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

16
PosteriorAtlantoaxialFusion:SurgicalAnatomyandTechniqueOptions
131
Anterior articular facet
Superior articular
facet
Lateral mass
Transverse process
Inferior articular facet
Figure 16-3
Anatomyofthe axis((2).
Dens
Posterior articular facet
Superior articular facet
Lateral mass
Transverse
process
Inferior articular
process
Spinous process
Articular facet for
transverse ligament
Dens
Articular facet
foroccipital
condyle
Axis (C2)
C3
C4
Figure 16-4
Anatomical relationship of the upper cervical spine
((1 -(4).

132
OccipitocervicalJunction:PosteriorApproach
Posterior atlanto-
occipital membrane
~SkUII
Axis(C2)
A
Ligamentum flavum
Alar ligament
Atlanta-occipital
capsule
Cruciate ligament
transverse portion
Atlantoaxial
capsule
Ligamentum
flavum
Anterior longitudinal
B
IiQament
c
Posterior
atlanta-occipital
membrane
Ligamentum
flavum
Ligamentum
nuchae
Atlas(C1)
Cruciate ligament
vertical portion
Posterior atlanto-
occipital membrane
Anterior atlanto-
occipital membrane
Atlanto-occipital
joint capsule
Atlas (C1)
Axis (C2)
Vertebral a.
Figure 16-5
Ligaments of the ocdpi-I
toatlantoaxial
region.
(A) Dorsal view'l
(B) Dorsal view with posterior
elementsl
removed. (e) Lateral view.

16
Posterior Atlantoaxial Fusion:Surgical Anatomy and Technique Options
133
. SurgicalTechniques
Anesthesia
Inpatientswith documented or suspected atlantoaxial
instability,it isrecommended to have the patient undergo
anawake,fiberopticintubation. It is imperative that exten-
siveneck flexion and extension be avoided. With any
procedureinvolvingthe atlantoaxial region, the use of in-
traoperativeelectrophysiological monitoring
should be
employed.We recommend
obtaining
a baseline
potential
forcomparison before and after the intubation.
Alterna-
tively,the patient may be intubated fiberoptically with a
wake-uptest immediately
after intubation
and again after
positioning.Awake intubation and positioning allow con-
tinualmonitoringofa patient's neurological status.
Standardvascularaccess should be obtained using sterile
techniques.and the degree of monitoring
required depends
onthepatient's exisiting comorbidities. In posterior ap-
proaches
tothe upper cervical spine, blood loss is generally
withinacceptablelimits and does not require use of a cell
saverorablood transfusion. Avoiding prolonged hypoten-
sionismandatoryfor accurate intraoperative physiological
monitoringandalso to prevent ischemia of the spinal cord,
particularlyin patients with severe canal stenosis.
Positioning
Oncetheintubation, establishment of vascular access and
othermonitoringdevices is complete, the patient is placed
inaproneposition. A Mayfield headrest or Stryker bed is
preferred.The endotracheal tube is secured in place and
three-pointhead fixation is applied, unless the patient has
beenplacedin halo traction. The head is held in a neutral
positionanda hard cervical collar may help in holding the
headasthepatient is rolled from supine to prone. After po-
sitioningis complete, the patient is locked into either the
halorthree-point pin adapter. Another evaluation of the
somatosensory
evoked potentials is done and compared
withthepreintubation and postintubation baselines. Addi-
tionally,afluoroscopicor x-ray image is obtained immedi-
atelyto evaluate the (1 and (2 anatomy as well as the
sagittalalignment. The articulations should be reduced as
muchaspossibleprior to final positioning because this wiII
facilitatethesurgicalprocedure.
Thetorsoissupported on firm jelly-rolls placed longitu-
dinallyfromshoulder to waist. Alternatively, one may use a
laminectomy
frame or simply pilIows.The thoracic cage and
abdomen
areleft as free as possible to allow for maximal
ventilationand minimal venous back-pressure which can
effectintraoperativebleeding. The eyes and face should be
wellpaddedand other pressure points, including the shoul-
ders,chest,iliac crests, and knees are appropriately
padded.
Infemales,the breasts should be between the rolls placed
tostabilizethe torso. In males, the penis and scrotum
shouldbefreeofcompression. In most of these procedures
aFoleycatheter is placed to evaluate urine output during
thecase.
Thepatient's hair is shaved from the inion down to the
hairlineinferiorly. Usually,the incision is marked from one
or two fingerbreadths below the external occipital protru-
berance to the (6 or (7 level. Forthis reason it is important
to assess the preoperative films to view the sizes of the
spinous processes to palpate approximately where the (7
(largest) process may be. Localanesthetic in the form of a
1%Iidocaine/1:200 epinephrine mixture is infiltrated along
the incision site. Prior to infiltration of the local agent, the
anesthesiologist is made aware of its administration to ob-
serveanycardiovascularchanges.
Exposure and Nuchal Musculature
For each of the following posterior fusion techniques to
be mentioned,
the exposure
to the vertebral
column
is roughly equivalent, with variations in the amount of
exposure needed depending on the procedure. The inci-
sion is usually marked from the external occipital protu-
berance to the fifth spinous process. The incision is made
in the midline and carried down through the soft tissue
with Bovieelectrocautery. Staying in the midline is imper-
ative to reach the avascular plane that separates the
posterior cervical muscles. The muscles of the posterior
cervical region are innervated by the dorsal rami of each
segmental level and are composed of three layers.The
muscles
are removed
from the bone subperiosteally
with electrocautery
and blunt dissection with periosteal
elevators.
The superficial layer of the posterior cervical musculature
contains the splenius capitis and cervicalis muscles.The lig-
amentum nuchae lies in the midline and is in the plane of
the trapezius muscle (Fig. 16-6). Traversing this structure
will expose the fascia separating the two splenius capitis
muscles. The splenius capitis muscles extend from the
lower portion of the ligamentum nuchae and the spinous
processes of C7-T4 proceeding laterally to attach to the
mastoid process and the lateral part of the superior nuchal
line. The splenius cervicalis originates similarly to the sple-
nius capitis but inserts on the posterior tubercles of the
transverse processes of (1 through (4. This layer lies deep
to the large trapezius muscle. The rectus capitis posterior
major muscle attaches to the (2 posterior elements supero-
medially, whereas the inferior oblique muscle attaches su-
perolaterally.
The intermediate
layer consists of the erector spinae
muscle groups and forms three columns (Fig. 16-7). Medi-
ally,the spinalis group inserts onto the spinous processes of
the cervical spine. The longissimus muscle forms the mid-
dle column and inserts onto the mastoid process. Laterally,
the iIieocostalis group inserts onto the posterior tubercles
of the transverse processes of (4 through (6. These muscles
all originate along the iliac crest, sacrum, and lower lumbar
vertebrae.
The deepest muscle layer in the posterior cervical spine
surrounds the extravertebral venous plexus (Fig. 16-7).
This area can often become a source of bleeding during the
surgical exposure. The muscles of this layer include the
semispinalis, multifid is, and rotators. These muscles do
not exist above the axis. The venous bleeding is generally
well controlled with electrocautery and the muscles are
reflected to expose the facet joints, with care taken to

134
Occipitocervical Junction: Posterior Approach
Superior nuchal line of skull
Posterior triangle
of neck
Semispinalis
capitis m.
Sternocleidomastoid
m.
Splenius capitis m.
Trapezius m.
Figure 16-6
Superficial layer of the posterior cervical musculature.
Posterior tubercle
of atlas (C1)
/
Superior
nuchal line of skull
Rectus capitis
__
,---=:P-
_
posterior
minorm.
"
.~~. .
11
Rectus capitis
posterior
major m.
Superior oblique
capitis m.
Longissimus
capitis m.
Semispinalis
capitism.
Inferior oblique capitis m.
Semispinalis
capitis m.
Splenius capitis m.
Spinalis cervicis
m.
Splenius cervicis
m.
Serratus posterior
superior
m.
Figure 16-7
Intermediate and deep layers of posterior cervical musculature.

16
PosteriorAtlantoaxialFusion:SurgicalAnatomyandTechniqueOptions
135
maintainthejoint capsules.The semispinalis capitis groups
originatefrom the transverse
processes
of T1 through
T6
andinserton the suboccipital bone. The semispinalis
cervi-
calisoriginatessimilarly but inserts on the cervical spinous
processes.
The (2 spinous process is large and bifid with the
attachmentof the semispinalis
cervicis muscles at its infe-
rioredges.The multifidis group lies beneath
this and con-
sistsofshort muscles spanning one to three segments
from
thelaminainferiorly to the spinous process superiorly.
The
lastgroup,the rotators, arise from the transverse
processes
andinsertat the base of the spinous process one level ros-
trally.
Forcertain procedures,
such as transarticular
screws,
theprocedure may necessitate
entrance
into
the joint
capsules.Between the occiput and C1,the vertebral
arteries
travelfromthe foramen transversarium
medially
to pene-
tratethe atlanto-occipital membrane.
If dissection
is
performedtoo far past the lateral
masses
the vertebral
arterycanbe injured. At the occiput/C1
region, dissection
isbestperformed with blunt (no electrocautery)
dissection.
Additionally,ectatic
or
anomalous
vertebral
arteries
mayoccurand must be kept in mind during the dissection.
Preoperativeassessment
of the
course
of the
vertebral
arteriesmaydecrease the risk of any inadvertent
vascular
injury.
Thesuboccipitalarea includes the craniocervical
junction
andhasa set of muscles that do not exist below C2. These
musclesliedeep to the semispinalis
layer. The rectus minor
muscleoriginates from the posterior
tubercle
of C1 and
fromthe(2 spinous process and attaches laterally to the
suboccipitalbone. Also projecting from the posterior
tuber-
cleoftheaxisare the inferior oblique muscles that attach to
thetransverseprocess of the atlas. Moreover, the superior
obliquemusclesspan the transverse processes of the atlas
andattachtothe suboccipital bone. The suboccipital trian-
gleconsistsof the inferior
oblique
muscle
inferiorly,
the
superioroblique laterally,
and the
rectus
major
muscle
superiorly.The suboccipital
nerve
and vertebral
artery
transitthis spaceas they perforate the posterior atlanto-
occipitalmembraneand may be used as reference in surgi-
caldissections.
Atlantoaxial
Stabilization Methods
CableFixationwith BonyWedgeCompression
If the C1posterior arch is intact, then the use of cable fixa-
tion from C1to C2is a viable option. Cablefixation of C1-C2
was first described by Hadra in 1891 and later by Cone in
1937.5More recently, three basic cable/wire fixation tech-
niques, the GalIie,Brooks,and Sonntag-Dickmantechniques,
are commonly used for C1-C2fixation.In each of these tech-
niques, it is imperative to perform meticulous sublaminar
dissections at C1and C2after removal of the occipitoatlanto
membrane and ligamentum flavum. Ensuring free access of
the wire between the lamina and dura will obviously mini-
mize the chance of dural tears. The use of somatosensory
evoked potentials (SSEPs)during these surgical procedures
may enable the surgeon to receive feedback during the wire
passage in this portion of the case as well as during the com-
pression of bone wedges with tightening of the wire. In each
of these techniques mentioned, risks include wire pullout or
breakage with potential neurological injury with wire pas-
sage. Neurologicalinjury with these techniques has been re-
ported as high as 5 to 7%.6
In 1939, Gallie placed a wire under C1 and attached it to
the spinous process of C2 below with an H-shaped bone
graft in between (Fig. 16-8).7 The graft usually consists of a
corticocancellous iliac crest bone measuring -1.5 cm by 3
cm and notched inferiorly in the midline to dock onto the
C2 spinous process. Generally, a 20-gauge wire is passed
under the arch of C1and a separate wire is passed through
the spinous process of C2.These wires are tightened, com-
pressing the bone graft over the arch of C1and to the lam-
ina of C2.In this technique a single midline wire with a sin-
gle sublaminar passage at C1is required.
In 1978, Brooks and Edwards refined this technique by
utilizing sublaminar wires at C1and C2with an interlami-
nar wedge bone graft.s In biomechanical
studies, this
fixation technique is superior to the GalIietechnique, but it
carries with it the risks of an additional
wire passage
beneath two laminae. In this technique two separate bone
grafts are fashioned to wedge between C1 and C2. The
Figure 16-8
Galliep05teriorfusion.
..

136
Occipitocervical Junction: Posterior Approach
superior portion of the C2lamina is fashioned to receive the
grafts on each side of the midline to minimize translation
during compression ofthe wires (Fig.16-9).
In the Sonntag and Dickman technique, one bicortical
graft is wedged between Cl and C2with a single sublami-
nar wire passing under Cl.9The sublaminar wire below Cl
is looped caudally behind the C2spinous process trapping
the graft between Cl and C2,avoiding the inherent risk of a
second sublaminar wire passage under C2(Fig. 16-10). In
all of these techniques, it is important to wedge the bone
graft as the wires are tightened to help prevent posterior
translation.
HalifaxClampFixation
The Halifaxclamp for Cl and C2stabilization is a technique
offering posterior lamina fixation without the risk of sub-
laminarwirepassage.toAnupper clampis placedabovethe
lamina of Cl and an inferior clamp is placed below C2,with
sequential tightening of the clamps to ensure secure en-
gagement of the laminae (Fig.16-11). Aninterspinous graft
Figure 16-9
Brooksposteriorfusion.
may provide additional
support
and increase the rate offu-
sion. However, the interlaminar
graft may dislodge into the
spinal canal without the security of a wire ventrally topre-
vent this translation.
With the cable wiring techniques pre-
viously described,
this is less of a risk because
the wireis
passing beneath the wedge graft preventing anterior move-
ment. The Halifaxclamp provides stability comparable with
the Brooks technique
but clamp loosening can occur.
Posterior Screw Fixation Methods
When the posterior elements are injured or incompetent
and wire passage or clamp positioning is not possible, then
posterior screw fixation techniques can provide stabiliza-
tion. Internal screw fixation with local autograft or allograft
is superior in strength and fusion rates when compared
with wiring techniquesY Additionally, severely osteopenic
patients may require fixation through articular facets
and/or extension of arthrodesis to the occiput. When
consideringscrew fixation,it is imperativeto obtainaxial
computed
tomographic (CT) images of the occiput-C2
Figure 16-10
Dickman-Sontagposteriorfusion.

16
PosteriorAtlantoaxialFusion:SurgicalAnatomyandTechniqueOptions
137
regiontodelineatethe course of the vertebral arteries. On
occasion,these techniques may not be feasible if the verte-
bralarteryistoo far medial and lies in the path of the screw
trajectory.
In1979,Magerland Seemann introduced
the technique
of
transarticularscrew fixation of (1-(2.12
This technique
pro-
videsthemoststable and rigid fixation for the atlantoaxial
joint.Ifsuccessful placement
of the transarticular
screw is
achieved,
thistechnique will provide adequate strength to
theatlantoaxialjoint, eliminating
the need for postopera-
tivehalobracing.Thetransarticular screw is placed through
theparsinterarticularis of (2 penetrating
through the
(1-(2facetinto each lateral mass of (1 (Fig. 16-12). Any
pathologyor anamolous anatomical structure that inter-
fereswith or is present within this trajectory is a con-
traindicationfor this technique. For example, a comminuted
fracturethroughthe pars or lateral masses of (lor
anom-
alousvertebral artery course will prohibit the use of
transarticular
screws.Vertebral artery ectasia or anatomical
malpositionis an absolute
contraindication
to this tech-
nique.Thus the (1-(2
bony anatomy
must be evaluated
withpreoperativeCTimaging.
Inplacementofa transarticular screw, the head must be
fixedinpositionand is best controlled with three-point pin
Figure 16-11
Halifax clamp posterior fusion.
fixation via a Mayfield fixator. Under fluoroscopic guidance
and with SSEPmonitoring,the head should be flexed as
much as possible while keeping (1-(2
reduced. The dissec-
tion should expose the (1-(2 articular joint surface by curet-
tage along the superior lamina of (2. During the exposure,
the (2 nerve root and its associated venous plexus is identi-
fied and protected out of harm's way during the drilling. The
(1-(2
joint capsule can be dissected free and flapped ros-
trally with the nerve enveloped because the nerve usually
passes mediallyand superficial to the (1-(2 articulation. Ve-
nous plexus bleeding generally can be controlled with bipo-
lar cautery or pressure with thrombin-soaked Gelfoampled-
gets. Anawl prepares the entrance site at 2 to 3 mm from the
facet joint at (2 - (3 and -2 to 3 mm lateral to the medial
border of the facetjoint. Dissectingmedially to expose the (2
pedicle defines the medial edge for screw passage. Under flu-
oroscopic guidance, a 2.5 mm drill is advanced forward and
superiorly, aiming toward the upper half of the anterior tu-
bercle of (1. Toachieve this trajectory with the proper angle,
a percutaneous entrance point at about C7is needed for the
drill sleeve to pass. A lateral trajectory may jeopardize the
vertebral artery and must be avoided. After drilling is com-
plete with penetration of the distal cortex, the depth is
checked and the trajectory tapped in preparation for screw
A
Figure16-12
Transarticular screw fixation.
(A) Lateral view. (B) Posterior view.
B

