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

182
Midcervical Spine: Pathology of the Midcervical Spine
A
Figure 22-6
(A) Sagittal magnetic resonance
imaging scans of a 17-year-old
male involved in a high-speed motor vehicle accident. There is a burst fracture of
C7withbonyretropulsion and spinalcord compression. (B) Lateralx-rayshow-
ing interbody strut grafting from (6 to T1 and anterior cervical plating across the
same segments using unicortical screws. (C) Anteroposterior
view of the same
construct seen in (A) showing midline placement of the graft and plate.
described and popularized by Roy-Camilleor the new rod-
screw systems are technically simple, produce immediate
stability of the cervical spine without the need for complex
orthoses such as the halo vest, and are not dependent on
the integrity ofthe laminae or spinous processes.19-22
Lateral mass screw fixation is ideal for facet dislocations
caused by fracturesor ligamentous injuries and is especially
useful in patients with laminar and spinous process frac-
tures when these structures cannot be wired.22Because the
constructs are placed bilaterally at the locus of movement
they
provide greater rotational
stability
than can be
achieved with wiring of posterior midline structures.
Thereare fewcontraindicationsto the useoflateral screwfix-
ation. However,theyshouldnotbe usedin patients with osteo-
porosis, metabolic bone disease, or conditions such as
ankylosing spondylitis where the bone is soft; in these
situations, screw pullout and loss of reduction are Iikely.23
Lateralmass screw fixation isalso contraindicated in patients
with residual neurological function and persistent anterior
compression of the spinal cord by bone, disk, or soft tissue.
These situations should be addressed viaan anterior approach.
Patients are brought to the operating room in cervical
traction. After intubation, a cervical collar is placed and the
patient is turned to the prone position and the head is fixed
(
in a three-pin
head holder. A midline
incision is made and
the posterior
elements
of the levels to be stabilized
areex.
posed. The muscles must be dissected
off the bone far later.
ally to expose the entire lateral mass at every locationwhere
a screw is to be placed. The levels are confirmed with fIuo.
roscopyor a lateral x-ray.
If there is a facet dislocation that could not be reduced
preoperatively, a curette or similar instrument
maybe
wedged into the facet joint and the dislocation reduced.If
this is not possible a small bur is used to remove the supe.
rior facet of the inferior vertebra involved in the subluxa-
tion, and reduction is then performed.
The technical details of operative placement of lateral
mass screws are straightforward and relatively simpleand
will be discussed subsequently. However, decision making
regarding the number of motion segments requiring stabi.
lization is frequently more complex; conceptual mistakesin
the location of plate or rod placement probably accountfor
more cases of inadequate fixation than technical failures.
The plates are always placed bilaterally and symmetri-
cally (Le., between
the
same
vertebrae
bilaterally).
Two-hole plates are ideal for patients with single-level
subluxations or facet dislocations (Fig. 22-7). Three-level
fixation is
used for instability at two adjacent motion

22
Traumaof the Mid- and LowerCervicalSpine
183
A
B
(
k_ __ J:
,~
~..J
D
Figure 22-7
(A) Lateral cervical spine x-ray showing
(4-(5
subluxation.
(8) Axial computed
tomographic
scan at the level of subluxation
shows a
jumped facet on the left.
(e)
Intraoperative
photograph
shows
plate
placement.
(D)
Postoperative
lateral
x-ray
shows
reduction
of the
subluxation
andcorrect plate and screw
placement
at (4-(5.
-..

184
MidcervicalSpine:Pathology of the Midcervical Spine
A
B
segments or when there is a fracture of the lateral mass or
pedicle, precluding fixation of the lateral mass at that level.
In this situation an additional adjacent motion segment
must be incorporated into the construct. For example, if
there is a subluxation at (4-(5
with an associated fracture
of the lateral mass of (4, two-level fixation between (4 and
(5 will immobilize this motion segment unilaterally only
on the side of the intact lateral masses. Rotational stability
will not be achieved and screw pullout and loss of align-
ment may occur. Application of three-level fixation from (3
(
Figure 22-8
(A) Lateralx-ray shows a (5-(6
subluxation.
(8) Axialcomputed tomography at the (5 level showsfracture
of the (5 lateral massand foramen transversarium on the left.
(C) Postoperativelateral x-ray showsexcellentreduction of the
(5-(6
subluxation. A screw could not be used to obtain fixa-
tion in the fractured left lateral massof (5. Therefore, lateral
massplateswere placedfrom (4 to (6. Note that there is only
one screwat the (5 level.
to (5 is necessary
in this situation
(Fig. 22-8). The needtt
stabilize three or four motion segments
using four- orfive.
level constructs
is infrequent
in traumatic
situations, but
necessary, longer constructs
will provide excellent posteric
fixation.
The paraspinous
muscles are reflected laterally to themOSI
lateral aspect of the lateral mass. The lateral massisdefiner.
by its four borders:
(1) the superior
facet, (2) the inferi~~
facet, (3) the edge of the lateral mass laterally, and (4)th<:
junction
of the
lateral
mass
and
lamina
medially. TIY1

Magerl25.
- 30.
22
Traumaof the Mid- and lower CervicalSpine
185
Roy - Camille 10.
techniques
havebeen described for screw-hole placement in
thelateralmass (Fig. 22-9). Roy-Camille et ap2 place the hole
intheexactcenter of the lateral mass and direct the hole 10
degreeslaterally and directly anterior. Magerl et ap4 advocate
holeplacement 1 to 3 mm medial to the center of the lateral
mass.The hole is directed
25 degrees
cranially and 25 de-
greeslaterally. The relative efficacy of the Magerl and Roy-
Camilletechniques has been compared by Heller et al.25
Regardlessof which technique
is used, the goals of hole
placementare the same:
to achieve
maximum
fixation
whileavoiding the cervical nerve roots and the vertebral
ar-
teries.Weprefer the Magerl technique of hole placement
becausethe more lateral screw trajectory is further from
thevertebralartery and the superior direction of the screw
islesslikelyto result in unwanted fixation of the superior
facetofthenext vertebra inferiorly.After marking the start-
ingpointofthe holes with an awl, we drill the holes 14 mm
deepwith a 2.7 mm diameter bit. The drill bit is passed
througha drillguide with a stop at 14 mm.
Severalplating systems that may be used for stabilizing
thecervicalspine from a posterior approach are commer-
ciallyavailable.In principle, these are generic plates, and
Figure 22-9
Line drawings show two tech-
niques for screw placement for lateral mass fix-
ation as advocated
by Mager! and Roy-Camille.
See text for details. (Reproduced with permis-
sion. Montesano
PX, Mager! F. Lower cervical
spine arthrodesis: lateral mass plating. In:Clark
C, ed. The Cervical Spine. 4th ed. Philadelphia:
Lippincott-Raven; 1998:510.)
none of the plating systems has been specifically approved
by the Foodand Drug Administration for fixation of the lat-
eral masses. In spite of this, lateral mass fixation now repre-
sents the standard of care for stabilization of the subaxial
spine from a posterior approach.
The two most common plates used are the reconstruction
plates marketed by Synthes26(Paoli,PA),and the Axisplates
marketed by Sofamor-Danek (Memphis, TN). Because of
their versatility
and well-designed
instrumentation
for
implantation
we prefer to use the Axis plating system
(Fig.22-10). Several companes manufacture screw-rod sys-
tems which may be used instead of plates for posterior cer-
vical fixation. These include
the Vertex system from
Sofamor-Danek (Memphis, TN),the Starlock and Axonsys-
tems from Synthes (Paoli,PA),and the Summit system from
Depuy (Raynham, MA).The latest generation screw-rod sys-
tems offer screws which have polyaxial heads into which a
rod may be fitted and secured. These systems are quite ver-
satile and are especially useful for multilevel fixation where
screws may not line up making plate fixation difficult.
Screw-rod systems also allow compression and distraction
to be applied segmentally, which can be useful in helping to

186
MidcervicalSpine:Pathology of the Midcervical Spine
,.--
11
mm
L-
I
15
mm
L
I
13
mm
L
~
8 14
mm mm
~
~
10 16
mm mm
~
correct deformities and reduce subluxations (Figure 22-11).
However, these systems are significantly more expensive
than plates, and are not generally necessary for straightfor-
ward one or two-level stabilization procedures. All subse-
quent descriptions of hardware and technique refer to the
Axisplating system. These plates are made of titanium to
minimize artifact if MRIscans are obtained postoperatively.
The plates have been manufactured with an interhole dis-
tance of 11,13,and 15 mm. Unfortunately the design of the
plates has been changed and the figure-of-eight holes will
not be availablein the future.
After the holes are drilled, templates (identical to the
actual platesbut made of soft metal) are placed over the lat-
eral massesto be stabilized and bent to conform to the con-
figuration of the lateral masses. In general, for stabilizing
three lateral masses (two motion segments), an interhole
distance of 13or 15 mm will line up best with the holes in
the lateralmasses.Aplate with an appropriate interhole dis-
~
12 18
mm mm
Figure
22-10
Titanium
bone
plates (Axis
plates) manufactured
by Sofamor-Danek. These
are generic bone plates but are ideal for platingof
the lateral mass. Plates are available in three sizes
with interhole distances of 11, 13, and 15 mm.
tance is chosen and cut to appropriate
length. It is then ben!
with a plate bender to match the bend in the template.
The necessity
for bone grafting with the use of posterior
cervical plates is controversial.
Posterior plates stabilizethe
facet joint so effectively that spontaneous
fusion occurs here
and at sites of bony injury.22 Therefore, in patients who haw
sustained
trauma within several weeks of operation, wedo
not use bone grafts. Although we have had patients whohaw
lost reduction,
this has always occurred
in the first weeks
after
operation
as a result
of faulty screw
placement or
placement of the plates at inappropriate levels. Evenifbone
grafts
had been
used
we
still would
have
lost fixation
because fusion would not have occurred that soon after
operation.
If bone grafts are to be used, one or more spinous
processes
may be resected,
cleaned
of soft tissues, andcut
into small pieces. The facet joints to be fused are then curet-
ted of articular cartilage and packed with this bone.
Figure 22-11
(A.B) Intraoperative
photographs
of an elderly gentleman
with central cord syndrome
following
a fall. He was brought
to the operat.
ing room for laminectomy
and fusion, and found to have severe splaying of the facet joints
at (5-(6.
The ability
to compress
across the rods facili.
tated reduction
of the splaying, and the patient healed well postoperatively.

Forthe most part, we have used screws 3.5 mm in diame-
terand14mm in length to secure the plates. Even if screws
ofthislength are directed too medially they will almost al-
waysbe too short to reach the foramen transversarium
and
vertebralartery. The screw is directed in the same trajectory
astheholeand is not completely tightened until all the
screwshavebeen placed. This will allow the plate to seat
properlyand to be manipulated to allow passage of all the
screwsthroughthe holes in the plate. The screws are then
insertedto"two-finger"tightness.
Thistechniqueis appropriate for fixation of the lateral
massesfrom (3 to C7. C7 is a transitional
vertebra
with a
narrowerlateral mass and larger pedicles than the four ver-
tebraerostral to it. Placement of cervical pedicle screws at
thislevelisaviablefixation option, but is technically more
demandingand associated with increased morbidity. Nev-
ertheless,excellentfixation of the lateral mass can usually
beachievedwithout utilizing the pedicle for fixation. At
thislevelthe vertebral artery rarely runs through the fora-
mentransversarium, precluding the possibility of injury.
Anoccasional patient will present
with instability
at the
O-Tllevel.The lateral mass ofT1 is not appropriate
for fixa-
tionbutthe pediclemay be used for screw placement.27An
awlholeisplacedinthe posterioraspect ofT1 at a point 2 mm
belowthe C7-T1facetjoint and midway between the medial
andlateralmarginsof the joint (Fig. 22-12). We drill an 18
mmdeepholeusinga 2.7 mm diameter drill bit. The hole is
directed5to10degreesmediallyand 20 degrees caudally.The
plateisfixedto the T1vertebra using an 18 mm long screw.
Lowercervicalholes are placed as described earlier in this
chapter.
Thetechnicaldetails of plate and screw placement
havebeensummarized in several publications.19.22When
crossing
thecervicothoracicjunction in this manner, use of a
screw-rod
systemmaymake the procedure technically easier.
Patientsare allowed out of bed the day after operation.
Theneckisimmobilizedfor 3 months using a Philadelphia
collar.Lateralcervicalspine films are taken once or twice in
thefirstweekafter operation and monthly until the collar is
removed.
At the end of 3 months the collar is removed, and
dynamicflexionand extension films of the cervical spine
aretakentoconfirmstability.
T3
14
22
Traumaof the Mid- andLowerCervicalSpine
187
Lossof alignment is infrequent and usually occurs in the
first days or weeks after application of lateral mass fixation.
Screw pullout almost always accounts for loss of alignment
at the stabilized level and may occur if the screw is placed
too laterally in the lateral mass or there is too little bone
lateral to the screw to hold it in place. Ifthe screw has been
tightened excessively, it may be "stripped," in which case
pullout is almost inevitable. If stripping is apparent at the
time of operation the screw should be replaced with a
larger 4.0 mm diameter screw.
Loss of alignment at levels adjacent to the fixated level
may occur if ligamentous injury is not recognized preopera-
tively or at the time of operation. Dynamic flexion and ex-
tension films are quite appropriately not obtained preoper-
atively in patients with obvious subluxations or instability
at one level. Therefore, a second level of ligamentous injury
may not be suspected if the patient's alignment is satisfac-
tory at the time of evaluation with lateral cervical spine
x-rays. In all patients, careful intraoperative inspection of
the facet joints adjacent to the level of plating should be
performed. This may reveal ligamentous injury and pre-
sumptive evidence of instability not appreciated prior to
operation. The presence of instability at these levels may be
determined by observation of the ligamentous complex at
the facet joints at the time of operation. The joints may be
stressed by grasping and distracting the spinous processes
with clamps. Ifthere is abnormal movement, this additional
motion segment should be incorporated into the construct.
Preoperative MRImay be useful in identifying ligamentous
instability not readily apparent on plain films.
Vertebral artery penetration during screw placement is
theoretically possible but will not occur if the screw is an-
gled 20 to 30 degrees laterally. Moreover, screws 14 mm in
length will almost always be too short to reach the vertebral
artery even if the angle of the screw is incorrect.
Root injury caused by screw penetration has not been
seen by us and should not occur if the screws are angled ros-
trally. Should a patient awaken after operation with severe
radicular pain or motor deficit, a (T scan should be obtained
to determine whether a screw has penetrated the neural
foramen.
5-10'
Figure22-12
Line drawing shows technique
for pedicle screw placement
in the upper thoracic
spine. The screw hole is drilled in the midfacet
line
1to2mm below the superior edge of the facet. The hole is directed
10 to 20 degrees caudally
and 5 to 10 degrees medially.
(Reproduced
with
permissionof the Journal of Neurosurgery.
From Chapman JRet al.27)

188
MidcervicalSpine:Pathologyof the MidcervicalSpine
An increase in neurological
deficit
is unusual
but may re-
sult from injury
to the spinal cord during
turning
of the pa-
tient or manipulation
of the spine during
instrumenatation
placement
or intraoperative
reduction
of subluxations.
Disk
herniations
may occur or be exacerbated
when the spine is
moved into a kyphotic
position
as the screws are tightened.
Preexisting
disk herniations
will
usually
be apparent
on a
preoperative
MRI and are a contraindication
to posterior
cervical stabilization.
CervicalFacetWiring
Two types of cervical facet wiring
have been reported.
Callahan et aJ28have described a technique that entails
drilling holes in the inferior facets of the vertebrae to be
stabilized. Two strands of twisted 24-gauge wire are passed
through each hole and tied around a corticocancellous iliac
crest graft. The technique was originally
described for the
control of postlaminectomy
instability
and may also be
used for patients with posttraumatic
instability. Becauseit
does not provide immediate internal
fixation,
it must be
used with an orthotic device such as a halo vest until the
bone graft fuses.This method of internal fixation is inferior
to lateral mass plates and is now of historical interest only.
Cahill et aJ29have described bilateral wiring of the facet
to the spinous process. They believe that this technique is
particularly appropriate when one or both facet joints are
disrupted by trauma, a situation
where spinous process
wiring may not provide sufficient rotational stability. Holes
aredrilled bilaterally in the inferior facet of the upper verte-
bra to be stabilized, and braided strands of 22- or 24-gauge
wire are passed through the holes in the facets and tied
around the inferior spinous process. Bilateral wiring is per-
formed even if only one facet has been disrupted. After the
wires are tightened, pieces of corticocancellous bone graft
are placedover the posterior elements. The technique can-
not be usedif the posterior elements of the lower vertebra
to be stabilized or the inferior facet of the upper vertebra
hasbeenfractured.Unfortunately, this precludes its use in a
high percentageof patients with spinal fractures. Moreover,
maintenance of stability depends on a thin piece of bone of
the inferior facet; pullout of the wire through the facet may
occur as the wire is tightened around the spinous process.
This technique has been supplanted by the use of lateral
mass screw fixation.
CervicalClampandHookSystems
Halifax clamps havebeen most frequently used to treat at-
lantoaxial instability but canalsobe used for stabilization of
the subaxial spine. The device consists of two small hooks
that engage the laminae of the vertebrae to be stabilized.
The hooks are connected by a threaded screw, which is
turned, resulting in progressivetightening ofthe cIamps.30-32
The more rounded hooks used at C1are not employed, and
only the square (more acutely angled) hooks are used to en-
gage the cervical laminae to be stabilized. The hooks have
several disadvantages in stabilizing the subaxial spine: (1)
they cannot be applied if there are fractures of the posterior
elements or pedicle; (2) the hooks hug the anterior aspect
of the laminae and are located within the spinal canal, cre-
ating the potential for iatrogenic injury to the spinalcord:
and (3) the hooks are poorly
designed,
with
loss of fixation
being
not uncommon.
For these
reasons,
they cannotbe
recommended.
'
The
ApoFix
cervical
hook
system
by
Sofamor-Danek
(Memphis,
TN) represents
a significant
design improvemem
over the Halifax
clamps and works
well
for atlantoaxial sta.
bilization.
The hooks are placed bilaterally
around the lami.
nae to be stabilized
and tightened
sequentially
and crimped
to secure fixation. The hooks are thicker than thoseofthe
Halifax clamps and cannot be used in patients with space.
occupying
lesions
of the spinal canal. We have usedthis
system
successfully
for atlantoaxial
fixation
but haveno
experience
with
it in the subaxial
spine.
Interspinous
Wiring
Interspinouswiring is the oldestmethodof posteriorstabi.
lization
of the subaxial spine.33It is simple and easytoper.
form and requires no specialized equipment. However,it
cannot be used when there are fractures of the spinous
process or laminae of the vertebraerequiring stabilizatioll
Becausethe wire is placed at the midline, it provideslessro-
tational stability than bilaterally applied lateral massfixa.
tion. Although this technique is less frequently employed
since the advent of lateral mass screws, it is an effective
means of stabilizing the subaxial cervical spine and isespe.
cially useful in patients with bone that is too soft to hold
screws. It may also be used to supplement
lateral mass
plates
and screws if there is concern about the adequacyof
screw fixation.
Patients are managed preoperatively and positionedin
the same manner described in the section on lateral mass
plates. After exposure of the posterior elements to be stabi.
lized, dislocated facets are reduced.If the levelof instabili~
is unclear at the time of exposure of the posterior element~
a lateral
x-ray is taken. A right-angle
drill or towel clipis
used to make a hole in the base of the upper spinous
process to be stabilized. It is essential that the hole be made
at the most rostral portion of the spinous process andas
close as possible to the base of the spinous process to mini.
mize the chances of the wire cutting through the hole.
A1.0or 1.2mm wire ispassed through the hole and brought
around
the lower spinous process. Alternatively, a multi.
stranded cable may be used to achieve fixation. The down-
ward slopeof the lower spinous processes will usuallyprevent
the wire from slipping off but a small notch may be madeat
the base of the spinous process to provide a seat for the wire.
The ends of the wire are brought around the lower spinous
process and are tightened using a wire twister. Arthrodesisis
then performed using pieces of cancellous and corticocancel-
lous iliaccrest autograft, which may be secured with the ends
of the wire (Fig.22-13). Closure is performed in the routine
fashion without drains. Patients are kept in a Philadelphia col.
lar for 3 months after which flexion-extension x-rays of the
cervical spine are obtained to assess stability.
Capen et aJ34have described a technique of interspinous
wiring that is used in patients with fractures of the verte-
bral body, in which the spinous process of the injured ver-
tebral body is skipped and wiring is performed from the
spinous process of the vertebra
above to the spinous

