Introduction
Traumatic spondylolisthesis of the second cervical vertebra is considered as hangman’s
fracture and it is accompanied by variable disruption of C2–C3 intervertebral disc,
ligamentous complex resulting in a spectrum of deformity in the cervical spine. It
contributes nearly 4 to 7% of all cervical spine fractures.[1]
[2] Hangman’s fracture involves complex biomechanics due to cervical hyperextension
with axial loading which forces the skull, atlas vertebra, and the body of C2 moving
as one unit, while the posterior elements of C2 along with the posterior elements
of third cervical vertebra moving as another unit.[3] The opinions regarding management of unstable hangman’s fracture are divided. Occipito
cervical fusion is usually performed with attendant loss of motion.[4] C1–C2 fixation may also be performed but also results in loss of significant mobility
at the C1–C2 joint.[5] Reconstitution of the C2 pedicle with C2 pedicle screws with additional fixation
of C3 is the most direct method to reduce and fix these fractures. Putting C2 pedicle
screws especially in this setting is a challenge and three-dimensional (3D) computed
tomography (CT)-based intraoperative navigation (O-arm) provides precise information
for accurate screw placement.
Material and Methods
In the present study, we included 18 patients who were operated by two surgeons where
C2 pedicle screw insertion with variable extent of subaxial cervical lateral mass
fixation was performed from September 2011 to August 2018. Patients’ demographic profile,
mechanism of injury, associated injuries, preoperative and postoperative neurologic
status, radiological parameters of fracture morphology, intraoperative events, postoperative
complications, bony fusion, and any progressive cervical spine deformity were assessed.
Preoperative and postoperative neurologic assessments were done by the operating surgeon
and each patient was assigned American Spine Injury Association (ASIA) score. Preoperative
and postoperative C2–C3 displacement and angulation were measured using the picture
archiving and communication system (Centricity, GE Healthcare).
Radiological diagnosis was done with 3D CT scans and fracture morphology was assessed
to measure two morphological parameters—C2–C3 displacement and C2–C3 angulation in
all cases. C2–C3 displacement was measured as the distance between parallel lines
drawn through the midpoints of C2 and C3 at the level of the intervertebral disc in
the mid-sagittal section. C2–C3 angulation was defined as the angle formed by lines
drawn along the inferior endplate of C2 and the inferior endplate of C3.
Magnetic resonance imaging (MRI) was performed in all patients to assess the integrity
of intervertebral discs, ligamentous complex, extradural thecal sac compression, spinal
cord signal changes/contusions, etc. Any intrinsic spinal cord injury detected on
MRI is particularly important for prognosticating neurologic recovery after the surgery.
Surgical procedure involved two essential aspects—(1) placement of C2 pedicle screws
and C3 lateral mass screws on both the sides and (2) exclusion of C1 from the construct.
Additional involvement of lower cervical vertebrae in the implants construct was done
in cases with prominent C2–C3 angulation resulting in subaxial cervical kyphosis.
ASIA scores were reassessed by the operating surgeon in the immediate postoperative
period to check for any new neurologic deficits. Postoperative CT scan was obtained
in follow-up before the patient is discharged. Postoperative scans were assessed for
(1) accuracy of screw placement, (2) reduction of the fracture displacement, (3) C2–C3
angulation, and (4) C2–C3 displacement. Accuracy of the screw insertion was assessed
on 3D CT scan images and were categorized as per modified classification of Gertzbein
and Robbins: grade 1 (screw completely within the pedicle), grade 2 (< 50% of the
screw diameter outside the pedicle), and grade 3 (> 50% of the screw diameter outside
the pedicle). The criteria used for the successful fusion included formation of callus
across the fracture. All patients were followed up clinically and radiologically in
the postoperative period at regular intervals on outpatient basis or telephonically.