138
Occipitocervical Junction: Posterior Approach
A
..:.
Figure 16-13
Harms (1 - C2 posterior screw fixation. (A) lateral view. (B) Posterior view.
placement. The procedure is repeated on the contralateral
side while either leaving the drill in place or placing a
threaded 3.5 mm screw to prevent redislocation.Three-point
posterior fixation can be obtained by coupling transarticular
screw fixation with an interlaminar wiring method previ-
ously described. The screw passage through the facet will
rigidlycouple (1 and (2 and limit rotation.
Biomechanical studies have shown that the Magerl tech-
nique for placement of transarticular
screws allows the
stiffest stabilization with the least amount of rotation and
lateral bending. This technique provides three-point fixa-
tion and follows most closely biomechanical rules on inter-
nal fixation; however, it can be a technically demanding
procedure.
References
1.
Dickman
CA. Crawford
NR. Paramore
CG. Biochemical
characteristics
ofC1-2
cable fixations.J
Neurosurg
1996:85:316-322
2.
Menezes
AH. van Gilder Jc. Anomalies
ofthe
craniovertebral
junction.
In: Youman JR. ed. Neurological
Surgery. Philadelphia:
WB Saunders:
1990: 1394-1400
3.
Von Torklus D. Gehle W. The Upper Cervical Spine. New York: Grune
and Stratton;
1972
4.
White M. Panjabi
MM. Clinical Biomechanics
of the Spine. Philadel-
phia: JB Lippincott;
1978
5.
Caglar YS. Pait TG. Ozgen S. The axis (C2): posterior
stabilization
op-
tions. Contemporary
Neurosurgery
1999;21: 1-6
6.
Geremia
GK. Kim KS, Cerullo L. Calenoff L.Complications
of sublami-
nar wiring. Surg Neurol 1985:23:629-625
7.
Gallie WE. Fractures
and dislocations
of the cervical spine. Am J Surg
1939;46:495
B
More recently, Jurgen Harms described a technique of
(1-(2
fixation utilizing a (1 lateral mass screw and aQ
pedicle screw coupled with a rod construct (Fig. 16-13).1J
This technique offers many advantages and can be usedin
patients who have compromised posterior elements (Le.
fractures of the lamina). Also, these screws can be placed
and then the (1-(2
region can be reduced using the rodas
a lever arm. Finally,this technique is quite similar to place.
ment of lateral mass screws in the subaxial spine and there-
fore is technically easier when compared with placementof
transarticularscrews.Longfollow-upperiodshavenotbeen
finalized; however, early results indicate this technique of.
fers a safer, viable option to transarticlar screw placement
for atlantoaxial instability.
8.
Brooks AL.Jenkins
EB. Atlantoaxial
arthrodesis
by the wedge com-
pression
method. J Bone Joint Surg Am 1978;60:278
9.
Dickman
CA. Sonntag
VKH. Wire fixation
for the cervical
spine: bio-
chemical
principles
and surgical techniques.
BNI Q 1993;9:2-16
10.
Aldrich EF.Crow WN. Weber PB. et al. Use of MR imaging-compatible
Halifax interlaminar
clamps
for posterior
cervical fusion. J Neurosull
1991 ;74: 185-189
11.
Grob D, GascoJJ, Panjabi
MM. Wang P. DvorakJ.
Biochemical
evalua-
tion of four different posterior atlantoaxial fixation techniques. Spine
1992;17:480-490
12.
Magerl F. Seeman
PS. Stable posterior
fusion of the atlas and axisby
transarticular
screw
fixation.
In: Kehr P. Weidner
A. eds. Cervic~
Spine. Berlin: Springer-Verlag;
1986:322-327
13.
Harms J.Melcher
RP. Posterior
C1-2 fusion with polyaxial
screw and
rod fixation. Spine 2001 ;26:2467-2471

17
(1-(2 Brooks Fusion
...
PrithviNarayan,Gerald E.Rodts, and Regis W. Haid
. Indications
. Advantages
. Disadvantages
. RadiologicalEvaluation
. Preoperative Planning
. SurgicalTechniques
Anesthesia
Positioning
Atlantoaxialinstability has been categorized into four dif-
ferentypesbased on etiology: congenital, traumatic, in-
flammatory,and neoplastic.
Congenital
causes
include
odontoidaplasia, hypoplasia of the odontoid
process, and os
odontoideum(separation of the odontoid process, which
mayalsobe acquired). Trauma can cause atlantoaxial
insta-
bilitysecondary to nonunion
of a fracture
of the odontoid
processor, less commonly,
rupture
of the transverse
liga-
ment.lnflammatory conditions
include rheumatoid
arthri-
tis(whichcauses bony erosion
and transverse
and apical
dentalligament laxity
or rupture)
and retropharyngeal
infections.
Thefirst successful treatment
of atlantoaxial
instability
wasperformedby Mixter and Osgood in 1910. In this proce-
dure,the posterior arch of the atlas was fixed to the spinous
processof the axis with a silk thread.
Since that time nu-
merousmethods have been described
using simple wiring,
applicationof bone grafts, or a combination
of both. Gallie,
in1937,revisedthis technique using a wire loop and an H-
shapedgraftforfusion.The atlantoaxial joint permits a high
degreeofphysiologicalmotion compared with other verte-
bralarticulations.Any fusion at this level should prevent
flexion,extension,rotation, as well as translational-shear
movements.The Gallie wiring technique
prevents
anterior
shearmotionand flexionbut does not restrict motion in the
otherdirections.In 1978, Brooks and Jenkins described a
wedge compression-fusion
technique
for
atlantoaxial
arthrodesis,which provided more immediate
stability than
theGallie fusion. Dickman
and Sonntag
have described
othertechniques, which combine
some aspects
of Brooks
Incision
Sublaminar Wire Placement
Bone Graft Harvest
Graft Placement
Closure
.
PostoperativeCare
.
Complications
.
Conclusions
and Gallietechniques and transarticular screw fixation. This
chapter describes the Brooks fusion technique for CI-C2
arthrodesis.
.
Indications
. Instabilityofthe Cl-(2 joints with intact posteriorarch
ofatlas
. Atlantoaxialdislocation secondary to transverse liga-
ment rupture or laxity caused by trauma, rheumatoid
arthritis,or infection
. Odontoid process incompetence secondary to type II
fractureswith> 6 mmdisplacement
. Chronicnonunionoffracturesor failureofconservative
treatment
. Instabilityoffractureina halovestor other rigidfixation
devicesfollowingtransoralodontoidectomy
. Destructionofthe densbytumors
. Advantages
.
Familiar approach
.
High fusion rate
.
Bonegraft placed under compression
139

140
Occipitocervical Junction: Posterior Approach
.
Disadvantages
. Fusionreduces cervical rotation by -50%.
.
Requiresplacement of sublaminar wires
.
Spontaneousextension offusion to occiput can occur.
.
Radiological Evaluation
Radiographicexaminationof the upper cervicalspine
consists of the anteroposterior and lateral x-rays. An open-
mouth view is helpful to evaluate the odontoid process and
the (1-C2 articulations. Alternatively the pillar view of the
odontoid
process (oblique) or thin-section
computed
tomographic (cr) scans can be obtained in patients who
cannot cooperate for an open-mouth view. One should con-
sider thin-cut cr for areas of pathology identified on plain
x-rays. This initial evaluation is followed by dynamic flex-
ion-extension x-rays, three-dimensional cr reconstructions,
and magnetic resonance imaging (MRI)if necessary. MRIis
an excellent modality to evaluate intrinsic spinal cord ab-
normalities, integrity of the transverse atlantal ligament
and intervertebral
disks, and
presence
of intraspinal
hematoma.
.
PreoperativePlanning
All patients with upper cervical spine injuries or instabil-
ity are treated with immobilization. Appropriate mea-
sures are instituted for patients with acute spinal cord
injuries. Cervical traction devices may be used to attempt
preoperative
reduction. Care must be taken to avoid
overdistraction.
/
Fusion of the atlantoaxial joint results in almost 50!
reduction in cervical rotation and the patients shouldb!
counseled regarding this prior to surgery.
. Surgical Techniques
Anesthesia
The premedicated patient is carefully intubated and general
anesthesia is administered with the patient in the supine
position on a stretcher next to the operating table. Care~
required
during
intubation
to prevent
flexion or extension
of the head and neck. Fiberoptics may be used for bettervi-
sualization during intubation to minimize movement oftht
head and neck. Paralytics
may be administered
to aidin
muscle retraction.
Positioning
Once adequate
general anesthesia
is obtained,
a three-point
head fixation
device, like the Mayfield
headholder,
is ap-
plied to provide rigid control of the neck intraoperatively.
The patient is then carefully rolled like a log onto the oper.
ating table to the prone position (Fig. 17-1). Duringthis
maneuver, the surgeon controls the head and neck by hold.
ing the head
fixation
device,
applying
firm longitudio~
traction.
The head holder is then attached
to the operatio!,
table with the neck in neutral position and the head slightly
flexed. Countertraction
is applied by taping the shoulders Ie
the end of the operating
table. This positioning
provides'
more room for dissecting
around the atlas. A lateral cervic~,
spine x-ray is then obtained
to ensure
proper alignment 01
the vertebrae.
Figure 17-1
The patient is in the prone position withhead
secured in fixation device. The head holder is attached
10the
operating table with the neck in neutral position and head
slightly flexed. The positioning
is facilitated
with the useIt
fluoroscopy.

Incision
Theskinisthen prepped and draped from the occiput to the
lowercervicalspine in the standard fashion. Prior to making
theincision,the skin may be infiltrated
with 1%lidocaine
with1:100,000 epinephrine to facilitate hemostasis. A mid-
lineincisionis then made from the occiput to the level of
thefourthor fifth cervical vertebra. The incision is extended
deeplywithin the relatively avascular intermuscular
sep-
tumor ligamentum
nuchae using
a combination
of
monopolarcautery and sharp dissection.
The spinous
processandlaminaeof the axis are exposed, taking care not
todisturbthe articular processesbetween the axis and the
vertebrabelow.The posterior arch of the atlas is then ex-
posedbysubperiostealdissection. Caremust be taken dur-
ingthisdissectionto avoid injury to the vertebral artery and
occipitalnerves.Werecommendblunt stripping of the soft
tissuewith a Cobb or periosteal
elevator
instead
of
monopolarcautery in the region of the vertebral arteries
andvenousplexus.The paraspinous muscles are retracted
laterally.Thisexposure is shown in Fig. 17-2. The poste-
rior/inferiorsurface of the atlas and the posterosuperior
surface
ofthe axisthat will make contact with the grafts are
curettedto removeany soft tissues. The anterior fibers of
theatlantoaxialmembrane should be preserved to prevent
Figure17-2
Theparaspinalmuscles dissected off the midline and
retractedlaterally.Exposureof the upper cervical spine is then ob-
served.
17
(1 - (2 BrooksFusion
141
17-
-......"- -
Figure17-3
A20-gaugestainlessteelwireispassedoneachsideof
the midlinebeneatheacharchof C1andC2.A right-angledclampis
usedto facilitatepassageofthecablebyfashioningit intoacurve.
graft displacement into the spinal canal. The occiput need
not be extensively exposed or decorticated to avoid inad-
vertent fusion to the skull base.
Sublaminar Wire Placement
The ring of C1and the lamina of C2are exposed circumfer-
entially using curettes to facilitate passing the wires. A20-
or 24-gauge stainless steel wire or braided titanium cable is
passed on each side of the midline beneath each arch of C1
and lamina of C2. An aneurysm needle or right-angled
clamp can be used to facilitate passage of the leader of the
cable by fashioning it into a curve (Fig. 17-3). One can also
tie the wire or cable to a suture and pass the blunt end un-
der the C1 arch. Alternatively, one may pass a double-
stranded wire or cable directly in the midline and then sim-
ply cut it into two single strands that can be moved over
laterally. Careful dissection of the atlantoaxial membrane
facilitates moving the cables to each side. Great caution
must be exercised during this maneuver to avoid injury to
the dura or spinal cord. The wires then come to lie on the
anterior portion of the atlantoaxial membrane (Fig. 17-4).
Bone Graft Harvest
Autologous graft is harvested from the posterior iliac crest
superficial to the sacroiliac joint (Fig. 17-5). The posterosu-
perior iliac spine is palpated and a diagonal or vertical inci-
sion is made over this prominence, down to the bone. A
horizontal incision may result in injury to the cluneal
nerves. The crest is exposed subperiosteally and a rectangle
of-2 cm by 6 cm is marked. Twofull-thickness rectangular
bone grafts measuring 1.5 by 3 cm are removed. Alterna-
tively, a single piece can be removed and then split. Hemo-
stasis is obtained using either Gelfoam or bone wax. The

142
OccipitocervicalJunction:PosteriorApproach
I)
Figure
17-4
The two sublaminar
wires are now ready to be used to
anchor a bone graft between (1 and C2.
graft site is copiously irrigated with saline. The incision is
closed
in layers using generic
absorbable
sutures
for the
muscle fascia. and the skin is stapled.
Graft Placement
The sides of each graft are beveled, with the apex of the
graft to fit the space between the arch of the atlas and the
Figure 17-6
The sides of each graft are beveled to fit securely in the
space between the arch of the atlas and the lamina of the axis.
lamina ofthe axis (Fig. 17-6). Care must be taken to ensure
no impingement on the canal, the vertebral arteries. orthe
C2 nerves. Notches may be placed on the upper and lower
cortical surfaces of the grafts to prevent the wires fromslip-
ping. The grafts are placed against the superior surfaceof
the denudedlaminaeand the two wiresare tightenedover
them to secure them in place (Fig.17-7). The arch ofthe at.
las is carefullymanipulated to check for stabilization.
Figure 17-5
An autologous bone graft is harvested from the posterior iliac crest superficial to
the sacroiliacjoint asshown here.

Figure17-7
Thewires are tightened
over the grafts to secure them
intoplace.
dosure
Thewoundiscopiouslyirrigated with saline. The wound is
closedin multiple layers using interrupted
absorbable
suturesand approximating
the
ligamentum
nuchae!
intermuscular
septum.The skin is reapproximated with sta-
plesorrunningnylonsutures. Suction drains may be used in
theusualfashion.A sterile dressing is applied. The head
andneckare splinted prior to turning, extubation,
and trans-
ferofthe patient to a bed. The head holder is then removed.
. Postoperative Care
Perioperativeantibiotics may be continued
for 24 hours. The
patientismobilized as soon as possible in the postoperative
period.Arigid cervical collar or a cervicothoracic
orthosis is
usedinthepostoperativeperiod for immobilization.
References
1. BrooksAl. Jenkins EB. Atlantoaxial
arthrodesis
by the wedge
com-
pressionmethod.J BoneJoint
Surg Am 1978:60:279-284
2. GriswoldDM.Albright JA. Schiffman
E.Johnson
R. Southwick
WOoAt-
1antoaxialfusion for instability.J
Bone Joint Surg Am 1978:60:285
- 292
17
(1 - (2 Brooks Fusion
143
.
Complications
Several complications have been reported in the literature.
. Recurrentanterioratlantoaxialsubluxationin the im-
mediate postoperative period may be prevented byade-
quate external bracing.
.
Spontaneous extension of fusion to the occiput or to the
lower cervical vertebrae may be avoided by limiting dis-
section to the areas intended for fusion.
.
Spinal cord injury during passing of the sublaminar
wires has been reported, so extreme care should be
taken during this maneuver.
.
Injury to vertebral arteries or to the vertebral venous
plexus is possible during this procedure, so these struc-
tures should be identified and preserved during dissection.
.
Conclusions
The Brooksfusion technique for atlantoaxial arthrodesis has
been described. This fusion technique blocks all potential
motions of the atlantoaxial joint. A 93%success rate has
been reported with this procedure.! Modifications of this
technique have been reported in the literature. Griswold et
al have used four double wires instead of two for anchoring
the bone grafts.2This technique reportedly provides imme-
diate stability and reduces the chance of failure of internal
fixation because of the four wires. It also provides better
control of rotation and flexion and extension by the lateral
positioning of the wires. Dickman and Sonntag have com-
bined Brooksand Gallie fusion techniques with one bicorti-
cal graft and passing of the wire only under the (1 arch.3
This technique reportedly may be less likely to pull the (1
posteriorly as in a GaBiefusion and also avoids the inherent
dangers of passing a (2 sublaminar wire as in a Brooks fu-
sion. This technique also places the bone graft under com-
pression between the inferior aspect of the C1arch and the
superior aspect of (2.
3.
Dickman
CA. Sonntag
VK, Papadopoulos
SM. et at. The interspinous
method
of
posterior
atlantoaxial
arthrodesis.
J
Neurosurg
1991 :74: 190 -198

18
Extreme Lateral Transcondylar
Transtubercular Approach to the
Anterior Craniocervical Junction
Sean McNatt, LarryT.Khoo, Steven Giannotta, and John Diaz Day
.
Indications
.
Contraindications
.
Advantages
.
Disadvantages
.
Objective
.
RadiologicalEvaluation
.
SurgicalTechniques
Anesthesia
Lesions of the anterior aspect of the foramen magnum
and
craniocervical junction
present
unique
surgical
challenges because of the complex anatomical relationship
between the bony elements, brain stem, exiting cranial
nerves, and vertebrobasilar
vascular
system. Anterior
approaches, such as the transoral or transcervical approach,
provide direct access to the region but are hindered by
limited lateralexposure,increased incidence of cerebrospinal
fluid(CSF)fistulaeand infection,and the need forcorpec-
tomy and fusion. Aposterior approach, the extreme lateral
transcondylar transtubercular approach, avoids these prob-
lems and provides excellent exposure of the ventral brain
stem and related neural and vascular structures (Fig. 18-1).
.
Indications
Intra- or extradural neoplasm of the anterior foramen mag-
num or craniocervicaljunction
.
Extradural
.
Chordomas
.
Metastases
.
Rheumatoid pannus
.
Epidural abscess
.
Bonycompression
144
Positioning
Skin Incision and Superficial Dissection
Vertebral Artery Exposure
Lateral Suboccipital Craniectomy and
Hemilaminectomy
Reduction of Occipital Condyle and Jugular Tubercle
Intradural Exposure
Wound Closure
.
Postoperative Care
.
Osteochondromas
.
Synovialcysts
.
Intramedullary
. Gliomas
.
Fourth ventricle tumors (medulloblastomas, ependy-
momas, ete.)
.
Hemangioblastomas
.
Metastases
.
Extramedullary, intradural
.
Vertebrobasilar dolichoectasia
.
Meningiomas
.
Aneurysms
.
Schwannomas
. Dermoids
.
Epidermoids
.
Paragangliomas
.
Arachnoid cysts
.
Contraindications
. Lifeexpectancy less than 3 to 6 months
.
Medical illness that would preclude major surgery

18 ExtremeLateralTranscondylarTranstubercularApproachto the AnteriorCraniocervicalJunction
145
. Advantages
. Does
not require
corpectomy
and fusion.
. Nocontaminationwith oral flora
. Improvedvisualization of the lesion-brain stem inter-
faceandthe lateral extent of lesion
. Minimalretractionofthe brain stem and cerebellum
. Exposureand control of the vertebral artery and its
branches
. Disadvantages
. Risksof lower cranial nerve deficits
. Increasedincidence of aspiration
pneumonia
. Moredifficultdural closure with CSFleak
. Objective
Thisapproachobtains adequate exposure of the ventral
brainstemand craniocervical junction.
. RadiologicalEvaluation
Preoperativeimaging should
include
magnetic
resonance
imaging(MRI)with gadolinium enhancement to fully char-
acterizethe interface between the lesion, brain stem, and
Posteriorinferior
cerebellara.
Vertebral aa.
Figure18-1
Surgicalapproach to anterior craniocervial junction.
related vasculature. Computed tomography with thin-slice
"bone windows" depicts relevant anatomy, including the
occipital condyle, jugular tubercle, and jugular foramen.
Magnetic resonance angiography can help identify a domi-
nant vertebral artery, dominant venous sinus drainage, or
vascular anomalies. Intraoperative neurophysiological mon-
itoring is imperative.
. SurgicalTechniques
Anesthesia
Ideally, general anesthesia
is induced with the patient
awake under endoscopic guidance to avoid hyperextension
of the neck.
Positioning
The patient is placed in the lateral position with the head
fixed in a Mayfieldclamp. The head is positioned so that the
face and vertex are each angled slightly downward toward
the floor. The ipsilateral shoulder is gently retracted and
taped so as not to obstruct the surgical view (Fig.18-1).
Skin Incision and Superficial Dissection
The skin incision begins 1 em behind the body of the
mastoid at the level of the top of the pinna and extends
as a "lazy S" alongthe posterior marginof the sternoclei-
domastoid muscle to the level of C3or C4,depending on the
exposure
needed
(Fig. 18-2). The superficial
muscles

