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76 Procedure 10 | C2 Translaminar Screw Fixation
Evidence
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the placement of C2 laminar screws. Spine 2006;31:2767-71.
Dorward I, Wright NM. Seven years experience with C2 translaminar screw
fixation–clinical experience and review of the literature. Neurosurgery 2011;
68(6):1490-9.
Gorek J, Acaroglu E, Berven S, Yousef A, Puttlitz CM. Constructs incorporating
intralaminar C2 screws provide rigid stability for atlantoaxial fixation. Spine
2005;30:1513-8.
Jea A, Sheth RN, Vanni S, Green BA, Levi AD. Modification of Wright’s technique
for placement of bilateral crossing C2 translaminar screws: technical note. Spine
J 2008;8:656-60.
Lehman RA, Sasso RC, Helgeson MD, et al. Accuracy of intraoperative plain
radiographs to detect violations of intralaminar screws placed into the C2
vertebrae—a reliability study. Spine 2007;32:3036-40.
Leonard JR, Wright NM. Pediatric atlantoaxial fixation with bilateral, crossing C-2
translaminar screws. Technical note. J Neurosurg 2006;104:59-63.
Menendez JA, Wright NM. Techniques of posterior C1-C2 stabilization.
Neurosurgery 2007;60:103-11.
Parker SL, McGirt MJ, Garces-Ambrossi GL, et al. Translaminar versus pedicle screw
fixation of C2: comparison of surgical morbidity and accuracy of 313 consecutive
screws. Neurosurgery 2009;64:343-8; discussion 348-9.
Reddy C, Ingalhalikar AV, Channon S, et al. In vitro biomechanical comparison of
transpedicular versus translaminar C-2 screw fixation in C2-3 instrumentation.
J Neurosurg Spine 2007;7:414-8.
Wang MY. C2 crossing laminar screws: cadaveric morphometric analysis.
Neurosurgery 2006;59:84-7.
Wang MY. Cervical crossing laminar screws: early clinical results and complications.
Neurosurgery 2007;61:311-5.
Wright NM. Posterior C2 fixation using bilateral, crossing C2 laminar screws: case
series and technical note. J Spinal Disord Tech 2004;17:158-62.
Wright NM. Translaminar rigid screw fixation of the axis. J Neurosurg Spine
2005;3:409-14.
P R O C ED U R E 1 1
Posterior C1-C2
Fusion: Harms and
Magerl Techniques
Steven K. Leckie, Joseph M. Zavatsky, Ishaq Syed,
and Joon Y. Lee
Technique A: Posterior C1-2
Polyaxial Screw and Rod Fixation
(Harms Technique) (Harms and
Melcher, 2001)
Indications
n
Atlantoaxial instability resulting from
• Fractures of the odontoid (type II and III) (Figures 11-1 and 11-2)
• Adjacent fractures of C1 and C2
• Rotatory subluxation
• Rheumatoid arthritis
• Os odontoideum
• Postodontoidectomy without basilar invagination
• Congenital malformation (i.e., Klippel-Feil)
• Malignancy
n
Nonunions
• Odontoid nonunion (type II and III)
• Failed posterior C1-C2 fusion
• C1-2 osteoarthritis
FIGURE 11-1 FIGURE 11-2
78 Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques
I N D I CAT I O NS P E A R L S
• Similar risk of vertebral artery injury
compared to transarticular screws
(Yoshida et al, 2006).
• Does not require the use of sublaminar
wires, thus decreasing the risk of neural
injury.
• Screws can assist in the C1-2 reduction.
• Integrity of the posterior arch of C1 is
not required.
• Can be incorporated as part of fusions
to the occiput and/or the subaxial
spine.
Examination/Imaging
n
Neurologic and musculoskeletal examination.
n
Preoperative imaging should include plain radiographs (Figure 11-3, A), com-
puted tomography (CT) (Figure 11-3, B), CT angiography, and magnetic resonance imaging (MRI) (Figure 11-3, C ) of the cervical spine.
• Radiographs should include anteroposterior (AP), lateral, and open mouth.
Combined lateral mass displacement in excess of 7 mm or an atlantodens
interval (ADI) greater than 3 mm suggests transverse ligament disruption.
