint, far-lateral removal of residual ligamentum
flavum,which inserts into the facet joint, then incising the
disk with a no. 15 blade, using reverse-angled curettes or
small (3-4 mm wide) osteotomes to remove any hyperos-
totic ridge at the end plate obviates the need for total face-
tectomy in most cases. Carefuluse of a 3 mm Kerrisonto re-
move the hyperostotic ridge at the disk end plate may be
useful, always visualizing the root above to avoid injury. A
radical diskectomy with thorough cleaning out of the disk
space, leaving cartilaginous end plates intact if possible,
helps to prevent recurrence. Adownbiting curette is used to
push fragments away from the root into the disk space, then
retrieved and removed with a pituitary rongeur. Frequent
checks with a Woodson double-ended elevator is used to
milkout fragments from lateral (underneath the facetjoint)
to medial. Because fibrous bands at the lateral extent of its
foramen may tether the root, care must be taken to avoid
compressing it by an overlylarge instrument. The disk space
isflushedwith antibiotic-containing saline using a 10 mLsy-
ringe and 20 gauge spinal needle to (1) ensure there are no
loose fragments and (2) dilute any chemically irritating me-
diators of inflammation from residual nucleus. Retractors
Figure 87-2
Paramedian approach. A5 cm paramedian incisionis
located 4 cm offmidline.
are removed; the fascia is closed with 0 or 1-0 Vicrylsuture,
and 3-0 Vicrylis used in a subcuticular closure. Steri-Strips
are placed over the skin edges.
A
I
,
I
I B
Figure 87-3
(A) The subcutaneous
tissue and fascia are cauterized.
(8) The fascia is tied back and the plane between the multifidus and longis-
simus muscle can be identified.

Incisionand Approach: Paramedian
Aparamedianincision of 5 em is placed 4 to 5 em off mid-
line(Fig.87-2). The subcutaneous
tissue and fascia are cau-
terized.Thegroove between the multifidus and the longis-
simusmusclesis identified (Fig. 87-3) and split gently.
Bluntdissectiondeeper identifiesthe superior transverse
process,the lateral border of the facetjoint. and the inferior
transverseprocess. After x-ray confirmation of the spinal
level,a hemilaminotomy retractor is placed. and the micro-
scopeisbroughtintothe field.Careis takento preservethe
capsuleofthe facet joint. Aposterior branch of the lumbar
arteryiscauterized (Fig.87-4) and the intertransverse liga-
mentisvisualized, and separated from the medial third of
thetransverseprocess above and below. The artery lies be-
tweenthe medial border of this ligament and the lateral
edgeofthe ligamentum flavum as it attaches to the facet
jointcapsule.6Removing the hypertrophied lateral margin
ofthesuperior facet joint by undercutting with an angled
Kerrison(Fig.87-5) or use of a high-speed drill exposes the
borderofthe disk. From there. the root can be approached
fromcaudalto cephaladwhere it is typicalIydisplaced,im-
mediatelybelow the pedicle. Once identified. the root is
minimallyhandled to avoid dysesthetic pain from ganglion
manipulation.
Thedisk fragment is found. often medial and inferior
tothe ganglion (Fig. 87-6). It is removed with a pitu-
itaryor peapod rongeur. Reverse-angled
curettes
may
be used to push hypertrophied/bony
anular protuber-
87
Far-Lateral Microdiskectomy
641
ances away from the root. into the disk space where they
can be retrieved with a pituitary. At the completion. pass-
ing a right-angled Woodson elevator underneath
the root
up along its foramen ensures there is no residual com-
pression.
The two proceedings may be combined by using a mid-
line skin incision, lengthening it, and cutting the fascia in a
gentle arc toward the pathologicalside.6
Incision and Approach: Endoscopic Diskectomy
Endoscopic diskectomy is performed under local anesthesia
with IVsedation. with the patient prone on a radiolucent
frame. Imaging capabilities must be present for both APand
lateral fluoroscopy throughout the procedure. The prone
position is most frequently utilized, although some sur-
geons prefer the lateral position. The hips are slightlyflexed
to decrease lumbar lordosis and to open the foraminal
space. The appropriate level is identified using real-time in-
traoperative fluoroscopy. Localanesthetic of Marcaine and
epinephrine is placed in the skin paralIel to the involved
disk space, and -10 to 12 em lateral to the midline.Agener-
ous skin wheal is made and local anesthetic is carried down
through the lumbosacral fascia at approximately a 60 de-
gree angle. A smalI incision is made using a no. 11 blade,
and a 0.62 mm guidewire is inserted to the level of the anu-
Ius fibrosus just anterior to the facet. As the guidewire
strikes the lateral portion of the facet it is withdrawn
slightly, then advanced at a steeper angle to negotiate past
Figure 87-4
Posteriorbranch ofthe lumbar artery ismedial
to the intertransverseligament.The medialdetachment ofthe
intertransverseligamentisrequiredforadequate exposure.

642
LumbarandLumbosacralSpine:PosteriorApproach
the facet. When the K-wire is in ideal position. it will pro-
ject fluoroscopically as being at the interpedicular line on
the APprojection and at the posterior vertebral body on the
lateral projection. The guide-wire is passed into the disk
space providing an anchor for the subsequent dilator sys-
tem, used to create a channel prior to endoscope placement.
Once the foraminal space has been approached with the
dilator. a cannula for the inters cope is place over the dila-
Figure 87-5
Removal of the hypertrophied
lateral margin ofthe su-
perior facet joint exposes the border of the disk.
tor. the dilator is withdrawn, and an endoscope is intro-
duced. The working-channel endoscope is then connected
with normal saline irrigation at -40 mL/min with passive
outflow. This allows for the foraminal space to remain
slightly distended with improved visualization as the pro-
cedure progresses. The foramen and exiting nerve rootare
visualized.Amicropituitaryforcepsis usedto removedisk
through the working channel. However, it is the author's
Figure87-6
A disk fragment isseenmedial
and inferior to the ganglion and may bere-
moved with a pituitary rongeur.

87
Far-LateralMicrodiskectomy
643
preferenceto use a holmium:yttrium-aluminum-garnet
(Ho:YAG)laser.The 2. I-JLwavelength of the Ho:YAGlaser
ishighlyabsorbed in tissue with penetration
depth of
-0.4 mm. The Ho:YAG laser shrinks
collagenous
tissue.
andnewmodels with a side-firing
mechanism
allow visu-
alizationof the target without
the laser blocking
the line
ofsight.
References
1. AbdullahAF.Wolber PG.Warfield JR.et al. Surgical management of ex-
treme lateral lumbar disk herniations:
review
of 138 cases. Neuro-
surgery1988:22:648-653
2. MaroonJC.Kopitnik TA. Schulhof LA.et al. Diagnosis and microsurgical
approachto far-lateral disk herniation
in the lumbar spine. JNeurosurg
1990;72:378-382
3. Angtuaco
EJ. Holder JC.Boop WC. et al. Computed tomographic diskog-
raphy in the evaluation
of extreme
lateral
disk herniation.
Neuro-
surgery1984;14:350-352
Diskremoval is accomplished until the exiting nerve root
is well visualized and no longer compressed by displaced
disk material. Frequently. this occurs concurrent with the
patient's resolution symptoms because they are awake and
quizzed during the entire procedure. The laser fiber and the
endoscope are then withdrawn after irrigation with saline.
and the skin closed with a single figure of eight suture.
4.
Segnarbieux
F. Van de Kelft E. Candon
E. et al. Disko-computed
tomog-
raphy
in extraforaminal
and
foraminallumbar
disk herniation:
influ-
ence on surgical
approaches.
Neurosurgery
1994;34:643-647
5.
Melvill
RL. Baxter
BL. The intertransverse
approach
to extraforaminal
disk protrusion
in the lumbar
spine.
Spine 1994:19:2707-2714
6.
Jane JA. Haworth
CS. Broaddus
WC. et al. A neurosurgical
approach
to
far-lateral disk herniation:
technical note.J Neurosurg 1990;72:143-144

88
Repair of a Cerebrospinal Fluid Leak
Emily Friedman
.
Advantages
.
Disadvantages
.
Objective
.
SurgicalTechnique
Anesthesia and Positioning
IncisionandApproach
Cerebrospinalfluid(CSF)leakage may occur spontaneously,
in the setting of raised intracranial pressure,1.2following
trauma (often associated with bone fractures), or during a
surgical procedure.3-sThe traumatic leak may resolve spon-
taneously or may require one of the forms of treatment this
chapter discusses. Medicaltreatment includes analgesics to
alleviate headache, modified bedrest, and thorough hydra-
tion. Persistent symptoms (for instance following a lumbar
puncture) may respond to a single epidural blood patch. A
fraction of spontaneous CSFleaks do not respond to these
measures and require direct surgical intervention: ligation of
the meningeal diverticulum (if identified), primary suture of
the dural and arachnoid tear, augmentation of the suture
closurewith fibringlue,6an autologous muscle patch, and/or
Gelfoam.The focusof this chapter is the direct microsurgical
repair of the traumatic or iatrogenic spinal fluid leak.
PostoperativeCSFleaks should be addressed immediately
and effectively because the risk of CSF-cutaneous fistula
with resulting infection is high.7 Oversewing the wound
with a locked, nylon suture can sometimes stop a minor
leak in a healthy patient. Anyleak that saturates the dress-
ing, particularly in the elderly where tissue healing is not as
vigorous, requires reexposure of the operative site and di-
rect suture of the dura, if possible.
.
Advantages
. Prevention of CSFfistula
. Reductionininfectiouscomplications
.
Disadvantages
. Additionalsurgicalprocedure
. Potentialfornerveinjuryduringclosure
644
.
Objective
The microsurgical
obliteration
of a CSFfistula using primary
suture closure
. Surgical
Technique
Anesthesia and Positioning
General endotracheal anesthesia is recommended. How-
ever, if the surgeon regularly performs lumbar surgery un-
der spinal anesthesia and if medical issues make a spinal
anesthetic preferable, the procedure can be performed with
the patient awake, sedated, under a spinal anesthetic. The
patient is positioned prone, either on bolsters, on a Wilson
or Andrew's frame, or on a spinal operating table such as
the Andrews orJackson table. It helps to have the abdomen
decompressed to minimize epidural bleeding.
IncisionandApproach
The operative field or prior incision is widely prepped. Itis
important to have adequate visualization of the normal dura
above and below the tear, so if there has been an earlier
laminotomy,the incisionshouldbeslightlyenlarged.When
the leak follows an open spinal fracture, the surgeon should
carefully plan a layered closure, taking into account the via-
bility and vascularity of the skin flaps. One can either enlarge
the existing wound or create a fresh, midline incision,which
is preferred. Using standard procedure, the muscles are
displaced from the midline and held retracted with self-
retaining retractors. Ifthere is not clear exposure of the full
length of the dural rent, additional bone removal fromthe ad-
jacent laminae is necessary. Prior to use of the operating mi-
croscope, any epidural bleeding is tamponaded with narrow
Gelfoamstrips of3 mm width, covered by dry cotton patties.

....
88
Repair of CSFLeaks
645
Theoperating microscope is brought into the field. set
upwithopposing heads so that the surgeon and assistant
canwork across the table. A 300 mm lens is fine, but a
350mmlens gives the surgeon a longer working distance.
Typically,there is CSFegress with each assisted ventila-
tion,whichallows the surgeon to define the limits of the
tear.Ifnot, the anesthesiologist can assist with a Valsalva
maneuver.Nerve rootlets may be herniated through the
duraandshouldbe gently returned to the subarachnoid
spaceusinga microPenfield.Placinga cotton patty over
them,underneaththe dura.will help prevent their migra-
tionbackout.In the setting of trauma. if nerve roots are
avulsedor torn any devitalized tissue should be ampu-
tatedand hemostasis secured with the Malis bipolar
cauteryon low setting.
Afinesuture on a taper needle is used for the closure. A
7-0Gore-Tex suture on an RB-1 needle is ideal but 7-0
ProleneorTevdekis an alternative. The size of the needle is
importantbecause using a large or cutting needle may
causeleaks from the needle tract. Microsurgical instruments
arerequiredto manipulate the dura: fine Debakey forceps.
andmicroscissors.Usinga fine. nontoothed forceps protects
theduraledges.Adural tear of only a few millimeters can be
wellapproximated with several interrupted sutures. Tears
ofovera few millimeters are best sewn with a running.
lockedsuture (Fig.88-1A)
Oncethe tear has been closed. the anesthesiologist
shouldperform Valsalvamaneuver to assure the closure is
watertight.Anyleaks can be oversewn with a single stitch.
Fibringlueis then prepared, either the commercially avail-
ableform that comes in two attached 1 mL syringes for
simultaneousinjection, or the hospital's blood bank can
prepareautogenous fibrin glue using an aliquot of the
A
patient's blood withdrawn at the start of the procedure. The
fibrin glue is injected generously over the suture repair and
covering the dura -2 to 3 mm in depth (Fig. 88-18).
It
should solidify within seconds. One can reinforce the clo-
sure with a piece of muscle or a patch of Gelfoam.
Closure of the spinal wound follows standard procedures,
with this caveat: it should be a multilayered. meticulous
closure. The muscles may be loosely approximated with
2-0 Vicrylor any absorbable suture, but this is a matter of
surgeon's preference because the keylayer is the lumbodor-
sal fascia. This should be tightly closed with a 0 or 1 Vicryl
placed in interrupted fashion. The superficial fascial/fatty
layer should also be closed to giveanother layer of support,
with 2-0 Vicryl on a taper needle. The skin is then closed
with a running, locked nylon suture (3-0). Alight dressing
is applied.
Large or complex dural tears may warrant placement of
a "diverting" CSFdrain to aid closure. If there is a large
area of normal dura exposed at the operative site the drain
can be positioned through a separate dural puncture above
the suture repair and drawn out percutaneously, away
from the midline fascial closure (Fig. 88-2). Otherwise, the
drain is placed percutaneously above the operative site af-
ter the incision is closed. This diverts the head of pressure
from the suture line, maximizing the chance for closure. If
entry into the thecal sac above the tear is not possible, the
drain may also be placed below. with good effectiveness.
The patient is placed in the lateral decubitus position. and
the drain placed prior to awakening the patient. An exter-
nal drainage system is set up. and the patient undergoes
CSFdrainageforthe next 3 to 5 days(Fig.88-3). Approxi-
mately 80 mLof CSFevery 8 hours should be removed to
allow decompression of the CSFpressure. Positioning the
B
Figure88-1
(A) A dural tear of over a few millimeters should be closed using a running, locked suture. (B) Fibrin glue is injected over the suture
repair covering
the dura - 2 to 3 mm in depth.

646
Lumbar and Lumbosacral Spine: Posterior Approach
"
Figure 88-2
With the patient in lateral position, a Touhey needle is inserted into the subarachnoid space through a separate dural puncture above
the suture
repair and drawn
out percutaneously,
away from the midline fascial closure.
(SF reservoir on an IV pole separate from the patient's
bed makes it easy to regulate the slow, steady gravity
drainage. If possible, the patient should be encouraged to
ambulate after 24 hours, clamping the drain prior to being
upright. Removal of the drain several days later is a bed-
side procedure.
In situations where the dura is severely lacerated or so
friable that suture repair is not possible, a wide incision in
the dura and arachnoid is made, and then the musclesare
closed primarily using absorbable suture. Atight fascialclo-
sure follows.The skin is closed with a running locked,nylon
suture. Amembrane or "pseudodura" forms underneath the
muscle with time. Opening the dural tear widely ensures
that the nerve roots will not get trapped in a small rent,act-
ingas a ballvalvemechanismwith egressoffluidwitheach
deep breath or Valsalvamaneuver.
Figure 88-3
The external drainagesystemis
set up, andthe patient undergoescerebrospinal
fluid drainagefor the next3 to 5 days.