146
Occipitocervical Junction: Posterolateral Approach
Splenius capitis m.
Sternocleidomastoid
m.
I
Splenius cervicis m.
A
Sternocleidomastoid
m.
B
encounteredincludethe sternocleidomastoidandtrapezius,
which are divided and retracted with the scalp. The middle
muscle layer includes the splenius capitis, longissimus capi-
tis, and splenius cervicis muscles (Fig. 18-3). The splenius
capitis and longissimus capitis are detached from their inser-
tions at the occiput and retracted posteriorly. The splenius
cervicis is detached from its insertion on the transverse
process of(1 and retracted posteriorly (Fig.18-4). The verte-
bral artery lies deep to this muscle as it courses between the
transverse processes of(1 and (2.
Figure 18-2
(A) The patient
is placed
in a lateral or
similar-type
position
with the
face oriented
slight~
downward
toward
the
floor.
The vertex
is oriented
slightly
downward.
The
incision
usually
begins just
above the level of the zygoma,
2 cm posterior
to the
mastoid.
and extends
inferolaterally
over the posterior
aspect of the sternocleidomastoid
to the area of (3-(4.
(B) Scalp, galea, pericranium,
and investing fascia ofthe
neck are incised
and retracted.
This reveals the stern-
ocleidomastoid,
trapezius,
splenius capitis, and splenius
cervicis muscles.
Vertebral Artery Exposure
The deep muscle layer forms the suboccipital triangle,
which is delimited by three muscles, the obliquus capitis
superior, the obliquus capitis inferior, and the rectus capitis
major (Fig. 18-4A). Within the dense fibrofatty tissue
bounded by the suboccipital triangle lies the vertebral
arteryas it coursesoverthe archof(1, aswellastheventral
ramus of (1. Theobliquuscapitis superior is resecteden.
tirely, and the obliquus capitis inferior is detached fromits

18 ExtremeLateralTranscondylar Transtubercular Approach to the Anterior Craniocervical Junction
147
Splenius
Longissimus cervicis m.
capitis m.
insertionat the transverse process of C1 and retracted
pos-
teriorly.The laminae of Cl and C2 are exposed
via subpe-
riostealdissection. The fatty tissue and dense venous plexus
surroundingthe vertebral
artery
are resected
to expose
the artery from
the
atlanto-occipital
membrane
to
C2
(Fig.18-48). The atlanto-occipital
membrane
is sharply
incisedand resected to expose the underlying
dura.
lateral Suboccipital Craniectomy
and
Hemilaminectomy
Aburholeis placed slightly inferior and posterior
to the as-
terion, which overlies the junction
of the transverse
and
sigmoidsinuses.Aroughly 3 x 4 cm craniectomy is created
that is bounded by the sigmoid
sinus anteriorly,
the
midline posteriorly,
and the foramen
magnum
inferiorly
(Fig.18-4C). The rim
of the foramen magnum can be drilled
offwith a cutting bur (Fig. 18-4D).
Bleeding is commonly
encounteredfrom the prominent
condylar emissary vein as
it passestoward the jugular bulb. A hemilaminectomy
of Cl
completesthe extradural exposure. (Fig. 18-5A)
ReductionofOccipitalCondyle and Jugular Tubercle
Theatlanto-occipital joint is exposed with sharp dissection
ofthesynovial capsule. A medium
diamond
bur is used to
reducethe posterior third
of the occipital
condyle. The hy-
poglossalcanal is skeletonized
by removing bone superiorly
toward the jugular
bulb. The jugular
tubercle
is medial and
inferior to the adjacent
jugular bulb. The tubercle is reduced
byhollowingthe bony prominence
until a thin shell of bone
remains.The "egg-shelled"
bone is then dissected free from
thedura(Fig. 18-58).
Cranial
nerves IX, X, and XI are vul-
nerableduring
this maneuver
as they pass superiorly
from
thebrain stem to the jugular
foramen.
Reduction
of the
jugular tubercle
maximizes
the intradural
exposure
of the
ventralaspect of the brain
stem.
Figure 18-3
The trapezius isretracted mediallyand the
sternocleidomastoid isdivided near the insertion overthe
mastoid and reflected laterally.Thisrevealsclearlythe mid-
dle muscle layerwith the splenius capitis and the splenius
cervicis. Anterolaterally, the internal jugular is often en-
countered initsextracranialcourse.
Intradural
Exposure
The dural incision begins just medial to the upper bend of
the sigmoid sinus and extends inferiorly to C2,passing me-
dial to the vertebral artery. Aperpendicular incision is then
extended laterally just superior to the site where the verte-
bral artery penetrates the dura. Trimming a dural cuff
around the vertebral artery facilitates mobilization and sub-
sequent closure. Careshould be taken to avoid the posterior
spinalartery,whichisoftenincorporatedintothe duralcuff
(Fig. 18-6). Thedural leafletsare reflectedanteriorlyand
secured with sutures. Aself-retaining retractor is placed on
the cerebellarhemisphere.Resectionof thelesionproceeds,
facilitated by exposure and mobilizationof the vertebral
arteryandthe lowercranialnerves.
The arachnoid is sharply opened to reveal the lateral
medulla, the vertebral artery and its branches, and the
lower cranial nerves. It is crucial to clearly identify and fol-
low the course of cranial nerves XII,XI.X,IX,VII,VIII,and VI
as well as the posterior inferior cerebellar artery (PICA),an-
terior inferior cerebellar artery (AICA),and vertebrobasilar
junction (Fig.18-7). Lesionsofthis area (e.g.,foramen mag-
num meningiomas, schwannomas, etc.) will often be adher-
ent to and deform the normal regional anatomy. At this
point, resection of the lesions proceeds with the use of
standard microsurgical techniques.
Wound Closure
Whenever possible, the dura should be closed in a water-
tight fashion with
either
running
or interrupted
4-0
Neurilon sutures. Often due to dehydration, cautery, or ia-
trogenic injury, the dura cannot be primarily closed.For
thesecases,allograftdural substitute(bovinepericardium,
synthetics) can be useful. When available, pericranium is an
excellent graft material. An autologous fat graft (e.g.. ab-
dominal fat graft) or rotational posterior cervical muscle

148
Occipitocervical Junction: Posterolateral Approach
Transverse
process of C1
C2
-in: "" '
~~
'r'
B
'T""'"..:
~
i
..
Figure 18-4
(A) The suboccipital triangle is bounded by three muscle groups: (1) SOb (obliquus capitis superior), (2) lOb (obliquus capitis inferior),
and (3) RCMa(rectus capitis major). The C2 nerve root is also seen in this deep layer crossing over the vertebral artery. (8) The anatomical dissection.
A. the suboccipital triangle, in the depths of which the vertebral artery courses behind the atlanto-occipital joint and across the posterior arch of(1,
issituated inthe depths ofthe area between the superiorand inferiorobliqueand the rectus capitisposterior major.B,the superiorobliquemuscle
A
11

18 ExtremeLateralTranscondylarTranstubercularApproachto the Anterior CraniocervicalJunction
149
Posterior
condylar
foramen
Jugular
foramen
Area of bony
resection
Condylar
fossa
Mastoid
process
Jugular
tubercle
Hypoglossal
canal
Occipital
condyle
Anterior rim of
foramen magnum
Vertebral a.
D
Figure18-4(Continued) hasbeen reflected laterallyand the rectus capitisposteriormajormuscle inferomedially.Thefloorofthe suboccipital
triangleisformedbythe posterior atlanto-occipital membrane and the posterior arch ofthe atlas. The vertebral artery and the C1nerve root,
whicharesurroundedbythe vertebral venous plexus,course along the upper surface ofthe posterior archof the atlas. C,the musclesforming
themarginsofthe suboccipital triangle have been reflected to expose the vertebral artery ascending through the C1 transverse process and be-
hindtheatlanto-occipital joint and the surrounding venous plexus. 0, the venous plexus around the vertebral artery has been removed. The ver-
tebralarterygivesoff muscular branches, passes medially behind the atlanto-occipital joint and above the posterior arch of C1, and turns upward
andanteriorto penetrate the dura. (e) The area of bony resection, which is bounded by the sigmoid sinus anteriorly, the midline posteriorly, and
theforamenmagnum inferiorly. (D) The rim of the foramen magnum can be drilled off with a cutting bur. The drawing demonstrates
the surgical
view after the suboccipital
craniectomy.

150
OccipitocervicalJunction:PosterolateralApproach
A
Dura
A
-I
Figure18-5
(A) The anatomical
dissection.A,a suboccipitalcraniec.
tomy hasbeen completed andthe
right halfof the posterior archoW
has been removed. The posterior
root of the transverse foramenof
the atlas has been removedwhi~
preserving the portion of the tipd
the transverseprocessof theatlasto
which the rectuscapitislateralis,lev.
ator scapulae,and superioroblique
musclesattach. Theatlanto-occi~.
tal joint and the posterior condylar
emissaryveinareexposed.Theven-
tral rami of the C1 and C2 nerve
roots pass behind the vertebral
artery. Thedorsal ramusof C2give!
rise to the greater occipital nerve,
which passes through the semi.
spinaliscapitisto reachthe posterioc
scalp.B,the areaabovethe occipital
condyle has been drilled to the
depth of the cortical bonesurround-
ing the
hypoglossal canal. The
change from cancellousto cortical
bone indicatesthat the hypoglossal
canal has been reached. C.thehy-
poglossalcanalhasbeenopenedto
expose the venous plexus, which
surrounds the hypoglossalnervein
the canal and connects the basilar
venous plexuswith the marginals~
nus, which encircles the foramen
magnum. The dorsal ramusofthe
C1nerve root, alsotermed thesub-
occipital nerve,passesbackwardbe-
tweentheposteriorarchoftheatlas
and the vertebral artery, supplies
the musclesbordering the suboccip-
ital triangle, and sendsfiberstothe
rectus capitis posterior minorand~
the semispinalis capitis muscles.
(8) Reduction
of one third of the '
posterior aspect of the occipital~
condyle isremoved until the jugular.
bulb isencountered. Boneremoval
isthen directed superiorly withthe
bone between the bulb andcond~e
removed to
skeletonize the hy-
poglossal nerve. Thejugular tuber.
cle is located medial and inferiorto
the adjacent jugular bulb. 1, poste-
rior fossadura; 2,terminalsigmoidl
jugular bulb; 3, hypoglossalnerve;4,
occipital condyle;5,vertebralartery:
6, C11ateralmass.

18 ExtremeLateral Transcondylar Transtubercular Approach to the Anterior Craniocervical Junction
151
Occipital condyle
napmaybe placed to prevent
CSF leakage. We have found
thatplacement of such fat grafts may also be helpful in re-
ducingpostoperative headaches by minimizing contact of
the dura with the
overlying
musculature.
The
muscle
retractorsare removed and the wound is irrigated
with co-
piousantibioticirrigation. Meticulous hemostasis is estab-
Figure 18-6
The dural incision begins just medial to
the upper bend of the sigmoid sinus and extends inferi-
orly to the C2 lamina, passing medial to the vertebral
artery. A perpendicular
incision is then extended
later-
ally just superior to the site where the vertebral artery
penetrates
the dura.
lished. Careful closure of the middle and superficial muscu-
lar layers is important
to reestablish anatomical planes
and to minimize dead space. If needed, a JP-drain can be
placed in the suboccipital/CI-C2
area to further prevent
hematoma and seroma accumulation. Staples are placed at
the skin and a mastoid pressure dressing is applied.
~~.,
,
-~~,
Figure
18-7
Intradural
exposure
is completed
with
the dural flaps retracted
to reveal the anterior dival,
foramen magnum,
and spinal structures.
1, cerebellum;
2, C1-rootlets;
3, dentate
ligaments; 4, choroid plexus;
5, vertebral artery; 6, posterior inferior cerebellar artery;
7, facial nerve; 8, vestibulocochlear
nerve; 9, glossopha-
ryngeal nerve; 10, vagus nerve; 11, accessory nerve.

......
152
Occipitocervical
Junction:
Posterolateral
Approach
.
Postoperative Care
The patient is managed in the intensive care unit postopera-
tivelywith particular attention to respiratory status. Traction
on the lower cranial nerves and subsequent swelling creates
a significant risk of aspiration. As such, we have often kept
Suggested
Readings
1.
Arnautovic
KI. AI-Mefty O. Foramen
magnum
meningiomas.
I and II.
Contemp Neurosurg
2000;22:1-6
2.
Bertalanffy
H. Seeger W. The dorsolateral.
suboccipital.
transcondylar
approach
to the lower clivus and anterior
portion
of the craniocervi-
cal junction.
Neurosurgery
1991 ;29:815 -821
3.
Day JD. Tschabitscher
M. Microsurgical
Dissection
ofthe
Cranial Base.
New York: Churchill
Livingstone;
1996: 107 -123
4.
Matsushima
T, Matsukado
K. Natori
Y. Inamura
T, Hitotsumatsu
T.
Fukui M. Surgery
on a saccular
vertebral
artery-posterior
inferior
patients electively intubated
until postoperative
day 1or2to
prevent respiratory
airway complications.
Speech and swal.
lowing evaluation should begin after extubation. Oralfeeds
should be withheld until the patient can safelytoleratethem
Parenteral nutrition
should be instituted
early on to improve
wound healing and to prevent sepsis.
cerebellar
artery
aneurysm
via the transcondylar
fossa (supracondy-
lar transjugular
tubercle)
approach
or the transcondylar
approacb:
surgical
results
and indications
for using two different
lateral sku!.
base approaches.J
Neurosurg
2001 ;95:268-274
5.
Rhoton ALJr. The posterior
cranial
fossa: microsurgical
anatomy and
surgical approaches.
Neurosurgery
2000;47:S151-
S209
6.
Sen CN. Sekhar LN.An extreme
lateral approach
to intradural
lesions
of
the
cervical
spine
and
foramen
magnum.
Neurosurgery
1990;27:197-204

SectionII
MidcervicalSpine
A.Pathology of the Midcervical
Spine
. 19.CongenitalOsseous Anomalies of
the Mid-to lower Cervical Spine
. 20.CervicalSpine Degenerative
Diseaseand Cervical Stenosis
. 21. Intramedullary Tumors of the
Spinal Cord
. 22.Traumaof the Mid- and lower
CervicalSpine
B.Anterior Approach
. 23. CervicalSpine: Anterior Approach
. 24.AnAnterior Microforaminotomy
(Transuncal)Approach to the
CervicalSpine
. 25.Odontoid Screw Placement
C.Posterior Approach
. 26. PosteriorApproaches to the
CervicalSpine
. 27. Cervicallaminectomy
. 28.Cervicallaminoplasty
. 29.Posterior Cervical Foraminotomy
.
30. Posterior Cervical Diskectomy
.
31. Posterior Stabilization UsingThe
Bohlman Triple-Wire Technique
. 32 Posterior Stabilization Using the
Titanium Rectangle Technique
. 33. Posterior Exposure and Release
of locked/Perched
Facets
.
34. Posterior Subaxial Cervical Spine
Stabilization Using Sublaminar
Cables
. 35. Posterior Cervical Spine
Stabilization Using Interfacet
Wires
. 36. Posterior Cervical Spine
Stabilization Using lateral Mass
Plates
.
37. Surgical Management of
Intramedullary Spinal Cord
Tumors
. 38. Posterior Approach for Resection
of Intradural Extramedullary
Tumors

CongenitalOsseous Anomalies of the
Mid.to lower Cervical Spine
JamesT.Guille and Henry H. Sherk
. Classification
. PhenotypicFeatures
Torticollis
PterygiumColli
FacialandOcular Deformities and Hearing Deficits
Sprengel'sDeformity
CongenitalScoliosis, Kyphosis, and Lordosis
ofthe Thoracolumbar
Spine
SagittalPlane Deformities
of the Cervical Spine
OtherCongenital
Musculoskeletal
Anomalies
CardiopulmonaryDefects
GenitourinaryDefects
Thepresenceofa congenital osseous cervical spine anom-
alyisperhapsmost significant in that it often heralds other
underlyingcongenital systemic malformations. This factor
isof paramount importance
to the
treating
physician,
whosemainattention may be directed solely toward the
patient's
neck.Thetopic of congenital osseous anomalies of
thecervicalspine is dominated by the subject of Klippel-
Feilsyndrome.Becausethis entity has the most important
clinicalrelevance,the thrust of this chapter will focus on
thediagnosticworkup, including physical and radiographic
examination
ofthe syndrome itself and of the various con-
genitalsystemicmalformations that are known to occur in
conjunctionwith Klippel-Feilsyndrome. Forease of discus-
sion,thetermKlippel-Feilsyndrome will be used throughout
thisdocumento refer to congenital fusion of the cervical
vertebrae.
Thischapter, however, does not discuss the prob-
lemsuniqueto fusionsof the craniovertebral and atlantoax-
ialjunction.
Theprevalenceof Klippel-Feil syndrome is unknown be-
causethemajority of individuals who have this condition
areasymptomaticand may not have any other associated
anomalies.
Ina study of the skeletal specimens of 1400 cer-
vicalspines,Brownet al found that only 10of the 75 (0.71%)
fusedsegmentsdiscovered below the second cervical verte-
braewerecongenitalin nature.! Radiographs of 1158speci-
menswereavailable, and congenital fusion was noted in
only0.60%, mostcommonlyseen as the so-calledwasp-
.
Radiological Evaluation
Radiographs
Cineradiography
Tomograms and Computed Tomography
Magnetic Resonance Imaging
.
Evaluation of Stenosis and Instability
.
Neurological Problems
.
Spinal Stenosis and Instability
.
Treatment
.
Conclusion
waisted vertebrae. Although congenital fusion may occur at
any levelin the cervicalspine, -75% of cases occursome-
where in the first three cervical vertebrae, and -50% of
cases involvethree or fewer vertebrae.!2Ip!1In the majority of
series,the mostcommonsite of fusionis between the sec-
ond and third cervical vertebrae, with fusion of the fifth and
sixth cervical vertebrae seen next most commonly. These
sites of fusion may be inherited in an autosomal dominant
or autosomal recessive fashion, respectively.3
.
Classification
Various classification schemes have been offered in the lit-
erature. Some are only descriptive, whereas others attempt
to correlate anatomical and radiographic findings with clin-
ical pictures. Some classifications were designed to predict
future neurological status based on radiographic findings.
Aswill be seen, many of the classifications are variations of
each other.
Klippeland Feilclassified the syndrome into three groups
based on the site and extent of the fusion.4Type I is fusion
of the cervical and upper thoracic vertebrae. Type IIis fu-
sion isolated to the cervical spine. Type IIIis fusion of the
cervical vertebrae associated with lower thoracic or lumbar
fusions. Noclinically relevant correlations have been made
155