• A CT scan with axial, sagittal, and coronal thin-cut (1-mm) reconstruction
images through the upper cervical spine is an important part of preoperative
planning. First, it provides accurate detail of the bony anatomy (associated
ligamentous injury are often found on MRI). Second, it delineates the position
of the foramen transversarium through which the vertebral artery runs. Third,
FIGURE 11-3, A-C
A
Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques 79
I N D I CAT I O NS P I T F A L L S
• Contraindicated for
• Comminuted fractures of the lateral
mass of C1 or pedicle of C2.
• A large C2 transverse foramen
obstructing the pedicle of C2.
• Anatomic limitations of the lateral mass
of C1 could prevent the use of a
3.5-mm screw (Tan et al, 2003)
• Potential risk of irritation of the C2
ganglion causing occipital neuralgia
it allows measurement of the length of the screws that will be utilized in the
C1 lateral mass and C2 pars.
• Approximately 20% of patients requiring atlantoaxial fusion show anatomic
variations in the path of the vertebral artery and osseous anatomy that would
preclude screw placement (Jun, 1998; Madawi et al, 1997). In addition to
evaluating vertebral artery dominance, CT angiography can delineate the
spatial relationship of the vertebral artery relative to the C1 lateral mass and
C2 pars.
B
FIGURE 11-3, cont'd Continued
80 Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques
E X A M IN AT I ON / I M A GI N G
P E A R LS
• Unless specifically indicated, the authors
do not routinely use MRA to evaluate
the vertebral artery anatomy because of
its inability to define the spatial
relationship between the artery and
surrounding bony architecture.
C
FIGURE 11-3, cont'd
T R E A T M E N T OP T I O N S
• Techniques for posterior C1-C2 fusion
include
• Posterior C1-2 polyaxial screw and
rod fixation (Harms technique)
• C2 translaminar screws
• C1-2 transarticular facet screws
(Magerl technique)
• Gallie “bone block” graft placed
posteriorly between the arches of C1
and C2 secured with sublaminar wire
• Brooks “wedge” bone graft secured
to the posterior laminae with
sublaminar wire
• Halifax interlaminar clamp
• MRI allows enhanced visualization of any soft tissue injuries, including
injury to the transverse atlantal ligament, as well as visualization of the
spinal cord.
◆
Odontoid fractures with transverse atlantal ligament injury can be addressed
with a posterior approach.
◆
MRI is also useful in rheumatoid patients to give a more accurate assess-
ment of the space available for the cord, which can be underestimated in
patients with soft tissue pannus that can be a source of cord compression
not visualized on CT or a radiograph.
n
Noninvasive magnetic resonance angiography (MRA) can be utilized to evaluate
vertebral artery injury, patency, and/or dominance (in lieu of CT angiography
that requires administration of dye contrast).
Surgical Anatomy
n
The posterior arch of C1 and the C1-2 facet joint are key anatomic landmarks
for the placement of C1 lateral mass screws. The dorsal root ganglion of C2 lies
just posterior to the starting point of the C1 screw and must be gently retracted
caudally for adequate exposure (Figure 11-4, A). The starting point for the C1
screw is at the midpoint of the inferior portion of the C1 lateral mass at its
junction with the posterior arch. The more superior and medial trajectory of the
screws, when compared with transarticular screws, decreases the risk of vertebral artery injury (Figure 11-4, B and C )
n
The ponticulus posticus or congenital arcuate foramen is a common bony
anomaly of the atlas (Young et al, 2005) (Figure 11-4, D). It is a bony arch on
the cephalad aspect of the C1 lamina that contains the vertebral artery. If
present, it can easily be confused with the lamina of C1 and must be identified
during the posterior dissection and placement of C1 lateral mass screws to
prevent vertebral artery injury.
Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques 81
A
C
FIGURE 11-4, A-D
P O S I TI O N I N G PE A R L S
• An open-mouth view is obtained by
placing an appropriate-size roll of sterile
gauze in the patient’s mouth to
facilitate a clear open-mouth view.
• In very osteopenic bone, inverse
(negative) radiologic images can be
utilized for better bony visualization.
