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2
Anterior Odontoid Resection
Dimos Bouramas and Alan Crockard
Goals of Surgical Treatment
1. Decompression of the neuraxis at the craniovertebral junction.
2. Correction of an anterior irreducible pathologic entity causing signifi-
cant distortion of the cervicomedullary junction.
3. Ventral access to the craniovertebral space-occupying lesions (ex-
tradural and rarely intradural tumors).
Diagnosis
The factors that influence specific anterior odontoid resection are whether
the bony abnormality can be removed or reduced to its normal position according to the etiology of the lesion and the direction and the biomechanics of the compression. It is axiomatic that the spinal cord or neuraxis be
decompressed in the direction from which it is compromised; therefore,
anterior compression at the cervicomedullary area should be accessed ventrally. Decompression must be considered in every case where there is significant compression, prior to craniovertebral fixation or stabilization. The
apparently stable lesion in this area may not be stable under special circumstances (anesthesia, skull traction, decompression, and removal of
some of the compressive material). Thus, it is essential to repeat studies
postoperatively to ascertain if a fixation in addition to decompression is required.
The patients’ presentation varies widely. The symptoms can be nonspecific and difficult to localize. In spite of these variations, however, there
is usually the following:
1. Neck pain, particularly suboccipital pain with reflection behind the
ear (irritation of C2 root), especially when spinal instability superimposes on the compressive signs and symptoms.
2. Deformity (limitation of neck movements, shorter and/or twisted neck,
torticollis).
3. Progressive spastic quadriparesis (stiff legs) with wasting of the small
muscles of the hands. The latter sign should alert the examiner as to
the possibility of craniovertebral junction pathology.
4. Lower brainstem signs (slight change in voice, occasional difficulty in
swallowing, or recurrent episodes of aspiration pneumonitis). These
patients with bulbar signs, when asleep, display abnormal respiratory
patterns.
Preoperative Neuroradiologic Investigations
Plain Radiographs of the Craniocervical Area (Flexion and
Extension)
These radiographs are important in assessing every patient with a
craniocervical junction abnormality, abnormal mobility of any joint from
the occiput down to lower subaxial levels, particularly in cases of rheumatoid atlantoaxial subluxation. In addition, calcification, expansion, erosion, or destruction of bony anatomy will be seen.
Computed Tomography (CT; Thin Slice 1.2 mm) and Three-
Dimensional Reconstruction of Images to Visualize the Bone
The value of this diagnostic modality, especially in sagittal reconstruction,
to outline bony abnormalities is very useful. Measurement of atlantoaxial
subluxation and of the canal diameter of the atlas can be easily obtained.
While McGregor’s line was important in the past, we do not use these
measurements now.
Magnetic Resonance Imaging (MRI)
This mode of imaging provides the most exquisite soft tissue detail, including the quality of the cervicomedullary junction (the presence of spinal
cord atrophy preoperatively is a bad prognostic sign). MRI with
gadolinium enhancement and MR angiography are only occasionally used
to outline the vertebral arteries and to ensure that there is a competent
circle of Willis.
Neural Navigation (Fig. 2–1)
Navigational systems use dynamic referencing technology to establish a
computer map between all locations on the preoperative images and the
corresponding anatomic locations in the surgical field. Using the registration probe, the surgeon selects diverse points over the surgical anatomy to
approximate the surgical space surface. These modern navigational systems enable the surgical team to operate with more confidence, speed, and
accuracy, resulting in better surgical efficacy.
Indications: Surgical decompression via transoral odontoidectomy of
the cervicomedullary junction is required in patients with irreducible ventral pathology.
Rheumatoid Arthritis
1. Irreducible atlantoaxial subluxation causing significant neuraxial dis-
tortion.
2. Significant soft tissue mass (the pannus).
3. Translocation of the odontoid peg with extensive lateral mass erosion.
Anterior Bony Decompression
1. Basilar invagination (congenital or acquired due to bone softening con-
ditions).
2. Atlantoaxial subluxation and pseudotumor (Down syndrome, spondy-
loepiphyseal dysplasia, Ehlers-Danlos syndrome, Morquio-Brailsford
disease).
3. Basilar impression, in-folded skull base (Klippel-Feil anomaly, osteo-
genesis imperfecta).
4. Posttraumatic deformities (undetected or untreated odontoid peg frac-
ture).
Ventral Access to Extradural Lesions in the Foramen Magnum
1. Chordomas and chondrosarcomas of the clivus and C1–C2 complex.
2. Metastatic depositions of the C1–C2 complex.
3. Osteoblastomas.
4. Abscesses.
5. Pseudotumors of the transverse ligaments and foreign bodies removal.
Contraindications: Ventral access for pure intradural lesions (e.g., foramen magnum meningiomas). A far lateral approach allows the access
and better visualization of the entire pathology with surrounding anatomic structures.