156
MidcervicalSpine:Pathologyof the MidcervicalSpine
with this classification, although many authors continue to
useit.
Hensinger has popularized
a classification
based on a
variation of the findings made by McRae that described
three patterns of potentially
unstable fusions.5-7Type I is
fusion of the second and third cervical vertebrae with oc-
cipitalization of the atlas. Type II is a long fusion with an ab-
normal occipitocervical junction. Type III is two segments of
block fusion with a single open interspace. Type I and II fu-
sion patterns involve the upper cervical spine and will be
discussedelsewhere in this book. The Type III pattern of fu-
sion, with its two long lever arms and one open disk inter-
space,has long been suspected of having a poor outcome,
which has been attributed
to the mechanics of overuse at
the one open disk space.Long-term data from other studies,
however, have not shown an increased incidence of neuro-
logical problems from this fusion pattern.
Mitchie and Clark placed 13 patients with osseousanom-
alies of the cervical spine (eight with congenital fusions)
into clinical groups based on presentation.s The groups in-
cluded root compression, cord compression, myelopathy,
syringomyelia,
vascular
disorders,
and internal
hydro-
cephalus.No correlations or predictions were made, and the
significance of this clinical grouping is unknown, especially
basedon such a small number of patients.
Nagib et al divided the nine patients in their series who
had neurological deficits (21 total patients in the series) into
three groups based on the most significant anomaly and the
probable mechanism of injury.9 Type I is an unstable fusion
pattern, such as two long segments of block vertebrae with
an intervening open disk space.Type II includes cranioverte-
bral anomalies. Type III is congenital fusion associated with
spinal stenosis.Patients with type I and II patterns were ad-
vised to avoid contact sports; if any neurological symptoms
or deformity developed, operative stabilization was recom-
mended.Patientswith type III patterns were advised to avoid
strenuousphysical activity and have decompression and sta-
bilization if neurological symptoms developed.
Three patterns of fusion were observed in the series of
Cuille et al.lOType I is isolated block vertebrae anywhere in
the cervical spine. Type II is two segments of block verte-
brae separated by one isolated unfused vertebra with open
disk spaceson either end. Type III is two segments of block
vertebrae separatedby an open disk interspace. No correla-
tion was seenin reference to the type of fusion pattern and
the later presence of signs or symptoms that could be at-
tributed to the syndrome.
Pizzutillo
et al described a functional
classification.11,12
ClassI is normal range of motion in the upper and lower cer-
vical spine with no translational instability. ClassII is inter-
segmental hypermobility of the upper cervical spine, basilar
impression, or iniencephaly. ClassIII is intersegmental hy-
permobility
of the lower cervical spine, or spondylosis. Class
IV is a combination of classII and classIll. Treatment recom-
mendations were basedon this classification. Asymptomatic
patients in class I should be followed with serial observa-
tion. Class II patients should be followed annually, or more
frequently if necessary.These patients should avoid contact
sports. Class III patients should be treated symptomatically
for spondylosis. ClassIV patients should be treated asthose
patients in class II and class Ill. This study concluded that
patients
with
hypermobility
of the upper
cervical
spine are
at increased
risk for neurological
problems,
whereas those
with
involvement
of the lower cervical
spine are likely to de-
velop early degenerative
disease.
.
Phenotypic Features
The original description
of the Klippel-Feil
syndrome in-
cluded not only congenital fusion of the cervical vertebrae
but decreased range of neck motion and a short neckwitha
low hairline. This triad has been reported in approximately
half of the patients with the syndrome, partly due to the
subjective nature of what is considered a short neck or low
hairline (Fig. 19-1 ).2.13The most consistent
finding in these
patients is limited range of motion of the neck, especially
lateral side bending. Flexion and extension, which occur
primarily
at the occipitocervical
junction,
and rotation,
which occursprimarilyat the atlantoaxialjunction,are usu-
ally preserved unless these levels are fused or anomalous.
Someauthorshaveobservedthat iflessthan three vertebral
levels are fused, loss of motion may be unnoticeable,
and
much of neck motion may be compensated
at adjacent
unfused levels.
Figure19-1
A child with
Klippel-Feil
syndrome,
with a short neck.
low hairline,torticollis, and a Sprengel'sdeformity on the left side.

Torticollis
19
Congenital Osseous Anomalies of the Mid. to Lower Cervical Spine
157
Torticollisis often a clinical manifestation of congenital
osseouscervicalspineanomaly,usually cervicothoracicscol-
iosisorahemivertebra.Tumors of the posterior fossa or in-
fectionmayalsocreate apicture of torticollis.The deformity
ischaracterizedbya lateral tilt of the head with rotation of
theface.Oftenthe deformityis mild and is compensated un-
consciously
bythe patient. Facialasymmetry, which may be
permanent,
canoccurin longstanding, untreated situations.
Whenthereis no fixed bony deformity, the condition re-
sponds
welltostretching;tenotomy of the sternocleidomas-
toidmayberequired in recalcitrant states and yields good
resultswhenperformedat a young age. Ifthe etiology is of a
bonynature,aunilateralhemiepiphysiodesis or fusion could
beperformedon the convex side of the curve in a young
childinthehopethat continued growth on the concave side
wouldprovidecorrection. Ofcourse, there has to be the as-
sumptionthat growth potential exists on the concave side,
asdemonstratedby open disk spaces and pedicle shadows.
Allchildrenwho present with torticollis should have cervi-
calspineradiographsdone to rule out osseous etiologies.
PterygiumColli
Patientswith Klippel-Feilsyndrome may have pterygium
colli,whichisvarious degrees of webbing of the skin from
thesideofthe neck to the shoulders (Fig. 19-2).14When
Figure19-2
A child with Klippel-Feil syndrome showing bilateral
pterygiumcolliandtorticollis. Note the hearingaid.
pterygium exists bilaterally, it gives the appearance of a
short neck; when unilateral, it can give the appearance of
torticollis.
Pterygium colli is commonly
seen
in girls
with Turner's syndrome. Various techniques
describing
Z-plasties and rotational flaps have been described to ad-
dress the deformity. Rarely,however, do these procedures
improve range of motion of the neck.These cosmetic defor-
mities are usually referred to a plastic surgeon for further
consideration.
Facial and Ocular Deformities
and Hearing Deficits
The face and head of individuals with congenital cervical
spine problems should be inspected for abnormal faciesand
ear anomalies.IS.16Facial asymmetry may be secondary to
longstanding torticollis. Congenital cervical spine anomalies
have been associated with Apert's syndrome and Crouzon's
disease. Block and hemivertebrae in the cervical and tho-
racic areas, as well as facial and ear deformities, have been
reported in patients with oculoauriculovertebral dysplasia
(Goldenhar's syndrome). Cervico-oculo-acoustic dysplasia
(Wildervank syndrome) consists of Klippel-Feil syndrome,
abducens nerve paralysis, retraction of the eyeball, and
deafness. Duane lateral rectus contracture and lateral rectus
palsy has been reported
in patients
with Klippel-Feil
syndrome.
Ahistory for hearing impairment should be sought and a
basic hearing test performed in all of these patients.17-19
Hearing loss has been reported to occur in -30% of patients
with Klippel-Feilsyndrome. Eardeformities, with and with-
out deafness, and facialmalformations can occur in patients
with Klippel-Feilsyndrome. The outer ear, ossicles, semicir-
cular canals, mandible, and parts of the maxilla and hyoid
bones arise from the mesenchyme of the branchial arches.
Therefore, if the cervical somites are damaged during
embryogenesis, the nearby branchial arches are at risk as
well. Sensorineural impairment
or conductive or mixed
hearing loss is usually the basis of the deafness. As men-
tioned earlier, the ossicles may be congenitally malformed
with resultant conductive hearing impairment. An aware-
ness of these problems is especially important for the oto-
larynologist because several cases of operative complica-
tions, such as stapes gushers, have been reported.20
Sprengel's Deformity
Congenital elevation of the scapula, also known as Spren-
gel's deformity,isseen in -25 to 35%of patients with Klippel-
Feilsyndrome (Fig.19-3). Clinically,the appearance is that
of uneven shoulder heights, and bilateral Sprengel's defor-
mity can give the appearance of a short neck. Normally the
scapula descends to its normal thoracic position by the age
of 8 weeks. In Sprengel's deformity, not only does the
scapulafailto descendto its usuallocation,but the bodyof
the scapula is often hypoplastic and malrotated. Thismayor
may not be seen in association with an omovertebral bone,
which is a bony or fibrous band of tissue spanning from the
cervical or upper thoracic vertebrae to the medial border of
the scapula that acts as a tether to scapular descent and
shoulder motion. An omovertebral
bone should not be

---
158
MidcervicalSpine: Pathology of the Midcervical Spine
\
I
\
\.
(
""
Figure 19-3
Congenital elevation of the scapula (Sprengel's defor-
mity) on the right side with an omovertebral
bone at the level of the
fourth cervical vertebra.
confusedwith a cervical rib, which can occur in up to 15%of
patients, especiallywomen (Fig.19_4).21,22Cervical ribs are
usuallyasymptomatic, although a cervical rib at the seventh
cervical vertebra can cause thoracic outlet syndrome.23 If
the elevation of the scapula is cosmetically unacceptable
and if the range of motion of the shoulder is decreased, the
scapula can be operatively released from its muscular at-
tachments and reattached in a more anatomical position by
either the Woodwardor Green procedure.
Congenital Scoliosis,Kyphosis,and Lordosis
of the Thoracolumbar Spine
Congenital scoliosis, kyphosis, and lordosis individually, or
in combination, can occur with congenital cervical spine
fusions in more than half of patients711.24-26The exact
prevalence is unknown because many studies combine all
types of deformities and much of the research has come
from tertiary
referral centers that specialize in these
problems. What is known is that these deformities can be
severe and of such a magnitude as to require operative
treatment. Theiss et ai, in their series of 120 patients with
Klippel-Feilsyndrome of whom 65 had scoliosis,found that
no particular fusion pattern put the patient at risk for
neurological symptoms and that neither the number of
Figure 19-4
Anteroposterior radiograph showing congenital cervi.
cothoracic scoliosis and cervical ribs.
vertebrae fused nor the levels fused were predictive of
symptomatology.24
Clinically, the most relevant of these deformities forthe
present discussion would be cervicothoracic scoliosis,21A
cervicothoracic curve, by definition, has its apex at the
cervicothoracic junction, with a hemivertebra often found
at this level. The curve may have a congenital component
or it may be a compensatory curve above another curve.
Outwardly, this deformity may be manifested by uneven
shoulder heights, rotation of the upper thorax, and torti-
collis. Ideally, these deformities should be addressed early
because
cosmetic
improvement
is often a challenge.
Bracing has been shown to be ineffective in controlling
congenital
spinal deformities,
especially
in the cervi-
cothoracic region, and spinal arthrodesis is often the only
option.
Sagittal Plane Deformities of the CervicalSpine
Congenital osseous anomalies of the cervical spine can
also create lordosis and kyphosis in the sagittal plane. Se-
vere lordosis is usually seen in patients with iniencephaly.
Iniencephaly is characterized
by a short immobile neck
with a hyperextension
deformity of the head.28 Thereis
also an occipital defect and cervical spina bifida. Becauseit
occurs at the craniovertebral junction, this topic is dis-
cussed elsewhere in this book. Congenital cervicothoracic
kyphosis is rare, with a high incidence of neurological
problems, especially if the deformity
is the result ofa
failure of formation. For curves less than 50 degrees,
posterior spinal arthrodesis in situ is usually sufficient,
and the potential exists for continued
correction with
-

19
Congenital Osseous Anomalies of the Mid-to LowerCervical Spine
159
growthif anterior growth centers exist. Larger deformities
arebest treated
with
combined
anterior
and
posterior
arthrodesis.
OtherCongenital Musculoskeletal Anomalies
Othercongenital musculoskeletal anomalies have been de-
scribed,but with less frequency. These are listed in part in
Table19-1.
Cardiopulmonary Defects
Congenital anomalies of the cardiovascular system are said
to occur in 4.2 to 14%of patients with Klippel-Feilsyndrome.
especially girls.13,29,3o
Aventricular septal defect has been the
most common anomaly reported in most series. Atrial septal
defects. dextrocardia. aortic stenosis,and patent ductus arte-
riosus have also been reported. The cardiopulmonary tree is
a common site for anomalous development, with reports of
Musculoskeletal
Table 19-1
Associated Anomalies Reported with Klippel-FeilSyndrome
Genitourinary
System
facial/palate/eye/ear
deformities
Torticollis
Pterygiumcolli
Sprengelsdeformity
Scoliosis
Vertebralanomalies
Cervicalribs/rib anomalies
Syndactyly/polydactyly
Thumbanomalies
Supernumerarydigits
Carpaland metacarpal fusion
Shortphalanges
Clinodactyly
Congenitaldislocation
of radial head
Radial/ulnaraplasia or hypoplasia
Radioulnarsynostosis
Pectusexcavatum/carinatum
Pectoralismuscle asymmetry
Pterygium
Hipdysplasia
lowerlimb asymmetry
Cavusfoot/club foot
Peripheral/CentralNervous System
Synkinesia
Cranialnerve palsy
Homer'ssyndrome
Ptosis
Nystagmus
Duanelateral rectus contracture
lateralrectus palsy
Deafness
Microtia
Absentauditorycanal
Speech
retardation
Agenesis/dysgenesisof kidney (unilateral> bilateral)
Duplication of collecting system
Bladderdeformities
Horseshoekidney
Tubularectasia
Renalectopia
Hydronephrosis
Vaginalagenesis
Ovarianagenesis
Uterine anomalies
Hypospadias
Cryptorchidism
Cardiovascular/Pulmonary System
Ventricular/atrial septal defects
Patent ductus arteriosus
Truncus arteriosis
Coarctationof the aorta
Dextrocardia
Aortic stenosis
Valvularmalformations
Conduction defects
Agenesisor hypoplasiaof lung
Pulmonarystenosis
Gastrointestinal System
Megacolon
Neurenteric cysts
Situs inversus
Tracheoesophagealfistula
Hepaticdeformities

.
RadiologicalEvaluation
Radiographs
160
MidcervicalSpine:Pathology of the Midcervical Spine
pulmonary aplasia and hypoplasia and pulmonary stenosis.
Signs of heart failure can include cyanosis, dyspnea, short
stature, and fingernail clubbing. A baseline electrocardio-
gram is warranted for all patients with a known fusion in
the cervicalspine,especially if an operation is planned.
Genitourinary Defects
The prevalence of genitourinary defects in patients with
Klippel-Feil syndrome has ranged from 2 to 64%.2.13.31
The
most common anomaly is unilateral renal agenesis, which is
said to occur 400 times more frequently in patients with
Klippel-Feil syndrome than in the general population. The
second most commonly seen anomaly is malrotation of a
normally functioning kidney. Renal pelvic and ureteral du-
plication occurs 25 times more frequently in these patients
than in the general population. Pelvic renal ectopia is usu-
ally unilateral and involves a normally functioning kidney
(Fig. 19-5). Renal dysgenesis occurs 40 times more often in
patients with Klippel-Feil syndrome than in the general
population and may predispose these patients to uremia.
Allpatients with Klippel-Feil syndrome should have an ul-
trasound evaluation of the renal system. An intravenous
pyelogram need only be done if abnormalities are found on
the sonogram or if the study is inconclusive.32If the sono-
graphicstudy reveals abnormalities in the renal system, the
Figure 19-5
Intravenous pyelogram showing an ectopic kidneyin
the confinesof the pelvis.
internal female reproductive organs should be scanned~
well.
The standard cervical spine series is the firstsetofradio
ographicstudies to obtain.Thisshouldincludeanantero-
posterior view, an open-mouth odontoid view,andlaterl
neutral,
flexion,
and
extension
views.33
Hemivertebraea~
best seen on the anteroposterior
view. The three later~
views provide the most information. First,the levelsoffu.
sion are easily identified
on the neutral
view. If thereis.
question
whether
two levels are fused, the flexion
andel'
tension
views will demonstrate
a change in the sizeoft~
distance
between
the spinous
processes.
Evidence ~i
translational
instability
is best seen comparing the nexiOi
and extension views. Measurement
of spinal stenosis [I
done on the lateral filmsas well.StandingposteroanteriOi
and lateral radiographs of the thoracolumbosacral Spill!
should be done to evaluate for any other congenitalspinl
deformity.
Asidefrom beingfused.the vertebraeareoftenwidenet:
and flattened. The vertebrae may assume a wasp-waistap-
pearance,
with the anterior
and posterior
cortices concave
toward the center of the vertebral body. The neural fora.
mena should be inspected for osteophytes, which may be
present in older individuals with degenerative changes.
Diskspacesmaybeabsent or narrowed.Ithas been shown
by magnetic
resonance
imaging
(MRI) that protrusion orl
disk material may occur in levels thought to be fused onra.
diographs.1OIn general, fusion of the posterior
elements
parallelsfusionofthe vertebralbodies.However,in young
children,carefulattention should be paid to the laminae
and posterior elements because these areas may ossifybe.
fore the intervertebral
spaces.34
Cineradiography
Cineradiography
is a means to evaluate dynamically
the sta-
tus of the cervical spine through its range of motion under
fluoroscopy.This method is an important tool for the evalu.
ationofthe upper cervicalspine but has lessimportantap-
plications in the evaluation of the mid- to lower cervical
spine.
Tomograms and Computed Tomography
Tomograms are helpful in identifying hemivertebrae andin
determining whether vertebral levels are fused; however.
they are not routinely
ordered.
Computed
tomography (G'
may be done to better define osseous anatomy and evaluate
for intraspinal anomalies; again, these studies are rarely
performed routinely.
Magnetic Resonance Imaging
The advent of MRI has greatly enhanced
our ability to eval-
uate the soft-tissue anatomy in patients with congenital