A
22
Trauma of the Mid-and LowerCervical Spine
189
Ilium
Graft
B
Figure
22-13
(A)
Line drawing
shows
technique
of wiring two spinous processes.
Stainless
steel wire
is passed
through
a
hole at the base of the spinous
process of
the rostral vertebra
and tightened
around
the base of the caudal vertebra.
A piece of
corticocancellous
iliac crest graft
is placed
bilaterally
against
the
spinous
processes
and secured with
a second wire. (8) Tech-
nique for stabilizing
three
vertebrae
with
interspinous
wires. The most rostral
spin-
ous process is wired to the middle
spinous
process. which
is in turn wired
to the cau-
dal spinous
process.
Bone grafts
may be
placed as shown in (A). (Reproduced
with
permission
of
Journal
of
Neurosurgery.
From Benzel and Kesterson.33)

190
Midcervical Spine: Pathology of the Midcervical Spine
process of the vertebra below. Inclusion of the vertebrae
adjacent to the level of the injury is essential if the disk
spaces adjacent to the vertebral body fracture have been
injured. However,we prefer to include the spinous process
of the injured vertebral body in the fusion construct.33.35
Stabilization of two motion segments is also necessary
when there is a fracture of the lamina, spinous process, or
pedicle of a vertebra that was to be wired. In this case the
fractured posterior element is skipped and wiring is per-
formed to the spinous process above or below the frac-
tured one.
The use of methyl methacrylate as an adjunct to posterior
wiring has been advocated by Branch et a(36They contend
that the technique avoids the necessity for bone grafting and
results in immediate stability. Their reported results using
the technique have been excellent. However, others37have
questioned the use of methyl methacrylate instead of bone
grafting and have reported a high incidence of failure of im-
mobilization. It is our opinion that methyl methacrylate is
rarely,if ever,indicated for stabilization of the cervical spine
following trauma. Methyl methacrylate poured over wire
constructs adds little or no strength to the construct, it never
fuses to bone, and forever remains a foreign body suscepti-
ble to infection. Bonegrafts, on the other hand, are vascular-
ized and are fused to adjacent posterior elements. They be-
come stronger with time rather than weaker and provide
more strength
over the long term
than does methyl
methacrylate.
The complications of posterior wiring techniques relate
mostly to wire breakage or dislodgment. Failure of inter-
spinouswiringmay result if the wire cuts through the hole in
the upper spinous process as a result of incorrect hole place-
ment. Softbone in patients with osteoporosis or metabolic
bone diseasemayalso result in wire pullout. Carefulpreoper-
ativeassessment with CTand intraoperative observation are
essentialto rule out fractures of the pedicle, spinous process,
or facetofthe vertebrae to be stabilized.Injuryto any of these
structuresprecludeswiring ofthe involvedvertebra.
Ifthe wire is insufficiently tightened or does not engage
the lower spinous process at its base, the wire may slip off
with loss of fixation. Because interspinous wiring provides
less than optimal rotational stability, it is possible for facet
dislocations to recur.In practice, however, this is infrequent.
Wire breakage is a distressing complication that may re-
sult in loss of reduction and necessitate reoperation. It oc-
curs because of inadequate external mobilization or failure
to use wires of sufficient diameter. Breakage of wires 1.0to
1.2mm in diameter is unusual.
References
1.
Marshall
LF,Knowlton S. Garfin SR. et al. Deterioration
following spinal
cord injury: a multicenter
studY.J Neurosurg
1987:66:400-404
2.
Wright
SW, Robinson
GO, Wright
MB. Cervical spine injuries
in blunt
trauma
patients
requiring
emergent
endotracheal
intubation
[see
comments].
AmJ Emerg Med 1992:10:104-109
3.
Gunby I. New focus on spinal cord injurY.JAMA 1981 ;245:1201-1206
Sublaminar
Wiring
Sublaminar wiring is infrequently
used in the subaxialcervi.
cal spine. Because the spinal canal in the lower cervicalreo
gion is smaller than at C1-C2, sublaminar
wiring techniqu1\
carry the risk of spinal cord injury and should be avoided.
The Hartshill Rectangle
The Hartshill rectangle (SurgicraftWorchestershire,UKLtd.)
a rectangular
stainless
steel loop, which is a modificationol
the Luquerod, has been used for posterior segmentalwiring
of the spine.39 The rectangles are preformed and their usea\).
viates the disadvantages
of having to bend a rectangle intra.
operatively
from Luque rods. A rectangle
of appropriate
length is chosen so that the upper end of the rectanglelies
above the upper
spinous
process
to be stabilized andthe
lower end below the lower spinous process. The rectangleis
secured in place by multiple sublaminar
wires. Asdiscusse{\
in a prior section, placement of sublaminar wires inthe
lower cervical spine is potentially dangerous and shouldbe
avoided. However,wires may be passed through holesinthe
spinous processes
to secure the Hartshill
rectangle orafac.
simile fashioned
from Luque rods thus
avoiding the
disadvantages of sublaminar wires. Atthis time the Hartshill
rectangle is not available in the United States.
Combined Anterior and Posterior Stabilization
Combined anterior and posterior
stabilization
of the subax.
ial cervical spine is indicated
when there
is injury toboth
the anterior and posterior elements.4o Such patientspre-
sent with kyphosis,
CT and plain film evidence
of separa.
tion of the facets, and vertebral
body fracture.
Ifvertebrec.
tomy must be performed
to accomplish
decompression of
the spinal canal, bone grafting and anterior
plating willfre.
quently not provide sufficient
fixation;
plate loosening and
graft extrusion
are likely. In this situation
we first perform
anterior
operation
and then turn the patient and placepas.
terior instrumentation
to include two motion segments.
Ifthe vertebral body is fractured but not retropulsedinto
the spinal canal and vertebrectomy
is not necessary, poste-
rior stabilization with wiring or lateral mass plates alone
may be sufficient
to stabilize
the spine. However, compro-
mise of anterior
column support
due to compression
frac-
ture and loss of height of the vertebral
body may place can.
siderable
stress
on the
posterior
instrumentation
and
predispose
the construct
to failure.
4.
Bracken MB. Shepard
MJ, Collins WF Jr. et al. Methylprednisoloneor
naloxone
treatment
after acute
spinal
cord injury:
1-year
follow-up
data. Results of the second National Acute Spinal Cord Injury Study
[see comments).
J Neurosurg
1992:76:23-31
5.
Young W. Bracken MB. The Second
National
Acute Spinal Cord InjUI)'
StudY.J Neurotrauma
1992:9(Suppl1):S397-S405

6.AebiM.MohlerJ.Zach GA. Morscher
E. Indication.
surgical tech-
nique.and results of 100 surgically-treated
fractures and fracture-
dislocationsof the celVical spine. Clin Orthop 1986:244-257
7. GrantGA.Mirza SK.Chapman JR.et al. Risk of early closed reduction in
cervicalspinesubluxation injuries.J Neurosurg Spine 1999:90:13-18
8. EpsteinNE.Somatosensory evoked potential
monitoring
in cervical
spinesurgery.In: Cooper PRoed. Neurosurgical Topics: Degenerative
Diseases
of the CelVical Spine. Park Ridge. IL: American Association of
NeurologicalSurgeons; 1992:73-90
9. BulgerRF.RejowskiJE.Beatty RA.Vocal cord paralysis associated with
anteriorcelVicalfusion: considerations for prevention and treatment.
JNeurosurg1985:62:657-661
10.GrahamJJ.Complications of cervical spine surgery. In: The Cervical
SpineResearchSociety Editorial Committee. ed. The Cervical Spine.
Philadelphia:Lippincott; 1989
11.KaufmanHH.Jones E.The principles
of bony spinal fusion. Neuro-
surgery1989;24:264-270
12.ProloOJ.Biologyof bone fusion. Clin Neurosurg 1990:36:135-146
13.ZdeblickTA.Ducker TB.The use of freeze-dried allograft bone for an-
teriorcelVicalfusions. Spine 1991:16:726-729
14.BrownJA.Havel p.Ebraheim N. Greenblatt
SH.Jackson WT. Cervical
stabilizationby plate and bone fusion. Spine 1988:13:236-240
15.CasparW.Anterior stabilization
with trapezoid osteosynthetic
tech-
niqueincelVicalspineinjuries. In: Kehr P.Weidner A. eds.Cervical
SpineI.NewYork: Springer-Verlag: 1987:198-204
16.KalfasIH.The anterior cervical spine locking plate: a technique
for
surgicaldecompression
and stabilization.
In: Fessler
RG. Haid RW.
eds.Techniquesin Spinal Stabilization. New York: McGraw-Hill;
1996:25-33
TippetsRH.Apfelbaum RI. Anterior celVicalfusion with the Caspar in-
strumentationsystem. Neurosurgery 1988;22:1008-1013
18. McAfeePC.Farey ID. Sutterlin
CEoGurr KR. Warden KE.Cunningham
BW.Device-related osteoporosis with spinal instrumentation.
1989
VolvoAwardinbasic science. Spine 1989:14:919-926
19. CooperPRoCohen A.RosielloA.KoslowM. Posterior
stabilization
of
cervicalspine fractures and subluxations using plates and screws.
Neurosurgery1988;23:300-306
20.Roy-CamilleR.Saillant G. Berteaux
D. Early management
of spinal in-
juries.In: McKibbon B. ed. Recent
Advances
in Orthopedics.
New
York:Churchill Livingstone:
1979:57-87
21. Roy-Camille R. Saillant
G. Judet T. Mammoudy
P. [Recent injuries
of
the last 5 celVical
vertebrae
in the
adult
(with
and
without
neurologic
complications)]. Sem Hop 1983;59:1479-1488
22. Roy-Camille R. Saillant
G. Laville C. Benazet
JP. Treatment
of lower
cervical spinal
injuries:
C3 to C7. Spine
1992:17:S442-S446
23. Eismont FJ.Bohlman HH. Posterior
methyl methacrylate
fixation
for
cervical trauma.
Spine
1981 :6:347-353
24. Magerl F. Grob D. Seemann
D. Stable dorsal
fusion
of the cervical
spine(C2-Thl)
using hook plates. In: Kehr P.Weidner
A. eds. CelVical
Spine I. New York: Springer-Verlag:
1987:217-221
22
Traumaofthe Mid. andLowerCervicalSpine
191
25. Heller JG. Carlson
GD. Abitbol JJ.Garfin SR.Anatomic
comparison
of
the Roy-Camille
and Magerl techniques
for screw
placement
in the
lower celVical spine. Spine 1991; 16:S552-S557
26.
Anderson PA.Henley MB.Grady MS.Montesano PX.Winn HR. Poste-
rior cervical arthrodesis with AO reconstruction plates and bone
graft. Spine 1991 ;16:S72-S79
27.
Chapman
JR.Anderson
PA. Pepin C.Toomey S. Newell DW. Grady MS.
Posterior
instrumentation
of the unstable
cervicothoracic
spine. J
Neurosurg
1996:84:552-558
28. Callahan RA.Johnson RM.Margolis RN.KeggiKJ.Albright JA.South-
wick WOo Cervical
facet fusion
for control
of instability
following
laminectomy.JBoneJoint Surg Am 1977;59:991-1002
29.
Cahill DW. Bellegarrigue R. Ducker TB. Bilateral facet to spinous
process
fusion:
a new
technique
for posterior
spinal
fusion after
trauma.
Neurosurgery
1983:13:1-4
30.
Aldrich
EF. Crow
WN.
Weber
PB.Spagnolia
TN. Use
of
MR
imaging-compatible
Halifax interlaminar
clamps
for posterior ceIVi-
cal fusion [see commens]. JNeurosurg
1991 :74: 185-189
31.
Aldrich EF.Weber PB.CrowWN. Halifax interlaminar
clamp for poste-
rior
cervical
fusion:
a long-term
follow-up
review.
J Neurosurg
1993:78:702-708
32.
Holness
RO. Huestis
WS. Howes WJ. Langille RA.Posterior
stabiliza-
tion with an interlaminar
clamp
in cervical
injuries:
technical
note
and
review
of the long term
experience
with
the method.
Neuro-
surgery
1984:14:318-322
33.
Benzel EC.Kesterson L.Posterior cervical interspinous compression
wiring
and fusion for mid to low cervical
spinal
injuries. JNeurosurg
1989:70:893-899
34. Capen DA. Garland DE. Waters RL.Surgical stabilization of the celVical
spine:
a comparative
analysis
of anterior
and posterior
spine fusions.
Clin Orthop
1985:229-237
35. White MD 3rd. Panjabi MM.The role of stabilization in the treatment
of celVical spine injuries. Spine 1984:9:512-522
36.
Branch CLJr. Kelly DLJr.Davis CHJr. McWhorter JM.Fixation offrac-
tures of the lower cervical spine using methyl methacrylate
and wire:
technique
and results
in 99 patients.
Neurosurgery
1989;25:503-512:
discussion
512-513
37. Whitehill R. Cicoria AD. Hooper WE. Maggio WW.Jane JA.Posterior
celVical reconstruction
with methyl methacrylate
cement
and wire: a
clinical review.J Neurosurg 1988;68:576-584
38.
Geremia GK.KimKS.Cerullo L. Calenoff L.Complications of sublami-
nar wiring. Surg NeuroI1985;23:629-635
39. DoveJ.Internal
fixation
of unstable
spinal fractures:
the Hartshill
sys-
tem. Injury 1989:20: 139-144
40.
Cybulski GR. Douglas RA. Meyer PRJr.Rovin RA.Complications in
three-column
celVical spine injuries
requiring
anterior-posterior
sta-
bilization.
Spine 1992;17:253-256

CervicalSpine:Anterior Approach
. Indications
. Advantages
. Disadvantages
. SurgicalTechniques
Anesthesiaand Positioning
Approach
Illuminationand Magnification
Dissection
Diskectomy
Grafting
Bailey
andBadgley,1Robinsonand Smith,2and Cloward3de-
velopedand promoted the anterior approach
to the cervical
spineinthe 1950s.In spite of their pioneering efforts for
decompressionand stabilization
of the cervical spine via an
anterior
approach,posterior decompression of the cervical
spineremained the preferred approach. Meyert was the
firstoreporta reversal in this preference. He detected a
majority
oftraumapatients being treated by an anterior ap-
proachathis institution in the 1980s. More recently Zde-
blick5hassupportedthe opinion that the anterior approach
~nowmorecommonlyutilized.
Thedebateconcerning the superiority of the anterior
versusposterior
approach
in a variety
of conditions
remainsspirited. Proponents on both sides remain stead-
fast.J-9Willie
Sutton, the bank robber, is credited with
Cloward Technique
Corpectomy
Anterior Cervical Plating
.
Complications and Avoidance
Exposure
Neurological
Vascular
Visceral
Graftingand InternalFixation
espousing the logic of "going where the money is." If the
predominant
compression
is anterior-go
anterior.
Al-
though this remains a logical guideline, the literature sup-
ports successful treatment of many conditions with either
approach.6.7.9.1o
Care should be taken in comparing decompression from
anterior and posterior approaches. It must be recognized
that anterior decompression usually entails fusion whereas
posterior decompression does not. Fusion may be desirable
or disadvantageous depending on the given clinical situa-
tion. Comparison should be made on equal grounds in cases
where motion or instability playa role in pathophysiology.
The anterior approach may be utilized for decompression
and stabilization of the cervical spine in a variety of condi-
tions2.10-12 (Fig. 23-1).
193

A
DP
C
Figure 23-1
Diskectomy and corpectomy.
(A) Diagramatic
representation
of a herniated disk (arrow) in both axial and lat-
eral views demonstrates
compression
(circled area). Anterior
cervical surgery is designed to relieve this compression.
(8)
Spondylosis (circled) is a degenerative
condition that also may
result in compression and signs and symptoms
similar to disk
herniation.
It is frequently referred to as a hard disk. Anterior
cervical surgery, again, allows for decompression
and stabiliza-
tion, which is an accepted form of treatment
for spondylosis.
(C) The distractor
pins (DP) accommodate
the distractor
(D).
Distraction
assists in diskectomy and with insertion of a well-
fashioned graft (G). (D) Lateral diagrammatic
illustration: Dis-
tractor
pins (DP) are in place. Diskectomies
have been per-
formed
at (5-(6
and (4-(5.
The posterior
longitudinal
ligament (PLL)has been resected to ensure adequate
decom-
pression, and a graft (G) is being inserted at (5-(6.
(E) Diagra-
matic illustration of corpectomy:
Adequate vertebral body de-
compression
is achieved by using a rongeur or a high-speed
drill. Final removal of bone from the PLLcan be done carefully
with a curette,
directing
forces away from neural structures
(sq.
Once adequate
decompression
is achieved, grafting and
stabilization can be undertaken. S(, spinal cord.
194
G

