n Feature Article
C1-C2 Pedicle Screw Fixation for Treatment
of Old Odontoid Fractures
Lei Qi, MD; Mu Li, MD; Shuai Zhang, MD; Haipeng Si, MD; Jingsong Xue, MD
abstract
Nonunion and C1-C2 instability of odontoid fractures usually result from delayed
diagnosis and inappropriate treatment. However, the available treatment options for
odontoid fractures remain controversial. The authors evaluated the effectiveness of
internal screw fixation via the C1 and C2 pedicle in cases of old odontoid fractures.
This retrospective study included 21 patients with old odontoid fractures (13 men
and 8 women; mean age, 46.5 years; range, 24-69 years). Internal screw fixation via
the C1 and C2 pedicle was performed in all patients. Fracture reduction and C1-C2
fusion were assessed with imaging. The neck pain visual analog scale score and cervical spinal cord functional Japanese Orthopaedic Association score (for those who
had cervical spinal cord injury) were used to evaluate the effectiveness of treatment.
Postoperative complications were recorded. Postoperative imaging showed that the
C1-C2 dislocation was satisfactorily repositioned in all patients. Bone fusion was
observed 1 year after surgery in all patients. No loosening or breaking of internal fixation occurred. The preoperative neck pain visual analog scale score was 5.9±1.5 and
improved significantly to 1.8±0.8 after surgery (P<.001). The Japanese Orthopaedic
Association score in patients with cervical spinal injury (n=14) was 9.2±1.9 and also
significantly improved to 13.8±1.9 at the last follow-up examination (P<.001), with
an average improvement rate of 61.0%. No iatrogenic vertebral artery injury or severe
spinal cord injury occurred. Screw fixation via the C1 and C2 pedicle was found to
be an effective and safe surgical approach for the treatment of old odontoid fractures
with C1-C2 dislocation or instability. [Orthopedics. 2015; 38(2):94-100.]
The authors are from the Department of Spine Surgery, Qilu Hospital, Shandong University, Jinan,
Shandong, China.
The authors have no relevant financial relationships to disclose.
This study was supported by the Independent Innovation Foundation of Shandong University,
IIFSDU (2012TS158), and the development of science and technology plan projects in Shandong province (2010GWZ20207).
Correspondence should be addressed to: Mu Li, MD, Department of Spine Surgery, Qilu Hospital,
Shandong University, No. 107, Wenhua Xi Rd, Jinan, Shandong, 250012, China ([email protected]).
Received: September 23, 2013; Accepted: April 28, 2014.
doi: 10.3928/01477447-20150204-52
94
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n Feature Article
F
racture of the odontoid (also
known as dens fracture) is a common type of cervical spine fracture (approximately 10% to 20% of all
cervical spine fractures).1-3 Most odontoid fractures are unstable, especially the
most common Anderson and D’Alonzo
type II4 fracture that could lead to necrosis and nonunion because of instability
and the poor blood supply of the odontoid process.2,5 Primary clinical symptoms and manifestations of odontoid
fractures are not always typical. Furthermore, patients might be unconscious or
might have other, more severe trauma.
As a result, odontoid fractures can easily be overlooked at first and may therefore evolve into old fractures. Delayed or
improper treatment of odontoid fractures
may result in nonunion or malunion, and
subsequent C1-C2 instability or dislocation can lead to cervical spinal cord
injury, causing upper- and lower-limb
symptoms, breathing difficulty, and other
life-threatening symptoms.6-9
Several surgical strategies for odontoid fractures and C1-C2 instability are
available, including external fixation,
anterior screw fixation, and posterior
C1-C2 fusion. However, the effectiveness of these strategies is controversial.10-13 External fixation of the cervical vertebrae with a halo vest for type
II dens fracture was reported to produce
no more than a 68% union rate.14,15 On
the other hand, anterior screw fixation
can increase surgical success rate up to
100%,16-18 but it may not be applicable
in patients with old fractures, poor repositioning, unfavorable fracture line
direction, dislocation, osteoporosis, and
comminuted fractures.17,19-21 The high
success rate of posterior C1-C2 fusion
makes it applicable in patients with
odontoid fractures with difficult healing
and those associated with C1-C2 instability, but this technique limits motion
of the cervical spine, especially rotation.
Indications for posterior C1-C2 fusion
have been extended by the Harms tech-
FEBRUARY 2015 | Volume 38 • Number 2
nique.22 In recent years, the approach using screw fixation in C1 via the posterior
arch and lateral mass has been developed
to overcome the disadvantages of the
Harms technique, including damage to
the paravertebral venous plexus and the
nerves and blood vessels anterior to the
lateral mass.23-26
Anterior odontoid screw fixation for
the treatment of odontoid fractures is
widely used in clinical practice and offers
a unique advantage: direct fixation without bone graft or external fixation, which
facilitates fracture healing. In addition,
odontoid screw fixation enables preservation of maximal C1 motion.16-18,27 However, the effectiveness of odontoid screw
fixation for old fractures is still controversial.19,28 Anterior odontoid screw fixation
was previously used for the treatment of
old odontoid fractures by Apfelbaum et
al,19 and they reported that 31% patients
had to undergo a secondary posterior surgery because of nonunion.