• On the lateral C-arm image, the
posterior occiput should be flexed off
the posterior arch of C1 to facilitate
screw placement at C1.
P O S I TI O N I N G EQ U I P M EN T
• C-arm fluoroscopic radiograph should
be positioned at the head of the
operating table.
• Mayfield headholder
• Bolsters or a four-poster frame
D
Positioning
n
After an awake fiberoptic nasotracheal intubation is performed, a nasogastric
tube is inserted for intraoperative gastric drainage.
n
If the patient is immobilized in a halo vest preoperatively, either the halo can
be left in place and attached directly to the Mayfield headholder using an
adapter or it can be removed. If the halo ring is removed, the patient is placed
in Mayfield tongs and a hard cervical collar before being turned into the prone
position. In coordination with anesthesia, the surgeon stands at the head of the
hospital bed and stabilizes the patient’s neck. The patient is cautiously turned
in the prone position on the operating table with the torso on bolsters or a
four-poster frame. The Mayfield tongs or the halo ring is fixed to the operating
table using a Mayfield headholder with the neck in a neutral position (Figure
11-5, A and B).
n
All bony prominences are well padded, and the patient’s arms are secured by
their side using a folded sheet that is tucked beneath them.
n
Using fluoroscopic C-arm, proper alignment of the atlantoaxial bony structures
is confirmed with the radiograph centered at C1-2. The lateral fluoroscopic
image must not be oblique at C1-2; otherwise, malpositioning of the drill can
result in erroneous screw placement (Figure 11-6).
• The appropriate C1 and C2 radiographic landmarks are visualized. The lateral
wall of the C1 lateral mass and medial wall of the C2 pars interarticularis are
important landmarks defined on the open-mouth view. The C-arm gantry is
canted in the cephalad or caudad direction until all bony landmarks are clearly
identified.
82 Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques
B
A
FIGURE 11-5, A-B
FIGURE 11-6
n
If necessary, adjustments can be made while the patient is in the Mayfield
headholder, to obtain reduction. Reduction should be confirmed on fluoroscopic
radiograph. If possible, extreme positions of the neck should be avoided.
n
Somatosensory evoked potential (SSEP) and transcranial motor evoked potential
(MEP) monitoring are neurophysiologic spinal cord monitoring methods that can
be utilized intraoperatively. Baseline readings can be obtained before and after
placing the patient in the prone position.
P O RTA L S / E X P O S U R ES
P E A R LS
• The C2 spinous process is an easily
identifiable landmark. The C2 spinous
process sits more posterior relative to
the arch of C1 and can be used to
orient your dissection.
• The cephalad orientation of the C2 pars
necessitates exposure down to C3. This
facilitates the placement of the C2 pars
screw.
• The lateral dissection should not be
carried past the lateral border of the
C1-2 articulation to avoid iatrogenic
injury of the vertebral artery.
P O RTA L S / E X P O S U R ES
P I T F A L L S
• In the setting of a C1 fracture, when
palpating the bony landmarks for
dissection, take care to avoid pushing
posterior fragments into the cord.
Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques 83
Portals/Exposures
n
An electric razor is used to remove all hair from the patient’s occipital, suboc-
cipital, and neck regions. If a definitive fusion is being performed, the posterior
iliac crest is also shaved for bone graft harvesting.
n
The skin surfaces of the neck and posterior iliac crest are prepared and draped
in a sterile fashion.
n
Using the inion of the occiput cranially, and the protuberance of the vertebral
prominens caudally, the midline is identified and marked from the occiput to
C3-4 with a sterile marker.
n
The subcutaneous skin of the planned skin incision can be infiltrated with 0.5%
lidocaine containing epinephrine diluted 1:100,000.
n
A 10-blade scalpel is used to sharply incise the skin in the midline from the
occiput to C3-4.
n
Bovie electrocautery is used for the subcutaneous dissection down to and
through the underlying ligamentum nuchae. Midline dissection of the nuchal
ligament provides a relatively avascular dissection and decreases the risk of
injury to the greater and third occipital nerves. Self-retaining retractors are
inserted for adequate visualization.