Surgical Procedure
Informed and written consent for the surgical procedure was taken. All patients were
operated in prone position on Allen spine table (Allen Medical Systems, A Hill-Rom
Company). Skull traction was applied after induction of the patient 1 cm anterior
to the tragus just below the superior temporal line and a weight of 3 to 4 kg was
used for traction. Iliac crest was prepared in all cases. O-arm intraoperative imaging
system (Medtronic, Inc.) with intraoperative CT scan and 3D navigation system was
used in all the patients. Vertical midline incision from C1 to C5 spinous process
was made, keeping in mind not to expose the facet capsules of the levels not planned
for fusion. A dynamic reference array was applied on the C1 posterior arch, and an
intraoperative CT scan using O-arm with center at C2 level was performed. The gantry
of O-arm rotates by 360 degrees, and the scanning and transfer of the images takes
only few seconds. The fracture site was defined by dissecting around the upper border
of the C2 pedicle. After registration with the help of 3D navigation, the entry point
and trajectory of C2 pedicle screws on both sides were defined. Kirschner wire (K-wire)
was then gradually drilled under guidance. When the K-wire tip reached the fracture
site, an intraoperative CT scan was repeated to confirm the position and the direction
of K-wire, and once the correct position was confirmed, the C2 lamina was compressed,
the K-wire was advanced, and its position was confirmed again with CT scan. The pedicle
was then tapped on both the sides, and before inserting the pedicle screws on both
sides, C2 lamina was compressed anteriorly so that there was no or minimal space between
the two fractured fragments and the C2 pedicle screws were then inserted. After this,
lateral mass screws were inserted in C3 and/or C4 and/or C5, depending upon the severity
of the disco-ligamentous injury, listhesis, lateral mass fracture, and the need to
correct the angulation. C5 lateral mass was only used when there was fracture of C4.
After screw placement, rods were inserted on both sides, the skull traction weight
removed, and the screws were tightened completing the screw-rod construct. Bone graft
harvested from iliac crest was placed after decortication. Patients were advised to
wear hard cervical collar for 12 weeks postoperatively.
Results
In total, 18 patients with unstable hangman’s fracture (Levine and Edwards classification)
underwent posterior cervical fixation where C2 pedicle screws were inserted as a part
of implant construct. C1 vertebra (atlas) was excluded in all the cases. There were
16 male and 2 female patients ([Table 1]). Sixteen patients presented early after injury, whereas two patients presented
after a long period after injury with persisting neck pain after trauma. Road traffic
accident was the most common mode of injury and was the cause in 11, followed by fall
from height in 6 patients, and fall of heavy object on the neck in 1 patient. Associated
vertebral fractures were seen in eight patients, five of these patients had an associated
C1 fracture only, two patients had associated C1 arch and C3 lamina fracture, and
one patient had an associated C6–C7 anterolisthesis. Associated right upper trunk
brachial plexus injury was present in one patient. The patient underwent spinal accessory
to suprascapular neurotization and Oberlin’s transfer (ulnar nerve fascicle to musculocutaneous
nerve) after few months of the spine surgery.
Table 1
Clinical, radiological, neurologic, operative, and follow-up details of the patients
included in this series
Serial no.
|
Age/
Sex
|
Mode of
injury
|
CT findings
|
Displacement
(mm),
angulation (degrees)
preoperative
|
Displacement
(mm),
Angulation (degrees)
postoperative
|
Breach
|
ASIA (preop)
|
ASIA (postop)
|
Procedure
done
|
Operative
time (min)
|
Intraoperative
blood
loss (mL)
|
Follow-up
duration
|
Follow-up
CT fusion
|
Abbreviations: ASIA, American Spine Injury Association; CT, computed tomography; F,
female; FFH, fall from height; LMS, lateral mass screw; M, male; RTA, road traffic
accident.