. Indications
. Degenerative
diskdisease
. Spondylosis(hard disk)
. Herniated(soft) disk
. Degenerativedeformity
. Spinalstenosis
. Instability
. Traumaand posttraumatic
deformity
. Neoplasia
. Infections
. Advantages
. Familiarapproach
. Applicableto a variety of pathological
conditions
. Lesspostoperative pain than posterior
approach
. Disadvantages
. Usuallyrequires fusion
. Riskofrecurrent laryngeal nerve palsy
. Potential risk to vascular
and visceral
structures
. SurgicalTechniques
Anesthesia
and Positioning
Intubationis required
in any surgical procedure
with gen-
eralanesthesia.Thismay be critical in myelopathic patients
undergoinganterior cervical procedures.
Mechanical
injury
asaresultof extension
during intubation
must be avoided.
Thepresenceof the surgeon may be advisable; although
not
mandatory,and fiberoptic
intubation
may be requested
in
selected cases.
Patientswith radiculopathy
and without
significant insta-
bilitymaybe intubated with minimal excursion from the
neutralposition.
Theloungingposition (knees and back slightly flexed)
preventsstretch injuries and allows optimal line of sight
downthediskspace (Fig.23-2). The head and neck should
besupported.The Caspar headrest
supports
the neck and
hasahalterto raise the chin. The device is narrow and facil-
itatesjuxtaposition
of the surgeons
while accommodating
boththefluoroscope and the microscope. The device also
allowsanteroposterior and lateral radiographic visualiza-
tionandisdesigned to hold weights if traction is desired.
Approach
R~ht- versusLeft-SidedApproach
Thereare various reasons for choosing
to operate
from the
-ightorthe left side of the patient.13-17 The variable course
23
CervicalSpine: Anterior Approach
195
of the recurrent laryngeal nerve on the right and its suscep-
tibility to injury is often given as a rationale for favoring a
left-sided approach (Fig. 23-3A-D). Recent investigations
suggest that the nerve may become trapped between the
retractor blades and the endotracheal cuff (Apfelbaum, per-
sonal comments). Momentarily releasing the cuff pressure
after retraction allows the nerve to shift its position and
avoid injury.
Right-handed surgeons tend to approach from the right
and the opposite is true for left-handed surgeons. Some sur-
geons prefer to approach from the side opposite the com-
pressive pathology for the sake of better visualization and
decompression.
The thoracic duct is a unilateral structure on the left side
and as such is susceptible to injury only from a left-sided
approach (Fig. 23-3D). Achylothorax is a serious complica-
tion that can be avoided with right-sided approaches.s
In spite of the various academic debates, it is my experi-
ence that a small and comparable incidence of vocal cord
paresis occurs regardless of which side is chosen. The level
of surgery may be a more critical factor given that C5-C6
surgery seems to have the highest incidence of associated
injury. Also the choice of blunt over sharp dissection may
result in more temporary paresis as a result of traction
injury.
In my practice I have occasion to operate with a left-
handed surgeon. Ioperate mostly from the right whereas he
operates mostly from the left. In reviewing our combined
experiences there were no significant differences in the in-
cidence of recurrent laryngeal injury.
One situation is exceptional. Ifa patient has had previous
surgery, I operate from the side of the previous surgery.
Aunilateral recurrent laryngeal injury is a complication but
bilateral injury can be devastating. Bilateral injuries can be
avoided in this manner.
Illumination and Magnification
In addition to adequate
exposure, illumination
is criti-
cal in any surgical procedure.
Modern surgical micro-
scopes
provide
both
illumination
and magnification.
Additional viewing heads allow assistant
surgeons im-
proved visualization and serve as an adjunct to teaching.
Attached cameras afford circulating nurses and ancillary
personnel
an opportunity
to be more cognizant of the
various stages of the procedure
and thus facilitate the
procedure.
Alternatively, headlight illumination and loupe magnifi-
cation are acceptable. Current technology allows small cam-
eras to be mounted with the headlight. affording benefits
similar to those of the microscope.
Dissection
If appropriate,
a convenient skin crease allows access
and will result in a more cosmetically pleasing outcome
(Fig.23-3A,B). Although anatomical landmarks can indicate
the level of incision, I routinely verify with fluoroscopy.
A horizontal incision is adequate for most procedures and

196
MidcervicalSpine:AnteriorApproach
B
cs
A
\
1--
I
Figure
23-2
Positioning.
(A) Lounge
position: Thelo~,,!
position
protects
the patient
from pressure
points andstrelil
injury.
Elevation
ofthe
back and neck allows improvedlineil
sight
down
the disk space
and is more ergonomicallycolT!!t:
for the operating
surgeon.
(B) The cervical spine issupportSl
by the Caspar
head
rest (HR), which affords close surgeonl'
taposition.
The incorporated
chin strap (C5) allowsimpr!
surgical
exposure,
especially
in the
upper
cervical area,al
the head holder will also support traction weightsasneed!/.
(C) Improved
accessibility
and
accomodation
are also
vided for the fluoroscope
and a microscope
ifdesired.
c
I rarely resort to a carotid longitudinal incision. Three
disks and four vertebral bodies can easily be exposed in
this manner. The key to exposure is a fascial release
(Fig.23-3C). This requires knowledge ofthe fascialplanes in
the neck.ISThe platysma is incised and a subplatysmal re-
lease is performed. For single-level surgery, an anatomical
splitting of the platysma is acceptable. The superficial layer
of the deep cervical fascia envelopes the sternocleidomastlil
muscle and must be released to obtain optimal exposure.
Next, the omohyoid muscle is encountered. Itisinvestl
in the
middle
layer
of the
deep
cervical fascia.Fascii
release
and retraction
are usually
adequate
to mobilil!
this structure;
occasionally,
however, it must be trans,
at its tendinous
midportion.
The trachea and esophaj

ML
(
E
Flgure23-3Surgicalanatomy.(A) The skin incision is lo-
cated
inaskincreaseifpossibleandextendshorizontally
Iromthe
medialborderofthe sternocleidomastoid muscle
(SeM)to
justpasthemidline(M). Thisincision isadequate
lDexpose
fourvertebralbodiesandthree diskswhen a sub-
platysma
Idissectionand fascial release are performed.
br~yisacarotid
incisionnecessary.(8) Theinitial skininci-
!i1nexposes
theplatysma(P),which may be incised, and
dJplatysmal
dissectioniscrucialin gaining adequate expo-
llJe.lc)Fascial
neuralrelations.Releaseof the investing
C!lVifasciaallowsexposureandprovidesa bloodlesssur-
tKalplane.
Thesuperficialayer(SL)investsthe sternoclei-
mastoid(SCM).Theomohyoid (0) is contained within
themiddle
layer(ML).asisthe trachea (T) and the esopha-
fISIE).Thealar(A)fasciaseparatesthe vertebral bodies
mthetracheaandesophagus.Thesurgicalcourseresults
ilthecarotial
(C)beingretracted laterally. (D) Neural rela-
lions.Therecurrentlaryngeal nerve (RLN) has a more
viablecourseonthe right and is theoretically therefore
Djectoincreasedinjury. It lies in the groove between
lletrachea
(T)andesophagus,and some authorities feel
~injuryactuallyoccurswithin the tracheoesophageal
ttstanceafterpenetrationof this nerve. This may result
iompressurebetween the retractor
blade and the
,otracheal
cuff.It should be noted that neural struc-
travelinamannerparallelto the trachea and esopha-
,aswellasthecarotidartery (CA).through the portion
theneckusuallyinvolvedin cervical surgery. The tho-
. duct(TO)isvulnerablewith left-sided approaches.
-
--
Surgical Course
23
CervicalSpine:Anterior Approach
197
p
B
ML
SL
---
D

198
Midcervical Spine:Anterior Approach
VA'
E
,
(
r'
f .
FT
M
F
Figure 23-3
(Continued)
(E) Vertebral artery. The vertebral artery (VA)enters into the foramen transversarium
at (6 and travels superiorlyunO
its exit at (1. Potential iatrogenic injury to this structure requires that the operating surgeon know how to expose the vertebral artery and undertal'e
direct repair and ligation. Unilateral ligation is usually tolerated,
but because of anatomical variation, ligation may result in ischemic complicatiOfl~
(F) The vertebral body. The axial view of the vertebral body displays essential anatomical relationships that are required for successful surgery.The
medialwallofthe foramentransversarium(FT)is-18 to 20 mm from its counterpart. Withthis in mind, 16to 18 mm ofvertebral bodycanbere-
moved (portion between dotted lines) as long as care is taken to center this on the midline (M). It can be appreciated
from this diagram thatUfi.
covertebraljunctions usuallyproject posteriorto the foramen transversarium, and unless significantlateraldeviation isundertaken, the vertebr~
artery is not subject to injury by Kerrison's rongeurs.
are contained within this layer and are gently retracted
medially.
The pulsatile carotid artery is located with a finger on the
nondominant hand and dissection is carried down to the
deep layer of the deep cervical fascia.This is also known as
the alar fascia and separates the trachea and esophagus
from the vertebral bodies and the longus collimuscles.
The longus collimuscles are usually equidistant from the
midline and thus serve to locate the midline. Occasionally
the longus colli coalesce, making identification of the mid-
line more difficult. Constant recognition of the midline pre-
vents lateral deviation and possible injury to the vertebral
arteries (Fig. 23-3E). The insertions of the longus colli are
bipolared, elevated, and serve as anchors for self-retaining
retractors. Anchoring retractors in this manner prevents in-
jury to adjacent soft tissue structures. Unsecured migrating
retractor blades can cause direct injury.Unsecured retractor
blades also subject soft tissue structures to increased ten-
sion and possible indirect injury.
Modern self-retaining retractors were developed specifi-
cally for cervical surgery. They provide excellent exposure
as well as a metal curtain of protection from instruments
such as the drill (Fig.23-4).
Diskectomy
Once exposure is obtained, the level of surgeryshould
be
identified
radiographically.
Interbody
distraction~
obtained by inserting pins into the midportion of appropriate
vertebral bodies and attaching a distractor (Fig. 23-4B,C).
After incising
the anulus,
gentle
distraction
can beap-
plied to facilitate
removal
of disk material.
Althoughthl!
may be accomplished
with
a curette,
especially inthe
case of a soft disk, I prefer
to use a high-speed
drilllor
spondylosis.
Caution
should
be used and the drill should
never be removed
from the disk space while still inmo-
tion. The benefits
of the Caspar-type
distractor
are unim.
peded
bilateral
visualization
of the disk space as wellas
posterior
separation
that
assists
in identification
ofthe
posterior
limits of the disk. The posterior
longitudinallig.
ament
(PLL) can then be identified
and incised. Although
controversy exists concerning sacrifice of the PLL,Ifindit
difficult
to obtain
optimal
resection
of osteophytes with.
out PLLresection.
Furthermore,
complete
removal ofsott
disk herniation
cannot
be verified without
removal ofthe
PLLand visualization of the dura against the posterioras.
pect of the vertebral body. The minor increased instabili~

created
byincisionof the PLLis justified.
Decompression
iscomplete
when a small blunt probe easily passes into
theneuralforamen.(are should be taken not to use a
Kerrison
punchextending more than 8 to 10 mm from the
midlinebecausethe vertebral
artery
may be injured
(Fig.23-3F).
Aprimarypurposeof diskectomy is decompression. Inter-
bodygraftingrestoresdisk height and increases the area of
theneuralforamina.19Although it is well recognized that
diskectomy
without grafting hasbeneficial aspects and ac-
ceptable
results,20the resultant decrease in the height of
theneuralforamenseemsto defeat the purpose of the pro-
cedure.
Futhermore,future foraminal
stenosis is risked.
Diskectomy
without grafting can result in contralateral arm
painandpostoperativekyphosis. Omitting
a graft may
avoidgraftdisplacementand harvesting autograft; how-
ever.
optionsexistthat havesimilar advantages.
Graftingwith banked bone is associated with
high
fusionratesand affords the biomechanical
advantages
23
CervicalSpine: Anterior Approach
199
B
Figure 23-4
Retraction and exposure. (A) Self-retaining retractors are
available that provide adequate
exposure. Byseating these retractors
beneath the insertions of the longus colli muscle. they remain in place
and do not transmit significant force to associated soft tissue structures.
In multilevel procedures,
blades (8) can be arranged
so that an "iron
curtain" can be formed to protect all soft tissue structures
within the
wound. This can be augmented
with additional malleable or handheld
retractors
(HHR) if necessary. A horizontal skin incision affords multi-
level exposure without resorting to a carotid incision. (B) Distraction
pins (DP) inserted into the mid portion of the vertebral body afford a
lever and allow application of the distractor. This assists in performing a
diskectomy in that it spreads the interspace, allowing determination
of
the end of the disk and the beginning of the posterior longitudinalliga-
ment. Gentle distraction after anulotomy allows for improved visualiza-
tion ofthe diskspace,aswell as adequate removalofdiskand cartilagi-
nous end plate. osteophytes.
and bone as necessary. (C) Grafts in place.
Once diskectomy is complete, distraction is utilized to insert well-fash-
ioned grafts (G).The DPare then removed as illustrated in this figure.
already outlined. Rich et aI21and others 22.23reported fusion
rates comparable to autograft but a somewhat slower rate of
fusion.
Various modifications in graft shape and positioning have
been reported. Also, both autograft and allograft
may be
taken from various donor sites. Various ways to graft have
been proposed (Fig.23-5).
The debate to graft or not to graft; bank bone versus auto-
graft, persists.24.25 The former, for the most part, concerns
single-level
procedures.
There are few advocates
for multi-
level procedures without grafting. Although I use bank bone
almost exclusively, the majority feel that autograft is "the
gold standard,"
Donor site complications
serve as the main deterrent
to
using autograftY
Risk of viral transmission
is the principal
deterrent to the use of bank bone.26
A variety of adjuncts to bone graft are available.These in-
clude coral, hydroxyapatite,
ceramic, or carbon.22.27-29These
structural substitutes may require addition of cancellous
autograft
or bone marrow aspirate. There is little long-term
experience
with
these
products.
Further
investigation
is
necessary
before
widespread
use can be recommended.

200
MidcervicalSpine:AnteriorApproach
Smith-Robinson
A
c
B
Figure 23-5
Grafting.
(A) Diagrammatic
representation
of graft preparation.
Allograft
or autograft
can be fashioned
to fill the defectcreatet1~
anterior
cervical decompression.
This should be undertaken
carefully
so that the graft precisely fits the defect, encouraging
bony fusion.IntheUl/
of diskectomy, graft height should be a minimum of 6 mm to withstand the mechanicalforces applied to it. Careshould betakento ensurethattif
graft does not encroach
on the neural cord. (8) Graft constructs.
1. Smith-Robinson.
2. Cloward. 3. Bailey-Badgely.
(C) Diagrammatic iIIustratior~
corpectomy
strut grafting.
The graft (G) can be countersunk
so as to prevent dislodgment
either anteriorly
or posteriorly,
and various modificaOOi"!
of these techniques
exist. (D) Corpectomy
graft using Harms' cage (HC). Titanium
mesh can be used to supply a structural
component withmooei-
lized autograft
or allograft
providing
the osteoconductive
component.

Manipulation
of bonehealing holds great promise and is a
veryactiveareaof investigation.
dowardTechnique
Theprecedingdiscussion dealt with the Smith-Robinson
typeofprocedure-mypersonal preference. Cloward uses a
similaranatomicalapproach but modifies the manner in
whichdecompressionis accomplished (Fig. 23-6). Adrill,
specially
designedtoremovea cylinderof disk and bone,
wasappliedtothe midpoint of a cervical motion segment
afterdiskectomy.A preset depth
allowed
disk and
bonetoberemovedto the level of the posterior cortex.
Residual
bone,osteophyte,and disk were then removed
withacurette.Aslightlylarger, cylindrical, corticocancel-
lousgraft
wasthen impacted into the drilled defect. Com-
plications
associatedwith this procedure are similar to
thoseof other diskectomyproceduers. Malpositioned
drillingandincorrect determination
of drill depth are
uniqueto this technique. The amount of bone removed
mayresultincollapseof the intervening body in multilevel
procedures.
Corpectomy
Diskectomy
maybe inadequate for obtaining satisfactory
neural
decompressionif the compression extends beyond
thediskspaceor there isa decreased canal diameter at the
mldvertebral
body level. In these situations corpectomy
mayberequired.
Inpreparationforcorpectomy, diskectomy is performed
aboveandbelow the vertebral body to be resected. This in-
suresadequate
foraminal decompression,
defines the limits
ofthevertebralcanal, and allows safe removal of the body
downto the posterior cortex. This may be accomplished
witharongeuror high-speed drill. The residual
cortex can
.
23
CervicalSpine:AnteriorApproach
201
Figure 23-6
The Cloward technique. (A) Approach and
diskectomy are standard. Following disk removal, measure-
G
ments are taken and drill depth is determined. Drilling is cen-
tered on the midline and stops short of the posterior longitu-
dinalligament (PLL).Residualdisk or osteophyte is removed
with a curette to ensure adequate decompression. A slightly
larger cylindrical graft (CG) is inserted. If multiple levelsare
addressed the drilling is offset to prevent encroachment of
defects on one another that can leadto collapse.
then be removed with a curette to direct forces away from
the canal and avoid neural injury (Fig. 23-1). The residual
PLLcan then be safely removed under direct vision.
The key to successful corpectomy is a clear understanding
ofthe relevant anatomy (Fig.23-3F). The foramen transver-
sarium are -20 mm apart. Todecompress the canal, a 16 to
18 mm trough of bone must be removed. Ifresection is cen-
tered on the midline, resection can be done safely without
vascular injury.
Reconstruction of corpectomy defects is accomplished
with struts of appropriate size. Avariety of constructs may
be employed (Fig. 23-SC,D). Autograft or allograft struts
may be keyed into the vertebral body in an attempt to
avoid displacement. The biomechanics of corpectomy in-
volve greater
displacement
forces as compared
with
diskectomy; this is the rational for the use of adjunctive
stabilization.
Internal fixation has advantages over external fixation
(halo). Improved patient satisfaction and early postopera-
tive mobilization are significant. These improvements have
resulted
in widespread
acceptance
of internal
fixa-
tion.22.30-33Recently, titanium mesh has become available
for reconstruction. The mesh can be used to contain graft of
either a structural or nonstructural nature. Additional inter-
nal fixation is recommended (Fig.23-SD).
Anterior Cervical Plating
Experience in long bone fractures led Bohler34to stabilize
the cervical spine in an attempt to facilitate arthrodesis.
Caspar3Sdeveloped self-retaining retractors and vertebral
bodydistractorsas wellas platesandscrewsspecificallyfor
arthrodesis of the cervical spine. This type of internal fixa-
tion allows earlier postoperative mobilization, avoids the
use of halo external stabilization, and optimizes conditions
favoring arthrodesis. The Caspar system requires bicortical
screw fixation to minimize the risk of screw loosening
(Fig. 23-7A,B). Penetration of the posterior cortex puts the