19
Congenital Osseous Anomalies of the Mid-to LowerCervical Spine
161
fusionsofthe cervical spine. Intraspinal lesions such as sy-
ringomyelia,meningioma,
and lipoma are clearly identified
(Fig.19-6). Evaluation of the intervertebral
disks by MRI
can show disk desiccation,
herniation,
and
protrusion
Jig. 19-7). In the series of Guille et al degenerative
changes
ofthe disks were seen in all of the patients,
as demon-
stratedby a low-intensity
signal on the T2-weighted
im-
ages.1ONineteen
of their
22 patients
(86%) had abnor-
malfindings on the MRI scans, including
disk protrusion,
osteophytes,and narrowing at the craniovertebral
junction.
Fourpatients had a cervical syringomyelia.
No spinal steno-
sisorinstability was documented
in their patients
at an av-
erageage of 35 years (range, 26-57
years). This is in con-
trastto Ritterbusch et al who documented
stenosis of 9 mm
orlessin five of 20 patients
(25%) and subluxation
greater
than5 mm in five of 20 patients
(25%) on MRI.35Four cord
abnormalities were
seen
in
three
patients:
one
hy-
dromyelia,one Arnold-Chiari
I malformation,
and
two
diplomyelia.Ulmer et al reported
the findings of 24 patients
evaluatedby MRI and CT studies.36 Ten of the 24 patients
(42%)hadcervicalspondylosis, most commonly seen in the
lowercervicalspine, or disk herniation. Fivepatients had
cervicalcord dysraphism
or diastematomyelia
and two
patientshadan Arnold-Chiaritype Imalformation.
Figure19-6
Magnetic resonance image of the cervical spine show-
inganintraspinal lesion.
Figure 19-7
Magneticresonance image of the cervical spine show-
ing marked degenerative changes. Note that the disk is approaching
the cord, but there isno bony stenosisof the cervicalcanal.
.
Evaluation of Stenosisand Instability
Different authors have used various criteria to evaluate
spinal canal stenosis and vertebral instability. These mea-
surements are notoriously difficult to make secondary to
the congenitally dysplastic vertebrae and, unfortunately, as-
sumptions or extrapolations are often made. The sagittal di-
ameter of the canal is measured on the neutral lateral view,
from the midpoint of the posterior aspect of the vertebral
body to the nearest point on the line representing the junc-
tion of the laminae and spinous process. Normal values vary
according to the age of the patient, vertebral level, and tar-
get distance.37.38Generally, in the subaxial cervical spine an
osseous canal less than 12 mm is considered stenotic. The
Torg/Pavlov ratio, which is the ratio of the spinal canal to
the vertebral body, is another method to evaluate for spinal
stenosis.39 The ratio is determined
by measuring the
distance from the midpoint of the posterior aspect of the
vertebral body to the nearest point on the corresponding
spinolaminar line divided by the anteroposterior width of
the vertebral body.Aratio less than 0.8 is considered abnor-
mal. Anterior or posterior translation of one vertebral body
relative to another of greater than 5 mm may signifyinsta-
bility, especially if associated with neurological findings.
Flexion and extension of the cervical spine may exacerbate
this relationship between the vertebrae. Thecombination of
radiographic findings and neurological signs makes the
diagnosis easier to make. Difficulty arises with what to do

162
MidcervicalSpine:Pathologyof the MidcervicalSpine
with an individualwith radiographic findings alone. Predic-
tion of future neurological risk based on positive radi-
ographic findings in an asymptomatic patient is important,
yet difficultto perform.
. Neurological Problems
Thedistinction between signs and symptoms is important.
Signsare a physical manifestation of a condition, whereas
symptoms are subjective assessments offered by the pa-
tient. There are no specific symptoms that can be attributed
directly to congenital fusions in the cervical spine. Gener-
ally. these are localized to the head. neck. and upper ex-
tremities and can include headaches. syncope, weakness.
and numbness, all of which may be nondescript. Radicu-
lopathies are usually the result of nerve root irritation or
impingement from osteophytes at the hypermobile seg-
ments adjacent to the fused vertebrae. Long-tract signs may
develop from longstanding spinal cord compression. Awell-
held belief is that signs and symptoms. and their magni-
tude, are related to the location and extent of the congenital
fusion; however. many investigators have found little truth
to this
statement.
Neurological problems
have been
reported in patients with isolated fusions of only two
vertebrae.40 Synkinesia is a phenomenon whereby mirror
movements are observed. most often in the upper extremi-
ties. 41-43The etiology is unknown. but a central nervous
system anomaly is suspected. The condition is more com-
mon in younger children and tends to improve with age.7
Individuals who exhibit synkinesis should be referred to an
occupational therapist as early as possible for rehabilitation.
Trauma to an individual with a congenital cervical spine
anomaly can be catastrophic. as has been demonstrated in
many reports.9.44-54Most of these reports. however.describe
patients who had congenital anomalies of the upper cervi-
cal spine. Torg et al noted an association between neuro-
praxia of the cervical spinal cord in football players with
congenital fusion and a decreased anteroposterior diameter
of the bony canal.39These authors recommend that players
with stenosis and a congenital anomaly should be treated
and counseled on an individual basis because no guidelines
have been established for this subset of patients.
. Spinal Stenosis and Instability
The topic of spinal stenosis and instability of the cervical
spine in individuals with Klippel-Feilsyndrome is a debated
References
1.
Brown MW, Templeton
AW, Hodges FJ III. The incidence
of acquired
and
congenital
fusions
in the cervical
spine.
AJR Am J Roentgenol
1964;92: 1255-1259
2.
Gray SW, Romaine
CB,Skandalakis
JE. Congenital
fusion of the cervi-
cal vertebrae.
Surg Gynecol Obstet 1964:373 -385
3.
Gunderson
CH, Greenspan
RH, Glasser GH, Lubs HA. The Klippel-Feil
syndrome:
genetic
and clinical reevaluation
of cervical fusion. Medi-
cine 1967;46:491-512
issue. First. it must be determined
if the stenosis is congeni.
tal and part of the syndrome
or secondary
to degenerative
changes. Therefore,
the levels in question
must be defined.
Some authors
believe that primary
spinal stenosis in this
patient population is uncommon. and some authors have
even found the canal to be enlarged.IO.51.55.56
Ritterbusch etal
found that stenosis occurred
in both the regions of the con.
genital
fusion as well as at the level of hypermobile
seg.
ments.as seenon MR1.35These authors
also found evidence
of vertebral subluxation>
5 mm on the radiographs infive
of their 20 patients. What is known is that coexisting spinal
stenosis and vertebral
subluxation
are an unfortunate
corn.
bination.
.
Treatment
Fewreports exist in the literature that discuss the operative
treatment of congenital mid- to lower cervical spine condi.
tions.9.57-60It is difficult to evaluate the results of mostof
these series because patients with upper cervical spinefu.
sions have been included. Some series report the entiresur.
gical management of these patients. including releaseof
pterygium colli. correction of Sprengel's deformity, and
spinal arthrodesis for scoliosis. Regardless of the underlying
condition.the anatomical deformity in the cervicalspine
must be identified and addressed with standard principles
applied.51
.
Conclusion
After reviewing this chapter. we hope that the reader may
better
appreciate
the statement
that the finding ofa
congenital cervical spine anomaly is "just the tip ofthe
iceberg." A review of systems and physical examination
from head to toe is mandatory
in all of these patients.
Becausethe majorityofthe associated findingsare repro.
ducible and consistent, a systematic approach shouldbe
undertaken. Aside from physical examination. associated
tests need to be ordered when indicated. MRIappears to
be the modality of choice when soft-tissue subtleties can-
not be appreciated on plain radiographs. Todate. no classi-
fication scheme can accurately identify those individuals
at risk for neurological injury or those who should be
treated with prophylactic surgery. Each patient mustbe
considered
individually
with
these
decision-making
processes.
4.
Klippel M, Feil A. Un cas d'absence
des vertebres
cervicales
avec eage
thoracique
remontant
jasqua
la base
due
crance
(cage
thoracique
eer-
vicale).
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Iconogr
Salpetriere
1912;25:223Ip21Ip31
5.
McRae DL Bony abnormalities
in the region of the foramen
magnum:
correlation
of the
anatomic
and
neurologic
findings.
Acta Radiol
1953:40:335-354
6.
Hensinger
RN. Congenital
anomalies
of the cervical spine. Clin Onhop
1991 ;264:16-38

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7. HensingerRN.MacEwen GD. Congenital anomalies of the spine. In:
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1982:188-315
8. Mitchie I. Clark M. Neurologic syndromes associated with
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andcraniocervicalanomalies. Arch Neurol 1968;18:241 -247
9. NagibMG. Maxwell RE. Chou SN. Identification
and management
of high-risk
patients
with
Klippel-Feil
syndrome. J Neurosurg
1984;61:523-530
10. GuilleJT.Miller A. Bowen JR. Forlin E. Caro PA. The natural history
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mag-
netic resonance imaging findings
at adulthood. J Pediatr Orthop
1995:15:617-626
11. Pizzutillo PD.Woods M. Nicholson L. MacEwen GD. Risk factors in
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Spine 1994; 19:21 10 -21 16
12. Pizzutillo PD. Klippel-Feil
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lippincott-Raven;
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GD. Klippel-Feil
syndrome:
a
constellation of associated
anomalies.
J Bone Joint Surg Am
1974;56:1246- 1253
14. McElfreshE. Winter R. Klippel-Feil
syndrome.
Minn Med 1973;56:
353-357
15. SherkHH. Black JD. Bony anomalies of the mid- to lower cervical
spine.In: Pang D. ed. Disorders of the Pediatric Spine. New York:
Raven; 1995:125-136
16. SherkHH. Uppal GS. Congenital
bony anomalies
of the cervical
spine.
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17. Myamato RI. Klippel-Feil
syndrome
and
associated
ear
deformities.
AmJOtolaryngol
1983;5:113-
119(p41
18. Mclay K. Maran AG. Deafness and the Klippel-Feil
syndrome.
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19. StarkEW. Borton TE. Hearing
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Am
JDisChild 1972; 123:233-235
20. Danilidis JL.Maganoris T.Stapes gusher and Klippel-Feil
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1978;88:1178- 1183
21. RoosD. Congenital anomalies
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outlet
syn-
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heritable
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23. SherkHH. Klippel-Feil
syndrome
and other congenital
anomalies
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AAOS instructional
course
lectures.
CV
MosbyCompany 1978;27:191-194
24. TheissSM. Smith MD. Winter
RB.The long-term
follow-up
of patients
with
Klippel-Feil
syndrome
and
congenital
scoliosis.
Spine
1997;22:1219- 1222
25. Winter
RB.Moe JH. Lonstein JE. The incidence
of Klippel-Feil
syn-
drome in patients
with
congenital
scoliosis
and
kyphosis.
Spine
1984;9:363-366
26. Thomsen MN. Schneider
U, Weber
M, Johannisson
R. Niethard
FU.
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syn-
drometypes I-III.
Spine 1997;22:396-401
'lI. Smith MD. Congenital
scoliosis
of
the cervical
or cervicothoracic
spine.Orthop Clin North Am 1994;25:301-310
28. Sherk HH, Shut
L. Chung
S. Iniencephalic
deformity
of
the
cer-
vical spine with
Klippel-Feil
anomalies
and
congenital
elevation
of the scapula:
report
of
three
cases.
J Bone
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29. NoraJJ.Klippel-Feil
syndrome
with congenital
heart disease. AmJ Dis
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30. Morrison SG. Perry LW. Scott LP. Congenital
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syndrome).
AmJ Dis Child 1968;115:614-620
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TJ, Rabinowitz
R. Genitourinary
anomalies
as-
sociatedwith
Klippel-Feil syndrome.
J Bone Joint Surg Am
1975;57 A:355-357
]2. Drvaric DM. Ruderman
RJ. Conrad
RW. Grossman
H. Webster
GD.
Schmitt EW.Congenital scoliosis and urinary
tract abnormalities:
are
intravenous pyelograms necessary?
J Pediatr
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1987;7:441-443
n. BrinkerMR.Weeden SH. Whitecloud
TS III. Congenital
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The
Adult
Spine.
Philadel-
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1997: 1205-1222
34.
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VG Jr. Fielding W. The Klippel-Feil
syndrome:
early roentgeno-
graphic
appearance
and progression
of deformity:
a report
of two
cases. J Bone Joint
Surg Am 1976;58A:891-892
35.
Ritterbusch
JF. McGinty
LD. Spar J. Orrison WW. Magnetic
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and subluxation
in Klippel-Feil
syndrome.
Spine
1991; 16:S539-S541
36.
Ulmer JL. Elster AD. Ginsberg
LE. Williams
DW III. Klippel-Feil
syn-
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and congenital
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37.
Keats TE. Atlas of roentgenographic
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St. Louis: Mosby
Yearbook;
1990
38.
Hinck VC, Hopkins
CEo Savara
BS. Sagittal
diameter
of the cervical
spine
in children.
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1962;79:97-108
39.
TorgJS. Pavlov H. Genuario
SE. et al. Neurapraxia
ofthe
cervical spinal
cord
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transient
quadriplegia.
J Bone
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1986;68A:
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40.
Lee CK,Weiss AB. Isolated congenital cervical block vertebrae below
the axis with neurological
symptoms.
Spine 1981 ;6: 118-124
41.
Baird PA.Robinson GC,BucklerWS.Klippel-Feilsyndrome: a study of
mirror
movement
detected
by electromyography.
Am J Dis Child
1967;113:546-550
42.
Gunderson CH. Solitaire GB. Mirror movements
in patients with
Klippel-Feil syndrome.
Arch Neurol 1968;18:675-679
43.
Bauman GI. Absence of the cervical spine: Klippel-Feil syndrome.
JAMA 1932;98:129-136/p5/
44.
Karasick D. Schweitzer ME. Vaccaro AR.The traumatized
cervical
spine
in
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imaging
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AJR Am
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RoentgenoI1998;170:85-88
45.
Strax TE.Baran E.Traumatic quadriplegia associated with Klippel-Feil
syndrome:
discussion
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1975;56:363-365
46.
Sherk HH. Dawoud
S. Congenital
os odontoideum
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Born CT.Petrik M. Freed M. Delong WGJr. Cerebrovascular accident
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Klippel-Feil fusion. Spine 1984:9:344-347
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1990;5:480-482
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M. Clinical
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Joint Surg Br 1956;38-B:440-449

20
Cervical Spine Degenerative Disease
and Cervical Stenosis
Kirk Wayne Jobe
. Anatomy
.
BiomolecularAnatomy
.
Biomechanics
.
Pathophysiology
The cervical spine provides support for the head,
protection for the spinal cord and neural elements, and
allows for multidirectional movement of the neck. Cervical
spondylosis is the term used to denote the progressive
degeneration
of the intervertebral
disks that leads to
changes in the surrounding bony and ligamentous struc-
tures.! As a natural process of aging, the prevalence of
these degenerative
changes is 10%at age 25 and ap-
proaches 95%of individuals at age65.2.3
. Anatomy
Understanding the pathophysiologyofthe cervicalspine ne-
cessitates first knowing the normal structure and function of
the region. From (3 to C7,the vertebral bodies consist of a
short, stout cylinder of bone wider in its transverse diameter.
Offboth sides of the body,a transverse processextends later-
ally.From(3 to (6 the transverse process harbors a foramen
for the passage of a vertebral artery. Offthe posterior body,a
set of pedicles arises on both sides extending posterior. From
the pedicles stem the laminae projecting posteromedial to
create the spinal canal underneath their bony arch. Where
both lamina meet in midline,a spinous process projects pos-
teriorly, allowing for the attachment of musculature. Arising
from the junction of the pedicle and the lamina,the superior
and inferior facets extend both cephalad and caudad to meet
with similar processes on neighboring vertebra forming the
facet joints. The facet joints are true joints, with hyaline-
covered articulating surfaces, synovium, and ajoint capsule.
The superior and inferior surfaces of the vertebral bodies
are concave and cup the intervertebral disk. The uncinate
process extends upward off the superior posterolateral rim
of the body, deepening the concavity,to meet with a promi-
nent inferior lip on a neighboring body to form the joint of
Luschkaor the uncovertebral joint. Thejoint of Luschkaand
164
.
Symptoms
.
CervicalStenosis
.
Radiological Evaluation
.
Summary
the facet joint define the anterior
and posterior
borderof
the
vertebral
foramen,
respectively,
through
which the
nerve root passes. Unlike the facet joints, the uncovertebral
joints are not true synovial joints, but represent
a bonybar.
rier keeping the disk from pushing
into the foramen paste.
rior or into the vertebral artery laterally.
The first two vertebral
bodies are unique, each requiring
its own description. The atlas, (1, is the pedestal on which
the skull rests. The atlas has no body but consists of anan.
terior arch and larger posterior
arch projecting
from large
lateral masses on either side. Projecting outward
from each
lateral mass is a large transverse
process. The superior sur.
faces of lateral masses articulate
with the occipital condyles
of the skull. The inferior surfaces of the lateral masses artic.
ulate with the superior
surface of the lateral masses ofa.
The axis, (2, is the largest cervical vertebra. (2 consistsd
a body and a superior
projection
off the body, the would.
be-body
of (1, which
is fused
embryologically
with the
bodyof(2, formingthe odontoidprocessor dens.Thedens
projects
upward
into the plane of (1 and serves as aful.
crum around which the rotation of the atlas on the axil
takes place. The large lateral masses of (2 support the artic.
ulation
with C1 and possess
foramina
through
which the
vertebral
arteries
pass. The posterior
elements
of (2 are
similar to those of the vertebral bodies below, with the infe.
rior facet articulating
with the superior facet of (3.
Afibrocartilaginous intervertebral disk lies between each
of the vertebral
bodies
from (2 and below. The height0['
each intervertebral
disk is roughly 45% the height of thead.
jacent body below. The overall bone to cartilage ratio ofthe
cervical
spine is roughly 4: 1. Although
the height ofeach
vertebral body is slightly taller posteriorly,
the overall cervi.
cal spine is lordotic because each of the disks is tallerante.
riorly than posteriorly.
The disks consist of two main components: the central
gelatinous
nucleus pulposis and the peripheral
layered anu-
Ius fibrosus. The disks are bounded
superiorly and inferiorlj