...
References
88
Repairof CSFLeaks
647
1.SchievinkWI. Morreale VM. Atkinson JL. et al. Surgical treatment
of
spontaneousspinal cerebrospinal
fluid leaks. J Neurosurg1998;88:
243-246
2. SchievinkWI. Meyer FB.Atkinson JL.et al. Spontaneous spinal cere-
brospinalfluid leaks and intracranial
hypotension. J Neurosurg 1996;
84:598-605
3. Kitchel SH.Eismont FJ.Green BA. Closed subarachnoid
drainage for
managementof cerebrospinal fluid leakage after an operation on the
spine.]BoneJoint SurgAm 1989;71:984-987
4. McCormackBM. Taylor SL.Heath S.et al. Pseudomeningocele.
I: CSF
'1stulain a patient with lumbar spinal implants treated with epidural
blood patch and a brief course of closed subarachnoid drainage. Spine
1996;21 :2273-2276
5. McCallumJ.MaroonJC.Jannetta PI.Treatment of postoperative cere-
brospinal fluid fistulas by subarachnoid drainage J Neurosurg 1975;
42:434-437
6.
Patel MR. Louie W. Rachlin J.Postoperative cerebrospinal
fluid leaks
of the lumbosacral
spine: management
with
percutaneous
fibrin
glue. AJNRAmJ NeuroradioI1996;17:495-500
7.
Shapiro SA.ScullyT.Closedcontinuousdrainageof cerebrospinal fluid
via a lumbar subarachnoid catheter for treatment or prevention of cra-
nial/spinal cerebrospinal fluid fistula.Neurosurgery 1992:30:241-245

89
Lumboperitoneal Shunt
Emily Friedman
.
Indications
. Contraindications
.
Advantages
.
Disadvantages
.
Objective
.
SurgicalTechnique
Anesthesia, Draping,and Positioning
IncisionandPlacement of Catheter
Thedecision to divert cerebrospinal fluid (CSF)from the
lumbar subarachnoid space to the peritoneum should fol-
Iowa thorough clinical and radiological evaluation of the
patient to ensure the raised ICPis not compartmentalized
but is distributed
uniformly
throughout
the neuraxis.
There are several advantages to lumbar diversion: avoid-
ance of cerebral puncture with all its attendant risks, low
infection rate, and ability to divert CSFin the presence of
slit ventricles. The most common indications for place-
ment of a lumboperitoneal
shunt in the adult population
are communicating
hydrocephalus,! benign intracranial
hypertension (pseudotumor),2-4 and CSFfistula. CSFleak-
age may be an indication, but epidural blood patch, reex-
ploration with primary suturing, the use of fibrin sealants,
combined with temporary CSFdrainage via lumboperi-
toneal drain are preferred treatments
that succeed in the
majority of instances.
.
Indications
.
Idiopathic communicating hydrocephalus
.
Benign intracranial hypertension (pseudotumor)
.
CSFfistula
.
Normal pressure hydrocephalus
.
Postmeningitis hydrocephalus
.
Posttraumatic hydrocephalus
.
Postcraniotomy meningocele
648
..
.
Contraindications
. Severe arachnoiditis with subarachnoid block
.
Systemic infection with bacteremia
.
Bacterial meningitis
.
Carcinomatous meningitis
.
Peritonitis
.
Tension pneumocephalus
.
Advantages
. Avoidcerebral puncture
.
Shuntevenwith small/slitventricles
.
Spinalanesthesia
.
Disadvantages
. High failure rate in some patients
.
Backpaindue to rootirritation
.
Migrationofcatheter (pediatrics)
.
Objective
To treat
raised intracranial
pressure,
or a persistent
CSFleak,by
diversion of spinal fluid from the lumbar subarachnoid spaceto
the abdomen, where the peritoneum absorbs the excessfluid.

. SurgicalTechnique
Anesthesia,Draping, and Positioning
Thepatient is placed under general anesthesia,
then turned
intothelateraldecubitus positon with both knees flexed to
reducelumbar lordosis, facilitating
access into the spinal
canal.Aright-handed surgeon will find the left lateral decu-
bituspositioneasier to work with. Using a small degree of
reverseTrendelenburg position expands the lumbar sub-
arachnoidspace and may be helpful in cases where (SF
pressureislowdue to a leak. The abdomen, flank, and back
areprepped with Betadine solution or "duraprep,"
wherein
arectangle of 8 to 10 inches wide is walled off with drapes
placedjust below the spinous
processes,
around
the flank
andhip,to 2 inches past the umbilicus
on the opposite side
of the abdomen.
Iodine-impregnated
steridrape
is then
usedto hold the towels to the skin, avoiding staples. Paper
towels work very well
and
are
less bulky.
Either
four
straightsheets or preferably
one large drape with a central
openingis positioned
over the steridrape
and secured. The
scrubnurse should stand at the patient's
head with a Mayo
stand, leaving access
to the
abdomen
unencumbered.
Advisethe anesthesiologist
to prepare
for side to side rota-
tionof the table, as needed.
A single dose of antibiotic
is
givenIV,on call to the operating
room.
Incisionand Placement
of Catheter
Itisusuallyeasier to puncture the lower lumbar subarach-
noidspace(L3through SI), and preoperative plain lumbar
89
Lumboperitoneal Shunt
649
x-rays may guide you to the most accessible level. The spine
is palpated to identify the interspinous ligament, then a 14
gauge Touhey needle is inserted percutaneously with the
bevel facing upward toward the ceiling (Fig. 89-1). The
needle is advanced until brisk flow of (SF is encountered,
then rotated so the bevel faces cephalad. Samples of (SF
may be sent for analysis at this time, if indicated. Six to
8 cm of Silastic tubing is advanced through the needle into
the cephalad subarachnoid space. Once flow of (SF is as-
sured through the tubing, the needle is then carefully with-
drawn, leaving the tubing in place.One must not attempt to
remove/withdraw the Silastictubing through the needle: if
the bevel cuts the tubing it may only be retreived by
laminectomy and open exposure.
Entry into the abdominal cavity is either percutaneously
via a trocar, or through a small linear incision placed 2 to 3
cm inferior and 2 to 3 cm lateral to the umbilicus,on the su-
perior side of the abdomen (Fig. 89-1). If an incision is
used, the rectus abdominis anterior fascia isopened sharply
with a no. 15 blade, the muscle not cut but spread longitu-
dinally with a straight hemostat, and the posterior fascia
grabbed with straight fine mosquito hemostats to make a 2
to 3 mm sharp cut through the fascia and underlying peri-
toneum. Bowelshould be visualized to be sure the surgeon
is not in the preperitoneal fat, which in some patients is
ample! Rotating the patient by tilting the table toward the
surgeon makes exposure easier.
The proximal tubing is tunneled subcutaneously
from
the spine around the flank, to the abdominal incision or
trocar entry site. Some LPSkits contain a curved Silastic
tunneler; alteratively one can use a long shunt passer or
Figure89-1
The Touhey needle is inserted
into the lower lumbar subarachnoid
space (below).
The shunt tubing
is inserted
into the abdominal
cavityalong the dotted
line (above).

650
Lumbarand Lumbosacral Spine: Posterior Approach
Table89-1
Complicationsof LPS
even a long umbilical clamp. Once the tubing is pulled
subcutaneously, CSFflow is again checked, prior to placing
the distal end into the abdomen. Some of the LPSkits in-
clude a valvein the distal tip. In the event a separate reser-
voir or valve is required, the tubing must be tunneled in
the reverse direction (from the abdomen back over the
flank to the midline incision), a tunnel made large enough
to permit the valve to slide easily, and then the tubing can
be cut and the valve interposed.
Pulling the distal end
should now bring the valve to lie subcutaneously, away
from the midline incision. If a reservoir or valve is indi-
cated, the tubing is cut appropriately
so the reservoir
dome will lie above the iliac crest, over the paraspinal
musculature. If desired, it can be anchored to the fascia,
requiring an additional small incision. If trocar entry has
been used, only a subcutaneous Vicryl suture and skin clo-
sure with staple or nylon is needed. Ifa small incision has
been used, a purse-string suture around the peritoneum
and posterior rectus sheath is recommended, using a no. 4
Vicryl on a small taper needle. The anterior rectus sheath
is closed with no. 3 Vicryl, and a subcuticular closure with
no. 4 Vicrylor monocryl is performed, with Steri-Strips for
skin.
In instances where a percutaneous approach is not suc-
cessful (extreme spinal stenosis or rotary scoliosis),an open
approach via unilateral hemilaminotomy will allow entry
References
1.
Selman
WR. Spetzler
RF.Wilson
CB. et al. Percutaneous
lumboperi-
toneal shunt:
review of 130 cases. Neurosurgery
1980;6:255-257
2.
Burgett
RA. Purvin
VA. Kawasaki
A. Lumboperitoneal
shunting
for
pseudotumor
cerebri. Neurology
1997;49:734-739
Meningitis
Arachnoiditis
Peritonitis
Subdural hematoma
Pneumocephalus
Intracranial hypotension
Brain herniation
Thoracic or lumbar radiculopathy
Mechanical malfunction
PEDIATRIC
CASES ONLY
Symptomatic tonsillar herniation
Scoliosis/spinal deformity
into the spinal subarachnoid space. The Touhey needleis
still used, through the ligamentum flavum, to puncturethe
dura and allow the surgeon to thread the catheter cephalad.
Closure of this incision is routine, paying careful attention
not to kink the catheter. Potential complications ofalurn-
boperitoneal shunt are listed in Table 89-1.
3.
Eggenberger
ER. Miller NR. Vitale S. Lumboperitoneal
shunt forthe
treatment
of pseudotumor
cerebri. Neurology
1996;46: 1524-1530
4.
Johnston
I. Besser M. Morgan MK. Cerebrospinal
fluid diversion in the
treatment
of benign
intracranial
hypertension.
J Neurosurg
1988:69:
195-202

90
Rhizotomyof the LumbosacralNerve Roots
FrederickA. Boop
. Indications
. Contraindications
. Advantages
. Disadvantages
. NeurologicalEvaluation
. Alternatives
. Objective
In1898,Sherrington published experimental results dem-
onstratingthat sectioning
of the dorsal rootlets
in the
decerebratecat could convert decerebrate rigidity
to flac-
cidity.1Sherrington believed the increased extensor tone
foundin his decerebrate model mimicked spasticity in the
human.Based upon these results, Foerster performed
a
seriesofdorsal rhizotomies on 159 patients who had spas-
ticity following stroke,2 including 88 patients with "con-
genital spastic paraplegia."
He reported
a significant
reductionin spasticity in those patients with congenital
spasticparaparesis, but not as good a response in patients
with hemiparesis secondary to stroke. Despite encourag-
ingresults, the procedure fell into disfavor because of a
highcomplication
rate related to loss of sensation and
proprioception.
The procedure
was abandoned
for years
thereafter until, in 1967, Gros3 demonstrated
that by par-
tially sectioning the involved dorsal roots, one could
achievea reduction in tone, yet preserve sensation. This
procedurewas modified in the 1970s by Fasano,4who used
intraoperative
neurophysiological
monitoring
to deter-
minewhich dorsal rootlets to cut. His technique was later
modifiedand popularized by Peacock,s who sectioned the
nerverootlets at their respective exit foramina from L2to
S2bilaterally.
Selective dorsal
rhizotomy
has now arguably
become
theprocedure of choice for treating spasticity in patients
with static encephalopathy who have ambulatory poten-
tial.The procedure may also be of value for patients with
spasticity secondary
to spinal
cord injury
and in spastic
tetraplegics
in whom
a reduction
in tone
can facilitate
nursing care.
. Surgical
Technique
Anesthesiaand Positioning
Incisionand Exposure
Performingthe Laminoplasty
NeurophysiologicalMonitoring andRootSectioning
Vertebral Reconstruction
.
PostoperativeCare
.
Conclusions
.
Indications
. Staticencephalopathyor spinalcordinjury
. Goodintrinsiclowerextremitymotorstrength (doesnot
use spasticityfunctionally)
. Sufficientcognitionto cooperatewith therapists
. Familysupport
.
Contraindications
. Progressive disorders (degenerative diseases)
.
Choreoathetotic cerebral palsy
.
Cerebellar ataxia
.
Significant fixed contractures
.
Advantages
.
Immediate relief
.
No cord involvement
.
Focaltreatment
.
Facilitate nursing care
.
Improve activities of daily living(ADL)
.
Reduce decubitus formation
.
Definitive treatment
651

652
Lumbarand Lumbosacral Spine: Posterior Approach
.
Disadvantages
.
Neuro-ablative
.
Potential for pain recurrence
. Potentialinjuryto sacralnerveroots
. Potentialweaknessin lowerextremities
.
Loss of useful spasticity
.
Neurological Evaluation
Spasticity is a velocity-dependent
increase in muscle tone
due to a loss of descending inhibition to the spinal cord.
Over time this increased tone may lead to progressive for-
mation of contractures, hip subluxation, pain, or functional
disability. Having said this, many patients with spastic
diplegia are intrinsically weak in their lower extremities
and rely upon the stiffness created by their spasticity to fa-
cilitate standing and transferring. As such, careful patient
selection makes the difference between an individual who
is functionally improved and one who is functionally wors-
ened following selective dorsal rhizotomy (SDR);further-
more, a host of treatment options now exist for the patient
troubled by spasticity. Determining the best treatment op-
tion for an individual is optimally done through a team
evaluation with input from the physiatrist, the orthopedist,
the neurosurgeon, occupational and physical therapists, and
social workers.
In general. the child with
static
en-
cephalopathy (as opposed to a progressive disorder) who
has good intrinsic lower extremity strength but is ham-
pered by Ashworth 3 or 4 spasticity is a potential candidate.
Those children with good balance and normal cognition are
more likely to become independent ambulators following
SDR.A simple clinical test to evaluate intrinsic lower ex-
tremity strength is to stand behind the child, stabilize him
by holding his hips, and have him perform repetitive squats
to stands. If one holds the child by the arms or hands, he
will often pull himself upright
using his upper body
strength, giving a false impression of lower extremity func-
tion.
In choosing the appropriate
candidate
for SDR, it is
worthwhile having input from a multidisciplinary team.
Children who have dystonic cerebral palsy or who have
rigidity will not be improved by the surgery. In fact, it has
been said that children with significant dystonia, athetosis,
or cerebellar ataxia may have their movement disorder dis-
inhibited by the procedure, thus worsening their function-
ality. There is ongoing debate regarding performing SDRin
severely retarded children as well. Tomake functional gains
in therapy, children have to have enough cognitive ability to
interact with their therapists. Onthe other hand, many par-
ents with severely affected children find them much easier
to manage in terms of toileting, bathing, and positioning in
a chair if the child's tone is reduced. Arelative contraindica-
tion is the child who has significant fixed contractures. In
such cases, reducing tone in the face of limited joint mobil-
ity will not improve functional ability or facilitate nursing
care. Finally,children who have very weak lower extremi-
ties may rely upon the stiffness in their lower extremitiesto
ambulate or to transfer. In such children, taking awaythat
stiffness may leave them limp and noodle-like. A formal
motor examination is imperative if ambulation isagoaLIn
the author's
experience,
the ability to perform repetitive
squats to stands is a means of determining whetherlower
extremity
strength
is adequate
or not. It is also imperative
that the parents
understand
that although SDRmayreduce
tone, it will not create in these patients a normalgait.Some
of my most
disappointed
parents
have had childrenin
whom we were pleased with our accomplishments, butthe
parents'
expectations
were
too high. Having the parents
view pre- and postoperative videotapes of other children
prior to surgery can be very helpful.
.
Alternatives
A variety of treatment
options
currently
exist for the child
hampered
by spasticity.
For children with mildly increased
tone, oral baclofen, ZanafIex, or Dantrium may be sufficient
to increase their level of function. In the child with onetight
heel cord or spasticity limited to one gastrocnemius,botu-
linum toxin injections coupled with serial casting or aggres-
sive physical therapy may be sufficient. Similarly,thechild
with one tight heel cord may be effectively treatedbyheel
cord lengthening
alone. In other cases, the child with signif-
icant spasticity
and contractures
may benefit from ham-
string,
heel cord, or adductor
lengthening
in additionto
SDR. In such cases, it is best to perform the SDRfirst,reserv-
ing the orthopedic procedure for several months downthe
road if the child continues
to be hampered
by contractures.
At present, intrathecal baclofen delivered by an implantable
pump is the best treatment for severe spasticity inchildren
who are not candidates
for SDR. I have also been usingitas
a nondestructive alternative in many children inwhomwe
would have performed SDRin the past. I currentlyutilize
SDRin children with good ambulatory potential (adequate
strength, balance, and cognition); for children inwhomre-
turning for pump refills is problematic; or for childrenin
whom intrathecal baclofen is contraindicated (allergies,in-
duced seizures, no third-party
coverage, etc.).
.
Objective
Topermanently reduce the spasticity associated with cere-
bral palsy or spinal cord injury, with hopes of improving
functional
abilities
and pain or preventing
progressionof
neuro-orthopedic
deformity6
.
Surgical Technique
Anesthesia
and
Positioning
General anesthesia is induced either with no musclerelax-
ants
or with
a very short-acting
agent
such as Vecuro-
nium, thus minimizing interference with the intraoperative