|
1
|
25/M
|
RTA
|
II
|
6 mm, 11.5
|
2.64 mm,–5
|
No
|
E
|
E
|
C2 P, C3–4 LMS
|
435
|
600
|
42
|
Yes
|
2
|
60/M
|
FFH
|
II
|
6.3 mm, 20
|
4.57 mm,14
|
No
|
E
|
E
|
C2 P, C3 LMS
|
195
|
300
|
50
|
Yes
|
3
|
17/M
|
RTA
|
II
|
3.5 mm, 7
|
1 mm, 3
|
Rt C2P,
grade 2 medial
|
E
|
E
|
C2 P, C3 P
|
260
|
300
|
55
|
Yes
|
4
|
50/M
|
Others
|
II
|
3.5 mm,–30
|
2.6 mm, 3
|
No
|
B
|
C
|
C2 P, C3–4 LMS
|
315
|
400
|
21
|
Yes
|
5
|
81/M
|
FFH
|
II
|
4.1 mm, 13
|
1 mm, 3
|
No
|
E
|
E
|
C2 P, C3–4 LMS
|
300
|
250
|
36
|
Yes
|
6
|
22/M
|
RTA
|
II
|
3.2 mm, 6
|
0 mm, 2
|
No
|
E
|
E
|
C2 P, C3–4 LMS
|
360
|
1,500
|
48
|
Yes
|
7
|
36/M
|
RTA
|
IIa
|
2 mm, 13
|
2 mm,3.5
|
No
|
E
|
E
|
C2 P, C3–4 LMS
|
280
|
400
|
49
|
Yes
|
8
|
22/M
|
RTA
|
IIa
|
2.8 mm, 12
|
2 mm, 4.0
|
No
|
D
|
E
|
C2 P, C3 LMS +
C6 corpectomy, iliac bone tricortical graft, and plating
|
225 + 150
|
600
|
58
|
Yes
|
9
|
25/F
|
RTA
|
IIa
|
2.9 mm, 24
|
2 mm, 3.5
|
No
|
A
|
D
|
C2 P, C3–4 LMS
|
345
|
400
|
56
|
Yes
|
10
|
28/M
|
RTA
|
II
|
9 mm, 3
|
3 mm,–8.5
|
No
|
E
|
E
|
C2P, C3 LMS
|
225
|
300
|
36
|
Yes
|
11
|
19/M
|
RTA
|
II
|
4.6 mm, 6
|
2 mm, 2.5
|
No
|
E
|
E
|
C2 P, C3 LMS
|
195
|
300
|
80
|
Yes
|
12
|
32/M
|
FFH
|
II
|
3 mm, 10
|
1 mm, 3.8
|
No
|
E
|
E
|
C2 P
|
180
|
500
|
62
|
Yes
|
13
|
36/F
|
FFH
|
II
|
3.5 mm, 2
|
0.5 mm, 1
|
Rt C2P,
grade 1 medial
|
E
|
E
|
C2P,C3–4 LMS
|
240
|
500
|
24
|
Yes
|
14
|
25/M
|
FFH
|
II
|
4 mm, 7
|
1 mm, 3
|
No
|
E
|
E
|
C2P, C3 LMS
|
195
|
250
|
32
|
Yes
|
15
|
37/M
|
FFH
|
II
|
3 mm, 4
|
2 mm, 2
|
No
|
C
|
E
|
C2P,C3–4-5 LMS
|
360
|
1000
|
31
|
Yes
|
16
|
28/M
|
RTA
|
II
|
4 mm, 5
|
2 mm, 3
|
No
|
E
|
E
|
C2P, C3LMS
|
255
|
350
|
18
|
Yes
|
17
|
31/M
|
RTA
|
II
|
9 mm, 6
|
2 mm, 3
|
No
|
E
|
E
|
C2, 3, 4P
|
260
|
400
|
14
|
Yes
|
18
|
42/M
|
RTA
|
II
|
6 mm, 5
|
2.5 mm, 2
|
No
|
E
|
E
|
C2P-3–4 LMS
|
310
|
400
|
11
|
Yes
|
All the patients complained of neck pain with restriction of neck movement. Thirteen
patients were ASIA E. The other five patients had neurologic deficits: of these, one
patient was ASIA A, two patients were ASIA B, and one patient each were ASIA C and
ASIA D. Injury to the C2–C3 disc along with disco-ligamentous complex injury was seen
on MRI in all the patients. All patients were operated as soon as possible, once they
presented to our center. One patient had preoperative respiratory arrest but was resuscitated
immediately and was operated after hemodynamic stabilization. Intraoperative period
was uneventful in all the patients.