6. Extradural tumors that do not arise from the midline, but may invade
the clivus and C1–C2 complex, require some dissection from the front
(far lateral approach is more suitable for these cases).
7. Surgery may not be of benefit in long-term bed-bound rheumatoid
patients (Ranawat III B).
Advantages and Disadvantages
1. Midline ventral access to odontoid peg has the advantage that there are
no important vessels or nerves sagittally.
2. Midline clival lesions with extension to the odontoid process or C1–C2
complex distort neurovascular structures around their lateral boundaries.
3. The spinal cord or the medulla is decompressed in the direction from
which it is compromised.
The main disadvantages are visibility,complex retraction of oropharyngeal structures, and the depth at which the surgeon is working (10 to
15 cm) from the dental margin. Surgical pathology in the mouth itself has a
profound effect on the execution of transoral procedures.
Procedure
Preoperative assessment of the oral cavity and its contents is crucial to
success in any transoral procedure: If the maximal interdental opening is
less than 25 mm, then a conventional transoral approach is unlikely to be
successful. In these rare cases the division of the soft palate alone may be
enough for the transoral odontoidectomy to allow exposure of the odontoid peg and foramen magnum, as well as in mild cases of basilar invagination. Division of both the hard and soft palate will be required as a minimum to expose the lower half of the clivus.
Anesthesia
1. A nasotracheal airway is the method most commonly employed in
comparison with orotracheal intubation. Tracheostomy is used now in
쏝15% of cases (patients in whom long-term ventilation problems are
anticipated and in cases of extended maxillotomy). In cases with instability of the craniovertebral junction, fiberoptic nasotracheal intubation is performed on the awake patient.
2. A nasogastric tube is inserted, first to empty the stomach before and
after surgery, as well as to prevent gastric contents from soiling the
pharyngeal wound, and second (after the first 24 hours) to introduce
fluids and alimentation for 5 days, allowing the best chance for healing
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Figure 2–1
(A) Schematic representation of the philosophy of navigational systems, in the approach of the C1–C2 com-
plex. (B) Computed tomography (CT) scan preoperative image, during the intraoperative establishment of
navigational lines, in anterior odontoid resection.
A
B
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2 ANTERIOR ODONTOID RESECTION
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A
Elevate handle of
retractor caudally
B
C
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Figure 2–2
(A) Insertion of the transoral retractor in the final position. (B) Elevation of the handle of the retractor with caudal rotation of the tongue
blade for wider exposure of the C1–C2 complex. (C) The soft palate has
been retracted by the attachment to the transoral retractor. The
pharyngeal incision is held apart by the pharyngeal retractor. Lower
exposure is obtained by tilting up the transoral tongue retractor handle
using a folded sheet.
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A
Figure 2–3
(A) Retraction of the soft palate and inspection of the posterior
pharynx. (B) Creation of the midline incision with center the tubercle
of C1, revealing the target of the operation. (C) Wound closure with two
layers of interrupted sutures.
Visual
field
Visual
field
B
C
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Figure 2–4
Appropriate exposure of craniocervical junction, via
open-door maxillotomy, in patients with congenital
anomalies.
2 ANTERIOR ODONTOID RESECTION
13
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in the area [longer alimentation by percutaneous endoscopic
gastrostomy (PEG)].
3. A wide-bore lumbar drain is inserted before surgery in a potential situation of cerebrospinal fluid (CSF) leakage, although it is unlikely to
occur in simple odontoidectomy (after the CSF escapes, the catheter
may very difficult to insert).
Patient Position
The patient is placed in the three-quarter supine position on the operating
table with the head slightly elevated compared to the feet, and held in the
Mayfield head holder. The lateral tilt facility of the operating table will almost provide this supine position. This position allows blood and washings to drain away from the operative field and lets the surgeon be seated
comfortably for a prolonged period. Placing the head in slight extension
makes the craniovertebral junction more accessible in patients with complex congenital malformations.
Prior to Surgery
1. Bacteriologic swabs should be taken and the sensitivity of any organisms known.
2. The mouth is cleaned with an aqueous cetavlon solution.
3. Antibiotics (cephalosporin and metronidazole) are given and continued for 2 days postoperatively.
4. A 1% hydrocortisone ointment is applied to the mouth, tongue, and
lips for prevention of intraoperative swelling (more effective than systemic steroids), and more is used during the postoperative period.