electromyographic(EMG)recording once the rootlets are
exposed.The patient is positioned
prone on chest rolls with
thearmsup on arm boards. EMG needle electrodes are then
placedin the quadriceps,
adductors,
gastrocnemius,
and
tibialisanteriorbilaterally.Intraoperative monitoring is per-
formedutilizing an intraoperative
EMG machine
with at
leastfour-and preferably eight-channel
recording
capabil-
ity(Viking, Nicolet, Madison,
WI). At times
during
the
operationthe legs will move in response
to stimulation.
A
loosestrapover the legs prevents them from falling off of
the,ableduring stimulation.
Incisionand Exposure
Amidlineskin incision is marked from the thoracolumbar
junctionto the midsacrallevel.
This is infiltrated
with dilute
lidocainewith epinephrine.
Once the skin incision is made,
thelumbodorsal fascia is opened,
leaving the supraspinous
and interspinous ligaments
attached
to the
spinous
processesof the lumbar
vertebrae.
The upper
half of the
sacrumisalsoexposed. Next, the paraspinous muscles are
elevatedfromthe laminae subperiosteally, taking care not
toviolatethe facet capsular ligaments.
Performing
the Laminoplasty
Alaminectomyis performed at 51 and 52, using a Kerrison
rongeurto remove any ligamentum flavum attached to the
caudadaspect of the L5 lamina. Next a footplated high-
speedairdrill is used to make cuts through the lamina and
ligamentumflavum on either side of the midline from L2to
Lt.Iprefer the Midas Rex with its B-5 drill bit to perform
thismaneuverbecause of the narrow cut it makes through
thelamina.The spinous process of L5 is then grasped
withasmall towel clamp and the dorsal construct, consist-
ing of the spinous
processes,
ligamentum
flavum,
and
supraspinous and interspinous
ligaments,
is elevated,
ex-
posingthe underlying
epidural
fat. Epidural hemostasis
is
obtained with bipolar
coagulation
and the epidural
fat is
partedin the midline and swept to each side rather than
beingresected. The dura is then opened in the midline and
epiduraltacking sutures are placed (Fig. 90-1).
Neurophysiological Monitoring and RootSectioning
Oncethe dura is opened, the microscope is brought into the
fieldand the roots inspected. As the roots exit the spinal
canal,they are divided anatomically
into dorsal and ventral
roots.Thelumbar roots gradually increase in size as the lev-
elsdescend. The last large root is the 51 root, with the 52
rootbeing notably smaller (Fig. 90-2). Using the insulated
rhizotomyhooks, the 52 ventral root is separated from the
90
Rhizotomyof the LumbosacralNerve Roots
653
dorsal rootlets and stimulated for threshold. The ventral
rootlets will generally create an EMGresponse at roughly
one tenth the amperage needed to stimulate the dorsal
rootlets. At times, this difference in stimulation threshold
may help differentiate a dorsal from a ventral rootlet. Once
the stimulation threshold isdetermined for the ventral root,
it is protected by a microcottonoid, and stimulation of the
dorsal rootlets is performed. Responses of the dorsal
rootlets are graded on a scale of 0 to 4 (see Table 90-1).
Those rootlets giving a 3 or 4 response are transected and
those giving a lesser response are spared. One should al-
ways leave at least one good-sized dorsal rootlet intact at
each level, regardless of its stimulation parameter. This will
help prevent postoperative sensory abnormalities.
Upon completion of the 52 rootlet sections, one repeats
the procedure at each level up to L2.Forthe larger dorsal
roots, the rhizotomy hooks are used to tease out the rootlets
for stimulation. Generally, one can expect to perform three
to six rootlets from each of the larger dorsal roots at the L5
and 51 levels. This division is somewhat artificial. Oncethe
dorsal rhizotomy is completed on one side of the spinal
canal, the process is repeated from 52 to L2on the opposite
side. At times, rotating the table side to side can facilitate
exposure of the neural foramina. At times, particularly at
the L2level, large veins will accompany the roots. These can
generally be spared. Once the rhizotomy is complete, the in-
tradural
space is irrigated
and meticulous
hemostasis
achieved prior to closing the dura in a watertight fashion.
Vertebral Reconstruction
The epidural fat is then swept back over the dura to cover
the suture line. The author place an epidural catheter
througha Touheyneedlewiththe cathetertip at the levelof
theconus.Thisisusedforpostoperativepainmanagement.7
The B-5bit and drill are used to create suture holes through
the lamina at each level for replacement of the bones. A
Penfield no. 1 is useful for protecting the roots and dura
during this portion of the operation.
Braided nylon sutures, such as 00 Ethibond (Ethicon),are
used to sew the lamina back into place. Igenerally alternate
the side of the saw cut gaps from one level to the next to fa-
cilitate bone healing (Fig. 90-3). In reapproximating the
paraspinous muscles, sutures are passed through the mus-
cles and through the interspinous ligaments to help anchor
the spinous processes in the midline during healing. Simi-
larly, as the fascia is closed, the sutures are passed through
the supraspinous ligaments. The subcutaneous and skin lay-
ers are closed in standard fashion. Myexperience has been
that laminar replacement in these children reduces the
long-term risk of postoperative musculoskeletal back pain
in this population of children.s Postoperative bracing is
generally not necessary.

654
Lumbarand LumbosacralSpine:PosteriorApproach
A
~
-"
B
D
c
Figure90-1
The patient is in the prone position
in slight Trendelenburg's
position to pre-
vent cerebrospinal
fluid overdrainage.
Following
laminectomy
from
L2 to 52, the dorsa
laminar construct
has been elevated and secured out of the way, leaving the ligaments in-
tact. The dorsal and ventral
roots are easily distinguished
at their respective
foramina of
exit by their anatomical
position
at the foramen.
Note the last large root is 51, with 52 being
notably smaller.
.

90
Rhizotomyof the LumbosacralNerve Roots
655
Figure90-2
Under the microscope, the nerve root at the foramen
againdemonstrates the anatomical relationship of dorsal and ventral
roots.Therhizotomy hooks are used to elevate the right L5dorsal root.
Noticethat 52 is notably
smaller
than
51, a useful landmark.
At times,
a
thirdrootlet or a conjoined
rootlet
will be encountered.
In such instances,
electrophysiology may differentiate
dorsal from ventral components.
Figure90-3
The dorsal laminarconstruct has been replaced using
braidednylonsutures. Anepiduralcatheter isleft inplaceat the time of
closurefor postoperative painmanagement. The spinousprocessesare
incorporated into the muscle and fascial closure to allow stability while
healing.Postoperative bracing is generally not required.
Table 90-1
Grading of SDRElectromyographic
Response
Grade
Response
o
Unsustaineddischargewithrapiddecrement
1
Sustainedresponseinsegmentallyinnervated muscles
2
Sustainedresponseinsegmentallyinnervated muscles
withspreadto adjacentmusclegroups
3
Sustainedresponseinsegmentallyinnervatedmuscles
withspreadto distant ipsilateralmusclegroups
4
Sustainedresponseinsegmentallyinnervatedmuscles
withspreadto distantipsilateralandcontralateral
musclegroups
.
PostoperativeCare
Following surgery, my practice has been to nurse the chil-
dren in the intensive care unit overnight, mainly to watch
for respiratory
depression
secondary
to the epidural
analgesia. Having said this, I have not had any major com-
plications in over 80 cases and one could argue that a
step-down unit with a pulse oximeter might be sufficient.
With a good dural closure, we have not been in the prac-
tice of keeping the child's head flat, but prefer to keep the
head of the bed elevated 10 degrees to prevent rostral mi-
gration of the epidural analgesic. Certainly, a cerebrospinal
fluid leak is a potential complication, but with a good fas-
cial closure, this has not been encountered.
If this should
occur, one can consider converting the epidural catheter to
a spinal drain for several days to allow healing of the over-
lying tissues.
The most common complication of SDRis that of dyses-
thetic pain in the lower extremities secondary to manipula-
tion of the nerve roots. This pain always goes away within
10 to 14 days but can be troublesome in the first few post-
operative days. This pain is usually well controlled by
adding local anesthesia to the epidural analgesia in a dose
that will cause a sensory block but not a motor block(0.25%
bupivacaine). The addition of intravenous solumedrol may
also hasten recovery.
Pulmonary atelectasis and fever secondary to hyperventi-
lation have been a problem with the use of systemic nar-
cotics, either orally or intravenously administered, but have
not been nearly the problem since switching to epidural
pain control. In children with swallowing dysmotility or
with drooling, one must watch carefully for aspiration.
Aggressive pulmonary toilet is critical in the first few days
following SDR.
Nearly all children having undergone SDRwill demon-
strate mild motor weakness in their lower extremities
following SDR.This has been attributed
to diminished
tone following the resolution of the spasticity
or per-
haps to an effect on that small percentage of the motor
fibers that may exit with the dorsal rootlets. At any rate,

656
LumbarandLumbosacralSpine:PosteriorApproach
IIIIII
. Conclusions
this weakness is generally gone by 6 months following the
surgery.
Bladderdysfunction is a rare complication of SDRand is
most commonly related to narcotic pain medications. Per-
manent enuresis has been reported to occur in up to 1/200
children followingSDR.Abbott and coworkers have re-
ported success in recording intraoperative pudendal neuro-
grams as a means of monitoring lower sacral root function
and have documented a reduced risk of bladder dysfunction
with this technique.9
References
1. Sherrington
C. Decerebrate
rigidity and reflex coordination
of move-
ments. J PhysioI1898;72:319-327
2.
Foerster O. On the indications
and results
of the excision of posterior
spinal nerve roots in men. Surg Gynecol Obstet 1913;16:463-474
3. Gros C. Ouaknine G.Vlahovitch B,Frerebeau P.Laradicotomie selec-
tive posterieure
dans Ie traitement
neuro-chirurgical
de I'hypertonie
pyramidale.
Neurochirurgie
1967;13:505-518
4.
Fasano VA. Barolat-Romana
G, Ivaldi A.Squazzi A. Functional
poste-
rior radiculotomy.
in the treatment
of cerebral
spasticity:
peropera-
tive electric
stimulation
of posterior
roots and its use in the choice of
the roots to be sectioned.
Neurochirurgie
1976;22:23-34
5.
PeacockWJ,Arens Lj. Selective posterior rhizotomy for the treatment
of spasticity in cerebral palsy. SAfrMedJ 1982;62:119-124
Selective dorsal rhizotomy is an effective means of per-
manently
reducing
spasticity
and thereby
improving
functional
abilities
in many
children
with
cerebral
palsy or spinal cord injury. Although
it is a relatively long
operation.
it is a safe procedure
with minimal long-
term side effects. Proper identification of surgicalcan-
didates
is key to a successful
outcome
following the
operation.
6. HeimRC.Park TS, Vogler GP.Kaufman BA, Noetzel NJ,OrtmanMR.
Changes in hip migration
after selective dorsal rhizotomy forspastic
quadriplegia in cerebral palsY.JNeurosurg 1995:82:567-571
7. CobbMA, Boop FA.Replacement laminoplasty in selectivedorsalrhi-
zotomy:
possible
protection
against the development of muscu-
loskeletal pain. Pediatr Neurosurg 1994;21 :237-242
8.
Lawhorn CD, Boop FA. Brown R.Andelman P.Epidural pain manage-
ment in the post-rhizotomy
patient.
Pediatr Neurosurg 1994;20:
198-202
9.
Deletis V. Vodusek DB.Abbott R. Epstein FJ,Turndorf H.lntraoperative
monitoring
of the dorsal sacral roots: minimizing
the risk of iatro-
genic micturition
disorders. Neurosurgery 1992;30:72-75

91
Resectionof CaudaEquinaEpendymomas
R.ShaneTubbsandW.JerryOakes
. ClinicalPresentation
. Pathology
ofTumors
. Treatment
. SurgicalTechnique
Ependymomas
are the most common intramedullary
spinal
cordtumors seen in adults. One variant, myxopapillary
ependymomas, are generally
seen only in the cauda equina
andfilum terminale.
Although
reported,
it is rare to see the
myxopapillaryvariety outside this domain. 1 Myxopapillary
ependymomas represent
40 to 50% of adult spinal ependy-
momas and 8 to 14% of these
have been seen in children
lessthan 16 years of age.2,3 Myxopapillary
ependymomas
arethought to originate
from ependymal
cell masses in the
terminal ventricle
and filum terminale.4-8
These
tumors
generally carry a favorable
prognosis
in the adult popula-
tionwith complete
excision. Myxopapillary
ependymomas
tendto be more aggressive in children; therefore, their
prognosisis somewhat
worse even with total gross removal
ofthe tumor.s
. ClinicalPresentation
Myxopapillaryependymomas appear to be slow-growing
tumorsin most patients, presenting in the third to fourth
decadeof Iife.3 Back pain is the commonest presenting
symptom.9This is usually described as a chronic problem
withan average duration of 2 years.3Approximately half of
patientsreport back pain that is made worse by being re-
cumbentand only by returning to the erect state is the pain
alleviated.
1Althoughnot as common,patients maypresent
withlegweakness, subarachnoid hemorrhage. papilledema,
andurinary dysfunction.s Urinary incontinence at presenta-
tionisa poor prognostic sign.s
Myxopapillary ependymomas
are seen as enhancing,
intradural, extramedullary
lesions. II-weighted magnetic
resonance images (MRI)are homogeneous and isointense
(Fig.91-1) and T2-weighted images are also homogeneous
but hyperintense.to Withcontrast enhancement the lesion
will enhance intensely (Fig.91-2). Hemosiderin deposition
in the pia and arachnoid is also common.s Plain radiographs
may demonstrate widening of the interpedicular distance,
erosion of the posterior elements, and an increase in the
size of the intervertebral foramina.ll
.
PathologyofTumors
Grossly,these tumors are well circumscribed and can com-
press or envelop the roots of the cauda equina. They are
usually cylindrical and described as sausage shaped.4-6
Myxopapillary ependymomas
are also highly vascular.
Microscopically these tumors have areas with both rosettes
and pseudorosettes
intermingled with papillary regions.
They characteristically have a vascular core with a mucoid
matrix; necrosis and mitotic figures are variable in their
occurrence.4,7,8.12,13
. Treatment
Surgical excision of the tumor is the primary treatment
of choice. Radiation therapy is a controversial treatment
option following surgical intervention.3
657

..
658
Lumbarand Lumbosacral Spine: Posterior Approach
Figure91-1
Midsagittalmagnetic resonance imagingofthe lumbar
spine with T1 weighting. Amass fillingthe lower lumbar and sacral
spineisapparent. Thelesionisisointense compared with other neural
tissue.
Figure91-2
Same patient and view as Figure 91-1 but following
intravenous
contrast
enhancement.
With this the tumor enhances
homogeneously.

. SurgicalTechnique
Theskinisopenedin the midline to encompassthe length of
theabnormality.A laminectomy is performed over the lesion
usingradiographicconfirmation of the level if necessary.The
useofalaminotomy could be considered in an attempt to in-
creasethe integrity of the spine postoperatively. With the
boneremovedthe lesion can usually be appreciated through
theintactdura mater (Fig. 91-3). The dural opening is begun
abovethelesionand extended over its entire length. The neo-
plasmitself is usually hemorrhagic, soft, and bluish gray,
causingthenerveroots to be displacedlaterally (Fig. 91-4).
Withthe dura completely open, the filum is located and
cut above the lesion. Using cotton pledgets the cauda
equinais separated from the tumor. Great care is taken to
keepthethin capsule of the tumor intact (Fig. 91-5). Adhe-
sionsfrom the capsule to the surrounding
roots are
common.Their separation can usually be accomplished. In
additionto maintaining the physical integrity
of the roots,
thevascularsupply to these small structures must be main-
tained.Slowly working around the circumference of the le-
sion,dealing with points of adhesion. is the best option
available.The further caudally the operator progresses the
fewerare the nerve roots and the easier the dissection.
Eventuallythe lesion will be freed and delivered. The clo-
sureisin the standard manner.
Figure91-3
Intraoperative view of the same patient as in Figures
91- 1 and91-2. The laminectomy has been performed but the dura
leftintact.Thesuperior poleofthe tumor can be appreciated through
the dura (arrow).
91
Resection of Cauda Equina Ependymomas
659
Figure 91-4
Nowwiththe dura opened superiorlythe cauda equina
can be seen displaced laterallyand the filumterminale appreciated in
the midline(arrow)asit enters the superiorpoleofthe neoplasm.
Figure 91-5
Thejunction ofthe tumor withthe cauda equina.