A total of 92 screws were inserted: 36 screws in C2 pedicle, 34 in C3 lateral mass,
20 in C4 lateral mass, and 2 in C5 lateral mass. Of these 92 screws, 36 C2 pedicle
screws were inserted under O-arm guidance. The mean preoperative C2–C3 displacement
was 4.5 ± 2.1 mm, and the mean postoperative displacement was 1.8 ± 1.1 mm with a
mean reduction of 2.7 ± 1.4 mm. The mean preoperative C2–C3 angulation was 10.2 ±
7.6 degrees and the postoperative angulation was 2.52 ± 4.62 degrees with a mean reduction
of 8.2 ± 11.6 degrees. Screw malplacement was seen in two C2 pedicle screws (2/36,
5.5%). All C2 pedicle screw breaches were grade 2.
One patient with associated with C6–C7 anterolisthesis underwent C6 corpectomy and
iliac bone tricortical graft placement with anterior cervical plate. In the postoperative
period, there was no new-onset neurologic deficit in any of the patients. All patients
who had preoperative neurologic deficits (5/18) improved after surgery. The patient
with ASIA A improved to ASIA D. Of the two patients with ASIA B, one improved to ASIA
C and the other one to ASIA D. Two patients with ASIA C and D improved to ASIA E.
Postoperative CT scan revealed good reduction in 17 cases and satisfactory reduction
in 1 case.
The mean follow-up period was 41.5 + 16.8 months. The average duration of hospital
stay was 13.6 ± 2.8 days ([Table 2]). Bony fusion was achieved in all cases after surgery, as demonstrated on CT scans
done at 4 to 6 months’ follow-up. Rotation was preserved at C1–C2 joint in all cases
as C1 was excluded in all of them. No complications related to the implant construct
were noted.
Table 2
Details of included patients and perioperative parameters
Serial no.
|
Characteristic
|
Value
|
1
|
Mean age (y)
|
34.3 ± 16.8
|
2
|
Sex ratio (female/male)
|
1:8
|
3
|
Fracture type
|
|
II
|
15
|
IIa
|
03
|
III
|
Nil
|
4
|
Mean operative time (min)
|
280.7 ± 70.4
|
5
|
Mean operative blood loss (mL)
|
488.1 ± 309
|
6
|
Mean hospitalization (d)
|
13.6 ± 2.8
|
7
|
Mean follow-up period (mo)
|
41.5 + 16.8
|
One case operated (patient number 4, [Table 1]) in this series is presented for illustration.
This patient sustained injury to the neck due to fall of object on his neck. He came
to us few days after injury with ASIA score B. MRI revealed cord signal change at
C2 with anterolisthesis and retroangulation of C2 body ([Fig. 1]). His CT scan revealed type II hangman’s fracture with 3-point fracture of C1 ring,
anteriorly on the left side ([Fig. 2A]) and bilateral posteriorly ([Fig. 2B]). He was operated under intraoperative CT guidance (O-arm), bilateral K-wires were
put in C2 pedicles under image guidance, CT scan was done to confirm trajectory ([Fig. 3A]
[B]), and tapping was done. After tapping, bilateral pedicle screws were put. Lateral
mass screws were put in both C3 and C4. As retrolisthesis is not corrected by traction,
slight distraction was done between C2 and C3 after putting rods on both sides. Patient
improved to ASIA C and follow-up CT revealed good healing of fractures of both C1
([Fig. 4A]
[B]) and C2.