Operative Steps
Step 1: The transoral retractor is inserted with the tongue blade (suitable
length) pulling the tongue down between the lower teeth and the countertraction applied on the upper alveolar margin (Fig. 2–2A). To obtain exposure lower than the arch of C1, elevating the handle of the retractor of the
chest will rotate the tongue blade caudally and provide this exposure (Fig.
2–2B).
The senior author uses a completely integrated system (Codman and
Shurtleff, Randolph, MA) with instruments of an appropriate length and
sufficient strength for retraction, protection of tissue, and visualization.
In cases of edentulous patients with mandibular resorption, placing
some form of packing under the handle of the tongue blade may help to
prevent slipping of transoral retractor (Fig. 2–2C).
Step 2: The palate is retracted using the palatal retractors, and the poste-
rior pharynx can be inspected. The soft palate is anchored on its nondependent aspect with the curved soft palate retractor itself firmly attached
to the transoral retractor. The other soft palate retractor is used to retract
the nasotracheal and nasogastric tubes out of the operative field into the
dependent tonsillar fauces (Fig. 2–3A).
The surgical anatomic landmark is the tubercle of C1; to it is attached
the anterior longitudinal ligament and the longus colli muscles (infiltrate
with lignocaine and 1:200,000 adrenaline at the tubercle on C1 to dissect
off the pharyngeal tissues from the deeper structures and to provide some
hemostasis).
Step 3: A midline incision (3 cm long) with the center at the tubercle of
C1 is made, and the pharyngeal retractor is the inserted, converting the vertical incision into a hexagonal exposure. The two blades of pharyngeal retractor act as a "ring of steel" around the area in which the surgery is being
carried out, preventing damage from instrument slippage during dissection. The longus colli muscles and the anterior longitudinal ligament are
separated with the "cutting" monopolar diathermy, revealing the arch of C1
and the odontoid peg (Fig. 2–3B).
Step 4: An angled, high-speed air drill is used to remove cancellous
bone (3 to 4 mm cutting bur) and a diamond bur is substituted for the cortical bone. With experience and in suitable cases it is possible to remove
only part of the anterior arch of C1 (12 to 15 mm), and to expose sufficiently
the odontoid peg to allow for its removal without dividing the intact ring of
C1 (Fig. 2–3B).
Hyperextension of the craniocervical junction will also aid the exposure of the odontoid peg underneath the arch of C1. If the odontoid peg is
deficient, then the arch of C1 may be felt to be intact to prevent lateral displacement of C1 lateral masses and craniocervical instability.
Step 5: With the arch removed, the odontoid peg is now defined. This is
"hollowed-out" and thinned until transparent. At this stage, using the 1- to
2-mm Kerrison "up-cuts," remove the rest of the thinned-out bone. The
odontoid peg grasping forceps is used to hold the distal fragment and it
pull it out and down, exposing the ligaments if still attached, and allowing
for delivery of the fragment without further bone work at the anterior
aspect of the foramen magnum. Decompression will have been achieved
where the dura can be visualized on each side and where there is brisk pul-
sation of the exposed surface. Soft tissues (tectorial membrane, postlongitudinal ligament, or cruciate ligament with inflammatory degeneration
may embarrass the dural contents) must be removed (Fig. 2–1A).
If there is tumor in the area, the tissue may be removed with the ronge-
urs or the Cavitron ultrasonic surgical aspirator (CUSA).
Bony decompression may continue down to the C2–3 space. At this
level the vertebral artery is at risk of iatrogenic injury (lateral dissection
쏝10 mm from the midline). If the disc space C2–3 is entered, all of the disc
must be removed.
Step 6: Routine wound closure with two layers of interrupted Vicryl sutures, one for the muscle layer (superior constrictor and the pharyngobasilar fascia) and the other for the mucosa (Fig. 2–3C).
Pitfalls
1. Rotatory subluxation at the atlantoaxial joint will distort significantly
the regional anatomy, and the anterior tubercle on the ventrally rotated
lateral mass may be mistaken for the midline anterior tubercle in the
arch of C1, with disastrous consequences to the underlying vertebral
artery.In these cases the disposition of the longus colli muscles and the
anterior longitudinal ligament, however, is constant, and despite rotation or distortion, this will define the anatomic midline.
2. The routine transoral procedure cannot be done on basilar invagina-
tion patients with a stiff neck. They will need a transpalatal open-door
maxillotomy, as will patients with osteogenesis imperfecta (Fig. 2–4).
3. Swelling of the tongue and lip can be avoided by careful placement of
the retractor. If the tongue is caught between the teeth and the retractor,
it will swell.
4. Postoperative instability must be carefully considered, as well as per-
sisting anterior compression. Usually it is failure to decompress the
lateral rather than the midline bone that is the problem.
