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66 Procedure 9 | Occipital-Cervical Fusion
P O RTA L S / E X P O S U R ES
P I T F A L L S
• Adequate exposure of laminae/lateral
masses must be achieved to direct
sublaminar wires or pedicle/lateral mass
screws.
• Avoid excessive electrocautery, which
damages underlying bone.
• Do not forget to decorticate cortical
surfaces. Doing so promotes fusion.
P O RTA L S / E X P O S U R ES
E Q U I PM E N T
• Fluoroscopy for pedicle/lateral mass
screws placement
• Neuronavigation for instrumentation
placement
P O RTA L S / E X P O S U R ES
P E A R LS
• Care must be taken when exposing the
space between the occiput and the C1
interspace. There is a risk of penetrating
the dura at this interspace with the Bovie
electrocautery or a spinal instrument.
• The vertebral artery lies within the
occipital triangle (superior and inferior
obliques, rectus capitis). Avoid
iatrogenic damage to the artery during
lateral dissection.
• Remove soft tissue that could interfere
with bony fusion, such as the
atlantooccipital membrane, interspinous
ligaments, and ligamentum flavum.
S T E P 1 P EA R L S
• Avoid excessive flexion/extension; a
near-anatomic position is preferred.
• Chin clearance must be obtained.
• Monitoring of SSEPs and motor evoked
potentials is recommended.
• If tolerated by the patient, the patient’s
neck may be positioned to optimize a
surgical approach and then repositioned
under fluoroscopic guidance for final
fixation.
FIGURE 9-8
Procedure
Step 1
n
Position the patient on gel rolls, in pins, in a prone, neutral position (Figure 9-8).
n
Shave and mark from the inion down the midline to C5.
n
Prepare skin in the usual sterile fashion.
n
Give preoperative antibiotics.
Step 2: Exposure of Inion to C5
n
Dissect using sharp, blunt, and electrocautery dissection down the midline
through the following layers (see Figure 9-7):
• Superficial fascia: identify the midline raphe.
• Identify the spinous process and the prevertebral fascia.
• Dissect bilaterally down the spinous processes. Preserve the ligamentum
nuchae as much as possible.
• Take care to identify the spinous process of C2 and the ring of C1. Dissection
here must be done very cautiously to avoid entering the occipital, C1, or C2
spaces or the C1-2 interspace.
• Expose laterally to identify lateral masses.
• Expose anteriorly to identify the inion.
• At a minimum, bony exposure of occiput to C2 lateral masses must be
achieved. Expose lower lateral masses as needed.
S T E P 1 C ON T R O V ER S I E S
• Some surgeons advocate using traction
and avoiding pin fixation (Menezes and
Sonntag, 1996).
S T E P 2 P EA R L S
• Minimize electrocautery to prevent
damage to the dura or underlying bone
(for fusion).
• Minimize the length of the exposure.
S T E P 2 P IT FA L L S
• Avoid past pointing into the
interlaminar or occipital lamina space
with electrocautery.
Procedure 9 | Occipital-Cervical Fusion 67
S T E P 3 P EA R L S
• Create the shortest construct possible
without sacrificing stability. Longer
constructs tend to minimize mobility;
on the other hand, to short a construct
may be inadequate for creating
appropriate stability.
• In traumatic injury, the construct should
include the first two levels with normal
ligamentous anatomy.
S T E P 3 P IT FA L L S
• Radiographically evaluate occiput
anatomy before placement of plate. Be
aware of thickness of occiput.
• Avoid excessive manipulation of spinal
instrumentation. Nicks, scratches, and
deformities will all serve as focal points
for mechanical failure.
S T E P 3
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Screw/rod constructs
• Wire-based systems
FIGURE 9-9
Step 3: Instrumentation and Fusion
n
Place the occipital Kiel plate in the midline (Figure 9-9).
n
Place an isthmus or pedicle screw at C2. (Expose the lateral masses of distal
vertebrae as needed.)
n
Contour the rods to the approximate neutral position of the occipital-cervical
junction. The rod bend should be approximately a 130-degree angle, but this
will vary with each patient.
n
Connect the rods to the Kiel plate and screw.
n
Decorticate the occipital-cervical junction.
n
Pack the construct with autologous/allograft material to encourage fusion.