202
Midcervical Spine:Anterior Approach
D
I
(\
---- ---...
C
Figure 23-7
Cervical plating. (A) Casparsystem (unconstrained). Diagrammatic axialviewshowing bicortical purchase requiredtominim",
"toggle" and screw backout. This type of system allows maximal variability of screw placement,
but there is no fixation of the screwtotheplatl
Although bicortical purchase can be performed
safely by experienced
surgeons,
fear of neural injury led to the development
of the unicortisystem. (8) Casparanteriorcervicalplate (ACP)and screw (5) (unconstrained
system). (C) Morscher system. Diagrammatic axialviewofafullyCOIf
strained system. The screw is rigidly fixed to the plate by an expansion head (EH)and locking screw (L5).Unicortical purchase avoidspotentialintru-
sion upon the neural canal. Fixed angulation of the screw restricts the surgeon and makes use of the fully constrained
plate more difficultatthe
uppermost and lowermostcervicallevels.(D)Morschersystem (fullyconstrained): photograph of plate (ACP),screwwithexpansionhead(EH),aIII
locking screw (L5).
spinal cord at risk and is a major source of concern to
surgeons critical of this technique. Published reports, how-
ever, confirm the utility and safety of the Caspar technique
in the hands of surgeons trained in the technique.22.30.33.35.36
In spite of the development of safe methods for bicortical
fixation, attendant risks led Morscher et ap7 to develop a
system that locks the screws to the plate (Fig. 23-7C,D).
This technique prevents screw loosening and requires only
unicortical purchase. The plate is made of titanium rather
than stainless
steel and allows better
postoperative radio
ographic
evaluation.
These changes
result in a moreuser.
friendly
system
that
is widely
accepted.
The Morscher
system is a constrained
device. The predetermined orienta-
tion of the screws restricts
its use in the upper andlower
cervical
spine. This is the trade-off
for the advantaged
unicortical
fixation. The Caspar system, an unconstrained
system, allows variable screw placement and is moreada~.
able to various anatomical
situations.
The trade-offhere~
A
'-'"
LS
B
--
EH

....
23
Cervical Spine: Anterior Approach
203
J
A
""~
. , ,..
~ :;,.;;:#-',
B
Agure23-8
A-Line(semiconstrained). (A) Graphic representation
of A-Line (semi-constrained)
anterior
cervical plate (ACP). Expansion head (EH)
allow>varible-angleplacementand locking screw (LS)fixes the screw to the plate. (8) Diagrammatic representation of 30 degree combined
Cf1)halocaudal
and30 degree mediolateral angulation
(variable screw placement).
theneedforbicortical purchase to minimize screw toggle
andbackout.
Internalfixationwith platesand screws is complicated by
hardware
failureif arthrodesis is not achieved. This is true
throughout
thebodyand not limited to the cervical spine.
Hardware
breakagecan occur in the presence of solid
arthrodesis
and is a reflection of the difference
in the
modulus
ofelasticitybetween bone and hardware. Asymp-
tomatichardwarefailure does not mandate
hardware
removal.lS
Widespread
acceptanceof internal fixation has spurred
furtherdevelopmentsin technology. Fixation systems are
nowavailablethat combine the benefits of constrained
andunconstrainedsystems, thus providing
improved
adaptability
andincreasedeaseof use.30Semiconstrained
systems
with variablescrew placement and mechanisms
forsecuringthe screw to the plate are now available
(Figs.23-8, 23-9).
Controversy
persistswith regard to indication for inter-
nalfixation.4.12.24.31.38
Certainly, in single-level
anterior
cervical diskectomy (ACD), the routine use of internal fixa-
tion is not mandatory. A prospective
randomized
series
would have to include thousands of patients to obtain a
power that would show statistical significance. This is re-
lated to the small pseudarthrosis rate of single-level ACD.
The main advantage of internal fixation remains in multi-
level ACD,corpectomy, or patients with medical problems
that impede arthrodesis.3! Some surgeons feel that the ear-
lier return to increased activity is justification
enough for
internal
fixation.
Controversy will
no doubt
persist for
some time.
Only well
designed studies with
extended
follow-up and valid outcome measures can put these issues
to rest.
The biomechanics of cervical plate fixation
have been
addressed.2.39.40Although
much useful information
has
been gained, cadaveric models suffer from the absenceof
functional
muscle, which
plays a major role in in vivo
biomechanics.
Finite element analysis may supplement
cadaveric testing and provide a more useful system for
analysis.

204
Midcervical Spine:Anterior Approach
A
.
Complications and Avoidance
Complications occur with anterior cervical surgeryaswith
any surgical procedure.
Many complications
can beavoided
by careful preoperative
planning,
detailed
familiaritywith
the procedure at hand, and attention to detail.Thesineqll4
non of successful
cervical surgery is neural decompression
and stability. Adjunts, such as internal fixation, are notsub-
stitutes
for poor surgical
technique.
Patient selectionreo
mains crucial. The technically
perfect procedure performed
on a patient
without
appropriate
indication
is a failure.
Patients with secondary
gain or unstable
psychosocialsitu.
ations
should
be approached
with caution. Successisob-
tained most reliably when a specific condition at aspecifK
site is recognized
and correlates
well with the clinicalpre.
sentation
of a psychosocially
stable patient.
The literature
is replete with reports concerning compli.
cations and their frequency.15.17,40-43Although theseserve
as
guidelines
they are not substitutes
for careful patientfol.
low-up and record keeping. This will prevent abandonment
of established
practice
for novel
new
techniques
withoUi
cause.
A careful
review
of a surgeon's
own
well-docu.
mented
experience
can
be
rewarding
or humbling bUI
forms the basis from which change should stem. Patienl~
deserve to be counseled
with the specific surgeon's expen.
ence, not that quoted in the literature.
.
Exposure
Figure 23-9
Reflexanterior cervicalplate (ACP).(A)Photograph of
the (semiconstrained)
ACP.Screws are fixed to the plate with an inte-
grated locking screw (LS).(8) Variable screw placement of ReflexACPis
shown in the diagram. Up to 10 degrees cranial and 10 degrees caudal
with 6 degrees medial angulations can be achieved with the system.
The anterior surgical incision and exposure is associateG
with postoperative pain and dysphagia.44Althoughthisisw
some degree unavoidable, it can be minimized by meticu-
lous surgical
technique.
The amount
of hemorrhageWI!
vary from case to case and is dependent on the pathology.1
hand. It can be minimized by stopping medicationtlldt
favors increased bleeding prior to surgery. Additionalh.
careful hemostasis should be sought prior to closure. Draim
are optional. Stridor and respiratory distress in the immed.
ate postoperative
setting should suggest hematoma andre.
quire immediate
evaluation
to determine
if reexploratiL'
and evacuation
are necessary.

Themostfrequently reported complication associated
withanteriorcervicalsurgery involves harvesting autograft
forfusion.Persistentpain,injury to the lateral femoral cuta-
neousortheilioinguinal nerve, hernia, fracture of the ante-
riorsuperioriliacspine, hematoma, and infection may oc-
curwith frequenciesas high as 30%.17,41These
are
all
technique
relatedand potentiallyavoidable or at least mini-
mizable.
Thishighrate ofcomplication is responsible for in-
creaseduse of allograft.
Neurological
Themostcommonneurologicalinjury involvesthe recurrent
laryngealnerve.Resultant vocal cord dysfunction causes
characteristic
hoarseness.Fortunately, the injury is fre-
quentlyneuropraxicin nature and recovery can be expected.
Hoarseness
persisting longer than 3 to 6 months should be
referred
toanear,nose,and throat specialist for direct laryn-
goscopy
andpossibletreatment. The relationship of injury to
sideofsurgery,levelof surgery,type of dissection, and mech-
anismofinjurywerediscussedearlier.
Lesscommonneural injuries include the superior laryn-
gealnerveandthe sympathetic trunk. The former may be
injuredwith surgery on the upper cervical (above (3)
whereas
thelatteris injured ifdissection is carried laterally
overthelonguscolli. Characteristic loss of vocal strength
andHorner'ssyndromeoccur,respectively.
Injuryto the spinal cord is a rare occurrence. Direct
traumamustbe suspectedin the absence of preexisting
myelopathy
and/orseverecanal compromise. Ischemic in-
JUrymayberesponsiblein the presence of advanced com-
pression,
advancedmyelopathy,or superimposed pathology
suchasdiabetes.Alternatively,in cases of advanced disease,
theabilityofthecordto contend with any additional insult
isgreatlyreduced.Minusculedirect or indirect trauma may
thenproducexaggerateddeficits.
Vascular
Thecarotidandvertebral arteries are rarely injured with
anteriorcervicalsurgery.16The potentially
catastrophic
re-
References
1. BaileyRW.Badgley CEoStabilization
of the
cervical
spine
by anterior
fusion.Amj Orthop 1960:42-A:565-594
2. RobinsonRA.Smith GW. Anterolateral
cervical
disc removal
and in-
terbodyfusion for cervical disc syndrome.
Bull Johns
Hopkins
Hosp
1955;96:223-224
J. ClowardRB.The anterior approach
for removal
of ruptured
cervical
discs.JNeurosurg 1958;15:602-617
4. MeyerPRoCervical spine fractures:
changing
management
concepts.
In: Bridwell KH. DeWald
RL. eds. The Textbook
of Spinal
Surgery.
Philadelphia:jB Lippincott; 1991: 1050
S. ZdeblickTA.ed. Anterior
Approaches
to the Spine. St. Louis: Quality
MedicalPublishing; 1999:ix
6. CusickjF. Pathophysiology
and Treatment
of Cervical
Spondylotic
Myelopathy(Clinical Neurosurgery).
Baltimore:
Williams
& Wilkins;
1989:661-681
7. FagerCA.Posterior surgical
tactics for the neurological
syndromes
of
cervicaldisc and spondylotic
lesions. Clin Neurosurg 1978;25:218-244
23
CervicalSpine:Anterior Approach
205
suItsof injury to these structures dictate that the surgeon
be cognizant of this potential and be prepared to deal with
these injuries should they occur. Direct repair is preferred
and not difficult
in the caseof carotid injury. Direct repair
of the vertebral artery is more difficult
and requires that
the surgeon be able to expose this structure
for repair.
Ligation after exposure is frequently
tolerated
but not
guaranteed.
Visceral
Although incidence of esophageal injury is low, diagnosis is
frequently delayed.17.42Injury usually occurs at the time of
surgery as the result of malpositioned retractors. I routinely
use large, toothed retractors anchored beneath the elevated
insertions of the longus colli muscle, with satisfactory re-
sults. Perforations in the course of redo dissection and in
both inflammatory
and infectious conditions
may occur.
Immediate recognition, direct repair, and antibiotic cover-
age usually result in uncomplicated
recovery. Dysphagia
and fever are early symptoms whereas mediastinitis
and
subcutaneous emphysema may develop later.
Grafting and Internal Fixation
Extensive literature on graft failure, extrusion, pseudarthro-
sis, and associated complications
exists. Likewise, reports
with regard to successof allograft and allograft are plenti-
fuI.21.23Aspects of these subjects have been discussedbriefly
in other portions of this manuscript.
Plating complications
include those associated with an-
terior surgery as outlined earlier.IS Increasedcomplica-
tions can be expected on the basis of the greater exposure
required for internal fixation
and the fact that plating is
more commonly undertaken
in more complicated
cases.
Comparisons should be made carefully
and matched to
compensate for these inequalities.
It is noteworthy
that
few surgeons in this country have more than 10 years' ex-
perience with internal cervical fixation. Few would argue
that internal
fixation
has extended the range of surgical
correction.
8.
Hart AK, Greinwald JH Jr. Shaffrey CI, Postma GN. Thoracic duct injury
during
anterior
cervical discectomy:
a rare complication:
case report.
J Neurosurg
1998:88:151-154
9.
Miller CA,Hurt WE. Correlation in Cervical Monoradiculapathy Syn-
drome. San Francisco: MNS;
1984
10.
Grob D. Surgery
in the degenerative
cervical
spine. Spine
1998;23:
2674-2683
11.
Bohlman
HH, Eismont
FJ. Surgical techniques
of anterior
decompres-
sion and fusion for spinal cord injuries.
Clin Orthop
1981 :154:57-67
12.
Whitecloud
TS III. Modern
alternatives
and techniques
for one-level
discectomy
and fusion. Clin Orthop Relat Res 1999;359:67-76
13. Daniels SK.Mahoney MC. LyonsGO. Persistent dysphagia and dys-
phonia
following
cervical
spine
surgery.
Ear
Nose
Throat
J
1998;77:470-475
14.
Graham
J. Complication
of cervical
spine
surgery.
In: The Cervical
Spine Research
Society, ed. The Cervical Spine. 2nd ed. Philadelphia:
JB Lippincott:
1989:831-837

206
MidcervicalSpine:Anterior Approach
15.
Lowery G. Appfelbaum
R, McDonough
R. Allen A. Hardware
complica-
tions: a review of 700 anterior
cervical
patients.
Proceedings
of the
11th annual
meeting
of North American
Spine Society
(NASS). Oct.
23-26. Vancouver. BC: NMS; 1996:170-171
16.
Pfeifer BA.Freidberg SRC.Sewell ER. Repair of injured
vertebral
artery
in anterior cervical procedures.
Spine 1994; 19:1471-1474
17.
Zeidman SM. Ducker TB. Raycroft J.Trends and complications
in cer-
vical spine surgery:
1989-1993.J
Spinal Disord 1997;10:523-526
18.
Grodinsky
M. Holyoke EA. The fasciae and fascial spaces of the head.
neck and adjacent
regions. AmJ Anat 1938;63:367-383
19.
Bayley JC. YooJU. Kruger OM. Schlegel J. The role of distraction
in im-
proving the space available
for the cord in cervical spondylosis.
Spine
1995:20:771-775
20.
Martins AN. Anterior cervical discectomy
with and without
interbody
bone graft.J Neurosurg
1976;44:290-295
21.
Rich BL.Mcadder JT. Penix JO. Anterior
cervical
fusion using homolo-
gous bone grafts. Surg NeuroI1976;5:119-121
22.
Goffin J.Plets C. Van den Bergh R. Anterior
cervical
fusion and os-
teosynthetic
stabilization
according
to Caspar:
a prosective
study of
41 patients
with fractures
and/or
dislocations
of the cervical
spine.
Neurosurgery
1989:25:865-871
23.
Zdeblick TA. Ducker TB. The use of freeze dried allograft
bone for an-
terior cervical fusions. Spine 1991: 16:726-729
24.
Dunsker
SB. Anterior
cervical
discectomy
with and without
fusion.
Clin Neurosurg
1977;24:516-521
25.
Sonntag VK. Klara P. Controversy
in spine care: is fusion necessary
af-
ter anterior
cervical discectomy?
Spine 1996;21 :1111-1113
26.
Buck BE. Malinin T. Brown MD. Bone transplant
and human immuno-
deficiency
virus:
an estimated
risk of aquired
immuno-deficiency
syndrome.
Clin Orthop 1989:240: 129-136
27.
Brooke NS. Rorke AW. King AT.Gullan RW. Preliminary
experience
of
carbon fibre cage prostheses
for treatment
of cervical spine disorders.
Br J Neurosurg
1997;11:221-227
28.
Takahashi
T. Tominaga
T. Yoshimoto
T. Koshu
K. Yokobori
AT Jr.
Aizawa Y.Biomechanical
evaluation
of hydroxyapatite
intervertebral
graft and anterior
cervical plating in a porcine
cadaveric
model. Bio-
med Mater Eng 1997:7:121-127
29.
Zdeblick
TA. Ghanayem
AJ. Rapoff
AJ. Cervical
interbody
fusion
cagesa: an animal model with and without
bone morphogenetic
pro-
tein. Spine 1998:23:758-766
30.
IIIgner A. Haas N. Tscherne HA. Review of the therapeutic conceplm
results
of operative
treatment
in acute
and
chronic
lesions ofthecen:.
cal spine: the Hannover
experience.J
Orthop Trauma 1991:5:100-i:'
31.
McLaughlin
MR. Purighalla
V. Pizzi
FJ. Cost
advantages
of two-Int
anterior
cervical
fusion
with
rigid
internal
fixation
for radiculopal:1
and
degenerative
disease.
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NeuroI1997;48:560-565
32.
Orozco
DR. Llovet
TJ. Osteosintesis
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de raquiscem:.
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33.
Randle
MJ. Wolf
A. Levi L. et al. The
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:36:181-189
34.
Bohler J. Immediate
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of traumatic
paraple~asl::
German].
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Ihre Grenzgeb
1967;103:512-529
35.
Caspar
W. Barbier
DO. Klara
PM. Anterior
cervical
fusion and Caspi:
plate stabilization
for cervical trauma.
Neurosurgery
1989:25:491-J[
36.
Tippets
RH. Apfelbaum
RI. Anterior
cervical
fusion
with the Caspar~.
strumentation
system.
Neurosurgery
1988:22:1008-1013
37.
Morscher
E. Sutter
F.Jenny
M. Olerud
S. Anterior
platingofthecel\:'
cal
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with
the
hollow
screw-plate
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of titanium
linGI;.
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1986;57:702-707
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Cauthen
JC. Kinard
RE. Vogler
JB. et al. Outcome
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and
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1998:23:188-192
39.
Coe JD. Warden
KE.Sutterlin
CE III. et al. Biomechanical
evaluatioc~
cervical
spinal
stabilization
methods
in a human
cadaveric modt.
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1989:
14: 1122-1131
40.
Tew JM. Mayfield
FH. Complications
of surgery
of the anterior (t!'/i(l
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Clin Neuro11975:23
41.
Flynn
TB.
Neurological
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of
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cervical fusic~.
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1982;7:536-539
42.
Gregory
CF. Complications
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cervical
fusion.] Bonejoir:
Surg
Br 1964;46B:715
43.
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TS. Complications
of anterior
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Manski TJ. Wood MD. Dunsker
SB. Bilateral
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fusion:
case report.] Neuro-
surg 1998;89:839-843