Complications
1. Dural opening and CSF leakage (particularly in the severely translo-
cated odontoid peg). Dural closure may not be possible, but a multilayer closure with thrombin fibrin glue, dermal fat, fascia, and living
mucosa covers the risk of permanent leakage and meningitis (reinforcement of the healing process with spinal drainage of CSF for 4 to 5
days postoperatively).
2. Infection (diffuse cellulitis, abscess formation, meningitis). Avoid
these problems with careful protection of the mucosal edges during the
operation; obliterate the dead space by two-layer closure of the posterior pharynx and avoidance of the patient’s alimentation until the
wound has healed. Reexploration indicates when there is a large
loculus of pus. The situation usually subsides with the appropriate antibiotics.
3. Bleeding from the vertebral artery (very uncommon) may be controlled
initially by Surgicel and bone wax impacted into the vertebral canal
(possible definitive ligation of the artery). Venous bleeding (large
epidural complex and venous channel communicating with the marginal sinus cephalad) may be controlled by Surgicel and gentle pressure
with a neuro-patty. Delayed hemorrhage may occur from the pharyngeal wall (7 to 10 days postoperatively) and is considered to be a consequence of infection.
4. Nasopharyngeal incompetence (multifactorial problem). If there is
palatal incision, it is more likely to break down and it must be very
carefully sutured initially with a single layer over the hard palate and a
double layer in the soft palate (recovery usually in 2 months). In many
patients with bulbar palsies there may be permanent swallowing problems because the nerves may not recover (postoperative tracheostomy
and gastrostomy for a few months).
Postoperative Care
1. The patient remains in the intensive therapy unit for 48 hours.
2. Great care should be taken with the mouth and the nose; 1% hydrocor-
tisone is applied at the end of the procedure and every 6 hours for the
first 2 days.
3. The airway tube is usually removed after a lateral cervical x-ray has
confirmed the absence of posterior pharyngeal swelling.
4. The nasogastric or pharyngogastric tube kept in place for 5 days.
5. Antiemetics and analgesia (slow infusion of morphine is used meticu-
lously).
6. Antibiotics are administered for 2 days in the absence of bacterial in-
fection.
7. Chest physiotherapy and mobilization are very important.
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Suggested Readings
Crockard HA. Irreducible atlantoaxial subluxation: anterior, lateral and
posterior approaches. In: Garfin SR, Northrup BE, eds. Surgery for Spinal Cord Injuries. New York: Raven Press; 1993:137–149.
Crockard HA, Heilman A, Stevens J. Progressive myelopathy secondary to
odontoid fractures: clinical, radiological and surgical features. J Neurosurg 1993;78:579–586.
Crockard HA, Johnston F. Development of transoral approaches to lesions
of the skull base and craniocervical junction. Neurosurg Q 1993;3:61–
82.
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2 ANTERIOR ODONTOID RESECTION
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Odontoid Fixation
3
Pasquale X. Montesano and Christopher O. Neubuerger
Goals of Surgical Treatment
Anatomic compression osteosynthesis to enhance fracture union; preser-
vation of atlantoaxial motion; early rehabilitation.
Diagnosis
Patients may complain of high cervical or occipital pain through the
greater occipital nerve. Odontoid fractures are identified on plain film
open-mouth anteroposterior (AP) and lateral cervical x-rays as well as
computed tomography (CT) and magnetic resonance imaging (MRI) sagittal and coronal images.
Indications for Surgery
Relative: any Anderson and D’Alonzo type II fracture (Fig. 3–1)
Absolute: Type II fracture with:
1. Greater than 4 mm displacement
2. Greater than 10 degrees of angulation
3. Age greater than 40
4. Posterior displacement
5. Multiple trauma
6. Nonunion
Contraindications
1. Failure of closed reduction
2. Osteopenia
3. Chronic obstructive pulmonary disease (COPD) with chest wall obstruction
4. Cervicothoracic kyphosis
5. Inadequate fragment size
6. Obliquity—anterior caudal to posterior cranial—without buttress
plate
7. Os odontoideum
8. Inability to extend neck—spinal stenosis or limited cervical motion
Advantages of Odontoid Fixation
1. Direct repair of fracture
2. Preservation of C1-C2 motion
3. Restoration of bony spinal anatomy
4. Immediate stability
5. Obviate halo
6. Earlier rehabilitation
7. Anterior approach less traumatic than posterior surgery
8. Can be used with C1 posterior ring fractures
9. Higher union rate
10. Lower cost
Disadvantages
1. Technically demanding.
2. Requires two-plane fluoroscopy and extensive setup.
Procedure
Positioning
1. Place patient in supine position.
2. Perform awake nasotracheal intubation with slight neck extension.
3. Sedate patient.
4. Apply Mayfield three-point head holder with local anesthesia.
5. Attach Mayfield to horizontal U-shaped crossbar for AP imaging
(Fig. 3–2).