660
LumbarandLumbosacralSpine:PosteriorApproach
References
1.
Wiss OA.An unusual cause of sciatica and back pain: ependymoma
of
the cauda equina: case report. j Bone joint Surg Am 1982;64:772-773
2.
Gagliardi FM, Cervoni L,Oomenicucci
M. et al. Ependymomas
of the
filum terminale
in childhood:
report
of four cases and review of the
literature.
Childs Nerv Syst 1993;9:3-6
3.
Nagib MG, O'Falllon MT. Myxopapillary
ependymoma
of the conus
medullaris
and filum terminale
in the pediatric
age group.
Pediatr
Neurosurg 1997;26:2-7
4.
Rubinstein
U. Myxopapillary
ependymomas.
In: Russell
OS, Rubin-
stein U, eds. Pathology
ofTumors
of the Nervous System. Vol 5. Balti-
more: Williams and Wilkins;
1989:203-206
5.
Schweizer jS. Batzdorf
U. Ependymoma
of the cauda equina
region:
diagnosis.
treatment,
and
outcome
in 15 patients.
Neurosurgery
1992:30:202-207
6.
Siooff jL. Kemohan jW. MacCarty
CS. Ependymomas.
In: Siooff jL, ed.
Spinal
Cord
and
Filum
Terminale.
Philadelphia:
WB Saunders:
1964:63-108
7.
Sonne land PRL, Scheithauer
BW, Onofrio BM. Myxopapillary
ependy.
moma:
a clinicopathologic
and
immunocytochemical
study of 77
cases. Cancer 1985:56:883-893
8.
Specht CS, Smith TW, OeGirolami U, Price 1M.Myxopapillary
ependy-
moma of the filum terminale:
a light and electron
microscopic study.
Cancer 1986:58:310-317
9.
Feamside
MR. Adams
CBT. Tumours
of the cauda
equina. J Neurol
Neurosurg
Psychiatry
1978:41 :24-31
10.
Yamada CY,Whitman
Gj, Chew FS. Myxopapillary
ependymoma
of
the filum terminale.
AJRAmJ RoentgenoI1997:168:366
11.
Friedman
A. Intramedullary
tumors
and tumors
of the cauda equina.
In: Rengachary
55, Wilkins
R, eds. Principles
of Neurosurgery.
Lon-
don: Mosby: 1994:39.2-39.3
and 39.9-39.10
12. Kernohan JW.Primary tumors of the spinal cord and intradural filum
terminale.ln:
Penfield
W. ed. Cytology and Cellular
Pathology ofthe
Nervous System. Vol 3. New York: Paul B Hoeber:
1932:993-999
13. Kun LE.Kovnar EH,Sanford RA.Ependymomas in children. Pediatr
Neurosci 1988:14:57-63

Releaseof the Tethered Spinal Cord
W. JerryOakes
. Advantages
. Disadvantages
.
Definition
. ClinicalPresentation
.
Neurological Evaluation
.
Surgical Technique
. Postoperative Care
. Complications
. Conclusion
Thetethered cord syndrome (TeS) is an increasingly recog-
nizedcause of pediatric and adult lower spinal cord dys-
functionand disability. Since its original description in the
1950sthis disorder has become more frequently diagnosed
becauseof increased ease of diagnosis and an expanded
definitionof the problem. The recognition of the association
ofathickened and taut filum terminale with other forms of
occultspinal dysraphism (lipomyelomeningocele, split cord
anomalies,ete.) has improved the surgical outcome of nu-
merouspatients. Section of the filum terminale is a simple
andsafeprocedure that should be employed at the time the
diagnosis is made.
. Advantages
. Operationis straightforward
. Lowcomplication rate
. Disadvantages
. Potentialfor pseduomeningocele
. Definition
Forthe purposes of this discussion the TeS will be consid-
eredone of the seven pathological entities that make up the
familyof diseases referred to as occult spinal dysraphism
(OSD).lt is characterized by excessive tension on the distal
spinal cord by a thickened filum terminale (Fig. 92-tA,B).
The pathological filum is almost always infiltrated with fat
to the extent that magnetic resonance imaging (MRI)can
detect it. The conus assumes a low position within the
spinal canal reflective of its anticipated position. Excessive
tension is applied to the spinal cord causing neurological
dysfunction and possibly pain.
.
ClinicalPresentation
Patients with the Tes present for clinical attention in a
similar
manner
as other
forms of occult spinal dys-
raphism (lipomyelomeningocele. etc.). Early in life infants
are quite unlikely to be symptomatic
but will come to
clinical attention
because of a cutaneous
signature of
OSD.Among these, the capillary hemangioma is by far
the most common. This is also the least reliable cuta-
neous sign. with surgically significant pathology occur-
ring in <20% of patients. Associated anomalies, which
raise the likelihood of the TeS, include anorectal atresia
and cloacal exstrophy.
After cutaneous signatures the next most common pre-
senting problems in order of their occurrence are neuro-
genic bladder, orthopedic presentations with foot and leg
length discrepancy, scoliosis.and asymmetry of the plantar
arches. The least likely presentation is with a neurological
661

662
LumbarandLumbosacralSpine:PosteriorApproach
Figure 92-1
(A)MidsagittalTl-weighted magnetic resonance imaging(MRI)ofa
typical patient with the tethered
cord syndrome.
Note the caudal displacement of
the conus, its elongated appearance, and the obvious fat in the filum (arrow). (B)Ax.
ial MRIof another patient through the sacral region. The enlarged
fatty infiltrated
filum hugs the dorsal dura (arrow).
deficit. either motor or sensory. Pain as the primary com-
plaint occurs in < 5%of children but> 50%of adults.
History patients with an isolated Tes have never been
followedexclusively to develop natural history data. Physi-
cians with knowledge in this area understand that neuro-
logical worsening from spinal cord fixation is a constant
and ongoing threat. surgical risk is exceedingly low. and
recovery from a preoperative neurological deficit is mar-
ginal but dependent
on the nature
and extent of the
deficit.
It is unlikely that any natural history study will ever be
performed and that clinicians will be swayed to offer early
intervention based on memories of significant fixed deficits
that were not reversible following operative intervention in
other patients.
. Neurological Evaluation
Thediagnosisand evaluation of patients with the Tes is rel-
ativelysimple.It begins with a history and physical exami-
nation.Specialattention is paid to the neurological function
of the lower extremities. Evidence of bladder dysfunction
can be impliedfromthe history but much more information
can obtained fromurodynamics testing. The position of the
conus, sizeand character of the filum, and presence and ex-
tent of a syrinxcanbe determined by ultrasound within the
first 3 to 4 months of life. After the loss of the acoustical
window in the dorsal lumbar spine. MRI is routinely
employed to assess these variables (Fig. 92- tA,B). Routine
radiographs of the lumbar spine add information concern-
ing the extent and degree of segmentation
errors of the
spine. The normal position of the conus by 3 months ofage
is at or above the L1-L2 disk space. This is true in 96%ofthe
population. Unusual normal patients will have the conus
lower than this. Tes patients usually have the conus below
L3. However. patients may develop symptoms with the
conus above L3with bony spina bifida. fat in an enlarged
thickened filum, and an elongated appearance of the conus.
The position of the conus is an important criterion forres
but rarely patients may be symptomatic and respond to
filum sectioning with the conus in a normal position.
. Surgical Technique
The patient is positioned prone with bolsters under the iliac
crest and chest to allow for free abdominal excursion. A
limited midline linear incision is made over Sl and S2
(Fig. 92-2A,B). Although the dura can be opened between
the laminae, I generally prefer to perform a standard S1
laminectomy and open the dura in the midline. Frequently
the filum can be appreciated through the intact dura. With
the dura open roots will be seen exiting ventrally and later-
ally.while the filum is infiltrated with fat. midline and exit-
ing dorsally. The filum will frequently have a bluish hue to
help separate it from the adherent roots, and on the ventral
surface is a characteristic vessel running the length of the

A
Figure92-2
(A) Position of an infant ready to undergo a sacral exploration for
tethered cord syndrome.
(8) The external
landmarks
and
incision
for a typical
openingto section the filum terminale.
structure.Ifroots are continuing
to be significant in number
andthe cul-de-sac of the subarachnoid
space is well below
51,the posterior elements
of 52 may be removed to increase
visualization.
Oncethe filum is identified
all neural elements
are sepa-
ratedand the structure
isolated
(Fig. 92-3A-E),
with very
lowsettings the bipolar forceps are used to coagulate
and
thencutthe filum in two places. This allows a specimen to
besubmitted for pathological
examination
and creates
a
gapbetween the cut ends of the structure.
Throughout the operation
no monitoring
is performed.
Withexperiencethe filum is appreciated as a distinct struc-
ture that would
be difficult
to confuse
with
any of the
neural elements.
All nerve
roots
have a pathognomonic
findingofalternating light and dark banding occurring ap-
proximately every
millimeter.
This banding,
easily
seen
withmagnification, is not present in the filum. With the
filumcut the dura and soft tissues are approximated. No
drainisnecessary.
. Postoperative
Care
Patientsare nursed flat for 3 to 5 days to allow some time for
duralhealingwithout the added effectsoforthostatic pressure
froman upright posture. This is easily tolerated in small in-
92
Releaseof the TetheredSpinalCord
663
B
fants but a bit more trying as the patient gets older. Pain relief
is usually easily accomplished. Occasionally, bladder catheteri-
zation will be necessary until the patient becomes upright.
.
Complications
Very few complications occur with this procedure other
then pseudomeningoceles. Care must be taken to open the
dura in the area of the cul-de-sac where all neural elements
have left the cord and are lateral. Including sacral nerve
roots with the section of the filum may give bladder incon-
tinence and sexual dysfunction. The risk is lower if all the
sacral points of exit are in view before selecting the filum
for sectioning.
.
Conclusion
Sectioning of the filum terminale for the TCSis one of the
simplest intradural
procedures performed by neurosur-
geons. The challenge lies in selecting patients for investiga-
tion and surgery at the earliest possible time before irre-
versible symptoms occur. Complications and postoperative
problems are minimal.

664
LumbarandLumbosacralSpine:PosteriorApproach
A
B
c
D
E
Figure 92-3
(A) Axial representation
of the separation
of the fatty infiltrated filum from the surrounding
roots. (8) Intraoperative
view of the in.
tradural
contents.
In this particular
case, the filum is quite large and obscures the visualization
of the sacral roots. It must be separated
from allof
these neural elements before (C) the filum is sectioned.
(D) Actual intraoperative
view of the sacral intradural
contents
with a suture around the eas-
ily separated
filum.
(E) Another
intraoperative
view with a much more complex
situation.
Roots are seen to course horizontally,
caudally, as well as
superiorly.
The "filum"
is a broad-based
end of the spinal cord in the cul-de-sac
of the subarachnoid
space. It is important
to disconnect
the distal
cord caudal to all exiting roots without
injuring any of these structures.

SuggestedReadings
I. BreigA.Overstretching of and circumscribed
pathological
tension
in
the spinal cord: a basic cause of symptoms
in cord disorders.
J Bio-
mech 1970:3:7-9
2. McLendonRE.Oakes WJ. Heinz ER. Yeates AE. Burger Pc. Adipose tis-
suein the filum terminale:
a computed
tomographic
finding that may
indicate tethering of the spinal cord. Neurosurgery
1988:22:873-876
1. SatoS.Shirane R.Yoshimoto T. Evaluation
of tethered
cord syndrome
associated with anorectal
malformations.
Neurosurgery
1993;32:
1025-1028
92
Releaseof the TetheredSpinalCord
665
4.
Sharif S. Allcutt D. Marks C. Brennan
P. "Tethered
cord syndrome":
recent clinical experience.
BrJ Neurosurg
1997;11 :49-51
5.
Tubbs RS.Wellons JC III. Iskandar
BJ.et al. Isolated
flat capillary
mid-
line lumbosacral
hemangiomas
as indicators
of occult
spinal
dys-
raphism. J Neurosurg Spine 2004; 100:86-89
6.
Warder
DE. Oakes WJ. Tethered
cord syndrome
and the conus
in a
normal
position. Neurosurgery
1993:33:374-378
7.
Yamada S. Zinke DE. Sanders
D. Pathophysiology
of "tethered
cord
syndrome."
J Neurosurg
1981 ;54:494-503

93
Resection of Lumbosacral Lipomas
w. Jerry Oakes
. Advantages
.
Disadvantages
.
Definition
.
Presentation
.
NaturalHistory
.
Radiologicaland NeurologicalEvaluation
Lipomas that occur in the lumbosacral portion of the spine
are congenital disorders that are usually associated with an
infant that is neurologically normal at birth and then gradu-
ally loses function over time. Inthe last 2 decades our un-
derstanding of the progressive natural history of the disor-
der combined
with advances
in minimally traumatic
removal of the fatty mass by ultrasonic aspiration has made
resection of these lesions a reasonable option. Gone are the
days of benign neglect for these lesions, where patients are
just followed and their neurological losses simply docu-
mented and attributed to their inevitable loss of function
that cannot be prevented.
.
Advantages
. Enables prevention of irreparable progression of dys-
function
.
Disadvantages
. Potentialforcerebrospinalfluidleakor pseudomeningo-
cele
. Potentialfornerverootinjury
.
Definition
Lumbosacral lipomas are congenital malformations of the
distal spinal cord where there has been a failure of disjunc-
tion of the neural tube from the epithelial surface. Mesoder-
mal elements destined to become adipocytes occupy the
666
.
SurgicalTechnique
Positioning
Incisionand Dissection
.
Complications
Postoperative
.
Conclusion
space between these embryological tissues and impedethe
development of dura and closure of the laminaeandlum-
bosacral fascia. The mesodermal elements mature intofat
that connects the subcutaneous space to the distal spinal
cord. The neck of the lipoma passes through the dura,bone,
and fascia and may exit the spinal canal primarilydorsally
or caudally. Alternatively some lesions bridge the gap
between these two and are transitional. havingbothcaudal
and dorsal aspects.
Other aspects of occult spinal dysraphism may alsoac-
companythe lipomawith elements of a thickenedfilum
terminale and terminal syrinx being commonly associated.
Because of their frequent association it is important that
they be sought at the time of operative exploration and,if
present, treated.
It is also of some interest
that
mothers who have
given
birth
to
a child
with
a
lumbosacral lipoma
(lipomyelomeningocele) have approximately the samerisk
as mothers of myelomeningocele or encephalocele infants
to have a second child affected by a neural tube defect
(3.5-5%). This means it is common within a spina bifida
clinic population to have multiple families with morethan
one child affected either by an open neural tube defector
the skin covered more "occult" expression of improper
neural tube formation (e.g.,lipomyelomeningocele).Thein-
fluence of folic acid in diminishing the occurrence ofopen
neural tube defects iswell established. What influencefolic
acid supplementation will have on subsequent pregnancies
in the occult spina bifida population at risk is still not
known with certainty.
Aunique subset of patients with asymmetric fattytumors
of the distal cord usually associated with anorectal atresia
or cloacal exstrophy is the cystolipomyelomeningocele.This
unusual lesion is a caudallipomyelomeningocele
usually
combined with a sizable terminal syrinx. These are particu-
larly difficult lesions to deal with operatively and appearto

93
Resection of Lumbosacral Lipomas
667
havea higher likelihoodof retethering because of the
caudalexit of the lipoma and the infiltration of the dura by
fatmakingthe dural closure problematic.
.
Presentation
Thevastmajorityof infants with a lipomyelomeningocelewill
have a detectable midline lumbosacral mass at birth (Fig.
93-1).Ifa paramedian cleft ispresent they are more likelyto
fallinto the category of cystolipomyelomeningocele with a
largeterminal syrinx(Fig.93-2). Theskin overthese lesionsis
intact.although hemangiomas are frequently associated. The
upperaspectofthe gluteal crease maybe deviated laterallyby
thesubcutaneous aspect of the lipomas.Attimes the lipomas
maybe subtle but if looked for will very likelybe visible and
palpable(Fig.93-3). More than half of patients will present
forinitialevaluationbecause ofthe subcutaneous mass or one
ofthe other associated skin changes.Thedifferentialdiagnosis
ofthese masses includes skin-coveredmyelomeningoceleand
sacrococcygealteratomas.
Thesecond most likely method of presentation in child-
hoodisa disturbance of bladder control or incomplete blad-
deremptying with resultant infection. This may be primary
orsecondary. Bowelincontinence will not precede changes
in the bladder. If the neurogenic bladder is severe, rectal
laxityand incontinence may then follow.
Figure 93-1
Aclinical photograph
of a child with a typical midline
subcutaneous mass from a lipomyelomeningocele.
Note the deviation
ofthe upper aspect of the gluteal cleft to the right and the capillary
hemangioma over the lipoma.
Orthopedic presentations
include foot and leg length
discrepancy and asymmetrical plantar arches. The problem
may be as subtle as an increased web space implying weak-
ness in the S2innervated small muscles of the foot. Scoliosis
as a primary presentation is unusual without some other ac-
companying complaint.
Although uncommon in childhood, in adults pain is by far
the commonest presenting symptom. The discomfort may
be in the back or legsbut isgenerally nondermatomal in dis-
tribution. Lateralization to one leg is typical. Byfar,the least
likely method of presentation is with a neurological deficit.
Figure 93-2
Similarlumbosacral mass but the center isdisplaced
slightlyto the right ofthe midlinewith a skincleft (arrow)represent-
ing the extension of the terminal syrinxto just under the dermis. A
thick velvetyhemangioma that ispartiallyinvoluted ispresent inthe
midline.
---
....-.
Figure 93-3
More subtle subcutaneous mass in a child with an
advanced neurogenicbladder.