n
At the cephalad end of the incision, a 1.5-cm fascial cuff of trapezius, along the
nuchal ridge, can be elevated to facilitate lateral exposure of C1-2, but this is
not usually necessary. Subperiosteal dissection of the paraspinous muscular
insertions from the suboccipital bone is completed.
n
The midline tubercle of the arch of C1 and the larger spinous process of C2 are
used as palpable landmarks during dissection. Starting at the midline, the periosteum of C1 and the tip of the spinous processes of C2 and C3 are incised
sharply.
n
Careful subperiosteal dissection is continued from C3 to C1, starting in the
midline and proceeding laterally. Periosteal elevators can facilitate the subperiosteal dissection of the paraspinous muscles as they are swept laterally. The
lateral masses and pedicles of C3 and C2 are exposed with care not to disturb
the C2-3 facet capsules.
n
The C1-2 joint can be exposed with dissection over the superior surface of the
C2 pars. Significant venous bleeding can be encountered with dissection around
the venous plexus of the C2 nerve. This can effectively be controlled with bipolar
electrocautery, thrombin-soaked Gelfoam, cotton pledgets, and various commercial gelatin thrombin preparations.
n
To decrease the risk of injuring the vertebral artery on the cephalic surface of
the C1 lamina, identify the lamina and follow the caudal edge of the posterior
arch during exposure of C1. If present, the ponticulus posticus or congenital
arcuate foramen must be identified during the posterior dissection, because it
can easily be confused with the lamina of C1 (Young et al, 2005).
n
The dissection is complete with exposure of the suboccipital rim of the foramen
magnum.
84 Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques
FIGURE 11-7 FIGURE 11-8
Procedure
Step 1
n
The dorsal root ganglion of C2 must be carefully retracted caudally to expose
the starting point for the C1 lateral mass screw. The starting point for the C1
screw is at the midpoint of the inferior portion of the C1 lateral mass at its
junction with the posterior arch.
n
C-arm imaging can be used to verify the midpoint and trajectory of the C1 lateral
mass screw.
n
A 2-mm high-speed burr is used to mark the starting point for the drill and
prevent the drill from walking off the convex surface of the posterior inferior
lateral mass of C1.
n
With the tip of the drill pointing anterior through the lateral mass of C1, a 2-mm
drill bit is used to drill a bicortical pilot hole in a straight to slightly convergent
trajectory in the anteroposterior plane, and parallel to the posterior arch of C1
in the sagittal plane (Seal et al, 2009). Drill position is confirmed on AP and
lateral C-arm fluoroscopic images (Figures 11-7 and 11-8).
n
A depth gauge can be used to confirm the measurement obtained from the
preoperative CT scan of the appropriate length screw and can be checked on
lateral fluoroscopic radiograph.
n
The drill hole is tapped and the 3.5-mm polyaxial screw is placed into the C1
lateral mass. An 8-mm unthreaded portion of the C1 polyaxial screw sits proud
above the bony surface of the lateral mass, allowing the polyaxial portion of
the screw to sit above the posterior arch of C1 so that the rod can be linked to
the C2 screw head. The proud segment of the screw is unthreaded and theoretically minimizes the risk of irritation of the greater occipital nerve.
n
Step 1 is repeated for the contralateral C1 lateral mass.
Procedure 11 | Posterior C1-C2 Fusion: Harms and Magerl Techniques 85
FIGURE 11-9
S T E P 1 P EA R L S
• Critical landmarks for the accurate
placement of C1 lateral mass screws
• The C1-2 joint
• The midpoint and lateral wall of
the C1 lateral mass (Figures 11-9 and
11-10)
• The ponticulus posticus or congenital
arcuate foramen can be confused with
the C1 lamina and must be identified
to prevent vertebral artery injury during
the posterior dissection and placement
of C1 lateral mass screws (Young et al,
2005).
• A superior and slightly medial trajectory
(0 to 10 degrees) of the C1 lateral mass
screw decreases the risk of vertebral
artery injury (Figure 11-11).
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
• Penfield elevators
• Blunt pedicle probe
• High-speed burr
• Pneumatic drill and 2-mm drill bit
FIGURE 11-10
FIGURE 11-11