r
I
20
Cervical Spine Degenerative
Disease and Cervical Stenosis
165
bythehyalinecartilage end plates of the vertebral body.
Smallperforationsin the end plate allow for vascular com-
municationbetween the disk and the vertebral body, and
nutrientandwasteexchangeoccur at this junction. The disk
isfixedto the end plate by a confluence of collagen fibers.
Thenucleuspulposisconsistsof 1 mL of gelatinous matrix
comprising
lessthan 50%of the entire cross-sectional areaof
thediskandis located slightly more posterior rather than
central.Thisgelatinous massis held within a fibrocartilagi-
nousring,the anulus fibrosus, in which the fibers are orga-
nizedinconcentriclamellae in alternating oblique directions.
Thefibersofthe annulus are anchored in the circumferential
compactboneandthe hyaline cartilage end plates.
Theoutmostfibers of the anulus become contiguous with
theanteriorandposterior longitudinal ligaments. The ante-
riorlongitudinalligament, continuous with the anterior at-
lanto-occipitalmembrane, runs down
the entire spine,
tightlyadherentto the anterior face of the vertebral bodies
andlooselyadherent to the disks. The posterior longitudi-
nalligamentis continuous above with the tectorial mem-
braneandis broadthroughout the cervical region, narrow-
ingbelowthis level,running behind and tightly adherent to
theposteriorface of the vertebral bodies. The ligamenta
flava,consistingof yellow elastic tissue, runs longitudinally
fromtheinneredgeof the posterior arch of the atlas down-
wardin the spinal canal, adherent to the posterior inner
surfaceofsuccessivelaminae.
. BiomolecularAnatomy
Thebiomolecularstructure of the nucleus pulposus allows it
uniqueliquidandelastic properties making it deformable but
incompressible.
The nucleus pulposus consists of a sparse
populationof cells surrounded by an abundant extracellular
matrix.Thecellssynthesizethe matrix and then maintain and
repairtheframeworkof macromolecules, which make up the
matrix.Thematrix is mostly made up of glycosaminoglycans
consistingof a proteoglycan core, to which sterically active
polysaccharide
chains,chondroitin, and keratin sulfate are at-
tached.Thesenegatively charged glycosaminoglycans are
boundtoacentralhyaluronic acid backbone like bristles on a
brush.Thesestructures imbibe water, creating an aqueous
environmentof large protein aggregates floating in a loose
areolarstromaof collagen fibers. The disks' integrity and me-
chanicalproperties depend on these macromolecules and
theirinteractionwith water. In a young person, the nucleus
pulposusis -90% water and by the eighth decade this
percentagedecreasesto less than 70%.With less water, the
nucleusbecomesmore compressibleand lesselastic.4.s
Initially,the nucleus contains primarily notochordal cells,
whichdisappearby early adult life leaving only chondro-
cyte-likecells.6Becausethe nucleus pulposus is avascular,its
cellsdependon the transport of nutrients through the ma-
trixfromthe cartilaginous end plate. The cells also rely on
theability of waste products to be carried out to the end
platethroughthe matrix. Both of these processesdepend on
thewatercontent of the disk, the functioning of the macro-
molecularframework, and the interface with the cartilagi-
nousend plate. The end plates are initially
composed of
hyaline cartilage and later consist of calcified cartilage and
bone.? The hyaline cartilage is avascular but the cartilage
canalsthat once carried vesselspersist through life.
The anulus fibrosus forms the concentric harness around
the disk in a radial fashion. Unlike the disk, the anulus hasa
much more organized lamellar pattern of fibrocartilaginous
material and very little glycosaminoglycan content. Collagens
account for asmuch as70%of the dry weight of the outer an-
ulus.7 Compressive forces on the nucleus pulposis are redi-
rected radially to be absorbed by the bulging concentric
lamellar sheets of the anulus. The outer anulus contains fi-
broblast and fibrocyte-like
cells whereas the inner anulus
contains cells that more closely resemble chondrocytes.6
.
Biomechanics
The disks perform two main tasks. First, the disk distributes
compressive forces.The deformability
of disks allows a dis-
tribution
of forces evenly over the entire surface area of the
end plates rather than having a concentration of loading or
torsional
forces to the periphery
of the vertebral bodies.
Second, the disks also allow a multiplanar
range of motion
between adjacent vertebrae. This motion, in conjunction
with motion at the facet joints, is summated over the entire
cervical region for a wide range of movement.
The disk, although ultimately deformable, is virtually
in-
compressible. Any forces applied to the disk are ultimately
redistributed
to the anulus and end plates. The alternating
lamellar collagen mesh of the anulus absorbs the redistrib-
uted pressure of the central nucleus. In this manner, with a
properly
functioning
disk,
loads are dispersed
evenly
around the structure.
Fifty percent of flexion and extension takes place be-
tween the atlas and the occiput; however, the remainder of
the movement takes place in the subaxial region from C3to
C7 for a total of 130 degrees of flexion and extension in the
cervical spine. Fifty percent of the rotation takes place be-
tween the atlas and the axis, and the remainder takes place
from additive movements between C3 and C7 for a total of
140 degrees of rotation. Lateral bending for a total of 75 de-
grees can be measured.
.
Pathophysiology
Thedegenerationof the cartilaginous end plates and the inter-
vertebral disk is central to the evolution
of degenerative
changes in the cervical spine. The changes to the end plates
and disk start occurring at a cellular and molecular level long
before anygrosschangesbecomeevident.8Cell lossin the car-
tilaginous end plate hasbeen shown to occur before changes
take place in the disk's macromolecular structure. The end
plate decreasesin thickness, and fissures start forming at the
empty vascularchannels.The lossof the end plate impairs the
nutrient and waste exchangewith the intervertebral disk.
With
the impairment
of oxygen delivery, nutrient
ex-
change, and waste removal through the end plate, the disk
begins to alter. As has been studied by Buckwalter,9 the
central portions of the disk undergo the earliest and most
extensive changes. There is a decline in the number of

--
166
OccipitocervicalJunction:Pathology of the MidcervicalSpine
viable cells and a fragmentation of proteoglycans resulting
in a decrease in nucleus pulposus proteoglycans and loss of
water content. As the matrix properties change, nutrient
delivery and waste removal through the matrix are further
impaired, resulting in cyclicaldysfunction.
Inaddition to the changes of the central disk, there ap-
pear myxomatous regions in the anulus. The number and
activity of fibroblasts in the anulus decrease considerably.
Tightly woven type I collagen are replaced by larger colla-
gen fibrils. The interwoven meshwork of the anulus is less
able to distribute the forces of the central nucleus pulposis.
This chain of events increases the load on the collagenous
matrix, precipitating failure of the matrix with a loss of disk
shape and mechanical function.
The resultant disk has a less elastic and more compressible
nucleus and an anulus that is predisposed to stretching and
tearing. Impaired functioning of the disk leads to a diffuse
bulging and a loss of disk height. This in turn leads to liga-
mentous laxity between neighboring vertebrae and an in-
crease in mobility between individual segments. Osteophyte
formation takes place as traction spurs form in reaction to
the new shear forces on the outermost anulus fibers.loThese
forces are greatest, with listhesis and retrolisthesis taking
place during flexion and extension, leading to the greatest
osteophyte formation offthe anterior and posterior edges of
the body. On plain films, the levels with the largest osteo-
phytes denote the regionofgreatest segmental laxity.
At this same time, age-related changes are taking place at
the facet joint. Lossof articular cartilage, subchondral scle-
rosis, and osteophyte formation enlarge the facets and can
cause an encroachment of neural tissue. Fromthe posterior,
hypertrophy of the yellow ligament further causes a nar-
rowing of the vertebral canal.
In this way, a circumferential narrowing of the vertebral
canal and the neural foramen takes place. In the anterior
canal, end plate degradation and impaired nutrient and
waste exchange with the disk lead to disk degeneration and
bulging or tearing ofthe anulus with or without disk hernia-
tion. Anterior compromise also results from disk space nar-
rowing, causing segmental laxity with resultant osteophyte
formation.
Posteriorly, hypertrophy of the ligamentum
flavum narrows the canal and posterolaterally facet hyper-
trophy impinges on both the canal and the neural foramen.
These changes are associated with the normal process of ag-
ing, and only when they begin to cause pain or dysfunction
of the neural tissue do they become pathological.
.
Symptoms
Three main clinical symptom complexes arise alone or in
combination as a result of cervical spondylosis: axial pain,
radicular pain, and myelopathy. Axialpain alone, in the ab-
sence of neurologicalfindings,iscommonand severelydebili-
tates 10%of the population at one time or anotherY However,
the source of axial pain is often difficult to elucidate.12Some
component of the axial pain maycomefrom the sinuvertebral
nerve innervating the portions ofthe disk,the posterior longi-
tudinal ligament, and the meninges.13.14Additionally, pain
may be generated from the facetsas they stimulate the dorsal
primary ramus.13,15Secondaryto the difficultywith localizing
the
source
of axial
neck pain,
treatment
should
be ap-
proached with caution. Goren reviewed the long-term follow.
up of 205 patients with neck pain and among the conclusions'
found that the outcome and treatment
are difficult to predict
from the clinical and radiographic data.
Radiculopathy
occurs with nerve root irritation and cIassi.
cally includes a level-specific dermatomal
pain and sensory,
.
motor, and reflex changes. The irritation
can be acute, suba.
cute, or chronic and most often is unilateral;
however, itcan,
be found bilaterally and with varying amounts
of symmetry.i
Theradiculopathiesoftenarise as the result of hardor50ft1
cervical disk disease. Soft disk herniations have been weill
described and categorized by Stookey16and Rothmanand!
Marvel.171ntraforaminal
herniation
occurs most commonlyf
and gives radicular symptoms
in a dermatomal
distribution..
The posterolateral
soft disk protrusion
produces
mostly mo-'
tor findings of weakness and atrophy. Finally, midline herni.
ations may present as myelopathy.
A hard disk is defined as
an osteophyte or fibrosed fragment of anulus protruding
,.
into the root causing irritation.
A hard disk is more likelyto.
cause radiculopathies in persons over age 55.18
.
When
cervical
spondylosis
causes
circumferential
nar.t
rowing of the cervical spinal canal to reach a critical level.
neural elements
or their blood supply may become compro-
mised resulting in myelopathy. Myelopathic
symptoms usu.
ally develop
insidiously.
Over months
to years the patient
may notice increasing
disability
most often manifesting as
spasticity and weakness. The variability of physical compro-
mise to the canal and the various susceptibilities of tracts
within the cord to pressure and vascular insufficiency lead
to a widely
varied
presentation.
Crandall
and Batzdorfll
carefully reviewed patients'
signs and symptoms
and distin.
guished five clinical syndromes
of myelopathy:
.
The transverse
lesion
syndrome
involves
the
corti.
cospinal
tracts,
spinothalamic
tracts,
and
posterior
columns below the cervical level with anterior horn
cells being involved segmentally.
This syndrome
hasof.
ten been present for over 5 years and may represent the
end stage of the disease.
Spasticity
and sphincter de.
rangement
are involved in over two thirds of the case~
.
The motor system syndrome presents in a similar fashiontOI
amy trophic lateral sclerosis. The cortical spinal tracts and
anterior horn cells are involved. Spasticity was presentin
three quarters of these patients.
.
The central cord syndrome
affects the upper extremities
more than the lower extremities and the distal upper
extremities
more than the proximal. The patients often
have useless hands with painful paresthesias
as wellas
deficits in the posterior
columns.
.
The Brown-Sequard's
syndrome
produces
a weakness ip-
silaterally
with
hypalgesia
on the contralateral
side.
Painful paresthesias
were also commonly
present.
.
Brachalgiaand cordsyndromepatients will havelong
tract signs with some associated upper limb motoror
sensory deficit. Radicular pain commonly occurred
within this group.
In diagnosing
myelopathy,
emphasis
should be placedon
obtaining
histories involving numbness
or clumsiness ofthe
hands, decreased fine motor movements, and subtlegait

20
CervicalSpine Degenerative Disease and CervicalStenosis
167
disorders.Oncemyelopathy is recognized clinically,this di-
agnosiscan be supported
by radiographic
studies.
. Cervical Stenosis
Thespinalcord within the cervical canal has an average an-
teroposterior (AP) diameter of 9 mm. With 1 mm cere-
brospinalfluid ((SF) space anterior
and posterior and 1 mm
dedicatedto the dural sac and epidural
structures
both an-
teriorlyand posteriorly,
it follows that the AP diameter
of
thecanalmust be at least 13 mm for unimpeded
passage of
thecordin the cervical region.20
Theelementsof cervical stenosis are both static and dy-
namic.Spondylosis, with the development
of disk space
narrowingand bulging, osteophyte
formation,
plus facet
andligamentous hypertrophy
results
in a circumferential
compromise to the
cord.
This
compromise
is further
magnifiedby the dynamic
changes
to the
canal.
With
flexion,the cord may be stretched
over vertebral body
osteophytes.In extension, there is retrolisthesis,
secondary
totheinclination of the plane of the facets, resulting in
canal-diameternarrowing.
In addition,
buckling of the lig-
amentumflavumduring extension may further narrow the
canaldiameter.These changes can result in loss of lordosis
ofthecervicalspine, which can further lead to a kyphotic
deformity(Figs.20-1, 20-2, and 20-3).
~t.tl'.<
()
.
'
'0,0'
~, 0
Figure20-2
Anatomy of the cervical spine with degenerative
changesandlossoflordosis.
Figure 20-1
Anatomy of the cervical spine with normal lordosis.
Figure 20-3
Anatomyofa cervicalspinewithextensive degenera-
tive changesand a kyphoticdeformity.

168
Occipitocervical Junction: Pathology of the Midcervical Spine
. Radiological Evaluation
The static definition of canal stenosis on plain radiographs
has been well described. Boijsen,21in 1952, described the
proper measure of canal diameter as the distance from the
midpoint of the back of the vertebra to the nearest point of
the same vertebral lamina as projected on lateral radi-
ographs. Using the Boijsen method of measuring, Pallis et
aJ22noted that spondylotic myelopathy occurred with a
measurement of less than 14 mm, with 18.5 mm being the
average measurement of normal subjects. In 1980, Ehni23
noted that Boijsenmeasurements of canal diameter found to
be 80 to 85%of the vertebral body anteroposteriorwidth
was a predictor of myelopathy. This finding was confirmed
by Pavlovet al,24who found a 92%accuracy for diagnosis of
canal stenosis resulting in myelopathy to be present in cases
of body to canal ratios of less than 0.82.
In patients under consideration for surgery, plain films
can be used initially to assess alignment, and flexion exten-
sion views can be added to assess for segmental motion.
However, if surgery is being considered, canal size can be
directly measured by myelogram, computed tomography
(0), or magnetic resonance imaging (MRI).MRIis the best
method to detect changes related to degenerative disks and
References
1.
Brain L.Wilkinson
M. Cervical Spondylosis
and Other Disorders of the
CervicalSpine. Philadelphia: WB Saunders: 1967
2.
Lawrence JS. Disc degeneration: its frequency and relationship to
symptoms.
Ann Rheum Dis 1969;28:
128-138
3.
Lees
F. Turner
JW. Natural
history
and
prognosis
of cervical
spondylo-
sis. BMJ 1963:5373:1607-1610
4.
Adams CBT. Logue V. Studies
in cervical
spondylitic
myelopathy.
I, II,
and III. Brain 1971 :94:557-594
5.
Blumenkrantz
N. Sylvest J.Asboe-Hansen
G. Local
low
collagen
con-
tent
may
allow
herniation
of intravertebral
disc:
biochemical
studies.
Biochem Med 1977:18:283-290s
6.
Buckwalter
JA. Fine structural
studies
of the human
intervertebral
disc.
In: White
AA. Gordon
SL. eds.
Idiopathic
Low Back Pain. St.
Louis: CVMosby; 1982:108-143
7.
Eyre D. Benya P. Buckwalter
J. et al. The intervertebral
disc: basic sci-
ence perspectives.
In: Frymoyer JW, Gordon SL. eds. New Perspectives
on LowBack Pain. ParkRidge.IL:American Academy of Orthopaedic
Surgeons;
1989:147-207
8. Ariga K. Miyamoto S.NakaseT.et al. The relationship between apop-
tosis of endplate
chondrocytes
and aging and degeneration
of the in-
tervertebral
disc. Spine 2001 ;26:2414-2420
9.
Buckwalter
JA. Aging and degeneration
of the human
intervertebral
disc. Spine 1995:20: 1307-1314
10.
Macnab
I. The whiplash
syndrome.
Orthop
Clin North Am 1971 :2:
389-403
11. Gore DR. Sepic SB.Gardner GM.Murray MP.Neck pain: a long-term
follow-up
of205
patients.
Spine 1987:12:1-5
12. Bohlman HH. Emery SE.The pathophysiology of cervical spondylosis
and myelopathy.
Spine 1988:13:843-846
to assess
nerve root or spinal
cord compression.
MRIcan
also assess the cord itself. A0 myelogram may be ofaddi.
tional benefit
to assess for compression
caused by osteo-
phytes
or calcified
disks. The 0
is better
than the MRIat
evaluating bony lesions.
. Summary
In summary, degenerative disk disease of the cervicalspine
is a normal condition
of aging that only becomes patholo~'
cal when neural elements are compromised or pain be.
comes intractable. Cervical spondylosis is a prevalent prob-
lem. It begins with degeneration of the vertebral end plate
and disk resulting in a cascade of events leading to a combi.
i
nation of disk bulging or rupture, osteophyte
formation. and,
facet or ligamentous
hypertrophy.
These changes ultimately
result in narrowing
of the cervical spinal canal and mayreo
suit in impingement
of neural
tissues.
Clinically, a patiem
may develop any combination
of axial pain, radiculopath~
or myelopathy. The etiology of the patient's clinical condi.
tion can then be investigated
using the appropriate
imaging
studies and treatment
may be considered.
13.
April! C, Dwyer A. Bogduk N. Cervical zygohypophyseal
joint patterns,
II:a clinical evaluation. Spine 1990: 15:458-461
14.
Bogduk N, Windsor
M. Inglis A.The innervation of the cervicalinter.
vertebral
discs. Spine 1988;13:2-8
15.
Bogduk
N. Marshland
A. The cervical
zygohypophyseal
joints aSi
source of neck pain. Spine 1988:13:610-617
16.
Stookey B.Compression
of spinal cord and nerve roots by herniatianli'
nucleus pulposus
in the cervical region. Arch Surg 1940:40:417-4321'
17. Rothman RH. Marvel JP. The acute
cervical disc. Clin Ort~
1975:109:59-68
18.
Dillin W. Booth
R. CucklerJ.et al. Cervical radiculopathy: a review
Spine 1986: 11:988-991
19. Crandall PH.Batzdorf U.Cervicalspondylotic myelopathy.JNeurosu~
1966:25:57-66
20.
Gore DR. Sepic SB. Gardner GM. Roentgenographic findings afth!
cervical spine in asymptomatic
people. Spine 1986:11 :521-524
21.
Boijsen E. Cervical
spinal
canal
in interspinal
expansive
proces~ ..
Acta RadioI1954:42:101-115
22.
Pallis C. Jones AM,Spillane JD.Cervical
spondylosis:
incidence and
implications.
Brain 1954:77:274-289
23.
Ehni G.Developmental
variations.
including
shallowness
of the cel'll-
cal spinal canal. In: Post MJ. ed. Radiographic
Evaluation
of the Cervi-
cal Spine. New York:Mason: 1980:469-474
24. PavlovH.TorgJS.RobieB,JahreC.Cervical spinal stenosis: determ.
nation with vertebral
body
ratio method.
Radiology 1987;164:
771-775