In the current study, patients had a relatively long disease course, with a maximum of 6 years. It is generally believed
that a longer disease course is associated
with a higher possibility of nonunion
with screw fixation only. In addition, C1
repositioning was unsuccessful in 11 patients before surgery and 6 patients had
posterior dislocation of C1. Therefore,
posterior fixation surgery was selected
for all patients in the current study. The
goal of this study was to investigate the
feasibility, therapeutic effect, and complications of internal screw fixation via
the C1 and C2 pedicle in old odontoid
fractures.
Materials and Methods
Patients
Twenty-one patients (13 men and 8
women; mean age, 46.5 years; range,
24-69 years) with old odontoid fractures
underwent screw fixation via the C1 and
C2 pedicle between October 2006 and
November 2010 in the Spine Surgery
Department of Qilu Hospital of Shan-
dong University, Jinan, China. Causes of
odontoid process injuries included traffic accident (n=10), falling injury (n=5),
crush injury (n=4), and low-energy damage (n=2). Inclusion criteria were: (1)
nonunion of an odontoid fracture with
C1-C2 instability; (2) more than 6 weeks
between fracture and surgery; and (3)
follow-up for more than 1 year. Exclusion criteria were: (1) severe lower cervical spinal stenosis; (2) cervical infection
or tumor; and (3) congenital malformation.
Four patients had injury to the brain/
cranium or to other vital organs, and
the diagnosis and treatment of odontoid fractures was delayed in their local hospitals. Seven patients underwent
conservative therapy, such as external
fixation, which resulted in nonunion of
odontoid fractures and late C1-C2 instability. Anterior screw fixation failed in
4 patients, and the remaining 6 patients
had mild initial symptoms that gradually
developed into cervical spine injury or
occurred after a secondary trauma. The
disease course from trauma to the current surgery ranged from 1.5 months to
6 years.
Seven patients had neck pain as their
single symptom on admission. Fourteen
patients had symptoms of cervical spinal
injury, such as sensorimotor dysfunction
in the extremities. Two of these patients
had obvious respiratory dysfunction.
The Japanese Orthopaedic Association score was used to evaluate spinal
cord function,29 and the visual analog
scale was used to evaluate neck pain.
Imaging
Preoperatively, all patients underwent
radiographic cervical anteroposterior
examination with open mouth, lateral,
and hyperextension views. Patients were
classified as either type II (n=16) or type
III (n=5), according to the Anderson and
D’Alonzo classification.4 C1-C2 dislocation was anterior in 13 patients and posterior in 6 patients. Two patients had no
95
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obvious dislocation. However, for the 2
patients without obvious dislocation, the
fractured bone did not heal after odontoid screw fixation and there was obvious bone resorption around the odontoid
screws.
All patients also underwent cervical
computed tomography (CT) scan with
sagittal reconstruction to clarify the type
of odontoid fracture and the features of
the anatomic structure.
Cervical spine magnetic resonance
imaging scan showed no obvious compression at C1 and C2 in 7 patients and
obvious compression in 14 patients. Furthermore, 8 of 14 patients showed high
signals in the spinal cord on T2-weighted
images at the compressed level, indicating severe spinal cord damage. No lower
cervical spinal stenoses or lower cervical
spinal cord injuries were noted.
Treatment
The 2 patients who had no obvious
C1-C2 dislocation (fractured bone did
not heal after odontoid screw fixation
and bone resorption occurred around the
screws) directly underwent posterior surgery. In another 2 patients who had failure of odontoid screw fixation, 1 had a
light shift of the screws after fixation and
was treated with direct posterior fusion
and the other had obvious loosening and
shift of the screws and underwent posterior fusion after the loosened screws
were removed via the original fixation
approach. The remaining patients who
had C1-C2 dislocation (n=17) underwent
preoperative skull traction for 2 weeks,
starting with 3 kg and reaching a maximum of 10 kg. After traction, 12 patients
achieved complete (n=6) or nearly complete (n=6) diaplasis and underwent posterior surgery; 5 patients with irreducible
C1-C2 dislocation underwent anteroposterior surgery.
Surgical Approach
For the anterior approach, oral cavity
disinfection was performed for 3 days
96
before surgery, an indwelling nasogastric
tube was placed, and general anesthesia
was performed with orotracheal intubation.
The posterior pharyngeal wall was
cut open to expose the odontoid bone
line. Hyperplasic tissues and callus
around the fracture lines were removed,
and adhesive tissues were further separated from the joints. Using skull traction, C1 and C2 were repositioned with
the assistance of a curette. However, repositioning was not stable with anterior
surgery in 3 patients and satisfactory
repositioning was finally achieved after
posterior surgery.