Step 4: Closure
n
Close layers sequentially.
n
Subfascial drain is used as needed.
S T E P 4 P EA R L S
• Appropriate approximation of skin rolls
is needed in patients with large necks.
C O N T RO V E R S IE S
• Use of autologous bone versus allograft
bone: Autologous bone has high fusion
rates, but there is higher morbidity
associated with hip graft harvest.
68 Procedure 9 | Occipital-Cervical Fusion
P O S T OP E R AT IV E P E A R L S
• For patients with poor bone quality,
postoperative halo fusion can be
considered.
• Consider use of bone stimulators for
patients at risk of poor fusion.
P O S T OP E R AT IV E P I T F A L L S
• Beware of postoperative radiation and
chemotherapy for oncology patients.
Do not start prior to 2 weeks after
surgery.
• Balance training and physical therapy
are important.
• Instrumentation will fail without bony
fusion.
P O S T OP E R AT IV E
C O N T RO V E R S IE S
• Not all surgeons advocate use of a hard
cervical collar postoperatively.
Postoperative Care and Expected Outcomes
n
Place the patient in a hard collar for 6 to 12 weeks with radiographic follow-up.
n
After 6 to 12 weeks, flexion/extension views should be obtained to determine
if fusion is noted radiographically.
n
Approximately 80% fusion rates are expected.
n
Complications include infection, neurovascular compromise from instrumenta-
tion, subdural or subarachnoid hematoma resulting from instrumentation placement, cerebrospinal fluid-flow abnormalities resulting from instrumentation
placement, pullout of screws/plate/instrumentation, and fracture/migration of
instrumentation.
Evidence
Abumi K, Takada T, Shono Y, Kaneda K, Fujiya M. Posterior occipitocervical
reconstruction using cervical pedicle screws and plate-rod systems. Spine
1999;24:1425-34.
Deutsch H, Haid RW Jr, Rodts GE Jr, Mummaneni PV. Occipitocervical fixation:
long-term results. Spine 2005;30:530-5.
Dvorak MF, Sekeramayi F, Zhu Q, et al. Anterior occiput to axis screw fixation.
Part II: a biomechanical comparison with posterior fixation techniques. Spine
2003;28:239-45.
Fehlings MG, Cadotte DW. Occipital cervical fusion: an evolution of techniques.
J Neurosurg Spine 2010;13:3-4.
Lee SC, Chen JF, Lee ST. Complications of fixation to the occiput—anatomical and
design implications. Br J Neurosurg 2004;18:590-7.
Menezes AH, Sonntag VKH, editors. Principles of Spinal Surgery. New York:
McGraw-Hill; 1996.
Oda I, Abumi K, Sell LC, et al. Biomechanical evaluation of five different occipito-
atlanto-axial fixation techniques. Spine 1999;24:2377-82.
Schmidek HH, Sweet WH, editors. Schmidek & Sweet’s Operative Neurosurgical
Techniques: Indications, Methods, and Results. Philadelphia: WB Saunders,
2000, p. 1934-45.
Takechi Y, Iizuka H, Sorimachi Y, et al. Non-traumatic posterior atlanto-occipital
joint dislocation. Case report. Eur Spine J 2010;20(Suppl 2):S172-5.
Vaccaro AR, Betz RR, Zeidman SM, editors. Principles and Practice of Spine
Surgery. St Louis: CV Mosby, 2003, p. 723-25.
Vender JR, Rekito AJ, Harrison SJ, McDonnell DE. The evolution of posterior
cervical and occipitocervical fusion and instrumentation. Neurosurg Focus
2004;16:e9.
Winegar CD, Lawrence JP, Friel BC, et al. A systematic review of occipital cervical
fusion: techniques and outcomes. A review. J Neurosurg Spine 2010;13:5-16.
Winn HR, Youmans JR. In: Winn HR, Youmans JR, editors. Youmans Neurological
Surgery. Philadelphia: WB Saunders, 2004.
P R O C ED U R E 1 0
C2 Translaminar
Screw Fixation
Neill M. Wright
I N D I CAT I O NS P I T F A L L S
• Compared with other posterior screw
fixation constructs, C2 laminar screws
require intact posterior elements of C2.