668
Lumbar and Lumbosacral Spine: Posterior Approach
either motor or sensory. Weakness or sensory loss may be
present but generally will not be the cause of presentation.
.
NaturalHistory
Nodetailed natural history study of a significant consecu-
tive group of lumbosacral lipoma patients has ever been
performed. Norandomized trial of surgery and conservative
care has been performed. With time. however. many sur-
geons working in this area have come to the conclusion that
lipomyelomeningoceles almost inevitably have progressive
loss of neurological function. However. Kulkarni et al have
recently concluded that. although a definitive randomized
study is required to clarify the relative efficacy of early
surgery in these patients. the incidences and patterns of
neurological deterioration seemed to be very similar. re-
gardless of whether early surgery was performed. The time
course for the loss of neurological function may be years to
decades in patients with this pathology. Infrequently. pa-
tients may escape symptoms in childhood and adolescence
and present for their primary assessment as an adult. At the
other end of the spectrum. I have seen a neonate that had
normal strength in the toes and ankle at birth and by 6
weeks of age had lost all motion below the knee. Surgically.
untethering the lesion did not restore any of the lost motor
function. That type of rapid progression early in life is un-
usual. Although a neurological deficit at birth is possible.
the vast majority of neonates are normal at birth. including
A
having normal urodynamics studies. The more typicaltime
course is the painless loss of function within the first few
years of life.
On rare occasions the loss of function may be acute and
secondary to vigorous physical activity or a rough ride ina
vehicle. For the adult female. pregnancy or simply being
placed in the lithotomy position may be a precipitating
event. The majority of patients. however. have the gradual
loss of function that may go unnoticed or simplydeniedun-
til it is severe and life is altered.
.
Radiological and Neurological
Evaluation
Routine radiographs will document bony segmentation errors.
scoliosis. and the levels and extent of bony spina bifida.The
usual method of diagnostic
imaging today is magnetic reso-
nance imaging (MRI).This will show the critical relationship of
the lipoma to the spinal cord (Fig. 93-4). Any degree of rota-
tion in the axial projection can readily be appreciated. as well
as the presence and extent of an associated syrinx (Fig.93-5).
I personally have not found any utility for computed tomo-
graphic (Cf) myelography in the past several years.
In addition to imaging studies to define the anatomy ofthe
lesion. a detailed
assessment
of the patient's
neurological
status is appropriate
in addition
to urodynamics.
I find this
study quite helpful in predicting
the risk of the procedure
and documenting
the extent of preoperative
injury prior to
B
Figure 93-4
(A)SagittalTl-weighted magnetic resonance imaging
(MRI)of the lumbar spine ina patient with a lipomyelomeningocele.
Note the large fatty mass within the enlarged lumbar subarachnoid
space.(8) AxialTl-weightedMRIof another patientthat demon-
strates the complex interdigitated relationship of the dorsal lipoma
(rightarrow)to the ventralcord(leftarrow).

93
Resection of Lumbosacral Lipomas
669
A
B
Figure 93-5
(A) Sagittal Tl-weighted
magnetic resonance
imaging (MRI)
of the lumbar spine in a patient with a lipomyelomeningocele
and terminal
syrinx (arrow). (8) AxialTl-weighted
MRIof another patient with a portion of
spinal cord centrally within a large lipoma (arrow). The surgeon must appreci-
ate this relationship in planning the resection.
any surgical manipulation. The greater the neurological
compromise to the bladder and legs preoperatively the
greater the risk of the procedure and the less likely is
neurologicalrecovery.
. Surgical Technique
Positioning
knowledge of the pathologicalanatomy to minimize injury to
the surrounding functioningneural tissue.
Incision and Dissection
With the patient positioned, a midline incision is made over
the lipoma and extended both cephalically and caudally to
encompass the entire length of the pathology (Fig. 93-6).
Thepatient is positioned prone and bolsters are placed under
theiliaccrest and chest to allow forfree abdominal excursion.
Urinarydrainage and routine intravenous access are estab-
lished.Corticosteroids are usually given in an effort to mini-
mizethe surgicalinjury to the functioning neural tissue. Ipre-
ferthe patient not be paralyzed during the critical portion of
theprocedure.Although Ido not use them, monitoring ofso-
matosensory evoked responses and a variety of other re-
sponsescan be performed. The reasoning for not monitoring
isthat the goal of the procedure is to release the adhesions
fixatingthe neural elements, debulk the fat sufficientlyto al-
lowforadequate visualization of the points of fixation, and
maintainanatomical integrity of the neural elements. Ifthe
monitoredresponses were diminished or lost before the cord
wasentirely untethered I would still recommend carefully
proceedinguntil the neural elements fell in a relaxed ventral
positionwithin the expanded spinal canal. Stopping short of
thispoint dooms the patient to continued expression of the
naturalhistory.This aggressive approach implies significant
Figure 93-6
Patientpositionand incision

670
Lumbarand Lumbosacral Spine: Posterior Approach
The subcutaneous lipoma has the fat separated from each
skin flap. The lumbodorsal fascia acts as a distinct layer to
developand separate from the subcutaneous lipoma. The fat
lateraland above this level can be removed with impunity to
gain visualization (Fig.93-7). Asone approaches the neck of
the lipoma as it comes through the fascial defect, adhesions
between the fasciaand dural cuff are cut. Careis taken not to
exert excessive tension or torque on the stalk of the lesion at
this point because this would be transmitted directly to the
spinal cord. With the subcutaneous lipoma debulked and
the neck freed, the midline fascia above the neck is opened
to expose the last intact laminal arch and spinous process.
These dorsal bony elements are removed exposing the dural
canal cephalad to the stalk of the lipoma.
The dura is opened in the midline and reflected laterally
to expose the cord (Fig.93-8). Itry at this point to maintain
the plane of the dissection in the subdural or extra-arach-
noidal space. This provides an excellent plane of dissection
and creates a barrier to prevent blood and other material
from contaminating the subarachnoid space.
The point of fusion of the dorsal dura with the neck of
the lipomas is the single most critical aspect of the dissec-
tion (Fig. 93-9). Cutting the dural investment frees the
lipoma from much of its attachment
and fixation. Mil-
limeter by millimeter, first one side then the other, this
dural attachment
is cut. In the cul-de-sac of the sacrum
these dural cuts are joined, completing the dorsal release.
With the freed dura reflected laterally, the central fat is
further
debulked
with
an ultrasonic
aspirator
(Fig.
93-10). This can be performed with quite low settings of
both power and suction. With the spinal cord in view and
the course of the roots visualized on the lateral aspect of
the lipoma-neural
complex, redundant
fat is removed.
Again this is done circumferentially. During this maneu-
Figure 93-7
Oblique drawing of subcutaneous
lipoma.
Planned removal
of the subcutaneous
lipoma is marked with dotted
lines.
Figure 93-8
Intraoperative view showing the lipoma comingfrom
the dural defect. Immediately above the emerging lipoma isanex-
tradural band, which frequently constricts the intradural contents.In
this illustration the band is being sectioned.
ver as well as the dural opening, the sensory roots are in
much more jeopardy then are the more ventral motor
roots. The fat is debulked primarily in a mid-dorsal posi-
tion until the neural tube can be reconstituted. The MRI
wiII predict the symmetry of the fat and degree of rota-
tion of the neural elements. The ultrasonic aspirator isa
great respecter of neural tissue and blood vessels, where
fat globules are readily removed. The pial surface of the
spinal cord is left intact as much as possible. With the fat
removed enough so the neural tissue can be replaced
loosely within the spinal canal the dorsal pia that had
been opened to allow the fat to be removed is reapproxi-
mated with inverted absorbable sutures (Fig. 93-11A,B),
ifthis can be performed without undue tension.Oncethe
fat is debulked and the cord reconstituted,
the filum ter-
minale is separated,
coagulated, and cut. This too may
cause significant relaxation of the neural elements. Fol-
lowing these maneuvers
the reconstituted
neural tube
should be in contact with the ventral dura and totally free
to move.
Issues that complicate this idealistic description include
the degree of fatty infiltration of the dura. If present, it
complicates both the dural closure and the opening. Ifthe
cord is significantly rotated this may expose the ventral

93
Resectionof LumbosacralLipomas
671
A
B
Figure93-9
(A) Point of attack where the dura unites with the neck of the lipoma (arrow). (8) It is this step, where the dura is separated
from the
neckof the lipoma, that neural injury may occur due to adhesion of roots to the undersurface
of the dura.
A
Figure93-10
Dural attachment
freed and reflected
laterally, fat
debulkedwith anultrasonicaspirator.
B
Figure 93-11
(A) Reapproximation
of the neural tube with fine in-
verted suture to maximizethe intact pialsurfaceover the dorsal neural
elements. (8) Cord and dura closed. Ideally there is a significant cere-
brospinalfluid spacebetween these linesof closure.

672
Lumbar and Lumbosacral Spine: Posterior Approach
Figure 93-12
Caudallipomyelomeningocele.
Note how the lipoma and distal neural elements intermingle
making separation more difficultin
comparison to lipomas that exit dorsally.
roots to the trauma of the dural opening (Fig. 93-12). Pre-
vious operation seriously increases the adhesions present
and makes each step much more dangerous with regard
to neurological injury. Afinal compounding variable is the
direction of the exiting lipomas. Ihave described the sim-
pler dorsal lipomyelomeningocele.
The more the exit is
caudal encompassing the sacral roots and having the fatty
stalk exiting the hiatus of the sacral canal the more diffi-
cult the dissection, release of tethering forces, and closure
(Fig. 93-13).
Once the release is accomplished the dura is closed, pri-
marily if the spinal canal is patulous, a split thickness lum-
bodorsal fascial graft is harvested and sewn in place. The
remainder of the soft tissue is closed in the routine fashion.
The patient is nursed flat until the dural closureishealedad-
equately to allow an upright position with the cerebrospinal
fluid(CSF)pressure exerted against the dural closure.
The cystolipomyelomeningocele is a particularlydifficult
variant
because
of the caudal
involvement
of the exiting
roots and dura as previously
described
(Fig. 93-13). Inad-
dition,
if the central
canal of the distal cord significantly
expands
and thins
the cord a myelotomy
should be per-
formed
through
the thinnest
portion
of the cord and the
syrinx
stented
with tubing
or simply
opened to the sub-
arachnoid
space. If the cord is not especially
thin and the
cord expansion
from the syrinx is only moderate, a more
conservative
approach
may be taken
and the syrinx size
followed by MRI.

93
Resectionof lumbosacral lipomas
673
I
\
..;:
A
c
D
B
Figure93-13
(A)Cystolipomyelomeningocelewitha parasagittalskincleft.(8) Cutawayviewto demonstrate the distalcordand lipoma.(C)Axial
cross section at the level marked. Note the fat infiltration of the dorsal cord and terminal syrinx (arrow). (D) Somewhat more caudal axial section.
Thedefinition of the dorsal neural elements is unclear.

674
lumbarandlumbosacral Spine:PosteriorApproach
.
Complications
Postoperative
Followingoperation significant concerns are limited but in-
clude(SFleaksand the development ofa pseudomeningocele.
There is a small risk of operative infection that is increased
by the presence of a superficial infection associated with an
overlying and involuting hemangioma or wound contami-
nation with stool after operation. Postoperative hemorrhage
at the operative site is quite unusual.
Resection of large subcutaneous lipomas may be associ-
ated with the development of a seroma. This is such a pre-
dictable occurrence that if the dural closure is secure the
surgeon might consider the placement of a subcutaneous
drain. Factors that increase the likelihood of a (SF leak in-
clude previous operation and especially fatty infiltration of
the dura. Igenerally keep the patient fIat for 3 to 5 days to
allow the dural closure time to adhere before exerting ortho-
static (SF pressure against it. Ifthe dura is infiltrated with
fat and the closure problematic I might keep the patient
down an additional period of time. Pain control is a major
Suggested
Readings
1.
Byrne RW, Hayes EA, George TM. McLone OG. Operative
resection
of
100 spinal lipomas
in infants
less than
1 year of age. Pediatr
Neuro-
surg 1995;23:182-187
2.
Catala M. Embryogenesis:
why do we need a new explanation
for the
emergence
of
spina
bifida
with
lipomas?
Childs
Nerv
Syst
1997;13:336-340
3.
Kanev
PM. Bierbrauer
KS. Reflections
on
the
natural
history
of
lipomyelomeningocele.
Pediatr Neurosurg
1995;22:137-140
4.
Kanev PM. Lemire RJ, Loeser JO, Berger MS. Management
and long-
term
follow-up
review
of children
with
lipomyelomeningocele.
1952-1987. J Neurosurg
1990;73:48-52
5.
Kulkarni
AV. Pierre-Kahn
A. Zarah M. Conservative
management
of
asymptomatic
spinal
lipomas
of the conus.
Neurosurgery
2004;54:
868-875
concern for all patients. Patient-controlled analgesia has
proven to be very effectiveeven in children as youngas6.
Long-term neurological stability is likely but not univer-
sal. At least 30%of patients will progress despite interven-
tion. The longer patients are followed. the higher isthe like-
lihood of recurrent problems.
. Conclusion
Lipomyelomeningoceles are complex congenital anomalies
that are associated with almost inevitable loss of neurolog-
ical function. This natural history can usually be signifi-
cantly improved by operative intervention. The operation
consists of the removal of fat adjacent to the neural tissues
and disconnection of the neck of the lipoma as it emerges
through the dura. The filum terminale must be inspected
and sectioned if taut or enlarged. Maintenance ofthe pre-
operative
neurological
status postoperatively is likely.
Some improvement. especially in pain relief.commonlyoc-
curs in adults.
6.
laMarca
F, Grant JA. Tomita T, McLone OG. Spinal lipomas in children:
outcome
of 270 procedures.
Pediatr Neurosurg
1997;26:8-16
7.
Pierre-Kahn
A. Zerah M. Renier O. et al. Congenitallumbosacrallipo-
mas. Childs Nerv Syst 1997;13:298-335
8.
Sathi S. Madsen JR. Bauer S. Scott RM. Effect of surgical repair on the
neurourologic
function
in infants with lipomeningocele.
Pediatr Neu-
rosurg 1993;19:256-259
9.
Wu HY, Kogan BA,Baskin LS. et al. Long-term
benefits
of early neuro-
surgery for Iipomyelomeningocele.J
UroI1998;160:511-514