Fig. 1 Magnetic resonance imaging of the illustrative case showing cord signal change at
C2–C3 disc space level with anterolisthesis and retroangulation of C2 body.
Fig. 2 Preoperative computed tomography scan show (A) 3-point fracture of C1 ring, anteriorly on the left side and (B) bilateral posteriorly and fracture of bilateral C2 pars.
Fig. 3 Intraoperative computed tomography scans show (A) right-sided C2 pedicle screw in the axial, coronal, and sagittal planes, and (B) left-sided C2 pedicle screw in the axial, coronal, and sagittal planes.
Fig. 4 Follow-up computed tomography scan revealed good healing (arrows) of fractures of
both (A) C1 and (B) C2.
Discussion
Schneider et al[6] in 1965 coined the term hangman’s fracture due to its similarity to the fracture
described in the autopsy report of a judicial hanging by Wood Jones and is the most
frequent upper cervical fracture after the fracture of odontoid process of C2. To
standardize the management of hangman’s fractures, Levine and Edwards proposed a classification
system modifying the one described by Effendi et al.[7]
[8] Presently, there is no consensus on the best management of hangman’s fracture and
it remains controversial. It includes both nonoperative and operative protocols.[9]
[10]
[11]
Type I fractures are considered as stable and are usually managed nonsurgically with
cervical hard collar immobilization/rigid orthosis/prolonged traction for 8 to 14
weeks. There are higher rates of pseudoarthrosis that may cause persistent cervical
pain, anterior dislocation, kyphosis, and pin-related problems, such as skull fracture,
scalp hematoma, and pin site infection.
Fusion rates after conservative management have been reported to be 60% in type II,
45% in type IIA, and 35% in type III.[12] In regions with hot and humid climate, as in tropical countries, halo immobilization
and prolonged traction are not tolerated well by patients. In many cases, hangman
fracture is associated with other injuries, which may conflict with rigid immobilization.
Considering the disco-ligamentous injury, the dislocation and angulations of fracture,
the desire to shorten recovery, and the high nonunion rates, many authors prefer surgery
for unstable hangman fracture.[12]
[13]
[14]
[15]
[16]
[17]
[18] We operated on all type II, IIA, and III fractures directly with no trial of conservative
treatment.
Type II, IIA, and III fractures are classified as unstable. Treatment goal in unstable
hangman fracture is to achieve anatomical reduction, maintain alignment, and maintain
the patients’ ability to live an active life without pain or disability and these
objectives can be achieved by internal fixation. In these cases having significant
displacement/angulation and instability, surgical reduction and stabilization by screw-rod
constructs are performed, usually by posterior fusion of the upper cervical vertebrae
or anterior fusion of C2–C3. There are many surgical stabilization techniques described
in the literature through the anterior, posterior, and combined anteroposterior (360-degree
fixation) approaches.[16]
[19]
[20]
[21]
Several anterior approaches, such as the classical anterior cervical discectomy and
fusion, and transoral or extraoral approaches were applied with C2–C3 discectomy and
segmental fixation with bony fusion. Anterior cervical discectomy and fusion addresses
C2–C3 disc herniation and C2–C3 stabilization.[17]
[19]
[20] This approach may be suitable for hangman’s fractures with intervertebral disc injury
with posterior disc herniation and subsequent spinal cord compression or spinal instability.
Anterior approach, however, does not address the posterior fractured part of the C2.
In addition, it may have the disadvantages of approach-related problems; a high anterior
approach risks injury to vital structures, specially the facial and hypoglossal nerves,
branches of the external carotid artery, contents of the carotid sheath, and the superior
laryngeal nerve.