24
AnAnterior Microforaminotomy
(Transuncal)
Approachto the Cervical Spine
Hae-DongJho and John Y.Lee
. Indications
. Contraindications
. Advantages
. Disadvantages
. AnteriorMicroforaminotomy for Cervical
Radiculopathy
SurgicalIndications
OperativeTechnique
Theidealsurgicaltreatment for diskogenic cervical spinal
disease
causingradiculopathyor myelopathywoulddirectly
removetheoffendingcompressive lesion while preserving
thephysiologicalintervertebral motion segment. Although
[hecurrentsurgical armamentarium
is diverse, most
optionsfall short of this ideal. For example. posterior
approaches
result in indirect decompression, and anterior
approaches
sacrifice a functional motion segment by pur-
posefulbone fusion or disruption of the intervertebral
disk.l-6
Althoughthe recent report of an anterior metallic
Implantin an attempt to maintain some motion at the
diskectomylevelisintriguing,the current practice of metal-
lichardware
installationthrough either the anterior or the
posterior
approachto enhance instantaneous stability has
notmadeanyadvances toward reaching the aforemen-
tIOnedideal.Thepractical use of an artificial disk is coming
buttheLongtermresultsare pending.
Topreservethe intervertebral disk, to eliminate the need
forbone-graftfusion,and to accomplish direct removal of
theoffendinglesion,the senior author (HDJ)has developed
thesurgicaltechnique of anterior microforaminotomy for
celVical
radiculopathy.7Although long-term preservation of
themotionsegmentremains to be proven, the short-term
outcomehasbeensatisfactory with minimal postoperative
patient
discomfort,well-preserved cervical motion shown
inpostoperative
dynamic roentgenoicgrams, and elimina-
hOnofthe
offendinglesion documented by magnetic reso-
nance(MR)scans.Jho's anterior microforaminotomy tech-
mquewidens the nerve root foramen by removal of the
anteromedialforaminalwall that is often the compressive
Postoperative Care
.
Spinal Cord Decompression for Spondylotic
Myelopathy or OPll
Surgical Technique
.
Anterior Microforaminotomy for Spinal Cord
Tumors located Anteriorly to the Spinal Cord
Surgical Technique
Complications and Avoidance
.
Discussion
pathology with a herniated disk or spondylotic spur. Only
herniated disk fragments or compressing bony spurs are re-
moved via a 5 mm anterior foraminotomy hole under the
operating microscope. The nerve root is decompressed un-
der direct vision along the segment from its origin at the
spinal cord to its distal exit behind the vertebral artery. The
remaining intervertebral
disk is preserved to maintain a
functioning motion unit.
The satisfactory outcome of anterior foraminotomy for
cervical radiculopathy that was encountered, encouraged
the senior author to apply the anterior foraminotomy tech-
nique to the surgical treatment of spondylotic myelopathy.
Spondylotic compressive lesions are removed diagonally,
across the midline posteriorly in the transverse axis, and
longitudinally
in
the
vertical
axis
through
anterior
foraminotomy holes.8Although a significant portion of the
intervertebral disk has to be trimmed out to accomplish an
adequate spinal cord decompression, the stable dynamic
condition of the intervertebral disk at the operative level
negates the need for bone graft fusion or postoperative im-
mobilization. This anterior foraminotomy technique is also
used for spinal cord decompression in patients with ossifi-
cation of the posterior longitudinal ligament (OPLL).Spinal
cord tumors located anterior to the spinal cord are removed
through an anterior foraminotomy hole as wel1.9This chap-
ter describes disk-preserving anterior microforaminotomy
for cervical radiculopathy, spinal cord decompression via
anterior foraminotomy holes for spondylotic myelopathy,
and spinal cord tumor removal via an anterior foramino-
tomy hole.
207

208
MidcervicalSpine:AnteriorApproach
.
Indications
. Cervicaldisk herniation
.
Cervicalstenosis
.
OPLL
.
Anteriorly located spinal cord tumors
.
Contraindications
.
Hypertrophic ligamentum flavum
.
Diffusecongenital stenosis
.
Advantages
. Minimally invasive anterior approach
.
Disk sparing
.
Preserves motion segment
.
Avoids posterior muscle dissection with its associated
pain and morbidity
.
Disadvantages
. Approach not familiar to most surgeons
. Proximityofvertebralartery
.
Anterior Microforaminotomy
for CervicalRadiculopathy
Surgical Indications
The selection of patients for anterior microforaminotomy is
essentially the same as that for patients undergoing proce-
dures such as anterior diskectomy with or without bone
fusion, or posterior foraminotomy.Although anterior micro-
foraminotomy is logically the ideal operation for patients
with foraminal or lateral disk disease compressing the uni-
lateral nerve root, it can be used for nerve root decompres-
sion caused by any sort of offending pathology located
anteriorly or medially to the nerve root. It can also facilitate
decompression of the midline spinal cord canal in addition
to that of the ipsilateral nerve root. The proximal portion of
the contralateral
nerve root can also be decompressed by
anterior microforaminotomy; however, decompression of
the distal portion of the contralateral nerve root is some-
what limited with this technique. Anterior microforamino-
tomy is an excellent surgical technique for patients who
have undergone either or both an anterior and a posterior
cervical disk operation with unsuccessful relief of their
radiculopathy. Six weeks of conservative treatment were
tried on all patients with cervical radiculopathy except for a
Operative Technique
few patients
who displayed
profound
motor deficits.Mi
scans of the cervical spine were obtained on allpatient\
When an MRscan was not definitive enough to makeadi
agnosis, an additional myelographic computed tomograp~
(CT)scan was performed. Surgery was only recommende(
when the clinical symptoms
and signs were relevanttothe
findings in the cervical spine imaging.
Positioning
The operation is performed with the patient positionetl
supine under general anesthesia. Baseline somatosensory
evoked potentials
(SEPs) of both the upper and thelowel
extremities
are obtained
prior to patient
positioningane
are maintained throughout the procedure. Asmallbolster
is
placed behind both shoulders
to maintain
gentle extensior
of the cervical spine. The patient's
head is positioned
straight without turning it to either side. Tofacilitateanef.
fective lateral view of the cervical spine on intraoperative
roentgenogram,
both of the patient's
shoulders aregent~
pulled
caudally
and
fixed
by adhesive
tape. A cervical
traction device is not utilized.
Approach
The surgical approach
is made at the side correspondinglO
the radiculopathy. It is important to place the skin incision
precisely at the spinal level being aimed at becauseangled
skin level entry toward the cervical spine eithercephalad
01
caudad can lead to erroneous and skewed anatomyatthe
neural foramen. Even if the skin incision is madecorrectly,
the surgeon must keep in mind that the straightsurgical
trajectory made in reference to the uncovertebraljoint leads
to the further caudal portion of the target posteriorly,which
is due to the normal downward sloping of the vertebral
body and intervertebral disk in the sagittal planeofthecer.
vical spine. The level of the skin incision canbedecided
in
reference to the palpable anterior transverse tubercleof(~
direct fluoroscopic visualization, or the anatomydemon.
strated on the sagittal MRscan of the cervicalspine.Theuse
of direct fluoroscopic visualization is the mostpreciseway
to determine the appropriate skin incision site.However,it
can be decided in reference to the C6anterior transversetu.
bercle when it is easily palpable. Determinationbythecor.
related anatomy in reference to the MRscanis tempting
but
imprecise. The anatomy
of the vocal cord, trachea, chinskin
fold, and sternal skin fold in relation to the cervical spine
can hint at the site where the skin incisionshouldbe made.
The skin incision line starts -2 cm away from the midline
and extends laterally -3 cm long along the skincrease.
For
upper cervical disk surgery, this skin incision staysentirely
medial to the sternocleidomastoid muscle but willberight
over the muscle for lower cervical disk surgery.Oncethe
skin incision line is determined,
the anterior neckis
prepared with antiseptic solution. The incisionlinealong
the skin crease and the medial margin of the sternocleido-
mastoid muscle is delineated with an aseptic markingpen
and draping is done in an aseptic manner. Onegramof

24
Anterior Microforaminotomy (Transuncal) Approach to the Cervical Spine
209
cephazolinisadministered intravenously
as a single-dose
of
prophylacticantibiotic.
Atransverseincision -3 cm long is made as was the pre-
viouslydrawnipsilateralto the radiculopathy, in a way that
ISsimilartothe incisionforan anterior cervical diskectomy.
Thesubcutaneous tissue and the platysma
muscle are in-
cisedwitha Boviealong the line of the skin incision. The
looseconnectivetissue layer under the platysma
muscle is
cleanlyundermined to define the medial margin of the ster-
nocleidomastoidmuscle and also to provide adequate
space
toaccommodateretractor
blades.
The carotid
artery
is
palpatedwiththe surgeon's index finger medial to the ster-
nocleidomastoidmuscle. The anterior tubercle of the trans-
verseprocessandthe longus colli muscle will be palpable
whenthesurgeonadvances the index finger medial to the
carotidartery.Theanterior column of the cervical spine is
alsopalpatedfurther medially. The prevertebral fascia is
openedlongitudinallyto provide adequate exposure while
keepingthe carotid artery
and the sternocleidomastoid
musclelateral,andthe strap muscle, trachea, and esopha-
gusmedial.Toapproach the C6-(7
level in patients
with
shorterandthicker necks, occasional division of the omohy-
oidmuscle is necessary.
Mostoften, the palpation
of the C6 anterior
tubercle
eliminatesthe need for an intraoperative
roentgenogram;
however,
operating at the wrong level can be avoided with
anintraoperativeroentgenogram,
if necessary.
A hemostat
isclampedatthe medialmargin of the longus colli muscle,
ora21-gaugespinal needle may be placed at the interverte-
braldiskspace.Thecorrectlevelis then corroborated with a
lateralcervicalroentgenogram. Before a hemostat
or spinal
needleis placed, a thorough
orientation
of the anterior
columnofthe cervical spine has to be made by finger pal-
pationto avoid confusion at the correct
level when
the
hemostator needle is removed. Thus far, this procedure
is
similartoaconventional anterior cervical diskectomy.
Ananteriorcervical diskectomy retractor
system is then
appliedincorporatingonlysmooth-tipped retractor blades.
Althoughanidealretractor system has not yet been found,
theauthorshave been using an original
narrow
and thin
bladeClowardretractor system (Codman, Randolph, MA).
Othercommerciallyavailable retractor
blades
have been
foundtobetoothickand wide, requiring a longer skin inci-
sionandmoreexposure.Retraction will naturally uncover
dieipsilateral
longuscollimusclerather than the midline an-
trriordisksurface.Theoperatingmicroscopeis applied using
magnification
of 10 to 16 times. The medial portion
of the
kmguscollimuscleisincisedmedial to the anterior tubercles
ofthetransverse
processesofthe upper and lower vertebrae.
kcanbeaccomplishedin two ways, by an incision of the
musclefollowedbybipolarmuscle stump coagulation, or by
tXCision
ofthesmall piecesofthe muscle located in between.
Excision
ofthelonguscolliwillbringthe vertebral artery into
viewanteriorlytotheG transverse process.When an opera-
tionisundertakenat (6-G, care must be taken not to dam-
Igethevertebralarterywhile excisingthe medial portion of
thelonguscolli.However,it is not infrequent that in some
patients
thevertebral artery mayenter at a different level of
thetransverse
foramen.Thus careful preoperative assess-
mentofthevertebralartery in the axial images of the MR
scansisessentialto avoid intraoperative surprises. At this
point, in operations involvinglevels above C6-(7, the verte-
bral artery is not purposefullyexposed.
The ipsilateral uncovertebral joint becomes evident after
the longus colli is excised between the medial margin of the
anterior tubercle of the transverse processes. The uncover-
tebral joint interface will be angled -30 degrees cephalad
from the midline horizontal intervertebral disk. This un-
covertebral interface angle is much more blunt at the lower
disk level than at the upper. When spondylotic changes are
advanced, the anatomy of the uncovertebral joint can be se-
verely distorted. Anatomical orientation of the anterior tu-
bercles at the upper and lower vertebrae in relation to the
anterior intervertebral disk will assist the surgeon in inter-
pretation of the deformed anatomy. This surgical technique
for the treatment of radiculopathy has been evolving since
it was first introduced. When it was first introduced, the
technique was described as a procedure performing resec-
tion of the uncinate process, which is the medial structure
of the neural foramen (Fig.24-1). That particular technique
often involved removal of the entire uncinate process and
subsequent sacrifice of the lateral portion of the interverte-
bral disk. The surgical trajectory of the foraminotomy per-
formed by that original technique often deviated further
caudally than directed due to the caudal sloping of the
--.
Figure 24-1
Thisschematicdrawingindicatesthe areaofbone to be
drilledat the anterior aspect ofthe cervicalspine.The medialportion
of the longus colliis incised mediallyto the anterior tubercle of the
transverse processat the upper and lowervertebrae. and the uncover-
tebral joint of the corresponding intervertebral diskis exposed. The
dotted area delineates the area to be drilled for the anterior micro-
foraminotomy. For anterior foraminotomy for radiculopathy, this
foraminotomyholeismade slightlyfurther rostrallywith a loweredge
of the foraminotomy hole butting the upper edge of the uncinate
process. When spinal cord decompression is required in addition to
the nerve root decompression. the foraminotomy is made as delin-
eated inthe dotted area.

210
MidcervicalSpine:Anterior Approach
cervical vertebra in the sagittal plane. The procedure has
since been modified to achieve a more concise foramino-
tomy around the nerve root as well as to preserve the inter-
vertebral disk as much as possible. The modified technique
removes a small portion of the bone at the very lateral and
inferior edge of the upper vertebra rather than at the un-
covertebral joint itself. Thus this procedure would be more
aptly named an anterior microforaminotomy rather than an
anterior transuncal approach.
The anterior entry point of the foraminotomy trajectory
at the bone is moved further cephalad to the uncovertebral
joint. The landmark is the inferior margin of the transverse
foramen at the upper vertebra of the selected intervertebral
disk level. The bone to be removed is -5 mm in size at the
very inferolateral portion of the upper vertebra and in-
cludes a small portion of the medial transverse foramen just
at the upper edge of the uncinate process. Although this an-
terior bone opening is somewhat superior to the uncoverte-
bral joint, this bony entry leads to the neural foramen more
precisely when drilIing advances posteriorly. The foramino-
tomy is performed with a high-speed microsurgical driII
connected to an angled handpiece. Frequent irrigation is re-
quired to avoid bone injury by heat. Aball-type 2 mm cut-
ting bit is employed. Use of a diamond drill bit is not recom-
mended because diamond bits are not as sharp as cutting
bits and subsequently generate bone-damaging heat. The
drilling starts at the medial margin of the transverse fora-
men toward the inferolateral aspect of the vertebral body of
the upper vertebra. The uncinate process is not removed at
all anteriorly. The medial margin of the transverse foramen
is exposed. When drilling advances further posteriorly, the
posterolateral margin of the intervertebral disk space is en-
countered. The very tip ofthe posterior uncinate process is
removed with drilling. DrilIingis continued until the poste-
rior longitudinal ligament is exposed. The posterior bony
edge is trimmed with a 1 mm Kerrison punch along the up-
per and lower vertebral bodies that constitute the posterior
medial neural foramen. Bynow, the spondylotic spurs that
were compressing the nerve root have already been elimi-
nated. In cases with free soft disk herniation, the free disk
fragments are encountered at this stage. Mostoften,fre
disk fragments
are located
between
the superficialall(
deeper
layer of the posterior
longitudinal
ligament.Whe~
disk fragments
are retrieved,
a hole wiII be obviousattho
posterior
longitudinal
ligament.
The posterior longitudil\!!
ligament is incised with microscissors
and resectedwitha:
mm Kerrison punch. The nerve root is exposedatthever!
lateral portion of the spinal cord. From there, thepostericr
longitudinal
ligament
is excised
laterally
followingth!
nerve root (Fig. 24-2). The epidural veins are locatedattht
juncture of the spinal cord and nerve root. Attentionispaic
so as not to rupture the epidural veins becauseitcanj)'
cumbersome to control the bleeding. When the MRscar
does not suggest the presence
of soft disk herniation,ane
the incision of the posterior
longitudinal
ligament infron'
of the spinal cord demonstrates
the dura mater just next~
the posterior
longitudinal
ligament,
removal of thepost~
rior longitudinal
ligament
may not be necessary. Thesizeo,
the hole made by drilIing at the neural foramenisusualt
-4 to 5 mm. When epidural bleeding
does occur duringre-
moval of the posterior longitudinal ligament, itusually
car
be halted by bipolar coagulation.
Hemostatic agentsarenc
employed to avoid any potential compressive material
be
ing placed on the nerve root or spinal cord. Removalofthe
posterior longitudinal ligament has proven to bethemosl
difficult part of this procedure due to epiduralbleeding.
Th'
disk within
the intervertebral
space is untouched andpre
served. A small amount of local anesthetic is infiltratedat
the stumps of the longus colli muscle while attention
I
given not to inject local anesthetic into the vertebralarteIJ
nerve root, or spinal cord. The retractor systemiswith.
drawn. Complete hemostasis
at every layer of surgicalexplt
sure is then ascertained
under the operating microscope.
Afew mLof local anesthetic is infiltrated subcutaneousl!
Finally,the platysma is closed interruptedly andtheskin~
approximated with subcuticular sutures. A small surgical
dressing is applied. This surgery can be performedatmulti.
pIe levels if needed. Resolution of the patient's radicular
pain has often been immediate but recoveryofmotor weak.
ness and sensory
numbness
takes a few weeks to afew
>'.
'0'
Figure 24-2
Anintraoperativephotographdemonstrat~
the decompressed nerve root that originatesfromth,
lateral
aspect
of the
spinal cord and exits behindthe..
vertebral
artery.