6. Position AP/lateral fluoroscopy unit with monitor opposite the operating surgeon.
7. Ensure that anatomic reduction and an unobstructed drill approach
angle has been achieved; image the Kirschner wire (K-wire) superimposed over the screw trajectory.
8. Perform modified wake-up test with patient moving all four extremities.
9. Administer general anesthesia.
10. Place radiolucent bite block for AP imaging.
Exposure
1. Perform a Smith-Robinson retropharyngeal approach at the C5-C6
level.
2. Carry the exposure to the C2-C3 level.
3. Insert Cloward retropharyngeal retractors.
4. Remove the anterosuperior C2-C3 disc and at times anterosuperior C3
end plate with a Kerrison rongeur.
5. Have an assistant manually compress the anteroposterior thoracic
diameter if necessary while placing wires or screws.
Technique: One Screw
1. Insert a 1.5- or 2-mm K-wire in the midline at the anterior caudal margin of the C2 body.
2. Advance the K-wire under C-arm control (AP and lateral images).
3. Gain purchase on the posterior cranial dens tip cortex.
4. Insert a cannulated screw over the K-wire with no threads crossing the
fracture site; or
5. Withdraw the K-wire and insert a lag screw by technique or design
(Fig. 3–3).
Technique: Two Screw
1. Insert a 1.5-mm K-wire 2 to 3 mm off the midline anterior caudal margin of the C2 body.
2. Advance the K-wire cranially parallel to the long axis of the spine
under C-arm control (AP and lateral).
3. Gain purchase on the posterior cranial dens tip cortex.
4. Insert a second wire on the contralateral side with the same technique.
5. Insert the cannulated screws sequentially over the wires with no
threads crossing the fracture site; or
6. Withdraw one wire and insert a lag screw by technique or design; repeat on the contralateral side (Fig. 3–4).
Technique: Oblique Fracture Anterior Caudal to Posterior
Cranial
1. Utilize the one-screw technique.
2. Place a contoured one-third tubular buttress/antiglide plate under the
screw to prevent shearing and anterior displacement at the fracture site
(Fig. 3–5).
Technique: Nonunion
1. Place a small curet across the nonunion site.
2. Debride the anterior fibrous tissue.
3. Insert two screws as described, if possible.
4. Harvest a small amount of anterior C3 body cancellous bone graft and
apply to the site.
Pitfalls
1. Ensure anatomic reduction is achieved before draping.
2. Ensure that the position and chest wall allow the proper drill bit approach angle by utilizing the lateral image with a K-wire superimposed
on the final screw position.
3. Starting the point too anterior on C2 will lead to a bad trajectory and
cutout in soft bone.
4. If the guidewire does not follow intended path, utilize a 2.5-mm small
fragment drill bit.
5. With the cannulated technique, use live C-arm images with screw insertion to ensure the wire is not advanced secondary to binding within
the screw.
6. If the screw will not engage and advance, tap the near cortex only.
7. Ensure compression across the fracture site has been achieved with a
partially threaded screw or overdrilling of the near fragment (Fig. 3–6).
8. Preoperatively plan for the one- or two-screw technique based on the
CT scan; one screw provides adequate biomechanical strength equal to
one-half the intact odontoid, but two screws provide improved rotational control.
9. Place the exact screw length as measured by the K-wire subtraction
technique to avoid inadequate posterior purchase.
10. Osteopenia secondary to patient age or in some nonunions can be evaluated by CT scanning preoperatively.
11. If the patient is large and likely to stress the repair, a solid screw is recommended.
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Figure 3–1
The Anderson and D’Alonzo classification of odontoid fractures.
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3 ODONTOID FIXATION
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A
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18
B
Figure 3–2
(A) Operative position of the patient using the Mayfield head holder. Note the horizontal crossbar. (B) A
close-up view of a different patient with an alternative Mayfield position.
SECTION I THE CERVICAL SPINE
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A
B
C
Figure 3–3
A 28-year-old man injured in a motorcycle accident and sustained a type II odontoid fracture. (A) A 5-mm anterior displacement of the odontoid at the base with slight
angulation. (B) Treatment with a single screw was elected. Note the displacement of the odontoid process has been reduced. Axial (C) and sagittal (D) reconstruction com-
puted tomography sections.
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3 ODONTOID FIXATION
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D
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