• The morphology of C2 laminae varies,
and a small number of patients will
have small laminae unable to accept
bilateral 3.5-mm diameter screws.
T E C H NI Q U E S
C O N T RO V E R S IE S
• For thinner patients, the dorsal location
of the C2 laminar screw head adjacent
to the spinous process may make the
hardware unacceptably prominent and
palpable under the skin.
Indications
n
Atlantoaxial instability resulting from the following:
• Unstable fractures of the axis or atlas
• Unstable os odontoideum
• Rotatory subluxation of C1-C2
• Postodontoidectomy
• Ligamentous laxity, such as in rheumatoid arthritis, Down syndrome
n
Failed posterior C1-C2 arthrodesis
n
C1-2 osteoarthritis
n
Aberrant foramen transversarium location precluding safe transarticular or C2
pedicle screw placement
Examination/Imaging
n
CT imaging is critically important to determine the suitability of the C2 laminae
to accept a 3.5-mm diameter screw. In this image the right laminae (
too narrow to safely place a laminar screw (Figure 10-1).
T R E A T M E N T OP T I O N S
• C1-C2 transarticular screw fixation:
Magerl technique (if vertebral artery
anatomy favorable)
• C1 lateral mass to C2 pedicle screw
fixation: Harms technique (if vertebral
artery anatomy favorable)
• Posterior C1-2 wiring techniques
• Brooks-Jenkins technique (wires
passed sublaminar around C1 and C2
with wedges of bone between the
posterior laminae of C1 and C2
bilaterally)
• Sonntag-modified Gallie technique
(wires passed sublaminar around C1
and then around spinous process
of C2, with shaped bone wedged
between the inferior lamina of C1
and the superior lamina and spinous
process of C2)
• Halifax interlaminar clamps FIGURE 10-1
arrow
) is
Figures 10-4 through 10-7 and 10-9 through 10-12 redrawn with permission from Leonard JR,
Wright NM. Pediatric atlantoaxial fixation with bilateral, crossing C-2 translaminar screws.
Technical note. J Neurosurg 2006;104:59-63.
70 Procedure 10 | C2 Translaminar Screw Fixation
P O S I TI O N I N G PE A R L S
• Although it is tempting to place the
neck in a flexed position to facilitate
surgical exposure, this should be
avoided.
• It is important to place the neck in an
anatomically neutral position.
• Gently taping the shoulders can
facilitate radiographic visualization of
the C1-2 complex.
• Gently taping the upper back can
reduce redundant neck folds in the
more obese patient, facilitating skin
opening and closure.
P O S I TI O N I N G PI T FA L L S
• Placing the patient in a flexed position,
while facilitating exposure, will result in
stabilizing the atlantoaxial complex in a
flexed position, resulting in permanent
difficulty with swallowing and high
patient dissatisfaction.
• Placing the patient in an overly
extended position will make surgical
exposure more difficult.
Surgical Anatomy
n
Intact posterior elements of C2 are crucial to the placement of translaminar
screws. The spinous process of C2 is typically bifid. The laminae thickness needs
to be evaluated preoperatively by computed tomography (CT), and the screw
length should be measured. Screw length is determined from the axial CT slice
that shows the thickest portion of the laminae of C2 (Figure 10-2).
Positioning
n
Similar to positioning for C1 lateral mass screws and other fixation techniques
for C2, the patient is prone in a Mayfield headholder. The neck is placed in a
neutral position.
n
Hair is shaved as needed to expose the inion rostrally down to the midcervical
spine.
Portals/Exposures
n
A skin incision is made from the inion down to approximately the C3 level.
n
After dividing the dorsal fascia in the midline, the paraspinal muscles are
reflected from the suboccipital skull, the dorsal arch of C1, and the spinous
process and laminae of C2 (Figure 10-3).
n
It is important to leave intact the muscular attachments on the caudal aspects
of the spinous process of C2.
P O S I TI O N I N G EQ U I P M EN T
• Mayfield headholder or equivalent
• Fluoroscopic C-arm
FIGURE 10-2 FIGURE 10-3
Procedure 10 | C2 Translaminar Screw Fixation 71
P O RTA L S / E X P O S U R ES
P E A R LS
• The electrocautery can be safely used
to reflect the paraspinal muscles off of
the spinous process and laminae of C2,
but this should not be used to expose
the lateral aspects of the dorsal C1
laminae to avoid possible vertebral
artery injury.