24
Anterior Microforaminotomy(Transuncal)Approachto the CervicalSpine
211
-"',
A
\,~ L.
_
--
~-
~
- - ... B
figure24-3
(A)Apreoperative magnetic resonance
(MR)scan of the cervical spine, axial image, demonstrates
a combination
of herniated disk
andspondyloticspur encroaching
upon the left (6 nerve root at the (5-(6
neural foramen. (8) The corresponding
postoperative
MRscan reveals
complete removalofthe compressive lesion and widened neural foramen.
months.Besidesoccasionalpostanestheticeffectssuch as
emesisanddiscomfort in the throat, actual postsurgical
pa-
bentdiscomforthas been very minimal and does not often
requireadministrationof strong analgesics. Patients experi-
encenormalrangeof motion in the neck postoperatively.
Externalimmobilization such as a cervical
collar
is not
necessary
and is not used. Patients do not experience
inter-
scapularorshoulder pain as do patients
after conventional
anteriorcervical diskectomy.
Thepatientsare instructed to uncover their surgical incision
andtotakeashower and shampoo the day after surgery. The
inclslonal
wound is exposed to the air. Patients are permit-
trdtodrivean automobile the day following surgery as long
isthegeneralanesthetic
effect has worn off completely.
Theyareadvisedto remain off from work for at least 1
month,butoften return to work a few days postoperatively
Wtheir
jobdoes not require strenuous
physical activity. All
p.ltientshaveobtained MR scans and flexion and extension
cervical
spineroentgenograms at 6 weeks following surgery
:Fig.24-3). Thesepostoperativestudies were obtained to
collectpostoperative information
on this surgery
but may
DOlbeneeded for treatment
itself. Although
the author
basnotcollectedall postoperative
data as of yet, the first
30patientsmaintainedtheir functioning motion segment
IpJltewell
whenreviewed1year postoperatively. Among 60
~viouslytreated patients, all were found to have gained
IfSOlution
oftheir radicular symptoms except one who con-
tinued to have radicular pain despite good anatomical de-
compression of the affected nerve root. One patient fell, in-
juring herself, and consequently suffered recurrence of her
radicular pain 3 months postoperatively. She underwent a
subsequent formal anterior cervicaldiskectomy.
. Spinal CordDecompression for
Spondylotic
Myelopathy
or OPLL
Surgical Technique
This technique can be used only when the compressive
pathology is located anteriorly to the spinal cord. Surgical
indications are very similar to those for an anterior verte-
brectomy for spondylotic myelopathy.
Approach
Atransverse incision, 3 to 6 cm long, is made at the anterior
neck along a skin crease. The skin incision is made ipsilater-
ally to the radiculopathy or to the narrower side of the
spinal canal. Once the medial parts of the transverse
processes of the upper and lower vertebrae have been iden-
tified, the ipsilateral uncovertebral joint between them can
be seen. Because advanced spondylosis often obscures
the anatomical landmark of the uncovertebral joint and
transverse
processes, anterior spondylotic spurs at the
intervertebral disk or anterior transverse tubercles can then

212
MidcervicalSpine:Anterior Approach
be used as a guide to lead one to the uncovertebral joint.
The ligamentous tissue, including the periosteum, is incised
vertically at the lateral aspect of the uncovertebral joint and
dissected and reflected toward the vertebral artery to act as
a protective layer of tissue while bone is drilled. The un-
covertebraljoint is drilled between the transverse processes
using a high-speed microdrill attached to an angled hand-
piece. For spinal cord decompression, 3 or 4 mm cutting
drill bits are used. When the uncovertebral joint is drilled,
the lateral cortical bone of the uncinate process is left at-
tached to the ligamentous tissue covering the medial por-
tion of this artery. Drilling continues down to the posterior
longitudinal ligament. Asdrilling advances posteriorly, the
direction of drilling is guided toward the midportion of the
vertebral bodies in the vertical axis and gently inclined me-
dially in the transverse axis.The depth of the vertebral body
is shallower at the midportion of the vertebral body than at
the intervertebral
level. When the posterior longitudinal
ligament is exposed along the edges of the upper and lower
vertebral bodies, the bony spurs located at the interverte-
bral disk level are identifiable at the center. Thedrillingis
performed to create a cavity that is shaped likea flask,with
a small opening at the entry point and a larger cavityposte-
riorly, in front of the spinal cord. The base of the uncinate
process is drilled further until the uncinate process loosens.
At this stage, a piece of thin cortical bone of the uncinate
process is kept attached
laterally to the periosteal andliga-
mentous
tissue
to cover the vertebral
artery. This lateral
remnant
of the uncinate
process is dissected
from theliga-
mentous
tissue,
fractured
at the
base
of the uncinate
process, and removed.
By now, the vertebral artery isiden-
tifiable by its pulsation
between
the transverse processesof
the vertebrae.
Drilling at the base of the uncinate process
has to be performed
cautiously
because
the nerve rootlies
just adjacent to it. After the uncinate
process becomesloos-
ened at its base, it is safer to remove the remaining boneof
the uncinate process by fracturing it from its baserather
than by continued
drilling (Fig. 24-4A). When the remain-
ing piece of the uncinate
process
has been removed,the
posterior
osteophytes
are drilled
by crossing the midline
A
B
Figure 24-4
(A) Anterior foraminotomy for spinalcorddecompres.
sion is performed with complete removal of the uncovertebraljoint
(8) The posterior spondylotic spurs are removed diagonallyacrO\\
the midline in front of the spinalcord. In patients with multiple-iel~
lesions, posterior vertebrectomy is performed with long-armedU9-
biting curettes that are utilized above and belowthe foraminotOl1'\
holes.This renderslongitudinal decompressionof the spinalcord.

24
Anterior Microforaminotomy(Transuncal)Approachto the CervicalSpine
213
Figure24-5
(A)Apreoperative magnetic resonance (MR)scan of the cervical spine, sagittal view, reveals multilevel cervical stenosis. (B) The cor-
responding postoperativeMRscan of the cervical spine, sagittal view, demonstrates
excellent spinal cord decompression.
B
diagonally
towardthe opposite margin of the spinal cord
duramater(Fig.24-4B). The size of the hole made by the
drillingat the uncovertebral joint is usually -5 to 6 mm
WIdetransverselyand 7 to 8 mm vertically.
Theposterior longitudinal
ligament
is incised
and re-
sectedto achieve decompression
of the ipsilateral
nerve
rootandspinal cord. The origin of the contralateral
nerve
rootisidentifiedfor adequate decompression
of the spinal
canalin the transverse axis. Multiple
anterior
foramino-
tomiesare performed as needed.
By using
the
anterior
foraminotomy
holes, the spinal cord canal is enlarged
in the
longitudinalaxis by removing the posterior
portion
of the
vertebralbodies with curved Kerrison rongeurs
and vari-
ouslyshapedcurettes.The curettes used for this operation
areleft- and right-side cutting as well as upcutting.
Throughthe foraminotomy holes, posterior
vertebrectomy
ISperformedas needed for adequate
decompression
of the
spinalcord.Bonebleeding is controlled with the applica-
lionofbonewax.The OPLLis also removed in a similar
fashion.Occasionally,removalof the calcified dura mater in
patientswithOPLLrequires dural graft reconstruction with
microclips.Hemostatic agents are not used in the epidural
space.Despite extensive posterior
vertebrectomy
through
foraminotomyholes, the spine remains
solid and stable. A
cervIcalcollar is not necessary postoperatively. Although
anteriormicroforaminotomy for cervical radiculopathy
has
been performed as outpatient surgery, this particular group
of patients with myelopathy were kept in the hospital
overnight to clinically observe spinal cord function and
were discharged home the next morning (Fig.24-5).
.
Anterior Microforaminotomy for
Spinal CordTumors Located Anteriorly
to the Spinal Cord
Surgical Technique
Spinalcord tumors located anteriorly to the spinal cord,with
or without an extradural component, can be approached
through an anterior foraminotomy hole.These tumors are of-
ten meningiomas or neurofibromas. Thisanterior foramino-
tomy technique eliminates the need for bone fusion that is
required for the conventional anterior vertebrectomy ap-
proach. Subsequently, this technique has displayed quick pa-
tient recoveryand has shortened hospital stays.The anterior
foraminotomy is performed as previously described for
spondylotic myelopathy. The foraminotomy is tailored to ac-
commodate the entire dimension of the tumor. The dura
mater is opened in curvilinear fashion with its base attached
medially.The dural flap iskept along the medial aspect of the

Figure 24-6
For spinal cord tumor removal,ana~
terior
foraminotomy
is made in the shapeofaflask.
with
a small outlet
and a rather large inletthatcar
accommodate
the extent
of the tumor completely,
The dura is opened with its base attached atthel11f-
dial side. When the tumor is excised,thedura~
closed with titanium
microclips.
214
MidcervicalSpine:Anterior Approach
foraminotomy hole with tack-up sutures. The tumor is ex-
cised with microdissection technique (Fig.24-6). Formenin-
giomas. the inner layer of the dura mater that isattached to
the tumor is peeled off (Fig. 24-7). Forneurofibromas. the
nerve fascicle from which the tumor originates is divided
proximally and distally.When the tumor isexcised,the dura
mater isclosed with titanium microclips.
Complications and Avoidance
The complications of this procedure can be numerous
and
grave if the surgeon
is not familiar with the microanatomy
and practical details of the operation.
Cadaveric studiesmay
minimize the risk of these complications.
A
Figure 24-7
(A)Apreoperative magnetic resonance (MR)scan, sagittal view,ofthe cervicalspine shows a contrast-enhancing meningiomair
addition to spondyotic spurs.(8) Thecorresponding postoperative MRscan, sagittal view,ofthe cervicalspinedemonstrates completeremovalof
the tumor.

Vertebral
ArteryInjury
24
Anterior Microforaminotomy (Transuncal)Approachto the CervicalSpine
215
Obviously,the riskforvertebral artery injury is the most se-
rioustheoretical complication
of this procedure.
Although
vertebralartery injury has not occurred in more than 150
patientsin our series, inadvertent
injury of the vertebral
arteryiscertainly possible because the operation is per-
formedjust next to it. There are several techniques that
minimizethe risk for vertebral
artery injury. Preoperative
examinationof the MR scan is essential
to exclude aberrant
anatomy.The MRscan should demonstrate
that the artery
liesbetweenthe transverse process of (7 and the longus
colliandenters the transverse foramen at (6. Hence, the
longuscollimuscleshould be incised at the level of the (6
transverseprocess superior to the artery's entrance
into the
transverse
foramenof (6. Use of magnification at this stage
iscritical.Another potential
site of injury to the vertebral
arteryislateral to the uncinate process. The periosteum
and
ligamentoustissue from the uncovertebral
joint is kept at
thevertebralartery to provide an extra layer of protection
whenthe uncinate
process
is removed
by high-speed
drilling.Thetip ofthe surgeon's suction catheter is always
placedatthe vertebral artery side to protect the vertebral
arteryincaseof the accidental slipping of a spinning drill
bi!.lnjurytothe artery can be avoided by leaving thin corti-
calboneofthe uncinate process to cover the artery when
theuncovertebraljoint is drilled. The remaining
thin corti-
calboneisthen dissected out from the ligamentous tissue
thatstillcoversthe vertebral artery. The third potential
site
ofinjuryis at the transverse foramen. When the medial
transverse
foramenis open, care has to be taken to protect
theartery.Evenif bleeding occurs at the transverse fora-
men,it isoftenfromthe perivertebral venous plexus rather
thanfromthe vertebral artery itself. Bipolar coagulation
willeasilycontrol venous bleeding. However, if vertebral
arteryinjuryoccursinadvertently, direct repair should be
undertaken
with both proximal and distal control. Use of
packing
or bipolar coagulation for vertebral artery injury
willmaketheinjuryworse. The vertebral artery should be
furtherexposedproximallyand distally for direct repair.
InjurytotheNerveRootor Spinal Cord
Thecervicalnerveroot abuts the uncinate process postero-
laterally.
Althoughthe ligamentous tissue and posterior lon-
gitudinalligamentact as a barrier between the uncinate
process
andthe nerve root, this protective layer can be very
thinwhenspondyloticforaminal stenosis is severe with
prominent
spurs.Asurgeon must be mindful of the nerve
root'sproximityto the uncinate process while removing it
withdrilling.Bonedrilling has to be performed under high
magnification
andwith great care. In addition, the posterior
longitudinal
ligament should be incised at its medial most
aspectofthe foraminotomy
hole to avoid inadvertent nerve
rootinjuryaswellas to avoid venous bleeding. Spinal cord
Injuryisanotherformidable complication that can occur
withcervicalspine operations. The positioning of the
patientmustbe performed carefully when the patient's
spinalcordcanalappears tight on MRscans. Preoperatively,
themobilityof the cervical spine should be tested in the
clinic,especiallythe degree of extension. When a patient
experiences spinal cord symptoms with extension of the
cervical spine, extreme caution has to be exercised during
the patient's positioning. Once general anesthesia
is in-
duced, it is recommended that SEPmonitoring be set up
prior to patient positioning. Although SEPonly monitors
posterior column function, it isoften sensitive enough to in-
form the surgeon of the integrity of the spinal cord. Actual
injury to the spinal cord by the surgical procedure itself can
occur, but rarely and most likely only in extremely myelo-
pathic patients.
EpiduralBleeding
Epidural bleeding can be cumbersome. Epiduralveins are lo-
cated between the thick anterior layer and thin posterior
layer of the posterior longitudinal ligament. Ifspondylotic
bony spurs are the only pathology shown on the MRscan,
one possible strategy to employ to avoid epidural bleeding
would be to skip removal of the posterior longitudinalliga-
ment. Thiscan be done as long as no obvious disk fragments
were seen intraoperatively protruding through the ligament.
However, ifexcision of the ligament is undertaken, it should
be incised at its most medial aspect because the location of
well-developed epidural veins is usually lateral at the junc-
tion between the nerve root and the spinal cord. When the
spinal cord dura mater is exposed, the posterior longitudinal
ligament is trimmed along the bony edges superiorly and
inferiorly first. Then the ligament is excised laterally along
the nerve root following the superior and inferior edges of
the neural foramen. Again, removing this lateral portion of
the ligament between the nerve root and spinal cord often
precipitates epidural bleeding. Nofurther decompression is
necessary if excessive epidural bleeding occurs at this stage
and there is no further disk material compressing the root.
Epidural bleeding is controlled with bipolar coagulation and
gentle compression with a micropatty. Hemostatic agents
are never placed in the vicinity of the nerve root or the
spinal cord to avoid inadvertent compression because they
may swell significantly. Positioning the patient in reversed-
Trendelenburg may help to minimize bleeding.
Horner'sSyndrome
Becausethe sympathetic nerve passes along the longus colli
muscle, resection of this muscle theoretically increases the
risk for Horner's syndrome. Because the sympathetic nerve
passes along the lateral portion of the longus colli,excision
of the longus colli medial to the anterior tubercle of the
transverse process does not cause Horner's syndrome.
Operations at the Incorrect Level
This problem is similar to the one that can occur with the
conventional anterior approach. An intraoperative lateral
view roentgenogram is always necessary to confirm the cor-
rect intervertebral disk.Despite roentgenographic corrobora-
tion to identify the correct level, it is still possible for a
surgeon to enter the wrong level.Fingerpalpation of the an-
terior surface of the cervical spinal column will provide the
surgeon with the anterior bony configurationand should pre-
cede placement of radiographic markers. Ifthe radiographic

216
MidcervicalSpine:AnteriorApproach
marker is placed after obtaining anatomical orientation of
the spine, the surgeon can easily confirm the correct levelby
repeated finger palpation. Becausethe uncovertebral joint is
a bit cephalad from the level of the intervertebral disk, exci-
sion of the longus colli has to be made at the appropriate
level.Ifthere isanydoubt as to the correct levelof the opera-
tion during surgery, a repeated roentgenogram has to be ob-
tained. Reference to the anterior tubercle of C6 is another
technique to confirm the correct level when the operation is
to be performed at the lower cervicalspine.
PostoperativeEpiduralHematoma
Postoperative epidural hematoma is a rare occurrence after
anterior cervical spine surgery. Although it has not occurred
in our patient series, it can still occur, especially in patients
who undergo multilevel spinal cord decompression. Com-
plete hemostasis has to be made under magnification. If
intraoperative epidural bleeding occurs, it has to be con-
trolled at any cost. When bipolar coagulation does not stop
the bleeding, gentle compression with application of a mi-
cropatty and elevating the patient's head for a few minutes
often stops the bleeding. Again, hemostatic agents such as
Gelfoam or Surgicel should not be used because hemostatic
agents may further swell with slow continuous bleeding
and may subsequently cause neurological complications. A
postoperative wound hematoma can be potentially lethal.
Fatality can occur when a patient develops airway obstruc-
tion from a wound hematoma and cannot be reintubated.
At the end of the operation, the retractor system should be
released, step by step, with careful observation for possible
bleeding under magnification. Once the retractor has been
removed, the wound has to be inspected again with a hand-
held retractor. Use of magnification is helpful so as not to
miss any minor bleeding.
VocalCordParalysis
Although conjectural, the mechanism of vocal cord paraly-
sis associated with anterior cervicalspine operations seems
to be laryngeal nerve injury at the larynx itself and caused
by compression between the endotracheal tube and the
medial retractor blade of the anterior cervical diskectomy
retractor system. Because this procedure is a lateral ap-
proach, which does not require medial retraction of the lar-
ynx, vocal cord paralysis does not seem to occur. Indeed, no
single case of vocal cord paralysis has been encountered in
more than 150 patients treated with this surgical technique.
Thus far,this technique seems to be advantageous in avoid-
ance of postoperative vocal cord paralysis.
.
Discussion
Verbiestin the 1960sadopted an anterolateral approach
to the cervicalspine. The anterior tubercles of the transverse
processes were resected and the vertebral artery was mobi-
lized to directly approach the lateral aspect of the cervical
spinal column. Bonegraft fusion was used in this technique.
He used this anterolateral technique for decompression of
the vertebral artery, foraminaldecompression,lateraldisk
herniation,and reconstructionof the postganglionicupper
brachial plexus. Hedid not utilize this anterolateral approach
forspinalcorddecompression.Thistechniquehas notbeen
well accepted due to its complexity and radical natureas
well as to the popularityof the anterior diskectomytech.
nique.JORecently, George et al reported their experience
with a modified Verbiest technique.11 Hakuba in 1976reo
ported a combined anterior and lateral technique, achieving
radical resection of the lateral osteophytes bilaterally,aswell
as removal of posterior osteophytes. Utilizing a conventional
anteriordiskectomytechnique,posteriorspondyloticspurs
were removed in addition to complete diskectomy. For
removal of posterolateral bony spurs, the ipsilateral un.
covertebral joint was excised as well as contralateral pos-
terolateral spur. Patient follow-up showed solid bone fusion
regardless of surgical bone graft fusion.12Lesoin et alre-
ported a similar technique of combined anterior and lateral
diskectomy.13The anterolateral approaches or combinedan-
terior and lateral approaches emphasized direct resectionof
the compressive lesion but did not attempt to preservethe
motion segment. Snyder and Bernhardt in 1989 reportedan-
terior cervical fractional interspace decompression, whichis
partial removal of the intervertebral disk at the lateralpor.
tion of the disk.14Although they tried to preserve a portion
of the intervertebral disk, the decompression of the nerve
root was very limited at 2 to 3 mm of the posterolateral
corner at the intervertebral
disk. The surgical technique
described here achieves direct removal of the compressing
lesion such as disk fragments or bony spurs and providesde-
compression of the nerve root from its origin of the spinal
cord to its distal root exiting behind the vertebral artery.In
addition, most of the intervertebral
disk is preservedto
maintain the functioning motion unit.
When this anterior foraminotomy technique is employed
for spinal cord decompression for myelopathy or tumorreo
moval, the operation involves a substantial portion ofthe
intervertebral disk. Flexion and extension roentgenogramof
the cervical spine showed good stability in all patientsat
postoperative day 1 as well as 6 weeks later. Althoughlong-
term follow-up data regarding the maintenance of motion
segments have not been gathered in this group of patients,
it is possible that the intervertebral motion segments may
ultimately fuse naturally by advanced spondylotic changes
and by the surgical effect of substantial bone resection.De.
spite most of the anterior intervertebral segmentsbeing
preserved, resection of the posterior spondylotic spursand
vertebral bodies with this technique is still quite extensive.
In addition, most of these patients had already experienced
advanced spondylotic changes with limited motion atthe
involved intervertebral motion segments. The main advan-
tages of this technique seem to be the patients' quickrecov-
ery and short hospital stay by the elimination of bone
fusion and immobilization. Although postoperative flexion
and extension lateral roentgenograms of the cervicalspine
did not show spinal instability, the true biomechanicalef-
fect of this surgical procedure remains to be tested. Because
this microsurgical procedure is technically demandingin
executingadequate decompressionofthe spinalcord,this
techniquemustbe practicedthoroughlyin cadavericstudy
before it is applied in actual patient treatment.
....