Posterior surgery was previously performed using C1–C3 wire fixation, this technique
requires adjunctive postoperative halo-vest immobilization. But this procedure has
several drawbacks. It carries the risk of intraoperative complications involved in
placing sublaminar wires like dural tears, cord injury, and neurologic deficits. It
also restricts motion at the atlanto-axial joint.[22] Also, it carries the complications associated with halo-vest immobilization as mentioned
earlier.
Direct osteosynthesis by putting pars screws, bridging the fracture line was described
by Leconte[23] and Bristol et al[24] with the advantage of retaining motion at the atlanto-axial joint. However, this
approach does not take care of the C2–C3 disc disruption,[13]
[25] and this may result in repeated dislocations at the fracture site.[26]
[27] It also fails to correct displacement, kyphosis, and loss of disc height.[25]
Several studies reported C2 pars/pedicle screw fixation combined with C3 lateral mass
screw fixation, or C1 lateral mass screws combined with C-3 lateral mass screw fixation.[28] Involvement of C1 in the implants construct is not justified as the pathology lies
at the level of C2–C3 disc, ligaments, and C2 pars interarticularis and it should
be avoided as it will cause loss of rotation at the C1–C2 joint.
Authors highlight the importance and versatility of the C2–C3 posterior fixation using
the C2 pedicle along with variable extent of subaxial lateral mass screw fixation.
This type of fixation provides the maximum biomechanical strength as it is known that
pedicle screws engage all the three spinal columns and thus have maximum pull-out
strength among any possible screw in a particular vertebra. In the biomechanical study
by Duggal et al,[12] posterior C2–C3 screw technique was more effective in the stabilization of the hangman
fracture than anterior cervical plating and C2 pars screw placement. Posterior treatment
is more effective because the construct acts as a tension band against flexion, lateral
bending, and axial rotation.[12]
[29] Compared with the anterior approach, this approach results in better stabilization
with multilevel fixation in unstable hangman’s fractures involving associated cervical
fractures. It provides a stabilizing 3-column spinal fixation.[16]
[29] It also avoids the need for external orthosis such as a halo-vest. The fracture
deformity objectively assessed by the morphological parameters of C2–C3 displacement
and angulation was also corrected, restoring the normal anatomical relations. Any
kyphotic deformity due to fracture at subaxial levels is also corrected by this construct.
Good anatomical reduction along with rigid construct resulted in solid bony fusion
after few months of surgery in all patients.
Putting a screw in the pedicle of axis is particularly challenging in view of its
complex anatomical relations with the vertebral artery with accompanying paravertebral
venous plexus, C2 nerve root, and thecal sac. Conventional techniques described in
the literature are performed under biplanar fluoroscopy and they are based on the
external anatomic landmarks to guide screw insertion but the rate of screw malplacements
are high. Yukawa et al[30] reported a grade 2 and grade 3 screw malplacement rate of 13.1% in 620 cervical
pedicle screw fixations using a fluoroscopy-assisted technique, whereas the malplacement
rate in C2 and C3 was even higher (21.6%).
With the use of continuous fluoroscopy with a two-dimensional (2D) view, potential
for screw malplacement of C2 is still present even in the experienced hands.[16] CT-based navigation may be very useful in avoiding these malplacements and consequent
neurovascular violations. CT-based navigation provide real-time navigation with the
option of planning the most appropriate screw trajectory based on intraoperative CT-based
registration of the exposed bony landmarks. Also, it provides the option of intraoperative
CT after inserting the K-wires and correcting any significant breach/malplacements
in the same surgery. Richter et al[31] reported excellent results of cervical screw placement using CT-based navigation
in a cadaveric study. Tian et al[32] showed good accuracy with grade 2 misplacement of 7.84% and no grade 3 misplacement
with intraoperative 3D fluoroscopy-based navigation; however, this was a C-arm-based
study, with a rotation of 190 degrees as compared with our study in which we have
used O-arm (360-degree rotation). Ito et al[33] reported a misplacement rate of no more than 2 mm in 2.8% of 176 cervical pedicle
screws using Iso-C 3D navigation. In our cases, there were only two grade 2 misplacements
(5.5%) of C2 pedicle screw. In one of these cases, there was some technical issue
with navigation during surgery after the placement of pedicle screw on one side. In
other case, complete alignment was not achieved in intraoperative period.