94
Transverse Process Fusion
Steven D.Wray, David S. Jones, and Charles L.Branch, Jr.
. Indications
.
Contraindications
. Advantages
. Disadvantages
. History
.
SurgicalTechnique
Positioning
Incisionand Dissection
. Closure
Intertransverse arthrodesis has been successfully applied
toa variety of indications in the thoracolumbar spine and
priorto the development of interbody fusion techniques
wasthe primary means of achieving fusion of the lumbar
spine.Applicable over a broad range of congenital, degen-
erative,traumatic. and pathological processes of the lum-
bosacralspine. the technique can be used in conjunction
with internal fixation as a means of immobilizing one or
morespinal segments or may be used as an adjunct to in-
terbodyfusion. Fusion rates with intertransverse grafting
depend.among other factors. on selection of graft mater-
ial,use of rigid internal fixation. patient smoking history.
level(s)fused. and general health of the patient. Success-
fulclinicaloutcomes do not always correlate with obtain-
inga solid arthrodesis and vice versa. Results are more fa-
vorable for primary operations
than for repeat salvage
surgery.
. Indications
.
Degenerative disk disease
. Traumatic or iatrogenic
instability
.
Augmentation of anterior fusion
.
Fusion following deformity
correction
.
PostoperativeCare
.
AllograftversusAutograft
.
ToInstrumentor Not
.
Complications
Intraoperative
Postoperative
.
Outcomes
.
Conclusion
.
Contraindications
.
Inadequate autogenous bone source
.
Multiple previous failed posterior fusions
.
Anterior column instability
.
Advantages
. Approach is direct and familiar
.
Fusionand instrumentation via a single approach
. Applicableto a broad range of disorders
. Maybe used in conjunction with instrumentation
.
Disadvantages
.
Extensivemuscle dissection
.
Significant pain and morbidity
.
Possible need for blood transfusion
.
Poor resolution of anterior instability
.
Unableto place grafts under compression
.
Potential for "fusion disease"
.
Potential for adjacent level degeneration
675

676
Lumbar and Lumbosacral Spine: Posterior Approach
. History
Mathieu and Demirleau pioneered intertransverse fusion in
1936 using it as an alternative to dorsal (interlaminar) fu-
sion.J Adkinslater applied the technique to patients with
degenerative spondylolisthesis and pointed out the utility
of intertransverse fusion in patients whose laminar arches
had been removed. thereby precluding dorsal (interlaminar)
fusion.2 Watkins performed intertransverse
fusion via a
paramedian
incision
and
approach
lateral
to
the
paraspinous muscles, preserving the spinous processes and
interspinous ligament.3 His 1953 report detailed the tech-
nique ofaffixing strips of autologous iliac crest to the trans-
verse processes using screws resulting in a 68%incidence of
solid fusion. Modern techniques of rigid spinal immobiliza-
tion have improved the fusion rates and clinical outcomes
with transverse process fusion. and the technique continues
to be a viable means of establishing arthrodesis in the lum-
bosacral spine.4-6
.
SurgicalTechnique
Positioning
Paramount to any procedure on the lumbar spine is proper
patient positioning. Optimal positioning eliminates external
pressure to the abdomen thereby reducing intra-abdominal
and consequently venous pressure. This results in less intra-
operative blood loss and is particularly important when
working around or lateral to the facet complexes around
which exists a network of large anastamotic segmental ves-
sels7(Figs.94- t and 94-2).
The intubated patient is placed prone on chest rolls or
any of a variety of commercially available spinal surgery
frames with all pressure points adequately padded and
Anterior
transverse artery
Intertransverse artery
Communicating
artery
special care given to the spiral groove (ulnar nerve) and
eyes. Abduction of the arm should be limited to 80 degrees
or less to avoid stretch injury to the brachial plexus.Pneu-
matic compression devices are applied to the lower ex-
tremities to prevent the development of a deep venous
thrombosis in the anesthetized patient. Bladdercatheteri-
zation is used routinely in most lumbar spinal fusionoper-
ations and should be considered for lengthy proceduresor
in cases where anticipated blood loss is significant.Prophy-
lactic broad-spectrum antibiotics are administered priorto
skin incision and with extensive exposure or instrumented
fusion are continued for 24 hours postoperatively.
Incision and Dissection
A dorsal midline skin incision is made following the injection
of epinephrine-containing
local anesthetic.
The subcuta-
neous tissue is dissected sharply or with monopolar electro-
cautery until the deep dorsal fascia is encountered. The fascia
is incised bilaterally
immediately
adjacent
to the spinous
process. preserving
the supraspinous
ligament. which pro-
vides a midline anchor for the fascia during wound closure.
The fascial incision may be extended
beyond the skin inci-
sion to facilitate better retraction
and improve exposure. The
paraspinal muscles are dissected off of the spinous processes
and lamina in a subperiosteal
fashion using monopolar elec-
trocautery
or a second periosteal
elevator. Once the muscle
dissection is completed bilaterally to the facets. self-retaining
retractors are placed to maintain the exposure.
Intraoperative
lateral radiographs
should be obtained to
verify the correct spinal segment
because anatomical land-
marks may be unreliable
in determining
the fusion levelin
posterolateral
lumbar
fusion.s Once the levels to be fused
havebeen identified.the subperiostealdissectionisperformed
lateral and ventral to the facet joints. exposing the dorsal sur-
face of the transverse
process. The terminal branches of the
segmental
vessels constitute
a rich anastamotic
network
Interarticular artery
Superior articular artery
Inferior articular artery
Figure 94-1
Anteroposterior
and lateral view demonstrating
the vascular anatomy around
the facet complexes and trans-
verse processes.

94
TransverseProcess Fusion
677
A
.
Communicating artery
ntenor
transverse artery
--
Intertransverse
artery
\
})~
locatedabove,below,and lateral to the facetjoints7(Figs.
94-1 and 94-2). These vessels should be identified early
andcoagulatedto prevent excessive blood loss. Coagulation
shouldbe performed using bipolar electrocautery to pre-
vent the transmission of thermal energy to the exiting
neuralelements in the intervertebral foramen. The pedicle
is identified ventral to the junction
of the transverse
processand superior articular process of the facet complex
anddemarcates the rostral extent of the intervertebral fora-
menbelow.
Meticulousremoval of soft tissue and coagulation debris
overthe extent of the transverse process should be per-
formedas well as decortication of the dorsal aspect of the
transverseprocess.This provides an optimal grafting surface
andcanbe performed using a combination of periosteal dis-
sectors,osteotomes, and rongeurs. Removalof the facet cap-
sularligamentsand intrafacet synovium with decortication
ofthedorsalfacet surface provides additional graft-host in-
terface.Careshould be taken not to fracture the transverse
process during dissection and decortication.
Dissection
shouldnot extend deep to the dorsal aspect of the trans-
verse process to avoid injury to the anterior transverse
arteryand exiting nerve root. The intertransverse ligaments
andmusclesserve as the ventral extent of safe dissection to
avoidinjuryto the spinal nerve root. Oncethe fusion surface
has been prepared, liberal amounts of corticocancellous
bone graft are placed over the decorticated
transverse
processesand bridging the intertransverse space (Fig.94-3).
Graftmaterial can consist of either corticocancellous bone
stripsor morcellized bone carefully packed onto the facets
Superior
articular artery
Figure 94-2
Anteroposterior
and
lateral view demonstrating
the vas-
cular anatomy around the facet com-
plexes and transverse processes.
Figure 94-3
Rightsidedemonstrates the prepared fusionbed with
decorticated transverse processes.Leftsidedemonstrates morcellized
bone graft inplace.

678
Lumbar and Lumbosacral Spine: Posterior Approach
.
AllograftversusAutograft
Figure 94-4
Lateral view of fusion mass consisting of morcellized graft.
and transverse processes beneath the overlying muscle (Fig.
94-4). Atarget volume of bone graft for each side of a single
intertransverse space should be 40 to 60 mL. Hemostasis
should be achieved prior to graft placement to prevent graft
migration. The use of bone wax is discouraged because it
impairs fusion. Internal fixation can then be performed over
the fused segments
using transpedicular
screws and
plates/rods or another fixation device.
. Closure
The wound is copiously irrigated with antibiotic solution,
and meticulous
closure
is performed
in layers. Care
should be taken to restore anatomical relationships and
eliminate dead space. A subcutaneous
tunneled suction
drain is left in place to prevent the accumulation of blood
products that could cause migration of the graft material.
The drain is left in place for 24 to 48 hours or until output
is minimal.
.
PostoperativeCare
Prophylacticantibiotics and bladder catheterization are dis-
continued on the first postoperative day, and early ambula-
tion in an external orthosis such as a corset or custom-fitted
rigid thoracolumbosacral orthosis is encouraged by the sec-
ond postoperative day.
Postoperative radiographs obtained in the recovery room
verify the integrity of the construct and serve as a baseline
for evaluating evolving spinal deformity. Plain film evalua-
tion is repeated with the patient upright in an orthosis to
again verify the integrity of the construct and ensure that
no kyphosis has occurred. Radiographs are repeated at 3
and 9 months postoperatively
and at regular intervals
thereafter until fusion has been established.
In addition
to meticulous
preparation
of the fusion surface,
careful
consideration
should be given to the selection of
graft material.
Autologous corticocancellous
bone from the
iliac crest can supply biologically
active graft but procure-
ment may result in donor site pain, blood loss, infection, or
other complications.12-14 Allograft banked bone may retain
some osteoinductive
and osteoconductive
properties but
has the added disadvantage
of being subject to immunolog-
ical responses
from the host. The biological properties of
the graft affect the eventual
development
of a solid fusion.
Some recent
reports
have demonstrated
a significantly
higher pseudarthrosis
rate in patients
receiving noninstru-
mented allograft fusion versus those receiving autograft.15.16
Jorgenson
et al conducted
a prospective analysis comparing
autograft
and allograft
in the same patient. Allograft was
placed over the intertransverse
space on one side and auto-
graft on the other. After 1 year, significantly lower rates of
arthrodesis
were achieved
in the allograft side when com-
pared with the autograft (p < 0.05).15The potential foran in-
creased rate of pseudarthrosis
using allograft must be care-
fully weighed
against the potential
for increased morbidity
related to autograft procurement.
The use of locally harvested
bone from the lamina and medial facets provides autograft
without the morbidity
of harvest at a distant site but maybe
inferior to uniform cancellous marrow from the iliaccrest.
.
ToInstrument or Not
The lumbar spine, because of its relative high degree of mo-
bility, presents an inherently unfavorable environmentfor
the development of a solid fusion. Despite this, intertrans-
verse grafting without instrumentation results in successful
fusion rates ranging from 46 to 100%.4-6.16.17
Rigidinternal
fixation using a pedicle screw rod/plate system has been
shownin biomechanicalstudies to significantlylimitmo-
tion over the instrumented segments but conflictingdata,
summarized in Table 94-1, exist in the literature as to
whether this results in a higher fusion rate.4.6.17-19
Schwab and colleagues
reported
a 91% fusion rate
among patients stabilized with an Edwards's instrumenta-
tion construct
versus a 65% fusion rate in noninstru-
mented patients.17 Zdeblick presented
prospective ran-
domized patient
data also demonstrating
significantly
higher fusion rates and better clinical outcomes in patients
treated with rigid or semirigid fixation compared with
Table 94-1
Fusion Rates with and without Internal Fixation
Series
Noninstrumented
Fusion Rate (%)
Instrumented
Fusion Rate (%)
Zdeblick
19934
Schwab et al199517
Bernhardt et al19916
65
65
78
77-95"
91
74
a71%fusion
rate using semirigid
pedicle
screw/plate
system and
95%with rigid pedicle screw/rod construct.

94
TransverseProcessFusion
679
noninstrumented fusion.4 Conversely, Bernhardt
et al
foundnosignificantdifferencein the fusion rates among
47patientsundergoing posterolateral fusion with or with-
outthe use of a variable spinal plating system.6 France et
alrecentlyreported prospective randomized data showing
nostatistical difference in patient-reported
outcome in
patientsundergoing posterolateral fusion with and with-
outpediclescrew instrumentation
despite a statistically
nonsignificantrend toward higher fusion rates in instru-
mented patients. IS
A higher rate of leg dysesthesias
has been reported
in
patientsreceiving internal fixation, and up to 15%of instru-
mentation systems have been removed
secondary
to so-
calledhardware-related
pain.6 Although debate exists as to
theuse of internal fixation in a primary operation,
most au-
thorsadvocate the use of internal
fixation in patients
with
severedegenerative disease,
patients
who require correc-
tionofan existing deformity, or repeat operations
for failed
fusion.4
Intertransverse fusion differs from anterior
cervical and
lumbarinterbody fusion in that axial compressive
forces are
notexerted upon the graft. Graft compression
is thought
to
promote fusion. Although
there
is no way to apply axial
compressionto intertransverse
grafts, the addition
of inter-
nalfixationmay enhance fusion by providing rigid immobi-
lization.
. Complications
Intraoperative
Intraoperative blood loss can be greatly reduced
if proper
patientpositioning is employed. Familiarity with segmental
vascularanatomy and early identification
and coagulation
ofanastomotic vessels are essential. Autologous repletion of
bloodproducts using a cell-saver can reduce transfusion
re-
quirementsand spare the patient the potential
infectious or
transfusion-reaction complications
associated
with banked
donor blood.
Compressionand traction injuries are avoided by care-
fulattentionto padding all pressure points, including the
knees,anterior superior iliac spines, elbows, feet, and
face.Particular attention
should be paid to the spiral
grooveofthe humerus wherein lies the ulnar nerve. The
eyeshouldbecarefullyexaminedoncein the prone posi-
tiontoensurethere is no compression. Limitingabduc-
tionofthearmsto 80 degrees or less can reduce brachial
plexusstretch injury.
Postoperative
Atroublingsyndrome of postoperative pain is felt to result
from excessive retraction
or devascularization
of the
paraspinalmuscles during lengthy fusion operations. This
has been referred to as "fusion disease." The periodic
releaseofself-retaining retractors should be performed to
avoidsofttissuecompression injury and ischemia.
The incidence of postoperative
wound infections in-
creaseswith the complexity of the procedure and ranges
from 1%for simple diskectomy, to 1 to 5%and 3.8 to 9.7%
for noninstrumented
and instrumented
fusions, respec-
tively.2o-23Preoperative factors associated
with an in-
creased incidence of infection include advanced age, pro-
longed
hospital
bed rest, diabetes
mellitus,
obesity,
immunosuppressed
state, infection at a distant site, cere-
bral palsy, and myelodysplasia.22,23Operative factors in-
creasing the likelihood of infection include
procedure
length exceeding 5 hours, high volume of personnel traffic
through the operating room, the use of internal fixation,
wound
hematoma,
and
extension
of fusion
to
the
sacrum.22,23
Prophylactic broad-spectrum antibiotic therapy should
be universally employed in spinal fusion operations.2o-22
Superficial wound infections are most often caused by
Staphylococcus aureus and, in some cases, can be managed
with parenteral antibiotics alone. Deep wound infections
should be treated early with a minimum of 6 weeks of
parenteral antibiotic therapy followed by a course of oral
antimicrobial
therapy tailored to culture results when
available. Surgical irrigation and debridement may be nec-
essary, as may the use of a suction-irrigation
system. In
most cases of deep spinal wound infection, the hardware
can be left in place, although it may harbor indolent infec-
tion for years. Consideration should be given to removing
the hardware
following the establishment
of a solid
arthrodesis.
The prevention of a deep venous thrombosis begins pre-
operatively and continues until the patient is discharged
from the hospital. Patients who have been nonambulatory
because of low back pain before surgery should undergo
preoperative Doppler evaluation of the lower extremities
to rule out a venous thrombosis. Segmental pneumatic
compression devices are placed on the patient prior to in-
duction of anesthesia and are maintained until the patient
becomes ambulatory. In the event of a deep venous throm-
bosis during
the perioperative
period,
consideration
should be given to a vena cava filter to prevent throm-
boembolic phenomena while avoiding the bleeding com-
plication of anticoagulation therapy in the postoperative
period.
Apseudarthrosis should be suspected clinically in a pa-
tient with pain persisting beyond the early postoperative
period. It is identified radiographically by the absence of fu-
sion mass on static views or computed tomography as well
as
the
presence
of motion
on
dynamic
views.
A
pseudarthrosis, once identified, may require subsequent
surgery with internal fixation. A stable arthrodesis
is
demonstrated radiographically by the presence of bridging
trabecular bone over the intertransverse
space and by the
absence of motion on dynamic views of the spine. It should
be noted that radiographic evaluation of fusion does not al-
ways correlate with intraoperative findings in a subsequent
"second look"surgery.9-n
With a solid arthrodesis comes the potential for acceler-
ated adjacent-segment degenerative change and increased
motion secondary to the added biomechanical stress placed
on the joints above and below the fusion.24The incidence of
adjacent-level degenerative problems following fusion with
instrumentation is particularly prevalent in postmenopausal
women.25