24
Anterior Microforaminotomy (Transuncal)Approachto the CervicalSpine
217
References
1. Henderson
CM.HennessyRG.Shuey HM. Shackelford EG.Posterior-lat-
eral foraminotomy as an exclusive operative
technique
for cervical
radiculopathy: a review of 846 consecutively
operated cases. Neuro-
surgery1983;13:504-512
2. ScovilleWB. Dohrmann
GJ. Corkill
G. Late results
of cervical
disc
surgery.JNeurosurg 1976;45:203-210
3. ClowardRB.The anterior approach for removal of ruptured
cervical
discs.JNeurosurg1958:15:602-614
4. RobinsonRA.Smith GW.Anterolateral cervical disk removal and inter-
body fusion for cervical disk syndrome.
Bull Johns Hopkins
Hosp
1955:96:223-224
5. Lunsford\.D. Jannetta PJ.Anterior
surgery for cervical disk disease:
treatment of lateral cervical disk herniation
in 253 cases.J Neurosurg
1980:53:1-11
6. MartinsAN.Anterior cervical diskectomy with and without
interbody
bonefusion.J Neurosurg 1976;44:290-295
7. JhoHD.Microsurgical anterior cervical foraminotomy:
a new approach
tocervicaldisk herniation. J Neurosurg 1996;84: 155-160
8.
Jho HD. Decompression via microsurgical
anterior
foraminotomy
for
cervical spondylotic myelopathy. J Neurosurg 1997;86:121-126
9.
Jho HD. Ha HG. Anterolateral approach for cervical spinal cord tumors
via an anterior
microforaminotomy:
technical
note. Minim
Invasive
Neurosurg 1999;42:1-5
10.
Verbiest H. A lateral approach to the cervical spine: technique and indi-
cations.J Neurosurg 1968;28:191-203
11.
George B. Zerah M. Lot G.et al. Oblique transcorporeal approach to an-
teriorly
located lesions in the cervical spinal canal. Acta Neurochir
(Wien) 1993;121:187-190
12. Hakuba A.Trans-unco-discal approach: a combined anterior and lateral
approach to cervical discs.JNeurosurg 1976;45:284-291
13.
Lesoin F. Biondi A.Jomin M. Foraminal cervical herniated disk treated
by anterior
discoforaminotomy.
Neurosurgery
1987;21 :334-338
14.
Snyder GM. Bernhardt
AM. Anterior
cervical
fractional
interspace
de-
compression
for treatment
of cervical
radiculopathy.
Clin Orthop
1989;246:92-99

25
Odontoid Screw Placement
Julie E.York and Ronald I. Apfelbaum
.
Indications
.
Contraindictions
.
Advantages
.
Disadvantages
.
Considerations
.
Surgical Technique
Odontoid fractures result in atlantoaxial instability and
carry significant risk for potentially catastrophic spinal cord
injury.1 Stabilizationofthese fracturescanbeachievedwith
either external immobilization or internal fixation. External
immobilization can allow for nonoperative fusion, but it
limits a patient's activity and is often unsuccessful. Surgical
stabilization has traditionally involved posterior atlantoax-
ial bone and wire fusion in conjunction with external im-
mobilization to increase the chance of success. Successful
posterior C1-C2 fusion will result in the loss of normal
C1-C2rotatory motion, and this loss is usually noticeable to
the patient because the motion at C1-C2 accounts for 50%
of the normal cervicalrotatory excursion.2In contrast to ex-
ternal immobilization and posterior C1-C2 fusion, direct
screw fixation of the odontoid provides immediate stabi-
lization and promotes healing while potentially preserving
normal C1-C2motion.
Conventional treatment of odontoid fractures has relied
on either immobilization in a rigid orthosis or posterior
C1-C2 fusion. Some authors advocate a period of external
immobilization for all patients, reserving surgery for those
who fail to achieve satisfactory bony union; however, re-
ported nonunion rates with external bracing alone range
from 7 to 100%.3-15
The senior author (RIA)has been involved in the develop-
ment of an approach that employs specially designed in-
strumentation
(Aesculap, San Francisco, CA)to allow reli-
able and relatively easy placement of anterior odontoid
fixation screws, with excellent results and low morbidity.
The procedure, detailed in this chapter, features a special
guide tube system to control drilling and screw placement
as well as to optimally align the dens.
Given the availability of such a procedure, many pa-
tients will opt for early surgery if informed fairly of all of
'I1
218
Anesthesia
Positioning
Approach
.
Postoperative Care
.
Outcomes
.
Conclusions
the issues in the management
of odontoid
fractures.Fol-
lowing
screw
placement
the fractures
are immediately
stabilized and have a very high rate of bony fusionwith
minimal
risk of morbidity.
If not otherwise
impairedby
their injury, patients can return to normal activitywithin
a few days.
.
Indications
. Type II odontoid
fracture
.
Contraindictions
. TypeIIfractures> 6 months
.
Obliquefractureinplaneofscrew
.
Barrelledchest(relative)
. TypeIodontoidfracture
.
Severeosteopenia
.
Disruptionofthe transverseligament
.
Osodontoideum
.
Advantages
. High fusion rates
.
PotentialmaintenanceofnormalC1-C2rotatorymotion
. Noexternal orthosis required

Disadvantages
Complicated
roomsetup requiring two fluoroscopes
Contraindicatedwhen transverse
ligament disrupted
Poorresultswith chronic fractures
Anterior
vascularand visceral structures potentially at risk
'. Considerations
Mostpatientswith acute type IIodontoid
fractures are con-
sideredgood candidates for odontoid screw fixation. Dis-
IUptionof the transverse ligament is an absolute con-
IRmdicationto
anterior
odontoid
screw
placement,
whereas severeosteopenia and obliquely anteriorly
sloping
hcturesare relative contraindications.
Concernsabout the integrity
of the
transverse
ligament
anbeaddressedwith magnetic resonance
imaging (MRI).16
Osteopenia isoften present in elderly patients
with odon-
D!idfractures.It is not an absolute contraindication,
but the
~Idingpowerof the bone needs to be assessed
at the time
oIsurgeryand if questionable,
an external
orthosis
should
beutilized.Obliquelyanteriorly sloping fractures may allow
thedensto slideanteriorly along the fracture line as the lag
screwpulls it inferiorly. This is usually not a problem
with
~te fractures because the irregular
bone surfaces engage
mdlocktogether, but it can be a problem
with fractures
thatareafew weeks to several months old.
Patientswith chronic nonunion
of the odontoid
process,
includingos odontoideum, are not good candidates
for this
procedure. Although screw fixation
can usually
be per-
formedto achieve initial stabilization,
the union rate is less
than50%.17
Patients with a larger-sized
odontoid
process, a
smallgapbetween it and the (2 body, and no evidence
of
iutofusionof the odontoid process to the anterior
arch of
(( maybe considered
good
candidates
for anterior
screw
fixation,but the success
rate
remains
less
than
that
25
Odontoid Screw Placement
219
achieved with acute fracturesY For patients with chronic
nonunion of the odontoid process who do not meet these
criteria, posterior (1-(2
fusion with transarticular screw
fixation is preferable.
. SurgicalTechnique
Anesthesia
Patients with an odontoid fracture may require a specialized
anesthetic intubation technique if extension of their neck re-
sults in abnormal motion.18.19Blindnasotracheal awake intu-
bation and fiberoptic intubation are most often employed in
this situation. Utilizing a lateral (-arm
fluoroscopic unit
prior to and during intubation allows one to monitor the ef-
fects of neck motion and assures a patient's safety.
Positioning
Patients are positioned supine with a folded sheet behind
the shoulders to allow for neck extension during the proce-
dure. Gentle halter traction is applied. If the patient's
fracture reduces with extension, the head is placed in an ex-
tended position; if not, a neutral position is initially used
with a support placed behind the patient's head. Head posi-
tioning is monitored with the lateral (-arm fluoroscopic
unit. Ifavailable, a second (-arm unit greatly facilitates the
procedure. It is positioned for anteroposterior
(transoral)
odontoid viewing, using a radiolucent (plastic or cork)
mouth prop (Fig. 25-1). Ifonly one (-arm is available, the
draping must be arranged to facilitate frequent swinging of
the (-arm from anteroposterior to lateral positions.
Approach
Toachieve a low enough trajectory for proper screw place-
ment, the cervicalspine isapproached through a low cervical
Figure 25-1
Patientpositionedon operating table.
Afolded sheet isplaced under the shoulders to in-
crease neckextensioninthis patient whose fracture
reduced inextension. Two(-arm fluoroscopicunits
for anteroposterior (transoral) and lateral fluoro-
scopic imaging.

220
MidcervicalSpine:Anterior Approach
incision(approximately C5-C6Ievel). Aunilateral skin inci-
sion is made in a natural skin crease, followed by platysma
muscle division and incision of the sternocleidomastoid
muscle fasciaalong the medial border of that muscle. This
provides access to natural tissue planes that open easily
with blunt dissection.
Proceedingmedial to the carotid sheath and lateral to the
trachea and esophagus, the prevertebral space is easily ac-
cessed. The longus colli muscles are identified bilaterally
and the anterior longitudinal ligament is incised in the mid-
line over two vertebral bodies at approximately the C5-C6
level.The longus coli muscle bodies are then detached and
elevated with a small periosteal elevator. Caspar sharp-
toothed blades are firmly anchored beneath the muscle and
held in place by a special retractor. It is important to use
sharp-toothed blades that hold firmly and to place them as
described to stabilize the retractor system properly.
The prevertebral space is then easily opened to the C1re-
gion using a Kitner or peanut dissector, which is swept from
side to side to open the loose areolar tissue anterior to the
longus collimuscles. Aspecially angled retractor blade is in-
serted into the space to create a tunnel up to C2 through
which the rest of the procedure is completed. This blade is
held by a special retractor that interdigitates with the previ-
ously placed lateral retractor. Under biplane fluoroscopic
guidance a K-wire is positioned on the anterior inferior lip
...
c,
'.(--~
I
I
of C2 at the exact entrance site desired for the fixation
screw (Fig. 25-2A). Ifone screw is to be placed,amidline
entrance site is chosen; if two are to be used, a paramedian
location -2 mm from the midline is selected. The K-wireis
impacted into the bone to secure it and create anentryhole
for the drill.
An 8 mm hollow driIl is placed over the K-wire andro-
tated by hand to create a shallow trough in the bodyofC3
and incise the C2-C3 anulus
without
cutting into theC2
body (Fig. 25-28-D). The driIl guide tube system,consist.
ing of an inner and outer guide tube, is then passedoverthe
K-wire. The anchoring spikes on the outer guidetube
are then impacted into the C3body to stabilize thesystem
(Fig. 25-3). The inner guide tube is then advancedinthe
previously created trough until it contacts the inferioredge
of C2. The K-wire is removed and a drill is passedup
throughout
the body of C2 to the fracture site (Fig.25-4).
Prior to engaging
the odontoid
process, the alignment can
be optimized by manipulating the C2-C3 complexrelative
to the odontoid-C1 complex. This is accomplishedbyexert-
ing either downward or upward pressure on the handleof
the guide tube as necessary.
In the case of retrolisthesisof
the odontoid
fragment,
downward
pressure
on the (2-C3
complex can be used to achieve anatomical
alignment.After
obtaining
satisfactory
alignment,
the pilot hole is drilledto
the apex of the odontoid.
If the driIl does not penetratethe
Figure
25-2
(A) After
properly
placing
retractors.
the K-wire is inserted as described
in the text. (8) Lat.
eral view and (e) anterior
view of hollow hand drill
creating
a trough
in the body
of C3 and (2-(3
anulus.
(D) Anterior
view of trough
after
removal
of hollow-
hand
drill. (Used with
permission
from Apfelbaum RI.
Anterior
screw
fixation
of odontoid
fractures.
Aesculap
Scientific
Info 24. Aesculap
AG. D7200.
Tuttlingen. Ger-
many: Aesculap; 1992)

25
OdontoidScrewPlacement
221
\
Figure 25-3
Thedrill guide system consists of an inner
and outer tube that are mated together and then placed
over the K-wire. Note that the spikes on the outer guide
tube are impacted into C3 to stabilize the system. (Used
with
permission from Apfelbaum
RI. Anterior screw
fixation of odontoid fractures. AesculapScientific Info 24,
Aesculap AG, D7200. Tuttlingen, Germany: Aesculap;
1992)
...
Figure 25-4
K-wireis removed and replaced
with the drill, which is fluoroscopically
guided
to the apex of the odontoid
after reducing
the
fracture.
A pilot
hole is drilled
through
the
apical cortex of the odontoid.
(Used with per-
mission
from
Apfelbaum
RI. Anterior
screw
fixation
of odontoid
fractures.
Aesculap Scien-
tific Info 24, Aesculap AG, D7200. Tuttlingen,
Germany: Aesculap; 1992)

222
MidcervicalSpine:Anterior Approach
distal cortex, screw placement may be difficult or impossi-
ble. Because the angle of drilling is coaxial with the long
axis of the odontoid, penetration into the spinal canal to-
ward the spinal cord is not likely.Frequent biplanar imaging
controls the drilling process.
The drill bit and inner drill guide tube are then removed
and the pilot holes tapped by insertion of the tap through-
out the outer guide tube. Both the drill and tap are
calibrated to allow measurement of the depth of penetra-
tion and hence the screw size that will be needed. A lag
screw is then inserted through the guide tube using a spe-
cial screwdriver with an internal retaining spring to hold
the screw (Fig. 25-5). If a second screw is desired, it is
placed using an identical series of steps, but it can be a fully
A
,
threaded
screw because no additional lag effect is necessary.
Fig. 25-6 demonstrates
pre- and postoperative
radiographs
of a patient in whom we placed two anterior odontoid
screws.
After placing the screws, stability
can be confirmed by
flexing and extending
the patient's
neck under fluoroscopic
monitoring.
This confirms
the integrity
of the bone-screw
interface as well as the competency of the transverseliga-
mentous
complex.
Standard
wound closure is achieved with absorbablein.
terrupted
sutures
in
the
sternocleidomastoid
fascia.
platysma,
and subcutaneous
layers, followed by adhesive
strips on the skin. Drains are not used and a cervicalcollar
is usually not required.
B
C I
"II.!
L
,~ 1 I
,.
---' 1m'
.
1\1
_I
D
Figure
25-5
(A) The screw
is inserted
through
the guide
tube
and advanced
through
the pilot hole. (8) In chronic
nonunion
bifaced curettesare
used to freshen the fracture site and enhance healing. (C) The screw is advanced with the ball driver. (D) The final position ofthe screwwith reap-
proximation of the odontoid fragment. (Used with permission from Apfelbaum
RI.Anterior screw fixation of odontoid fractures. AesculapScientific
Info24,AesculapAG,D7200.Tuttlingen,Germany:Aesculap;1992)

Figure25-6
(A)Preoperativelateraland (8) postopera-
tive lateral and (C) anteroposterior
radiographs of a patient
who underwent
anterior odontoid
screw placement
for
management
of an acute type IIodontoid fracture.
A
(
. PostoperativeCare
Mostpatientscanbe discharged from the hospital within
1
to2daysandquicklyresumenormal nonjarring activities. A
cervical
collarisnot routinely employed; however, it should
probablybe used in cases of questionable bone density.
Postoperative
fracture union is assessed by serial radi-
ographs
augmentedwith flexion-extension films and com-
putedtomographic(IT) scansasnecessary.
. Outcomes
Wehaverecentlyreviewed the surgical outcome of patients
whounderwentanterior odontoid screw fixation
at two
25
Odontoid Screw Placement
223
B
institutions.20 There were 147patients who had either acute
«
6 months; n = 129)or chronic (> 18months;n = 18)
odontoid fractures. These results include 138patients with
type II and nine patients with type III fractures.
There were 117patients with acute fractures available for
follow-up. Successful anatomical bony fusion was seen in
99 patients (85%),nonanatomical bony fusion in four (3%),
fibrous union in four (3%),and nonunion in 10(9%).The 10pa-
tients who had nonunion of the fracture were treated either
nonsurgically in hard cervical collars(n = 6) or surgically (n =
4). The six patients treated in cervical collars are currently
without pain and x-rays demonstrate progressivefusion. The
four patients treated surgically underwent either posterior
fusion (n = 2) or reoperationwith anterior screw placement (n
= 2).All four of thesepatientswent on to successfulfusion.