• Frequent repositioning of the retractors
to tension the paraspinal muscles
facilitates exposure.
P O RTA L S / E X P O S U R ES
P I T F A L L S
• Avoid exposure of the C2-3 facet joint
laterally unless C3 is included in the
intended fixation construct.
P O RTA L S / E X P O S U R ES
E Q U I PM E N T
• Angled Weitlaner retractor or
equivalent
• Electrocautery for C2
• Penfield dissectors for exposure of the
lateral C1 dorsal arch for C1 screws
Procedure
Step 1: Making the Entry Hole for the First Translaminar Screw
n
The high-speed drill is used to make a small cortical entry at the junction of the
spinous process and lamina on one side (Figure 10-4). The trajectory of the first
screw must take into account the planned trajectory of the subsequent second
translaminar screw (Figure 10-5). The author favors placing the more rostral
screw first.
S T E P 1 P EA R L S
• Placing the drill at the planned screw
entry point, at the same angle as the
intended screw placement, will allow
visual sighting down the slope of the
contralateral lamina. This helps confirm
that the entry point will access the
intralaminar space of the contralateral
lamina.
S T E P 1 P IT FA L L S
• Placing the entry point in the middle of
the rostral-caudal aspect of the spinous
process may not leave adequate room
for the contralateral screw to pass by.
• Placing the entry point too dorsally or
ventrally may lead to unsatisfactory
screw placement.
S T E P 1
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• High-speed drill
FIGURE 10-4
FIGURE 10-5
72 Procedure 10 | C2 Translaminar Screw Fixation
S T E P 2 P EA R L S
• Drilling with the hand drill allows tactile
feedback to alert the surgeon if the
ventral lamina has been penetrated.
• It is important to measure the length
of the lamina first and to set the drill
guide accordingly.
• For grossly unstable injuries, gentle
countertraction against the opposite
side of the spinous process with a
periosteal elevator will prevent rotation
of C2 during drilling.
S T E P 2 P IT FA L L S
• Drilling past the distal aspect of the
lamina could result in injury to the C2-3
facet joint or even potentially the
vertebral artery.
• Unrecognized ventral breakout into
the spinal canal could result in dural
laceration, cerebrospinal fluid leak, or
potential injury to the spinal cord.
Step 2: Drilling the Contralateral Lamina
n
The hand drill is used to drill the contralateral lamina to the depth determined
by preoperative imaging (Figure 10-6).
n
After placing the drill guide at the drilled entry point, the drill is angled to match
the down slope of the contralateral lamina (Figure 10-7).
n
For safe placement, the drill can be angled at a lesser degree than the contra-
lateral down slope such that any drill breakout will occur dorsally through the
laminar surface rather than ventrally into the spinal canal.
S T E P 2
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Hand drill and drill guide
• Periosteal elevator (or equivalent) to
provide countertraction
FIGURE 10-6
FIGURE 10-7
Procedure 10 | C2 Translaminar Screw Fixation 73
S T E P 3 P EA R L S
• Gently bending the tip of the ball-tip
probe at the distal end helps provide
directional palpation.
• If the ball-probe identifies a ventral
breakout, the length of the viable tract
before the breakout can be determined
by placing a straight clamp or mosquito
clamp on the ball-tip probe at the entry
point and measuring the distance to
the tip of the ball-tip probe once
removed. A shorter screw can be
placed to purchase the spinous process
rather than the lamina.
S T E P 3 P IT FA L L S
• If the integrity of the ventral tract is not
verified, a screw could inadvertently
be placed into the spinal canal, with
resultant spinal cord injury.
S T E P 3
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Ball-tip probe
Step 3: Verification of Safe Preparation
of the Lamina
n
Intraoperative or postoperative radiographs are of limited value in determining
accurate intralaminar screw placement.
n
The integrity of the drilled path must be verified before screw placement.
n
A ball-tip probe is used to palpate the tract, paying special attention to the
ventral aspect of the tract (Figure 10-8).