Intraoperative 3D navigation offers several advantages.[34] With this technique, motion artifacts are avoided as the images are obtained within
the operative room under general anesthesia, with the patient in the desired position.
This is especially important in unstable fractures where preoperative CT scanning
may not reflect the actual intraoperative anatomical relationships. The registration
is automatic and avoids the inaccuracies inherent to the manual registration, which
uses paired-points or surface-matching algorithm. Also, all the scanned vertebral
levels are autoregistered and there is no need to re-register at each vertebral level
individually. It offers superior quality higher-resolution intraoperative 3D images
than those of other intraoperative 3D fluoroscopy systems. The 3D images obtained
using the O-arm have nearly the same quality as those of recent multidetector helical
CT scans. Also, the option of movements allows 2D fluoroscopy views and multiplanar
3D images in any direction (anteroposterior, lateral, and oblique) without much effort.
Preoperatively, once the O-arm is draped in a sterile plastic drape, all moving parts
in the gantry are enclosed, and this system can easily obtain 2D and 3D images as
often as required, while keeping the surgical field sterile. In this regard, the O-arm
has an advantage over existing 3D fluoroscopy, which obtains 3D images by movement
of the C-arm throughout the 190-degree scan over a surgical site. The preparation
time for O-arm-based navigation is shorter than that for existing 3D fluoroscopy-based
navigation systems.[34] The per capita cost, of using O-arm navigation does not change as compared with
other methods of spinal navigation. Nevertheless, the initial cost of the O-arm is
much higher.
In the present series of 18 cases of type II and IIA hangman’s fracture, two neurosurgeons
have operated on all the cases. C2 pedicle and C3 lateral mass screw fixation and
sometimes C2 pedicle and C3–C4 and rarely C5 lateral mass screw fixation were used.
C5 lateral mass screws were inserted when C4 lateral mass was fractured. This technique
comprehensively addresses the detached posterior arch of C2 by reducing the fractured
pedicles or pars and also stabilizes the disco-ligamentous injury of C2 relative to
C3.[14] A rigid orthosis is also avoided after surgery, and rotation at C1–C2 is fully preserved.
C1–C2 rotation preservation is the main advantage of this procedure. The strength
of CT navigation for C2 pedicle screw placement in this setting is that it allows
for safe osteosynthesis of the C2 fracture and avoidance of fusion of the C1–C2 articulation,
which significantly impacts patients’ postoperative neck rotation and quality of life.
The present series has few limitations. It is a small-sized retrospective study. Also,
there is no control group for comparison, such as patients undergoing an anterior
cervical discectomy and fusion or traditional free-hand technique of posterior polyaxial
cervical pedicle screw placement. Another limitation is that the patients were exposed
to significant amount of radiation over a short time period, with each patient undergoing
CT four times from diagnosis to follow-up.
Conclusion
Hangman fracture is bilateral pars interarticularis fracture of axis and involves
significant impact. Posterior cervical fixation including C2 pedicle screws in the
construct is very efficient in reducing the fracture/dislocation. Pedicle screw insertion
in C2 is challenging due to the presence of surrounding neurovascular structures but
it can be put with precision under O-arm-guided navigation, and position of screws
can be confirmed by intraoperative CT scan. Patients can be operated and mobilized
early with preservation of motion at the C1–C2 joint. Excellent anatomical reduction
in all cases could be achieved as established by the improvement in morphological
parameters of fracture. This series using O-arm in unstable hangman fracture demonstrates
that intraoperative O-arm-based navigation is a safe, accurate, and effective tool
for screw placement in patients with unstable hangman fracture.
Note
No funds were received in support of this work. No relevant financial activities outside
the submitted work.