224
MidcervicalSpine:AnteriorApproach
..
.
Conclusions
Patients with chronic fractures had a significantly lower
rate of fusion relative to patients with acute fractures (88%
vs 25%,P < 0.5).
Postoperativehardware complications occurred in 14 pa-
tients. Thetwo most common hardware failures were screw
pullout (n = 5) and screw backout (n = 4). Screw pullout
fromthe bodyof(2 occurred exclusivelyin patients who had
fracturesextending into the body of (2. Although these frac-
tures were recognized preoperatively, at the time of surgery
we felt that the body would still provide acceptable substrate
forfusion.Basedon our current results, we no longer perform
this procedure on patients with evidence of comminuted (2
body fractures. Screw backout occurred in cases when the
odontoidscrew did not fullyengage the distal cortex.
References
1.
Crockard
HA, Heilman
AE, Stevens JM. Progressive
myelopathy
sec-
ondary
to odontoid
fractures:
clinical. radiological,
and surgical
fea-
tures. J Neurosurg
1993 ;78:579-586
2.
White
AA, Panjabi
MM. eds.
Clinical
Biomechanics
of the
Spine.
Philadelphia:
Lippincott;
1990:610-611
3.
Boehler j. Fractures
of the
odontoid
process.
J Trauma
1965;695:
386-391
4.
Chan RC, Schweigel
JF. Thompson
GB. Halo thoracic
brace immobi-
lization in 188 patients
with acute cervical spine injuries. J Neurosurg
1983:58:508-515
5.
Clark CR.White AA 3rd. Fractures
of the dens:
a multicenter
study. J
Bone Joint Surg Am 1985;67 A:1340- 1348
6.
Cooper PR, Maravilla KR.Sklar FH. et al. Halo immobilization
of cervi-
cal spine fractures. J Neurosurg
1979;50:603-610
7.
Dickson H, EngelS, Blum P.Jones RF.Odontoid
fractures.
systemic
dis-
ease and conservative
care. Aust N 2J Surg 1984:54:243-247
8.
Dunn ME, Seljeskog
EL. Experience
in the management
of odontoid
process injuries: an analysis of 128 cases. Neurosurgery
1986;18:306-310
9.
Fujii E, Kobayashi
K. Hirabayashi
K. Treatment
in fractures
of the
odontoid process. Spine 1988;13:604-609
10.
Hadley MN, Browner
C. Sonntag
VKH. Axis fractures:
a comprehen-
sive review of management
and treatment
in 107 cases. Neurosurgery
1985; 17:281-290
11.
Lind B,Nordwall A, Sihlbom H. Odontoid
fractures
treated
with halo-
Direct anterior
odontoid
screw fixation
is an effective and
safe method for treating odontoid fractures. It confers
immediate
stability,
potentially
preserves
(1-(2
rotatory
motion, and provides
optimum
conditions
for bony fusion.
The timing of surgery for odontoid fractures is important.In
our group of 147 patients,
those who were treated within
6 months of injury had a bony fusion rate of 88%,whereas
those who underwent
this procedure
greater than18
months
after
injury
had a bony fusion
rate of 25%.We
therefore
recommend
anterior
odontoid
screw fixationas
the preferred
treatment
for the vast majority of patients
with acute odontoid fractures.
vest. Spine 1987;12:173-177
12.
Maiman
OJ, Larson
SJ. Management
of odontoid
fractures. Neuro-
surgery
1982:11 :471-476
13.
Ryan MD. Taylor TK. Odontoid
fractures:
a rational approach totreat-
ment.J
BoneJoint
Surg Br 1982;64B:416-421
14.
Schiess RJ, Desaussure
RL,Robertson
JT. Choice oftreatment
ofodon-
toid fractures.J
Neurosurg
1982:57:496-499
15.
Wang GJ. Mabie KN, Whitehill
R, et al. The nonsurgical
management
of odontoid
fractures
in adults. Spine 1984:9:229-230
16.
Dickman
CA, Mamourian
A. Sonntag
VK. Drayer BP.Magneticreso-
nance imaging of the transverse atlantalligament
for the evaluation
of atlantoaxial
instabilitY.J
Neurosurg
1991 :75:221-227
17.
Apfelbaum
RI. Anterior
screw
fixation
of odontoid
fractures. In:
Camins
MB. O'Leary PF, eds. Disorders
of the Cervical Spine.Balti.
more: Williams & Wilkins;
1992:603-608
18.
Apfelbaum
RI.Anterior
screw fixation of odontoid
fractures. Aesculap
Scientific
Info 24. Aesculap
AG, 07200.
Tuttlingen.
Germany: Aescu-
lap: 1992
19.
Apfelbaum
RI. Anterior
screw fixation of odontoid
fractures. In:Ren-
gachary
55. Wilkins
RH, eds. Neurosurgical
Operative Atlas.Balti.
more: Williams & Wilkins;
1992:2:189-199
20. Apfelbaum RI,Lonser RR.Veres R.CaseyA.Directanteriorscrewfixa.
tion
for recent
and
remote
odontoid
fractures. J Neurosurg Spine
2000;93:227-236

26
PosteriorApproachesto the CervicalSpine
NitinTandonandDennisG.Vollmer
. Advantages
. Disadvantages
. Anatomy
. SurgicalTechnique
Anesthesia
Positioning
Procedure
ClosureandPostoperativeConsiderations
. Complications
Theearliestoperations on the cervical spine were from a
posteriorapproach.The last 4 decades have seen the devel-
opmentand expansion of anterior cervical approaches from
simpleanterior diskectomy
techniquesl,2 to multilevel
corpectomieswith anterior
instrumentation.
There have
alsobeenconcerns regarding the potentially
greater dis-
comfortandlonger hospital stays following
the takedown
ofparaspinousmuscles and an awareness of the incidence
ofpostlaminectomy deformity.
All of these factors have
dampenedthe enthusiasm of some surgeons for posterior
operations.Nonetheless,several pathological conditions de-
mandextensile approaches
and are best addressed
by pos-
teriorcervicalspine surgery. The availability of lateral mass
platesfor posterior segmental fixation of the cervical spine
andthe proliferation of laminoplasty techniques provide
thesurgeonwith greater latitude in choosing a posterior
operation.Although the choice of an anterior or posterior
approachmaybe a matter of preference and surgeon's ex-
perience,certain situations clearly dictate a particular ap-
proach(Table26-1 ).
. Advantages
. Theapproach is relatively straightforward
and is well
knownbyallneurosurgeons.
j
. Avoids risk to anterior vascular and visceral structures
.
Disadvantages
.
Potentiallygreaterdiscomfortand longerhospitalstays
followingthe takedownofparaspinousmuscles
. Increased incidence of deformity postIaminectomy
. Anatomy
Severalfacets ofcervicalspine anatomy bear relevanceto sur-
gical practice. The anatomy of the atlantoaxial spine is dis-
cussed elsewhere, and we restrict this discussion to the rele-
vant aspects of the posterior elements of the subaxial spine,
including the ligaments, musculature, and bony elements.
Theligamentumnuchae.a homologueof the supraspinous
and interspinous ligaments at subcervicallevels. spans the
space in the midline from the tips ofthe spinous processesto
the laminae.The laminae ofadjacent vertebrae are connected
by the ligamentum fIavum. In the upper cervical spine the
spinous processes are smaller and less shingled such that the
interlaminar space with the ligamentum fIavumcan be well
seen. It is composed of two sides separated in the midline by
a central raphe. which can be separated by a blunt dissector.
225

The posterior cervical musculature can be divided into
three main groups from superficial to deep (Figs. 26-1,
26-2). The trapezius is the most superficial muscle and
extends from the midline fascia to its scapular attachments.
The splenius capitis, splenius cervicis, and levator scapulae
make up the next layer.The deepest or paraspinous group is
composed of the oblique capitus superior and inferior,
semispinalis capitis, semispinalis cervicis, longissimus, and
multifidus muscles. In practical terms, the posterior ap-
proach takes advantage of the relatively avascular midline
plane that separates the muscles on the two sides.
Rostrocaudallocalization
is aided by the knowledge that
the spinous processes of C2 and C7 are the most easily
palpable and the spinous process of C6 is often the lowest
bifid process. This fact can be confirmed in the individual
patient by reference to computed tomographic (CT)scansor
plain radiographs. At the level of the laminae, the distinction
between laminar arch and lateral mass-facet complexis
readily observed, especially from (2-C3 to e6. At C7thisdis-
tinction is less obvious.The shoulder of the lateral massesis
also readily observed and provides a landmark for the lateral
extent of dissection in all but a handful of exceptional cases.
-.......
226
Midcervical Spine: Posterior Approach
Table 26-1
Choice of Surgical Approach Based on Location of Pathogenic Process
Pathology
Anterior
Posterior
Both
Either
Midline"soft"diskherniation
++
Lateral"soft"diskherniation
+
++
-
++
Midlineosteophyte
++
Lateralosteophyte
++
+
+
Spondyloticmyelopathywithkyphosis
++
++
+
++
Spondyloticmyelopathywithout kyphosis
++
+
+
Ossifiedposteriorlongitudinalligament-three levels
+
++
+
+
Ossifiedposteriorlongitudinalligament-two levels
++
+
+
+
Vertebralartery decompression
++
+
Vertebralbodyosteomyelitis
++
Ventralepiduralabscess
+
+
-
+
Posteriorelement osteomyelitis
-
++
Dorsalepiduralabscess
-
++
Antero-/posterolateralepiduralabscess
-
+
Spinalarteriovenousduralfistula
-
++
Intracanalicularextradural neoplasia
+
++
+
Intracanalicularintraduralneoplasia
-
++
Vertebralbodyfractures
++
+
-
+
Facetfracture-dislocation(reduced)
+
+
+
+
Facetfracture-dislocation(unreduced)
+
++
+
Occipitocervicalfusion
++

26
PosteriorApproachesto the CervicalSpine
227
semispinalis
capitus
m
rectus capitus
posterior minor
lesser
occipital
nerve
splenius
capitus m
vertebral artery
sternocleido-
mastoid m
rectus capitus
posterior major
oblique capitus
inferior m
ligamentum
flavum
spinous
process,
C2
interspinalis
m
semispinalis
cervi cis m
semispinalis
capitus
m
levator
scapulae m
splenius
capitus m
attachment
",..us cervicism ~ /
trapezIus
m
medial branches
of dorsal
rami of spinal nerves
rombold
major
and minor m
Figure26-1
Posteriorcervicalspinemusculature.

228
MidcervicalSpine:PosteriorApproach
nuchal ligament
m
spinous
process,
Cs
levator
scapulae m
longissimus
cervicis m
vertebral
artery
deep cervical
vein, artery
ligamentum
flavum
spinal cord
spinal nerve, Cs
sternocleido-
vertebral
body, C4
mastoid
m
Figure 26-2
Axial section through
the midcervical spine to demonstrate
the organization
of muscles into superficial.
middle. and deep layers.
.
SurgicalTechnique
Anesthesia
I'
Posterior exposure is performed under a general endotra-
cheal anesthetic. Standard neuroanesthetic techniques are
appropriate for most procedures. Awake fiberoptic intuba-
tion can be employedin a cooperative patient if there is con-
cern over producing cord compression during intubation or
patient positioning.Typicalcases where awake intubation is
routinely utilized include patients with an unstable spine
following trauma or those with pronounced spondylotic
myelopathy. If there are concerns about neck stability but
fiberoptic intubation is not an option, intubation can usually
be safely accomplished while maintaining the cervical spine
in a neutral position with or without in-line traction. The
use of evoked potential monitoring in such cases can pro-
vide useful data regarding neurological status both during
the operation as well as during intubation and positioning.
However, changes in electrophysiological monitoring suffer
from a time lag and are not reported in real time. Asense of
how well a patient with a stable but spondylotic spine will
tolerate neck extension required for intubation can some-
times be estimated by asking the awake patient to extend
and maintain the position for a few minutes.
Positioning
The prone position is utilized in essentially all circum-
stances. The seated position enjoyed some popularity in
the past. However, the rare possibility of air embolism,3
hypotension, and an increased risk for cord ischemia along
with the enhanced physical demands that this position
places on the surgical team, especially if hardware needsto
be implanted, have markedly decreased its use in routine
cervical operations. The benefits of reduced bleeding and
drainage of blood away from the operative site are, inthis
author's opinion, not sufficient to warrant the risks.Fur-
thermore, microsurgical techniques have made bleedingin
the prone-positioned patient easier to address.
Formostposteriorcervicaloperationsthe Mayfieldhead-
holder is used as will be describedhere. It is appliedafter
intubation and used to assist in controlling the neck asthe
patient is log rolled into the operative position. Early fluoro-
scopic visualization or a plain radiograph can be usedto
confirm satisfactory cervical osseous alignment and can
also serve as a "localizer" film. The Mayfield headholderor
similar three-point skull fixation is preferred for these cases
because it has the dual advantages of rigid fixation ofthe
cervical region along with the avoidance of pressure tothe
face and orbits.4 In some circumstances. such as when tong
traction is being applied or when significant reductionis
contemplated,
positioning on a well-padded
horseshoe
head holder may be employed. Under these circumstances,
orbital pressure must be scrupulously avoided to prevent
retinal ischemia and subsequent visual loss. Using either
the Mayfield or the horseshoe, the cervical spine is usually
placed in slight flexion, and it is important for most ofthis
flexion to occur at the rostral extent of the spine. This
"military chin tuck" serves to elevate the occiput out of
the way and tighten the skin of the posterior neck
(Fig. 26-3). A minimum of two fingerbreadths shouldbe

26
Posterior Approaches to the Cervical Spine
229
A
B
Figure26-3
Positioning for a posterior cervical approach. Note the conversion of the normal cervical lordosis to a kyphosis when the position is
changedfrom (A) military chin tuck to (8) flexion at all levels of the spine.
allowedbetween the chin and the sternum. Positioning is
harderin patients
with short wide necks, yet a few extra
minutesinvested in positioning
usually result in an accept-
ableresult.Conversely,it is important to avoid overflexion,
especiallyof the atlanto-occipital
region, if a fusion is being
performedbecause this may leave the patient with signifi-
cantpostoperativediscomfort and, in some, a sense of diffi-
cultyinswallowing.Asa general rule, if occipitocervical or
multilevelsubaxial fusion is being performed,
a neutral
or
naturallylordotic neck position is desirable
to prevent a fu-
sionofthe cervicalspine in kyphosis.
Chestrolls or a positioning
frame are used to reduce ab-
dominalpressure, and the foot of the table is slightly elevated
topromotevenous drainage from the extremities.
Sequential
compressiondevices are used to reduce the risk of deep ve-
nousthrombosis. When
radiographic
visualization
of the
lowercervicalregion will be required intraoperatively, we
placepadded wrist restraints
attached
to long straps during
positioning.This enables the circulating
nurse or other per-
sonnelto pull down on the shoulders at the appropriate
time.
Iffluoroscopy is to be used during the procedure
we pre-
ferto place it in position at this point and confirm the ade-
quacyof imaging. The C-arm is then draped
sterilely
and
leftinthis position. This avoids loss of visualization
or other
hazardsand technical challenges associated with placing it
duringthe operation.
Procedure
Theposterior approach
to the cervical
spine is relatively
straightforward and is well known by all neurosurgeons.
As
withall surgery, attention
to detail and gentle handling
of
tissuewill result in optimal results. Once satisfactory
opera-
tivepositioninghas been achieved, standard skin prep and
drapingare performed.
If a limited
skin incision
is to be
employedas in single-level cervicallaminoforamenotomy, a
localizingspinal needle is placed and a lateral radiograph
is
obtainedto confirm the level. The skin incision is infiltrated
withlocal anesthetic
to reduce
bleeding
from the wound
I
J
edges and to decrease immediate postoperative incisional
pain. We generally use 0.25%bupivacaine with epinephrine
(1:200,000). The incision is placed directly over the spinous
processes and carried to the level of the deep fascia. Bleed-
ing is controlled with bipolar electrocautery and the early
use of self-retaining Wietlaner-type retractors. The deeper
soft tissue dissection is usually performed with the Bovie
electrocautery (Fig. 26-4). The dissection is performed by
following the ligamentum nuchae, with the goal being to
avoid cutting through the paraspinous muscle. The progres-
sive spreading of the soft tissue by the self-retaining retrac-
tors greatly aids in this aspect of the dissection. Palpation of
Figure 26-4
Midlinedissectionalongthe ligamentum nuchae to ex-
posethe spinousprocesses.

230
MidcervicalSpine: Posterior Approach
Figure 26-5
Subperiosteal dissection with the Boviecautery. The
straightorthe angledCobbretractorsmaybe usedto exposethe plane.
the spinous processes allows for orientation to the midline.
The paraspinous muscles can be detached from the spinous
processes and laminae in a subperiosteal plane utilizing a
variety of techniques. We prefer to dissect with the Bovie
electrocautery using a small Cobbor similar periosteal ele-
vator to simultaneously retract and sweep the soft tissue off
the spine (Figs. 26-5, 26-6). Additional hemostasis is ob-
tained with a bipolar and bone wax. Care must be exercised
to avoid thermal damage to soft tissue or bone, whichcan
impair wound healing and osseous fusion. The rostrocaudal
extent of the incision is obviously determined by the spinal
levels to be accessed. though it should be remembered that
greater force of retraction may be required when shorterin-
cisions are used and this may compound muscle ischemia,
postoperative pain, and the like. The width of the exposure
is also determined in part by the goals of the operation.For
example. the placement of lateral mass plates requiresthe
exposure to include the fullextent of the lateral masses.Itis
important not to stray more lateral than the extent ofthe
lateral masses because this can produce persistent venous
hemorrhage from the venous plexus surrounding the verte-
bral artery. For keyhole laminoforaminotomy we generally
employ a skin incision and soft tissue dissection of aboutan
inch in length. centered at about the tip of the upper spin-
ous process. Narrow, hook-blade hemilaminectomy retrac-
tors. such as the Williams design. work well for this expo-
sure. Bilateral muscle exposures
for posterior
fusions.
laminectomies. and other procedures are done using cere-
bellar-type retractors in most instances (Fig.26-7).
Closure and Postoperative
Considerations
Upon removal of the self-retaining retractors there maybe
some hemorrhage from the paraspinous muscles. whichis
addressed prior to closure. The adequacy of hemostasis can
be further confirmed with a Valsalvamaneuver. It isgener-
ally adequate to simply approximate the fascia in the mid-
line in a watertight fashion. Under most circumstances we
use absorbable sutures (0 or 2.0 polyglactin). Attemptsto
reapproximate
paraspinous
muscles
usually
result in
greater postoperative pain and can result in necrosisof
fibers that are rendered ischemic. A subcuticular closure
with an absorbable suture supplemented
with Steri-Strip
Figure 26-6
The use of Weitlaner
or angled cerebellar retrac-
tors to provide sustained
retraction
for the lateral extent ofthe
exposure.

....
26
PosteriorApproachesto the CervicalSpine
231
Figure26-7
Two angled, self-retaining
cerebellar retractors
provide optimal
exposure prior to commencing
the decompressionflaminectomy.
skinapproximationis most frequently used. We do not rou-
tinelyusedrains but will when circumstances dictate.
. Complications
more of even one facet,lO.nor its capsule8produces a signifi-
cant risk for subsequent instability that should be weighed
against the added benefits of a possibly wider exposure. Air
embolism has been reported during spine surgery in the
prone position, though much more commonly during lumbar
spine surgery,12.13and should be considered if an unexplain-
able hypotensive event occurs,coupled with a sudden drop in
end-tidal C02' Pseudomeningoceles or cerebrospinal fluid
(CSF)-cutaneousfistulae may result from incidentalor inten-
tional durotomies and may need lumbar drainage, reexplo-
ration, or chronic CSFdiversion. Iatrogenic vertebral artery
injury from a posterior approach to the subaxialspine is rare14
and usually secondary to vagrant lateral mass screw place-
ment or an anomalous position of the artery. Brachial plex-
opathy has been reported following lumbar spine surgery15
and can conceivably occur from excessive and prolonged
traction on the upper extremities.
Complicationsfrom posterior
cervical spine surgery do not
usuallyariseas a consequence ofthe exposure per se but are
secondaryto positioning
and subsequent
to the removal of
posteriorelements.
Ocular injury, though
rare (incidence
around0.2%),can be serious enough to result in blindness.4lf
ahorseshoe-type head holder is used, direct pressure
on the
globecanbe prevented by the use ofumbilicaltape applied to
thefoam.sPostIaminectomy kyphosis6 is common if the
laminectomyis performed
in an immature
spine?
is com-
binedwith capsular or facet resection,8 extends over multiple
I~vels,or is performed in the presence of preoperative
sagittal
instabilityin a neutral or kyphotic spine.9 Resection of 50%or