21
Intramedullary Tumors of the Spinal Cord
KeithV.c. Goh and Fred J. Epstein
. Indications
. Advantages
. Disadvantages
. RadiologicalEvaluation
. SurgicalTechniques
Anesthesia
NeurophysiologicalMonitoring
Thefirst successful removal of an intramedullary
spinal
lOrdtumorisgenerally credited to Harvey Cushing, and the
earliestpublishedreports date back to Elsberg in 1911.1Un-
fortunatelythe surgical results were disappointing,
with
patientshavingsignificant postoperative neurological dis-
abilties.lnthe ensuing years, treatment was generally lim-
itedtobiopsyfollowed by radiotherapy. Not unexpectedly,
5-yearsurvival rates were in the region of 70%and about
halfofthepatients remained with severedeficits.2 Over the
past2decadeshowever, advances in radiological imaging,
neurophysiologicalmonitoring,
and microneurosurgical
operatingtechniques led to a significant change in the sur-
gicalapproachto these tumors. In the 1980s, Epstein advo-
catedradicalsurgical resections using intraoperative
neu-
rophysiologicalmonitoring
and the ultrasonic aspirator to
fragmentand suction the tumor, with
considerable im-
provementin surgical results.3,4Since then, other centers
havereportedsimilarly good results, and it is now gener-
allyacceptedthat in the majority of spinal cord tumors, a
radicalsurgical approach should be performed and does
notequatewith poor neurological
outcome.5-7 This fact
holdstrueonly because the majority of these tumors have
alow-gradehistopathology
(Le., ependymomas, fibrillary
astrocytomas,or gangiiogiiomas).8 In the case of higher-
gradetumors,such as anaplastic astrocytomas, the patient
usuallyhasa rapidly progressive course with unrelenting
neurologicaldeterioration,
paralysis,
and bladder
and
boweldysfunction.
.
Positioning
Surgical Details
Closure
.
Postoperative Care
.
Complications
Intraoperative
Postoperative
.
Conclusion
.
Indications
In our practice, we recommend surgery for patients who
present with the following:
.
Spinalcord lesionsthat arecausingsymptoms(e.g.,
pain, weakness, or sensory changes) and are radiologi-
cally suspicious for tumors
.
Lesionsthat are causingcord expansion,sometimes
with accompanying syrinx or cysts
.
Recurrentumors,in particularthosewith alow-grade
histopathology
.
Advantages
.
Posteriorapproachoftendoesnotrequirefusion.
.
Allowsdirectaccesstotheposteriormedianraphe
.
Disadvantages
.
Postoperativemotorandsensorychangesarecommon.
. Cerebrospinal fluid (CSF) leakage can occur if the clo-
sure is not watertight.
169

170
Midcervical Spine: Pathology of the Midcervical Spine
.
Radiological Evaluation
In evaluating a spinal cord lesion, the diagnostic modality of
choice today is magnetic resonance imaging (MRI),which
has almost entirely replaced myelography and computed
tomographic (Cf) scans.9 A complete study includes Tl-
weighted, T2-weighted, and contrast (gadolinium)-enhanced
Tl scansin both axialand sagittal planes (Fig.21-1). Generally
speaking,
it is unnecessary
to image the entire
spine, but
based on the symptomatology
and clinical signs, the appro-
priate level should be scanned and must include the rostral
and caudal limits of the lesion, including
cystic components
(Fig. 21-2). In the rare case of a hemangioblastoma, when
prominent
vasculature
may be seen on MRI, angiographyis
useful for demonstrating
the feeding vessels and, whenap-
propriate, for preoperative
embolization.
Figure 21-1
T2-weighted sagittal magnetic resonance imaging of the cervical spine showing an intramedullary spinal cord lesion causing cordeJ-
pansion
from C3 to C7. The pathology
was pilocytic
astrocytoma.

21
Intramedullary Tumorsof the Mid. and LowerCervicalSpine
171
Cyst
C2-4
Lesion
Cyst
Figure21-2 Tl-weightedsagittal magnetic resonance imaging(gadolinium-enhanced)ofthe cervicalspine showinga (2-(4
spinalcordtumor
withdistinctros..raland caudalcysts.The pathologywasependymoma.
. SurgicalTechniques
Anesthesia
Generalanesthesiawith endotracheal intubation is neces-
sary.Inour practice, because all spinal cord tumor resec-
tionsareperformed with neurophysiological monitoring,
thereisthe need to assess motor evoked potentials (MEPs),
whichrequiresnonparalytic anesthetic agents at the appro-
priatestageof the procedure. In addition, the patient
shouldbe securelystrapped to the operating table and all
pressurepoints well padded to prevent injury in case of
muscletwitching during the course of stimulating
and
measuringMEPs.Antibiotics are routinely given in the
perioperativeperiod, as well as steroids, usually dexa-
methasone.In the exceptional case when we expect a sig-
nificantneuropraxia postoperatively, such as in an exten-
sive holocord tumor
or
when
electrophysiological
monitoringpotentials are lost intraoperatively, spinal cord
protectiondosesof methylprednisolone are administered
for24hours.
Neurophysiological
Monitoring
Ithasbeenour experience that the use of continuous intra-
operativeelectrophysiologicalmonitoring during the resec-
tionofspinalcord tumors confers advantages in terms of
safetyandin guiding the extent of resection 10 (Fig. 21-3).
Thebasicprinciple involves measuring neural conduction
bytheapplicationof an electrical stimulus to a nerve at one
site and recording the compound action potential at an-
other site. In recent years, both sensory evoked potentials
(SEPs)and MEPscan be monitored and the data updated
every few seconds so that there is nearly real-time feedback
to the surgeon throughout the surgical resection.
SEPsare recorded over the spinal cord rostral to the le-
sion(spinalepiduralSEP)andoverthe cerebralcortex(cor-
tical SEP)after transcutaneous stimulation of the tibial
nerves bilaterally. MEPs (spinal epidural) are elicited by
transcortical electrical stimulation, and epidural recordings
are obtained. Intraoperative
limb muscle MEPs are also
recorded from the thenar and anterior tibial muscles bilat-
erally. These electrophysiological events aid the surgeon in
several ways.n First,they facilitate the identification of ner-
vous structures, particularly in cases where the cord is dis-
torted by tumor, trauma, or previous surgery. This is of par-
ticular importance when trying to determine the midline of
a distorted cord for placement of the myelotomy incision.
Second, they assist the surgeon in deciding the extent of
surgical resection so as to preserve neurological function.
SEPsare invariably lost at the time of myelotomy.However,
when MEPsare reduced intraoperatively, they are usually
associated with postoperative paralysis. As such, we stop
surgical manipulation when the MEPsapproach a 50%
decline from baseline. Third. they may help in identifying
the anatomical location of the pathology in nerves where
conduction is compromised. This is particularly reassuring
when resecting a tumor that may be causing significant
nerve root compression, and an improvement in SEPsor
MEPsmayindicatethat therewillbea degreeofpostopera-
tive recovery after successfuldecompression.

172
Midcervical Spine: Pathology of the Midcervical Spine
Midline raphe
Dorsal root
Dural sutures
entry zones
.
Positioning
Inalmost all cases of intramedullary spinal cord tumors, we
prefer the posterior approach with the patient in the prone
position where possible. This approach ensures that the
spine
remains stable despite
possible multisegmental
laminectomies, without the necessity of fusion procedures.
When the lesion is in the cervical spine, the head should be
securely fixed with pins. In pediatric cases, an osteoplastic
laminotomy or laminoplasty isthe procedure of choice. We
have found that this replaced bone flap undergoes posterior
fusion, leading to a reduced incidence of subsequent
kyphoscoliosis.12 Should reoperation
be necessary, the
planes of dissection are also more easily defined with less
risk of inadvertently injuring the dura. It is important to en-
sure that the laminectomy is performed at the correct level
(confirmed by lateral x-rays) and is of adequate extent su-
periorly and inferiorly so that the rostral and caudal limits
of the tumor can be accessed.
Surgical Details
Following the bony exposure, we routinely use the ultra-
sound probe to visualize the tumor intraoperatively.13This
Electrode
Figure 21-3
Intraoperative
photograph show-
ing the
placement
of the epidural
electrodes
both rostral and caudal to the operative site.
is important because there must be sufficient bone removal
to exposethe entire solidcomponentofthe tumor.Inaddi.
tion, tumor-associated cysts may be identified. The durais
then opened only to the extent that ultrasound demon-
strates the entire tumor mass. It is unnecessary to extend
the dural opening over normal spinal cord or over the ros-
tral or caudal cysts because these can be easily drained
when the solid part of the tumor is removed. The two edges
of the dura are then held apart with regularly spaced
Nurolon sutures. Careful identification of the posteriorme.
dian raphe is important, especially because the expanded
spinal cord is commonly rotated and distorted. Beforethe
myelotomy, one should also look for the dorsal root entry
zones bilaterally so as to avoid performing the myelotomy
in a paramedian position, which can result in severing
nervesalongthe dorsal entry zone.Themyelotomyisusu-
allystarted at the junction of the solidand cysticpartsof
the tumor either rostrally or caudally.
Once the myelotomy is completed, pial traction sutures
can be applied to improve the myelotomy opening and
enhance the tumor exposure. There is often a thin layer
of white matter overlying the tumor, which can be re-
moved with cautery and fine suction (Fig. 21-4). Thenor.
mal tissue is then carefully displaced sideways with the
help
of a "plated
bayonet"
(Codman and
Shurtleff.

21
Intramedullary Tumorsof the Mid- and LowerCervicalSpine
173
CD#5256),which is a modified simple bayonet in which
thetips have been replaced with spherical thin plates.
Theseare then placed between the tumor and adjacent
tissueand gently released, allowing the tension to be dis-
tributedequally over a wide area. In the case of ependy-
momaswhere there is a definite capsule, this can be eas-
ilyachieved.However, if a plane of dissection cannot be
easilyidentifed as is the case with most astrocytomas,
thisshouldnot be pursued because it will only cause un-
necessarymanipulation of functioning neural tissue. In
thissituation,the ultrasound probe is used to guide entry
intothe solid midportion of the tumor so as to begin
tumorresection.
Wherepossible,we routinely use the Cavitron ultrasonic
aspirator((USA),set at a low vibration and suction level, for
tumorresection, entering from the thinnest part of the
overlyingwhite matter and then debulking it from within
untilthewhite matter interface is reached14(Fig.21-5). The
principleof ultrasonic dissection is that fragmentation by
vibrationand simultaneous aspiration of the tumor frag-
mentsthroughthe tipofthe samehandpieceallowsa more
gentleremovalof the tumor. The laser has been used in
placeofthe(USAin some centers and allowsremovalof
residualtumor fragments with greater precision than the
eUSA.However,it is moretimeconsumingwhen there isa
largetumorbulkand the resultantblackened"char"makes
itdifficulttoidentifynormalwhite matter.Inaddition,the
heatgeneratedcanbe transmitted to adjacentnormalcord
andincreaseneurological trauma in the same way that pre-
viousuction-cauterytechinques did.
Where possible and depending on the histopathology, the
aim is gross total resection, or at least a significant reduc-
tion in tumor. Because the most common histological type
is a diffuse fibrillary astrocytoma, followed by gangli-
oglioma and ependymoma, most of these tumors can be
radically resected8 (Fig. 21-6). However, the most haz-
ardous part of surgery involvesremovalof the "poles" of the
tumor, which characteristically taper and are closely inter-
twined with normal neural tissue, rendering these seg-
ments vulnerable to surgical trauma. These last fragments
canberemovedbyworkingwithinthe myelotomyand dis-
tracting the residual tumor into the surgical cavitywithout
extending the myelotomy. It must be emphasized that un-
necessary retraction and manipulation of functioning cord
and neural structures during surgery should be avoided at
all costs.The extent of surgical resection should be assessed
by ultrasoundat the end ofthe procedureandconfirmedby
postoperative MRI.
Closure
A watertight dural closureisessential to reducethe likeli-
hood of CSFleakage. This should then be reinforced by mul-
tilayer closure of the overlying muscle and fascial planes
with strong PDSsutures. A drain is often placed in the
suprafascial plane, especially in multilevel laminectomies.
This will reduce dead space and possible postoperative col-
lection of tissue fluid in this layer until such time that the
tissues heal.
Pailretractionsutures applied
Tumor
Pial suture
Figure21-4
The myelotomy has been completed
and the underlying tumor is now visible. Penfield forceps are used to hold up the pia so as to ap-
plythe pialretraction
sutures.

174
MidcervicalSpine:Pathologyof the MidcervicalSpine
Figure 21-5
The Cavitron ultrasonic aspirator (CUSA)is now used to gently debulk the tumor from within the tumor substance until the interface
with white matter is seen.
Distract tumor without
extending
myelotomy
Figure 21-6
Inthis case, an ependymoma, which has a distinct capsule, is being removed in one piece.
.
Postoperative Care
In the immediate postoperative period, good analgesia is im-
portant for patient comfort,especiallyinthe case ofmultilevel
laminectomies. We routinely infiltrate Marcaine (0.5%)into
the incision area and use patient-controlled analgesic (PCA)
devices for the first 48 hours. Inthe case of cervicallaminec-
tomies, a soft cervical collar sometimes helps in reducing
postoperative discomfortby supportingthe neckmusculature.
Postoperatively, the patient will almost always experi-
ence sensory changes, including paresthesias and dysesthe-
sias, distal to the level of the lesion, and this can be very
disturbing. The patient should be reassured that these will
gradually improve over the following few weeks, but in ex-
treme cases, we have found that drugs such as Neurontin
are very helpful for symptomatic relief.
In almost all cases, there will be motor weakness distalto
the level ofresection, as well as sphincteric dysfunction.If
the MEPswere preserved intraoperatively, these neuroprax-
ias will improve with time and intense physiotherapy. The
only exception is in the case of a malignant or high-grade
tumor in which the patient usually develops progressive
and rapid neurological deterioration. A strict bladder and
bowel regime should be implemented
in the immediate
postoperative period, including adequate laxatives andene-
mas and intermittent
catheterization
to reduce large
postvoiding residual volumes.
Lastly,these patients areat riskof thromboembolic
com-
plications, and proper prophylactic measures should be
taken. We routinely make use of antiembolic stockings,
early mobilization and physiotherapy, and anticoagulation
in high-risk cases.

21
Intramedullary Tumorsof the Mid- and lower CervicalSpine
175
. Complications
Intraoperative
Inourexperience, there have been no directly related oper-
ativemortalities.Approximately 5 to 10%of cases develop
complicationsrelated to the surgical wound. There may be
woundinfections, abscesses,
or leakage of CSF.1S.16Wound
complicationstend to occur in compromised
patients
(Le.,
thosewhohavebeen previously irradiated, on chemother-
apy,oron steroids). We routinely
use perioperative
antibi-
oticsand remove drains early.
Postoperative
Postoperativepidural hematomas
occur extremely
rarely,
providedhemostasis is meticulous.
One should
be suspi-
ciousofthis complication
if the patient
shows evidence
of
neurologicaldeterioration
in the postoperative
period. An
MRIshouldthen be performed without hesitation, and
speedyreoperationperformed when necessary.
Duringthecourseof resecting the tumor, especially in the
caseoflarge tumors with an atrophic
spinal cord, vascular
References
1. Elsbergc. Beer E. The operability
of intramedullary
tumors
of the
spinal cord: a report
of two
operations
with
remarks
upon
the extru-
sionofintraspinal
tumors.
AmJ
Med Sci 1911 :142:636-647IpI1
2. Garcia OM. Primary
spinal
cord
tumors
treated
with
surgery
and
postoperative
irradiation.
Int
J Radiat
Oncol
Bioi
Phys
1985:11:
1933-1939
3. Epstein F, Farmer
JP. Freed
D. Adult
intramedullary
spinal
cord
ependymomas:
the
result
of surgery in 38 patients. J Neurosurg
]993:79:204-209
4. EpsteinF.Epstein N. Surgical
treatment
of spinal cord astrocytomas of
childhood: a series of 19 patients.J
Neurosurg
1982:57:685-689
5. BrotchiJ, Dewitte
0, Levivier
M. et al. A survey
of65
tumors
within
the spinal cord: surgical
results
and the importance
of preoperative
magnetic resonance imaging.
Neurosurgery
1991 :29:651-657
6. CooperPRo Outcome after operative
treatment
of intramedullary
spinal cord tumors
in adults:
intermediate
and
long-term
results
in
5] patients. Neurosurgery
1989;25:855-859
7. Zilleli M, Coskun E. Ozdamar
N. et al. Surgery
of intramedullary
spinal
cordtumors. Eur Spine J 1996:5:243-250
8. EichlerME. Ducey RG. Intramedullary
spinal
cord
tumors.
In: Bridwell
KH. De Wald D, eds. The Textbook
of Spinal
Surgery.
Philadelphia:
lippincott/Raven:
1997:2089-2090
injury to the anterior spinal artery can occur. For this rea-
son, we limit the use of diathermy and lasers within the
cord, preferring a gentle CUSAsetting.
Forlesions in the region of the conus, one should adopt a
more conservative approach. There is inevitable bladder
and bowel dysfunction after resections of such lesions, and
these give rise to tremendous postoperative disabilities.
. Conclusion
Surgical resection of intramedullary
spinal cord tumors
with minimal morbidity, good results, and long survival
time is clearly possible in experienced hands, compared
with 2 decades ago. Because the majority of these tumors
have a low-grade histopathology with no proven benefit
from radiation or chemotherapy, we believe that surgery
with the aim of good debulking should be attempted as the
initial treatment in all these cases. In the case of recurrence,
provided there is no change in histological type, repeat
surgery should be performed as though the patient were
presenting for the first time.
9.
Goy AM. Pinto
RS, Raghavendra
BN, Epstein
FJ. Kricheff
II. In-
tramedullary
spinal cord tumors: MR imaging with emphasis on as-
sociated cysts. Radiology 1986:161:381-386
10. Morota N,Deletis V. Constantini S.et al. The role of motor evoked po-
tentials during surgery for intramedullary
spinal cord tumors. Neuro-
surgery 1997:41:1327-1336
11.
Moller AR. Intraoperative
recordings that can guide the surgeon in
the operation. In: Brown CL. ed. Evoked Potentials in Intraoperative
Monitoring.
Baltimore: Williams &Wilkins:
1988:121-137
12.
Abbott
R, Feldstein
N. Wisoff JH. et al. Osteoplastic
laminotomy
in
children.
Pediatr Neurosurg
1992:18:153-156
13.
Epstein FJ, Farmer JP, Schneider
SJ. Intraoperative
ultrasonography:
an
important
adjunct
for
intramedullary
tumors.
J
Neurosurg
1991 :74:729-733
14.
Epstein
F. The Cavitron
ultrasonic
aspirator
in tumor
surgery.
CIin
Neurosurg
1983:31 :497-505
15. Epstein F.Spinal cord astrocytomas of childhood. In: Symon L.ed. Ad-
vances
and Technical
Standards
in Neurosurgery.
Vol 13. Vienna:
Springer-Verlag;
1986
16.
McCormick PC.Torres R. Post KD, et al. Intramedullary
ependymoma
of the spinal cord.JNeurosurg1990:72:523-532

22
Trauma of the Mid- and Lower
Cervical Spine
Bennie W. Chiles III and Paul R. Cooper
.
Initial Assessment and Stabilization
.
Radiological Evaluation
.
Surgical Techniques
Anterior versus Posterior Approach
Positioning and Anesthesia
Anterior Stabilization
Posterior Stabilization
COI.lbined Anterior and Posterior Stabilization
The middle and lower segments ofthe cervicalspine are the
most common site of spinal injury.Thisarea represents the
most mobile portion of the spinal column and is thus par-
ticularly vulnerable to mechanical deformation and resul-
tant structural damage when external forcesare applied.
The general goals of management of patients with in-
juries of the middle and lower cervical spine are (1) preser-
vation of function in patients who are neurologically intact,
(2) prevention of additional loss of function and reduction
of deficit in patients with neurologicalcompromise. and (3)
restoration of spinal stability.
. Initial
Assessment
and Stabilization
Management of patients with suspected cervical spine in-
juries begins at the scene of injury with strict immobiliza-
tion of the neck during extrication and transport to the hos-
pital. Rigidcervical collars. sandbags, and spine boards will
aid in protecting the patient with a potentially unstable cer-
vical spine injury. Fivepercent of patients with severe sys-
temic trauma have an unstable cervical spine, and two
thirds of these have no initial neurological deficit,1.2In re-
cent years the reported decrease in the incidence of com-
plete spinal cord injuries is likely related to wider recogni-
tion of the potential for secondary neurological injury in the
presence of an unstable spine.3
Proper airway management in spinal-injured patients is
vital to avoid hypoxemia, and clinicians should maintain a
low threshold for early intubation and assisted ventilation.
The technique used for intubation should take into account
176
the potential
for neurological
injury secondary
to excessive
neck manipulation.
Hypotension
may be present due tohe-
morrhagic
shock or loss of systemic sympathetic
vasomotor
tone. The latter will generally
respond to fluid resuscitation
and, if necessary,
pressors.
An indwelling
urinary catheter
should be placed to prevent bladder distention
and monitor
urine output. Nasogastric tube insertion will prevent aspira-
tion of stomach
contents
and avoid abdominal
distention.
which may contribute
to respiratory
difficulties. All patients
with neurological
deficit seen within
8 hours of the initial
injury
should
receive
the high-dose
methylprednisolone
protocol.4,5 A detailed,
accurate
initial neurological
evalua-
tion is essential
to specify areas for later imaging and toes-
tablish a baseline for the subsequent assessment of neuro-
logical improvement
or deterioration.
.
Radiological Evaluation
Standard x-ray films. particularly the lateral view, arethe
most important initial study in the imaging evaluationof
the patient with cervical spine trauma and will demon-
strate most cervical fractures and dislocations. Anadequate
examination must include the entire cervical spine includ-
ing the C7-T1 level. Axialcomputed tomography (Cf)scan-
ning through the areas of abnormality seen on the plain
film examination will better define the exact anatomyof
the bony injury and the extent of neural canal impingement
by osseous structures. Reformatting of images in the sagittal
and coronal planes will enhance the diagnostic yield ofa
in this setting.