680
LumbarandLumbosacralSpine:PosteriorApproach
.
Outcomes
Althoughfusionrates forintertransverse fusionrange from 46
to 100%,4-6.16.17
this does not always correlate with a patient's
clinicaloutcome.Dawsonet al reported a 92%fusion rate us-
ingautogenous iliaccrest intertransverse lumbar arthrodesis
but only a 70 to 80%economic and functional success rate.s
When internal fixation is used, the clinical outcome more
closelycorrelateswith the development of solid fusionY This
mayrelateto the factthat pedicle screw internal fixation pro-
vides biomechanical stability to the anterior and middle
columnsevenafter posterolateral fusion isachieved.19
Preoperativediagnosis affects outcome in patients treated
with intertransverse fusion. Patients with severe degenera-
tivespondylolisthesis or degenerative disk disease fare more
poorlythan those operated upon for isthmic spondylolisthe-
sis.4Ahistory of previous backsurgery lowers clinicalsuccess
rates independent of whether or not a solid arthrodesis is
achieved.4.sSuccessful lumbosacral arthrodesis is more reli-
ablyachieved at the LS-Sllevel than fusions extending to or
above L4.sThis also holds true for the clinical success rates.s
References
1.
Mathieu
P, Demirleau
P.Trautement
chirugical
du spondylolisthesis
douloureaux.
Rev Orthop
1936;23:352
2.
Adkins EWD. Lumbosacral
arthrodesis
after laminectomy.
J Bone Joint
Surg Br 1955;37:208-233
3.
Watkins
MB. Posterolateral
fusion
of the lumbar
and lumbosacral
spine.J Bone Joint Surg Am 1953:35:1014-1018
4.
Zdeblick TA. A prospective
randomized
study of lumbar
fusion. Spine
1993;18:983-991
5.
Dawson
EG, Lotysch
M. Urist
MR. Intertransverse
process
lumbar
arthrodesis
with
autogenous
bone
graft.
Clin Orthop
Relat
Res
1981 ;154:90-96
6.
Bernhardt
M. Swartz DE. Clothiaux
PL. Crowell RR.White M III. Pos-
terolaterallumbar
and lumbosacral
fusion with and without
pedicle
screw internal fixation. Clin Orthop
1992:284:109-115
7.
MacNab I, Dall D. The blood supply of the lumbar
spine and its appli-
cation to the technique
of intertransverse
lumbar
fusion. J Bone Joint
Surg Br 1971:53:628-638
8.
Ebraheim
NA, Inzerillo
C. Xu R. Are anatomic
landmarks
reliable
in
the determination
of fusion
level in posterolateral
lumbar
fusion?
Spine 1999:24:973-974
9.
Blumenthal SL.Gill K.Can lumbar
spine radiographs
accurately
deter-
mine fusion in postoperative
patients?
Correlation
of routine
ra-
diographs
with
a surgical
second
look
at
lumbar
fusion.
Spine
1993;18:1186-1189
10.
Brodsky AE.Kovalsky ES, Khalil MA. Correlation
of radiologic
assess-
ment
of lumbar
spine
fusions
with
surgical
exploration.
Spine
1986;11 :1942-1943
11.
Kant AP.Daum WJ. Dean MS. Evaluation
of lumbar
spine fusion: plain
radiographs
versus direct surgical exploration
and observation.
Spine
1995;20:2313-2317
12.
Kurz LT.Garfin SR, Booth RE. Harvesting
autogenous
iliac crest bone
grafts:
a
review
of
complications
and
techniques.
Spine
1989: 14:1324-1331
13.
Summers
BN. Eisenstein
SM. Donor site pain from the ileum:
a com-
plication
of lumbar spine fusion. J Bone Joint Surg Br 1989;71 :677-680
The presence of systemic nicotine has been shown in ani-
mal models to adversely affect fusion rates and, when fu-
sion does occur, it consists of biomechanically inferior
bone.26This evidence is substantiated clinically by a lower
fusion rate among smokers.4
Although beyond the scope of this technical chapter, cer-
tain secondary gain, compensation. or psychological issues
may affect patient outcomes after spinal fusion.
.
Conclusion
Transverse process fusion remains a viable means of achiev-
ing arthrodesis in the thoracic and lumbosacral spine. The
use of rigid instrumentation
systems has improved fusion
rates and expanded the indications for transverse process
fusion to include spinal deformity correction and severede-
generative pathology. A thorough knowledge of regional
anatomy and attention to complication avoidance can mini-
mize patient morbidity with the procedure.
14.
Younger EM, Chapman
MW. Morbidity
at bone graft donor sites.J Or-
thop Trauma 1989:3:192-195
15.
Jorgenson
SS. Lowe TG. France J, Sabin J. A prospective
analysis of au-
tograft
versus
allograft
in posterolateral
lumbar
fusion in the same
patient:
a minimum
of 1-year
follow-up
in 144 patients.
Spine
1994:19:2048-2053
16.
Nugent
PJ. Dawson
EG. Intertransverse
process
lumbar
arthrodesis
with allogenic
fresh-fozen
bone graft. Clin Orthop
1993;287:107-111
17.
Schwab FJ. Nazaarian
DG. Mahmud
F. Michelsen
CB.Effects of spinal
instrumentation
on
fusion
of
the
lumbosacral
spine.
Spine
1995;20:2023-2028
18.
France JC. et al. A randomized
prospective
study
of posterolateral
lumbar
fusion. Outcomes
with and without
pedicle screw instrumen-
tation. Spine 1999;24:553-560
19.
Kotani Y.et al. The role of spinal instrumentation
in augmenting
lum-
bar posterolateral
fusion. Spine 1996:21 :278-287
20.
Horwitz
NH, CurtinJA.
Prophylactic
antibiotics
and wound infections
following
laminectomy
for
lumbar
disk
herniation.
J Neurosurg
1975;43:727-731
21.
Levi AD. Dickman
CA. Sonntag
VKH. Management
of postopera-
tive infections
after
spinal
instrumentation.
J Neurosurg
1997:86:
975-980
22.
Massie JB. Heller JG. Abitbol JJ. McPherson
D. Garfin SR. Postoperative
posterior
spinal wound
infections.
Clin Orthop
1992:284
23.
Perry JW. Montgomerie
JZ, Swank S, Gilmore
DS. Maeder K.Wound
infections
following
spinal fusion with posterior
segmental
spinal in-
strumentation.
Clin Infect Dis 1997;24:558-561
24.
Eck JC. Humphreys
SC. Hodges SD. Adjacent-segment
degeneration
after lumbar
fusion:
a review
of clinical,
biomechanical.
and radio-
logic studies. AmJ Orthop
1999;28:336-340
25.
Etebar S. Cahill DW. Risk factors for adjacent-segment
failure follow-
ing lumbar
fixation
with
rigid instrumentation
for degenerative
in-
stability.J
Neurosurg
Spine 1999:90:163-169

-
95
Posterior Lumbar Interbody Fusion
andTranspedicular Screw Fixation
DavidS.Jones, Steven D.Wray, and Charles L.Branch, Jr.
. Indications
.
Contraindications
.
Advantages
.
Disadvantages
.
Historyand Development
.
Indications and Treatment
Options
. Advantagesof PLiF and Transpedicular
Screw
Fixation
.
BasicTechniques
Noninstrumented Allograft/Autograft
PLiF
Threaded Fusion Cage PLiF
Despitean increasein its popularityoverthe past decade,
theroleofspinal fusion in the management of degenera-
tiveconditions of the lumbar spine remains somewhat
controversial.Improvements in diagnostic imaging, fusion
techniques.and spinal instrumentation
systems and accu-
mulatingevidence regarding the safety and efficacy of fu-
sionprocedures contribute to a more widespread belief
that,in selected patients, fusion may be superior to non-
surgicaltherapy or decompression alone. Posterior. pos-
terolateral,and interbody fusions have been used success-
fullyeither alone or in combination. There has been a
recent resurgence of interest in posterior lumbar inter-
bodyfusion(PLlF)as a biomechanicallyand possiblyclini-
callysuperior fusion technique. Applicable to a variety of
degenerative, traumatic, and congenital conditions, PLIF
combinesthe traditional posterior approach to diskectomy
andneural decompression with an interbody fusion. PLIF
offersadvantages such as total diskectomy, neural decom-
pression, restoration
of disk space
height,
and solid
mechanicalarthrodesis. The addition of segmental instru-
mentationusing a pedicle screw and rod or plate construct
Carbon Fiber Rectangular Cage PLiF
Impacted Allograft/Autograft
PLiF
.
Surgical Technique
Anesthesia and Positioning
Incision and Dissection
Transpedicular Screw Fixation
Closure
.
Postoperative Care
.
Complications
. Results
.
Conclusions
as an adjunct to PLIFmay afford immediate stability and
enhance fusion rates.
.
Indications
.
Segmental instability
.
Treatment of lower back pain
.
Recurrent disk herniation
.
Failedback surgery syndrome
.
Symptomatic spinal stenosis
.
Degenerative disk disease
.
Contraindications
.
Significantperineural fibrosis (relative)
.
Arachnoiditis
.
Activeinfection
.
Lessthan 3-month life expectancy
681

682
Lumbarand Lumbosacral Spine: Posterior Approach
.
Indications and Treatment Options
.
Advantages
. Decompression while preserving
posterior
support
structures
.
Adequate blood supply to graft
.
Excellentvisualization of nerve root
.
Restorationof interbody distance
.
Applicableto a wide variety of conditions
.
Allowsfor neural decompression
.
Maintains posterior support structures
.
Containsa load-bearing graft
.
Possible for 360 degree fusion through a single incision
.
Disadvantages
. Riskof posterior extrusion of graft
1. Need for extensive posterior decompression
2. Riskof instability in the setting of pseudarthrosis
3. Risk of retraction injury of the nerve roots causing
endoneural fibrosis and chronic radiculopathy
4. Destabilization ofthe anterior column (radical diskec-
tomy) and posterior column (wide decompression)
requiring the addition of instrumentation
.
HistoryandDevelopment
Clowarddevelopedthe technique of PLIF using iliac crest
grafts after diskectomy in 1943. He presented his early re-
sults at various meetings between 1945 and 1951 and then
published his technique and results in 1953.1In a series of
321 patients, he reported limited complications and satis-
factoryresultsin "over85 per cent."ThePLIFconceptwas
met with little enthusiasm initially, presumably due to the
technical difficulty and the inability to duplicate clinical
outcomes and fusion rates. However, many authors have
sincedescribedvariousmodificationsto the PLIFtechnique,
including use of autologous iliac crest bone grafts, allograft
bone, dowel-shaped grafts, keystone grafts, tricortical
grafts, bone chips, metallic implants, carbon fiber implants,
and threaded cages.2-6
Steffee and SitkowskF reported pedicle screw and plate
fixationas an adjunct to PLIFin 1988.Some authors be-
lieved that immediate internal stabilization was an advan-
tage over PLIFalone. Variations in fixation devices have
since been developed. Threaded cages and metallic im-
plants that could be packed with cancellous bone graft
were developed to permit the performance of an "instru-
mented" PLIFwithout the need for additional posterior
segmental fixation or intertransverse fusion.6 Those who
developed this technique felt that a standardized interbody
support
could prevent
or diminish graft settling
and
retropulsion.
Improvements in surgical technique and instrumentation
and a better understanding of the theoretical advantagesof
PLIFhave greatly expanded the successful applications of
the procedure. Spinal fusions may be indicated when seg-
mental instability causes clinical symptoms. With the ex-
ception of obvious instability seen on dynamic radiographs,
the concept of what determines segmental instabilityisde-
bated, particularly as it relates to degenerative conditionsof
the spine. Kirkaldy-Willis and Farfan8proposed that pro-
gressive degenerative changes in the spine lead to a lossof
normal integrity of the functional spinal unit. Frymoyeret
al9defined segmental instability as a "loss of motion stiff-
ness such that force application to that motion segment
produces greater displacement than would be seen in a
normal structure, resulting in a painful condition and the
potential for progressive deformity." In practice, the deter-
mination of instability has rested on the interpretation ofa
variety of radiographic examinations. Greater than 4 mmof
translation or > 10 degrees of angular motion betweenad-
jacent end plates on lateral flexion and extension ra-
diographs is generally accepted as indicative ofinstability.1O
Cloward's global indication for PLIFwas "the treatmentof
low back pain with or without sciatica due to lumbardisk
disease."1 Others have attempted to refine the indications
for PLIFand have created lengthy lists of more specificcon-
ditions, but none have significantly narrowed the scopeof
Cloward's indications. Included in the list of indicationsfor
PLIFare spondylolisthesis, recurrent disk herniation, failed
back surgery syndrome, bilateral or massive midline disk
herniation, segmental instability, symptomatic spinalsteno-
sis,degenerativediskdiseasewith posturallyrelatedback
pain, and disk herniation in one with a very physicaloccu-
pation.4.11.12
It is very difficult to develop a scientifically derivedsetof
indications for PLIEIndeed, much of the controversy sur-
rounding spinal fusion is based on the difficulty of selecting
which patients would benefit from simple decompression
or diskectomy alone and which patients require fusion.Sev-
erallarge series have been reported that provide an analysis
of outcome for specific indications. However, differencesin
technique, differences in outcome, and a relatively vague
account of the clinical decision to perform PLIFas opposed
to a decompressive procedure or an alternative fusiontech-
nique make it difficult to apply this information to the de-
velopmentofa listofspecificindicationsforwhichPLIFwill
undoubtedly be the optimal procedure.
. Advantages
of
PLiF
and
Transpedicular
Screw Fixation
PLIF allows for decompression
of the neural elements
through a standard posterior approach while preserving
posterior support structures such as the spinous processes,
interspinous ligaments, and supraspinous ligaments. The
neural
elements
are decompressed
through
bilateral