Step 4: Placement of the First Screw
n
The appropriate-length screw (as determined by preoperative CT and intraopera-
tive verification of the drill tract) is placed (Figure 10-9).
n
Similar to step 2, the screw tip is placed into the entry hole, and then the
screwdriver is angled to match the down slope of the contralateral lamina
(Figure 10-10).
S T E P 3 C ON T R O V ER S I E S
• Some authors have recommended
making a cortical window in the distal
lamina with the high-speed drill to
directly visualize the distal end of the
intralaminar drill or subsequent screw.
S T E P 4 P EA R L S
• It is important to direct the screw along
the same trajectory as the verified drill
tract.
• For grossly unstable injuries, gentle
countertraction against the opposite
side of the spinous process with a
periosteal elevator will prevent rotation
of C2 during screw insertion.
S T E P 4 P IT FA L L S
• Inserting the screw at a steeper angle
than the verified tract could result in
divergence of the screw into the spinal
canal.
S T E P 4
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Screw
• Periosteal elevator (or similar) for
countertraction
FIGURE 10-8
FIGURE 10-9
FIGURE 10-10
74 Procedure 10 | C2 Translaminar Screw Fixation
FIGURE 10-11
S T E P 6 P EA R L S
• Biased angled screws at C2 may
facilitate rod placement.
• Do not tighten the set screws until the
rod is secured at both ends.
S T E P 6
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Rod, rod bender, and rod cutter
• Angled offset connectors, especially for
incorporation into constructs that span
C1-3
FIGURE 10-12
Step 5: Placement of the Second Screw
n
Steps 1 to 4 are repeated for the contralateral lamina.
n
For initial preparation of the entry point, a more caudal location is chosen
to allow passage of the drill and screw past the first screw (Figures 10-11 and
10-12).
n
Occasionally, a portion of the bifid spinous process needs to be resected to allow
entry into the contralateral lamina from a more caudal aspect.
n
It remains critically important to verify the integrity of the drill tract with the
ball-tip probe.
Step 6: Connection of the C2 Laminar Screws to C1 Lateral Mass Screws
n
For atlantoaxial constructs, the C1 lateral mass screws need to be connected to
the C2 laminar screws.
n
The right C1 lateral mass screw will be connected to the right-projecting head
of the left laminar screw, and vice-versa (Figure 10-13).
n
Because of the dorsal position of the C2 laminar screw heads, the rod should
not be allowed to extend past the screw head to avoid overlying skin
irritation.
n
A gentle curve in the rod is often needed. It is often easier to curve the rod
before cutting to the appropriate length.
n
Alternatively, angled offset connectors can be used to incorporate the dorsal C2
screw heads into longer constructs, shown here in an occipital–C1-2 construct
(Figure 10-14).
S T E P 7 P EA R L S
• Careful decortication of the C2 spinous
process, C2 laminar surfaces, and C1
posterior lamina will optimize fusion
rates.
Procedure 10 | C2 Translaminar Screw Fixation 75
FIGURE 10-13
S T E P 7 P IT FA L L S
• Overzealous decortication of the C2
laminae may expose the intralaminar
screws and weaken their purchase.
S T E P 7 C ON T R O V ER S I E S
• The main downside to C2 laminar
fixation is that a supplementary
Gallie-type wired fusion is not possible
because of the position of the C2 screw
heads.
P O S T OP E R AT IV E P E A R L S
• For those unfamiliar with C2 laminar
fixation, postoperative CT imaging is
helpful to verify accurate laminar
fixation, especially in the first few cases.
P O S T OP E R AT IV E
I N S T RU M E N T A T I O N /
I M P L AN TAT IO N
• Cervical orthosis
• Analgesics, muscle relaxants
FIGURE 10-14
Step 7: Arthrodesis
n
Graft material (of the surgeon’s choice) is placed to bridge from the C2 lamina
to the C1 lamina.
n
Graft material can be placed under the rod, wedged between the rod and the
C2 lamina to hold it in place.
n
As an option, the C1-2 facet can be decorticated and directly grafted as well.
Postoperative Care and Expected Outcomes
n
The author places patients in a hard cervical orthosis for 4 weeks.
n
Similar to other posterior cervical approaches, adequate pain relief and muscle
relaxers are administered in the postoperative period.