Magneticresonanceimaging (MRI)is the study of choice
forassessing compression
of neural
elements
by hemor-
rhage,bone,or disk. It is also useful for confirming sus-
pectedposteriorligamentous injury. CTmyelography may
beusedifMRIisunavailableor contraindicated.
Flexion-extensionx-rays are useful when there is uncer-
taintyabout spinal instability and should be done only after
plainfilms,cr, and MRIhave been performed.
. SurgicalTechniques
Thegoalsof surgery in patients with injuries of the middle
andlowercervical spine include: (1) decompression
of the
neuralelements to facilitate maximal neurological
recovery;
(2)immediate stabilization of injured and mechanically
un-
stablespinal segments to allow early mobilization
and avoid
thewide variety of medical complications
seen with pro-
longedrecumbence; and (3) arthrodesis
of these unstable
spinalsegmentsto prevent future deformity, pain, and neu-
rologicalinjury. Decompression
is accomplished
anteriorly
by diskectomy or
vertebrectomy,
and
posteriorly
by
laminectomyor laminotomy. Immediate
spinal stabilization
isgenerallyachievedwith metallic implants. Anteriorly,this
isalmostuniversallydone with screw-plate constructs. Pos-
teriorly,wiringtechniqueshave been used with good results
formanyyears.Morerecently, lateral mass screw fixation
hassupplantedwiring as the stabilization technique of
choicein the posterior cervical region. Arthrodesis can be
performedutilizinga variety of bone-grafting techniques.
AnteriorversusPosterior Approach
Thechoiceofan anterior or posterior approach for stabiliz-
ingthe cervical spine after trauma depends on (1) the
mechanismand type of spinal injury, (2) the presence of
residualspinalcord compression, (3) the type of neurologi-
caldeficit,if any,and (4) the skills and preferences of the
surgeon.Frequentlyeither the anterior or the posterior ap-
proachwill be satisfactory to achieve immediate stability
andpreventlong-termdeformity.
Theonlyabsoluteindication for anterior stabilization is
thepresenceofanterior compression of the spinal cord in
patientswith preservation of some neurological function
belowthe levelof the injury. There are no absolute indica-
tionsfor posterior stabilization except in the patient who
hasposteriorspinalcord compression.(e.g.,a bilaminar
fracturewith anterior displacement). In general though, it
makesmost sense to use the posterior approach to treat
instabilityresultingfrom injuries to the bony and ligamen-
tousstructuresofthe facetjoints. Although the anterior ap-
proachhasbeen used in such situations and is frequently
successful,it does not directly stabilize
the area of injury.6
Moreover,vertebrectomy or diskectomy initially increases
theamountof instability until bony healing can take place.
Similarlythe anterior approach is a more appropriate
meansof stabilizing injuries of the vertebral body. For ex-
ample,vertebral body compression fractures with angula-
tionare better treated with vertebrectomy, followed by
bonegraftingto restore the height of the anterior column
J
22
Trauma of the Mid-and LowerCervicalSpine
177
and anterior cervical plating than with posterior instrumen-
tation. Although posterior stabilization procedures may be
successful for these injuries, instrumentation
failure may
occur as the spine assumes a kyphotic position due to lack
of anterior support.
Operative fixation of the posterior elements is the pre-
ferred method of treating instability of the cervical spine
due to injuries of the capsular ligaments of the facet joints,
fracturesofthe facets,fractureseparationofthe lateralmass
from the vertebral body, or dislocations ofthe facetjoints. It
may also be used to supplement anterior fixation constructs
in severe dislocations with circumferential disruption of
bone and ligament or in patients with injuries to the verte-
bral bodies who are developing kyphoticdeformity.
Positioning and Anesthesia
All patients with acute, unstable injuries of the cervical
spine should be placed in traction to immobilize the spine
and improve or restore spinal alignment. Either Gardner-
Wells cervical tongs or a halo ring can be used. In both, the
traction may be adjusted to place the neck in a neutral,
flexed,or extended position.Dependingon the nature of
the injury,this canbea usefultool,suchas initiallyplacing
some flexion in an attempt to "unlock" bilateral jumped
facets. For most situations, however, extension is the posi-
tion of safety. There is little evidence to support the notion
that patients carry a significant risk of neurological deterio-
ration with cervical traction in the presence of a traumatic
disk herniation.7
Patients are transported to the operating room with cer-
vical traction still in place. Ideally,intubation should be per-
formed using an awake fiberoptic technique and the patient
should be evaluated prior to the induction of general anes-
thesia to confirm that no new neurological deficit has been
incurred during intubation. Ifelectrophysiogical monitoring
is to be performed, an appropriate combination of anes-
thetic agents is required, and baseline recordings should be
obtained prior to positioning the patient on the operating
table. The use of intraoperative monitoring has been recom-
mended as a means of detecting maneuvers during posi-
tioning or surgery that may result in increased neurological
deficit, allowing the surgeon to make appropriate technical
adjustments.s
Anterior procedures
are generally performed
in the
supine position with the head on a horseshoe head support
and with the traction tongs left in place. Just before the
induction of anesthesia and administration of muscle relax-
ants, the amount of traction weight should be reduced to
5 to 10 Ibto avoid spinal cord injury from overdistraction.
Posterior procedures are generally performed with the
patient prone on chest rolls, and the head secured in a
three-point
skull fixation device without
any traction
weight. In all cases, intraoperative fluoroscopy is extremely
useful for (1) confirming adequate positioning of the spine
prior to the start of the procedure, (2) allowing rapid identi-
fication of the correct spinal levels intraoperatively, and (3)
facilitatingcorrectplacementofmetallicimplants.Toallow
maximal radiological visualization intraoperatively,
the
shoulders and arms should be pulled down and secured to

.
178
Midcervical
Spine: Pathology
of the Midcervical
Spine
the sides of the table with wide tape. Care should be taken
to avoidexcessiveforce in this maneuver, which can lead to
a brachialplexusinjury.
Anterior Stabilization
Anterior Decompression and Arthrodesis
Anterior decompression and arthrodesis are indicated for
(1) traumatic disk herniation, with or without neurological
deficit; (2) extensive vertebral body injury, particularly if
accompanied by significant loss of vertebral body height;
and (3) anterior bony compression of the neural elements.
When a three-column injury is present and a combined an-
terior/posterior procedure is planned, the anterior approach
isgenerally performed first.
The essence of the anterior approach to the cervical spine
is dissection through a bloodless plane between the stern-
ocleidomastoid muscle and carotid sheath laterally, and the
trachea and esophagus medially (Fig. 22-1). The anterior
approach to the cervical spine can be performed through a
horizontal incision made in a skin crease in the anterior cer-
vicaltriangle, or an oblique vertical incision made along the
anterior border of the sternocleidomastoid (Fig. 22-2). The
former is appropriate for diskectomy and a one- or two-
levelvertebrectomy, and gives a better long-term cosmetic
result. The latter is generally reserved for resection of more
than two vertebral bodies when a greater amount of rostral-
caudal exposure is required.
The horizontal
incision begins at the midline and extends
laterally
to the medial border
of the sternocleidomastoid
muscle. Fluoroscopy can greatly aid in proper localizationof
the skin incision. Landmarks include the cricoid cartilageat
approximately
C5-C6 and the thyroid cartilage at approxi-
mately C4-C5.Aright-sided approach is generallyeasierfor
right-handed surgeons. The right recurrent laryngealnerve
is aberrant
in a small percentage
of patients;
the left recur-
rent laryngeal
nerve is never aberrant
and a left-sided ap-
proach therefore
carries a lower risk of recurrent
laryngeal
nerve injury, particularly
at lower cervicallevels.9
Recent
data, however, suggest a similar incidence
of postoperative
nerve injury regardless of the side of approach.
The skin, subcutaneous
tissue, and platysma
muscleare
sharply
divided
and retracted
with
a blunt-toothed
self-
retaining
retractor
to expose the superficial
cervical fascia.
The superficial
fascia is opened, and, using blunt dissection,
the
plane
between
the sternocleidomastoid
muscle and
carotid
sheath
laterally
and
the
trachea
and esophagus
medially
is developed.
The carotid artery
is identified and
retracted
laterally.
The
anterior
cervical
spine
will be
rapidly palpated
and identified.
The prevertebral
fasciais
opened
in the midline
in a rostral-caudal
direction. Proper
Middle layer of
deep cervical
fascia
Left
Posterior
Figure
22-1
Cross-section
through
the C6 level demonstrating
the correct
anatomical
plane through
which the cervical spine is
approached anteriorly.(ReprintedwithpermissionofWB. SaundersCompany.)

Figure22-2
Diskectomies at as many as three levels and single-level
vertebrectomiescan be performed
through
a horizontal
incision.
A
verticalskinincision provides better exposure for multilevel
vertebrec-
tomiesand anterior instrumentation.
(Reprinted
with
permission
of
W.B.SaundersCompany.)
identificationof the midline is obtained by noting the me-
dialattachmentsof both longus colli muscles, which lie on
theanterolateral aspect of the cervical spine bilaterally.
At
thispoint,a spinal needle is placed in a disk space and the
correctlevel is confirmed
with an x-ray or a fluoroscopic
image.With significant
bony trauma
such as a burst frac-
ture,one will also be able to visually appreciate
other signs
pointing to the
correct
level,
such
as
a prevertebral
hematomaor fracture of the affected vertebral body.
Afteradequateexposure and localization, the longus colli
musclesare elevated
bilaterally
from medial to lateral.
In
theverticaldirection, the length of longus colli mobilization
mustexceedthe length of the necessary decompression.
Variousself-retaininganterior cervical retractor systems are
available,the majority of which utilize curved blades whose
teethfit beneath the medial aspect of the longus colli
muscles.Verticalretraction is accomplished using curved
bladeswithout teeth to minimize the possibility of retrac-
tor-associateddamage to soft-tissue
structures
(Fig. 22-3).
(areshould be taken to avoid dissection lateral to the
longuscolli muscles, which may injure the sympathetic
chainandresult in a postoperative Horner's syndrome.10
After retractor blades are inserted
and the retractor
mechanismopened, the cuff on the endotrackael tube is de-
flatedfor20 seconds and re-inflated to just barely produce
anairtight seal between the cuff and the trachea. This will
22
Traumaof the Mid- and LowerCervicalSpine
179
further minimize the chances of recurrent laryngeal injury
in the larynx by reducing the pressure between the retrac-
tor blade and the endotracheal tube.
After completion of the soft tissue exposure, the spinal
portion of the procedure is performed. Occasionally, this
will consist of a diskectomy for a traumatic disk herniation.
Removal of an entire vertebral body is often required if
there is significant comminution, loss of height, and/or
retropulsion of bone into the spinal canal. Wewill describe
the steps in performing a single-levelvertebrectomy, proba-
bly the most common anterior operation performed in the
setting of middle and lower cervicalspine trauma.
The disk spaces above and below the vertebral body to be
resected are identified and incised with a fine-tipped knife
blade. Partial diskectomies are then performed by mobiliz-
ing disk material with small curettes and removing it in a
piecemeal fashion with pituitary forceps.The anterior halfof
the vertebral body can then rapidly be removed using a
rongeur. After creating a defect in this manner, the bone re-
moval is continued using a high-speed cutting bur.The de-
compressiontrough thus created should be shaped likea
rectangle whose ends liejust at the vertebral end plates and
whose sides are parallel to the sagittal plane (Fig. 22-4A).
Saferemoval of the posterior half of the vertebral body is ac-
complished with the use of the operating microscope. Asthe
ventral spinal canal is approached, changing the drill bit to a
diamond bur minimizes the possibility of drill-associated in-
jury to the dura or neural structures. The trough should be at
least 15 to 18 mm wide to assure adequate bony decompres-
sion, but should not exceed 20 mm to avoid inadvertent in-
jury to the vertebral arteries, which lie -30 mm apart in the
mid- and lower cervical spine (Fig. 22-48). The last bits of
bone may be removed with fine curettes or a nerve hook. To
avoid injury to the spinal cord instruments that intrude sub-
stantially on the spinal canal should not be used.
Afterbone removal has been completed, the posterior lon-
gitudinalligament
(PLL)should be resected to ensure com-
plete decompression of the epidural space. A small nerve
hook is initially used to lift and open the PLL,and its removal
is then completed with small Kerrison punches, taking care
not to compress the dura and underlying spinal cord.
Interbody arthrodesis is performed by placing a strut graft
between the end plates of the vertebral bodies adjacent to
the bony defect. Wegenerally cut the graft a few millimeters
longer than the measured rostral-caudal length of the defect
and tamp it into place while the neck is distracted by the
anesthesiologist (Fig. 22-5). This places the graft under
compression, and enhances the likelihood of successful fu-
sion. The graft should be countersunk 1 mm to prevent its
extrusion but should not exceed 13 mm in depth to prevent
intrusion into the spinal canal. Iliaccrest autograft and iliac
crest or fibular allograft are acceptable materials. Although
autograft has a slightly higher fusion rate, allograft fusion
rates are comparable, and the use of allograft eliminates
donor site morbidity.l1-13Furthermore, current methods of
obtaining and preparing allograft material virtually elimi-
nate the possibility of infectious disease transmission.
Metallic, polymeric, or carbon fiber cages packed with
morselized bone have become increasingly popular and are
acceptable as an alternative to strut grafting, but are associ-
ated with substantially greater cost.

180
MidcervicalSpine: Pathology of the Midcervical Spine
Feet
I
I~/.t.jf"
. __
_.,..
'J
. ~"
,
Head
Figure 22-3
Self-retaining retractors with teeth are placed under the longus colli muscles bilaterally. Smooth blades are placed in a vertical direc.
tion affording excellent exposure of the anterior cervical spine. (Reprinted with permission ofW.B. Saunders Company.)
AnteriorCervicalPlating
Screw-plate fixation of the anterior cervical spine has be-
come increasinglypopular to facilitate successful interbody
fusion in a variety of pathological processes, particularly
trauma. Anterior plates provide immediate rigid fixation,
thus reducing the incidence of graft complications such as
migration and pseudoarthrosis, as well as obviating the
need for postoperative halo vest immobilization.14-17We
routinely utilize cervicalplating with single- and multilevel
vertebrectomies performed for trauma.
Numerous cervicalplatingsystems from a variety of man-
ufacturers are available.Adetailed discussion of the differ-
ences between the availablesystems is beyond the scope of
this text, and the selectionofany particular plate is largely a
matter of the preference and experience of the surgeon.
Plates made of titanium are generally used because they
produce less artifact on postoperative MRI studies than
stainless steel implants. The earliest available systems re-
lied on bicortical screw placement, and, although they
achieved excellent screw purchase, screws could penetrate
the dura or cause spinal cord injury. Most current plating
systems utilize unicortical screw placement, which is safer
and technically easier to perform. Todecrease the possibil-
ity of screw backout, most systems have developed a
mechanism to lock the screw head to the plate. The screw
trajectorymaybe fixed,inwhichcasethe headofthescrew
is rigidlylockedto the plate,or variable,inwhichthehead
of the screw is nonrigidly locked to the plate.
The ability to vary the angle of screw placement to
achieve optimal screw placement allows surgeons greater
flexibility when confronted with abnormal anatomy ora
thin, partially resected vertebral body. The variable trajec-
tory systems may also be easier to use when working inthe
high cervical spine or near the cervicothoracic junction,
where the jaw and the clavicle, respectively, may make
standard instrument placement more difficult. Variabletra-
jectory systems are intrinsically less rigid than fixed trajec.
tory systems and over time will demonstrate subsidence.
which refers to a gradual load transfer from the implantto
the bone graft. This will, theoretically, facilitate the fusion
process by placing the graft under greater compression.ll~
For vertebrectomies,
we now prefer to use translational
plates such as the ABCplate manufactured by Aesculap
(Tuttlingen, Germany) or Premier plate manufactured by
Sofamor-Danek (Memphis, TN). These plates allow for
movement of the screws in relation to the plate, and conse-
quentlygreater load transfer to the interbody graft.Since
there is less load borne by the plate, and screws, these sys-
tems should have a lower incidence of construct failure
than rigid or semi-rigid systems and should theoreticallyfa-
cilitate faster and better bony fusion.