95
Interbody FusionandTranspedicularScrewFixation
683
laminotomies and medial facetectomies, and interbody
fusionisachievedafter near-total diskectomy.
The theoretical advantages of PLiF as described by
Cautilli13include: (1) a wider area of bone surface is in-
volved,(2) there is adequate blood supply to the graft
throughthe cancellous portion of the vertebral body once
thecorticalend plate has been perforated or removed, (3)
thefusionis proximate to the centers of motion and com-
pressionforces, (4) there is complete visualization of the
areaofnerve root compression, and (5) the interbody dis-
tanceis preserved or restored so that there is no further
diskspacecollapse or possible lateral stenosis as a sequela
ofdiskexcision. The interbody graft maintains disk space
height and the normal anatomical configuration of the
neuralelements and the motion segment.11-14Evans15pro-
posesadditional advantages such as: (1) the posterolateral
locationofload-bearing grafts is the optimal position in re-
lationto the load-bearing capacity of the vertebral bodies,
(2)posteriordistraction is enhanced by maintaining the an-
terioranulus and ligament, and (3) when adequate soft-
tissue connections are maintained
between
posterior
processes,or when they are supplemented with instrumen-
tation,the graft is stable enough for early weight-bearing.
Lin5.14
states that the greatest advantage of PLiFis that "it
dynamicallydecompresses the neural structures by holding
theadjoining vertebral bodies apart and then fusing them
into a single motion segment." He adds that near-total
diskectomyprevents recurrent disk herniation and that ar-
rest of motion by fusion prevents further disk space col-
lapseand degenerative changes.
Posterior lumbar interbody fusion may also have disad-
vantages.tOThese include: (1) need for a wide, potentially
destabilizingposterior decompression, (2) risk of posterior
extrusion of the graft, (3) risk of retraction injury of the
nerveroots causing endoneural fibrosis and chronic radicu-
lopathy,and (4) destabilization ofthe anterior column (rad-
icaldiskectomy) and posterior column (wide decompres-
sion)requiringthe addition of instrumentation.
Theadditionoftranspedicularfixationto the PLiFproce-
durehas been advocated by some authors as an advantage
overpreviously described techniques, especially after the
removalor disruption of the posterior elements3.12,15and
whenmultiple levels are fused. Segmental internal fixation
augments correction of deformity and restoration of the
posteriortension band. In biomechanical studies, segmental
internalfixation greatly enhances the initial stiffness of the
fusionconstruct for axial compression, axial torque, and
flexion-extensiontorque.3This allows for early mobilization
and lowers complications from pseudarthrosis
and graft
retropulsion.3.7.tO.16.17
PLiFprovides a load-bearing graft and,
therefore, should theoretically
result in superior fusion
rates that can be further enhanced by posterior fixation
throughthe same exposure. Conferring immediate stability
tothe spinal segment, trans pedicular fixation acts as an in-
ternal strut until the biological fusion can strengthen.3.tO
Sidhuand Herkowitztolist the advantages of pedicle screw
instrumentation, including: (1) the ability to control all
three columns of the spine from a posterior approach, (2)
the abilityto restore and maintain coronal and sagittal con-
tours of the spine, (3) the ability to achieve spinal fixation
in the absence of space-occupying implants in the spinal
canal, and (4) the possibility of minimizing the role of post-
operative bracing.
One must also consider the risks of instrumentation prior
to its routine use as an adjunct to fusion. Disadvantages as-
sociated with instrumentation can include increased infec-
tion rate, increased blood loss, increased operative time,
increased cost, instrumentation
failure, steep
learning
curve, neurological injury, and increased morbidity and
mortalityinthe elderlypopulation.to
. BasicTechniques
There are several PLiF techniques
currently
available to the
spine surgeon. Though a detailed
description
of the merits
of each is beyond the scope of this chapter,
we will briefly
mention four basic techniques.
Noninstrumented
Allograft/Autograft
PLiF
Clowardl achieved high fusion rates and clinical success
rates with his original PLiFtechnique. He performed wide
laminectomies and facetectomies and radical diskectomy to
place as much large allograftas possible in the intervertebral
space. He favored the placement of large grafts at the ex-
pense of facet integrity, stating it is "not necessary to pre-
serve the facets" because one is "fusing a larger area, the
vertebral bodies." Un and colleaguesl4.18later modified the
Cloward PLiFtechnique, stressing adherence to four biome-
chanical principles to enhance the rate of osteosynthesis: (1)
preservation of the posterior portion of the motion segment,
(2) near-total diskectomy,(3) partial decortication ofthe end
plate, and (4) use of the "unigraft" concept in which four to
six unicortical autogenous peg grafts are tightly inserted in
the disk space, thereby avoiding the retraction complica-
tions associated with the large Cloward grafts. In both the
Cloward and Un techniques and in subsequent modifica-
tions, radical diskectomy and meticulous end plate prepara-
tion were important, but technically demanding, concepts.
Threaded
Fusion Cage PLiF
In an attempt to further simplify the PLiFprocedure, stan-
dardized threaded fusion cages were developed. The first
commercially available cages included Raythreaded fusion
cages (Surgical Dynamics, Norwalk, CT)and BAKthreaded
fusion cages (Spine Tech, Inc., Minneapolis, MN).Threaded
fusion cages are hollow titanium alloy cylinders that can be
filled with autograft bone. They are available in a variety of
sizes. Theoretically,they provide the possibility of perform-
ing an "instrumented" PLiFwithout the need for additional
posterior segmental fixation and lower complications asso-
ciated with bone graft extrusion, bone graft settling, and
pseudarthrosis.6 However, difficulty assessing fusion in-
tegrity on postoperative imaging and the excessive neural
retraction required for posterior insertion may be problem-
atic with widespread use. Additionally, their application
may be
restricted
to
a
limited
patient
population.

684
LumbarandLumbosacralSpine:PosteriorApproach
Incision and Dissection
Contraindications include osteoporosis, grade IIor higher
spondylolisthesis, adjacent-level degeneration, three-level
fusion, and disk space height>
12 mm due to inability to
obtain adequate cage purchase.6
Carbon Fiber Rectangular Cage PLiF
Brantigan
interbody
fusion
cages
(DePuy Acromed,
Cleveland, OH) are made of a radiolucent carbon fiber-
reinforced polymer that allows radiographic visualization of
the fusion mass. These are rectangular
cages that are
packed with autogenous bone graft and impacted into a
prepared disk space. They have an open design to increase
bone graft to end plate surface contact, and they have stiff-
ness that matches that of bone. This theoretically reduces
stress shielding by transferring compressive load to the
graft while maintaining
disk space height. Meticulous
diskectomy and end plate preparation with a variety of
tools are required with this technique. Brantigan cages are
indicated for a posterior approach in patients with degenera-
tive disk disease at one or two lumbar levelswhose condition
requires an interbody fusion combined with posterolateral
fusion and pedicle screw fixation.
Impacted Allograft/Autograft PLiF
Development of and modifications to instrumentation
to
facilitate safer, more rapid, and more standardized
disk
space preparation and graft placement continue to evolve.
The Tangent posterior diskectomy and grafting instrumen-
tation set (Sofamor Danek, Memphis, TN) uses a cutting
chisel device that prepares the disk space and cortical end
plate for reception of a preformed cortical allograft. The
chisel is tapped into the disk space at an angle that parallels
the cortical end plates and creates a fusion surface that mir-
rors the dimensions of the preformed allograft. Cancellous
autograft bone is packed into the disk space between two
allograft struts. The cortical bone provides mechanical
strength while the cancellous bone promotes rapid fusion.
Although a carefully performed lumbar spine fusion from
either the posterior interbody, posterolateral, or anterior ap-
proach has a high rate of fusion in the appropriate patient, it
is our opinion that the familiarity of the surgical exposure,
the potential for neural decompression, and the capacity to
preserveor restorediskspaceheight makesthe PLIFtech-
nique superior to other techniques for lumbar fusion.
.
Surgical Technique
Anesthesiaand Positioning
Regardlessofthe PLIFtechniqueto beemployed,the prepa-
ration, positioning, and initial exposure are similar to those
of patients undergoing diskectomy or decompression alone.
After induction of adequate generalized endotracheal anes-
thesia and bladder catheterization, the patient is placed in
the prone position. Toavoid excessive epidural venous en-
gorgement and bleeding, chest rolls are used to support the
patient and prevent anterior abdominal wall compression.
Prior to incision of the skin, each patient receivesprophy-
lactic broad-spectrum intravenous antibiotics. Thespineis
exposed through a dorsal midline incision, and a combina-
tion of sharp dissection and monopolar cautery is usedto
reflect the paraspinous
musculature in a subperiosteal
fashion to expose the facets and transverse processesat the
involved levels. An attempt is made to preserve the spinous
processes,
supraspinous
ligament,
and
interspinous
ligaments because these provide an element of posterior
stability.
Intraoperative radiographs or fluoroscopy canbe usedto
verify the correct spinal segment. Aftercareful dissectionof
the soft tissue from the involved lamina, the initialbilateral
laminotomies, medial facetectomies, and foraminotomies
are performed in a fashion similar to that required forsim-
ple decompression of lateral recess stenosis. Thiscan be
done with Kerrison rongeurs, osteotomes, or a high-speed
air-powered drill. Boneremoved during the decompression
can be saved for later use as autograft. Boneremovaliscon-
tinued laterally to the medial border of the pedicle.This
provides adequate exposure so that disk space and end
plate preparation
may be accomplished with minimal
neural retraction. Care is taken to preserve as muchofthe
facet as possible because this maintains some of the me-
chanical integrity of the joint. Because transpedicularfixa-
tion restores the posterior tension band, its use mayallowa
more aggressive approach to bone removal. Followingre-
moval of the ligamentum flavum, the exposed dura and
nerve roots should be freed of compression and adhesions.
The neural elements should be freely mobile, especiallyin
patients with previous lumbar surgeries, becauseduralad-
hesions may prevent safe dural retraction and lead todural
lacerations or nerve root injury.
Careful attention is paid to epidural hemostasis. Epidural
vasculature is coagulated with bipolar cautery and then
incised.
Surgicel Uohnson
& Johnson
Company, New
Brunswick,NJ)and Gelfoam(TheUpjohn Company,Kalama-
zoo, MI)may help control bleeding. In multilevelprocedures
where excessive bleeding may be encountered, a blood
product-recycling unit may also be of value.
The posterior longitudinal ligament and posterioranulus
are incised bilaterally, and various disk rongeurs and
curettes are used to perform the initial diskectomy.The
main goal of this step is to remove extruded disk fragments,
decompress the neural elements, and provide entry intothe
disk space for distraction. Ifsignificant disk space collapse
exists, complete diskectomy may be difficult until the disk
space is distracted. The remainder of the procedure de-
pends on the specificPLIFtechnique to be employed,and
these will be discussed briefly.
Noninstrumented
PLiF as Described
by Cloward
and Un
A near-total
diskectomy
is performed
with rongeurs,
curettes, and disk space shapers. Aradical diskectomyisim-
portant because it provides a greater surface area forgraft
contact with the vertebral bodies. Anyosteophytes arere-
moved with a chisel.

-
95
Interbody FusionandTranspedicularScrewFixation
685
Achisel.curette. or osteotome is then used for partial
decortication of the end plate. It is important to ensure
goodgraftcontactwith bleedingcancellousbone to facili-
taterevascularization of the graft material and more rapid
osteosynthesis.Un believes that total decortication is "not
necessary.nor is it desirable" because this may lead to graft
settlingdue to the softness of cancellous bone.s Instead.
"islands"ofdecortication are created.
Thedisk space is then filled with bone graft material. Se-
lectionof graft material is important. and many authors
havereported successful outcomes and high fusion rates
withvarious grafts. including use of autologous iliac crest
grafts,allograft bone, dowel-shaped grafts. keystone grafts.
tricorticalgrafts. and bone chips.1.2.4.12.14
Cloward1inserted
iliaccrest bone plugs into the interspace using a large
punchand hammer. ensuring that the cancellous portion of
thegraftswere in contact with the bleeding surfaces of the
vertebralbodies.The neural elements were retracted gently
topreventinjury. and as many bone plugs as possible were
driveninto the interspace (Fig.95- t). Uns favored the "uni-
graft"concept in which four to six unicortical autogenous
peggrafts were tightly inserted. with the cortical bone of
the peggraft parallel to the longitudinal axis of the body.
Autogenouscancellous bone strips were then tightly packed
betweenthe peg grafts. Bonegrafts are countersunk -5 mm
belowthe posterior vertebral margin. Asmall notch created
inthislocation during end plate preparation may help pre-
ventposteriorextrusion of the graft. Clowardand Un do not
recommendroutine use of segmental internal fixation.
purUsingThreadedFusionCages
Threadedfusion cages are hollow titanium cylinders that
are to be filled with autogenous
cancellous bone. Templates
representing
various
cage
diameters
and
lengths
are
available to overlay
imaging
studies
during
preoperative
planning to determine the appropriate cage size. Proper
cage selection and placement are critical because an under-
sized cage will seldom fuse,and an oversized cage increases
the risk of neural retraction injury. Fluoroscopy is recom-
mended because it allows rapid sequential images to assess
proper retractor placement and cageinsertion. Designedto be
placed bilaterally. cages should be inserted near the midline
to assure close approximation to one another (Fig.95-2). In
general. the midline of the inserted cage should be in line
with the medial edge of the pedicle. Threaded fusion cages
should be inserted parallel to the end plates. and they should
obtain 3 mm of bony purchase ineach end plate.
BAKcages utilize distraction plugs to distract the disk
space. Once this is accomplished, a toothed drill tube and
protective sheath are anchored into the vertebral bodies to
enable effective disk space preparation. Great care is taken
to protect the dura and nerve roots during placement of the
drill tube to prevent neural entrapment. The exiting nerve
root at the superior level may be at increased risk because it
is often difficult to visualize. Ahand drill is used to ream the
disk space of any remaining disk material. and the disk
space is then tapped. ABAKcage is packed with cancellous
bone and inserted into the disk space under fluoroscopic
guidance. The procedure is then repeated on the opposite
side.
Raycages utilize a Tang retractor to distract the disk space
and to guide end plate preparation
and cage insertion.
Proper retractor placement is critical. The prongs of the re-
tractor are placed into the interspace. and the retractor is
hammered into position. It should feel quite tight in the in-
terspace. The medial prong should be at or near the midline
to assure proper positioning of the cage. The Tang retractor
must be parallel to the vertebral end plates so that the
prongs do not penetrate either end plate. There must also be
no medial or lateral angulation of the retractor because this
would cause misplacement of the cage. The hand drill is
A
~
B
Rgure 95-1
(A) Noninstrumented
posterior lumbar interbody fusion described by Cloward. Large iliac crest bone plugs are driven into the disk
spacefollowing wide laminectomies
and facetectomies.
(8) Lateral view of iliac crest grafts in the interbody space and bone chips placed over inter-
laminaropening.

686
Lumbar and Lumbosacral Spine: Posterior Approach
A
B
Figure 95-2
(A) Posteroanterior
and (8) lateral views of a threaded fusion cage inserted for posterior lumbar interbody fusion. There is3 mmof
bony purchase in the end plate by each cage. and each cage is countersunk below the posterior vertebral body margin.
used to drill the end plate to a preset depth and to remove
remaining disk material. The hole is tapped. and the cage
is inserted under fluoroscopic guidance. The cage should
be countersunk -3 mm below the posterior margins of the
vertebral bodies. The procedure is then repeated on the op-
posite side. and the cages are filledwith graft material.
PUFUsing Brantigan Cages
The Brantigan cage technique uses disk space spreaders to
achieve disk space distraction. Spreaders are placed sequen-
tially into the interspace parallel to the end plate and then
A
rotated 90 degrees to distract the disk space.Diskspace
shavers are then used to remove remaining disk material.
After placement of a retractor to protect the neuralele-
ments, an implant channel is prepared using a reamerand
broach instruments ofappropriate size(Fig.95-3).These
are tapped into the interspace in the followingsequence:
reamer, pilot broach, and finish broach. Trial implantscan
be inserted to verify the fit and depth of the preparedrec-
tangular channel. Cancellous bone is packed into thecage,
and the implant is tapped into place using an insertiontool.
The cage should be placed as far laterally in the interspace
as possible.Additionalbone graft is packedintothedisk
B
Figure 95-3
Posterior lumbar
interbody
fusion using Brantigan
carbon fiber cages. (A) A dural retractor
is used to expose the disk space andto
protect
the neural elements.
A broach completes
a square cut to prepare the end plates. (8) An implant
filled with cancellous bone graft is inserted
into the rectangular
channel. Note the "teeth"
of the cage that engage the vertebral
bone.

95
InterbodyFusionandTranspedicularScrewFixation
687
space around the cages, and the interbody
fusion is supple-
mented with bilateral posterolateral
fusion and transpedic-
ular fixation.
PUFUsingtheTangentTechnique
TheTangent instrumentation
system utilizes sequentially
placed disk space distractors to restore disk space height.
After careful dural retraction with the nerve root protec-
tor, a rotating cutter is used to remove residual disk mate-
rial (fig. 95-4). The remaining soft tissue and end plate
coverings are then removed with a round scraper. This is
performed with the intent
to debride
the end plate
surface to optimize graft incorporation. A cutting chisel
A
B
provides final end plate preparation. The size of the cut-
ting chisel can be estimated
by preoperative
planning
with templates or by using the height restored with the
disk space distractor. The chisel is impacted parallel to the
end plates to a depth of 30 mm, and then removed with a
slap hammer. The procedure is then repeated on the op-
posite side. Once the entire disk space has been prepared.
two preformed allograft wedges are impacted into the
previously
created tracts with an inserter. The grafts
should lie 2 to 3 mm below the posterior rims of the ad-
joining vertebral bodies. Locallyharvested autograft can-
cellous bone is packed into the disk space around the allo-
graft bone. Segmental trans pedicular fixation is routinely
used with this technique.
c
Figure 95-4
Posterior lumbar interbody
fusion using the Tangent impacted
posterior
lumbar
interbody
fusion instrumenta-
tion. (A) The disk space is prepared with a rotating
cutter. The dural retractor
protects
the neural elements
from injury during
diskspace presentation.
A disk space distracter
remains in place while disk space preparation
is performed
on the opposite
side.
(8) A cutting chisel prepares the end plates for reception
of the graft. (e) The preformed
allograft
bone is attached
to an inserter
and impacted
into the disk space. Autograft
cancellous
bone is then packed into the prepared
disk space beneath the midline
structures.