The posterior arch of C1 and the axial
lamina were accessed with the posterior
approach, and the posterior arch of C1 was
exposed from the middle line of the spinous process to both sides (approximately
1.5 cm wide). The surgeon continued to
strip along the posterior and inferior margins of the posterior arch of C1 to both
sides until the nerve dissector detected the
inner margin of the C1 pedicle. The inner
and superior margins of the C2 pedicle
were identified with a nerve dissector.
After determination of the screw entry
points in the C1 and C2 pedicle, screw
implantation in the C1 and C2 pedicle was
completed. The position and length of the
screws and C1 repositioning were monitored intraoperatively with C-arm radiography. Nine patients underwent posterior
surgery without complete C1 repositioning. They underwent adjustment of the
screw and plate/rod position to reach satisfactory C1 repositioning. The surfaces
of the posterior arch of C1 and the lamina
of C2 were appropriately ground for bone
graft bed preparation, and an autogenous
iliac bone graft was implanted after being
shattered. The incision was closed after
the indwelling drainage tube was placed.
Postoperative Treatment and Follow-up
The drainage tube was removed 48
hours after surgery. Bed rest was not necessary for all patients; off-bed activity
was suggested according to the patient’s
condition. Acupuncture, electrical stimulation, and neurotrophic drug treatment
were routinely advised for patients who
had symptoms of spinal cord injury to facilitate recovery of neurologic function.
Radiographic examination was performed at 3, 6, and 12 months after operation. Sagittal CT reconstruction was
performed 6 and 12 months after surgery
to monitor fracture repositioning and C1C2 fusion. Bone fusion was defined as trabecular continuity through the posterior
arch of C1, with visibility of the lamina of
C2 on CT reconstruction. Japanese Orthopaedic Association scores were recorded
at the last follow-up examination to evaluate cervical spinal cord function. Japanese
Orthopaedic Association score improvement rate=(postoperative score−preoperative score)/(17−preoperative score)×100%.
Neck pain was also evaluated at the last
follow-up examination by visual analog
scale score.
Statistical Analysis
Changes in Japanese Orthopaedic Association and visual analog scale scores
are presented as mean±SD and were analyzed with paired t tests. P<.05 was considered statistically significant. Data were
analyzed with SPSS version 17.0 software
(SPSS Inc, Chicago, Illinois).
Results
Baseline characteristics of the 21 patients are shown in Table 1. Postoperative
imaging showed that the C1-C2 dislocation was satisfactorily repositioned in all
patients. Trabecular continuity through
the posterior arch of C1 and the lamina of
C2 was shown by radiograph and CT reconstruction 1 year after surgery, and the
bone fusion rate was 100%. The position
of the screw did not change. No loosening
or breaking of internal fixation occurred,
and no C1 redislocation occurred during
follow-up.
The visual analog scale score for neck
pain was significantly improved at the last
ORTHOPEDICS | Healio.com/Orthopedics
n Feature Article
follow-up examination (P<.001). No new
onset of spinal cord injury occurred after
surgery. Symptoms of spinal cord injury
were improved in 14 patients who had
cervical spinal damage before surgery. At
the last follow-up examination, Japanese
Orthopaedic Association scores were significantly improved, with an average improvement rate of 61.0% (P<.001) (Table
2).
No severe surgical complications were
observed, such as iatrogenic vertebral artery or spinal cord injury. Although postoperative CT scan showed a C2 pedicle
screw penetrating the wall of the vertebral
artery foramen in 7 cases, penetration
was less than 1 mm and no symptoms of
vertebral artery injury were observed. No
infection occurred in the pharyngeal posterior wall or the posterior cervical incision. Three patients (14.3%) had upper
cervical and occipital pain, numbness, or
hypersensitivity. These symptoms were
relieved after 3 months of symptomatic
treatment, without the need for medication. Neck stiffness and limited neck
rotation occurred after operation. In the
current study, 7 patients had limited neck
rotation and gradually adapted their work
and daily activities to accommodate this
limitation. Typical cases are shown in Figure 1 and Figure 2.
Table 1
Patient Characteristics
Patient No./
Sex/Age, y
Dislocation
Direction
Symptoms
Surgical Route
Follow-up,
mo
1/M/51
Posterior
Neck pain, myelopathy
Anterior and
posterior
18
2/M/35
Anterior
Neck pain
Posterior
36
3/F/69
Anterior
Neck pain
Posterior
19
4/M/56
Anterior
Neck pain, myelopathy
Posterior
22
5/F/43
Posterior
Neck pain, myelopathy
Posterior
25
6/F/28
Anterior
Neck pain, myelopathy
Anterior and
posterior
20
7/M/50
Anterior
Neck pain, myelopathy
Posterior
12
8/M/43
Posterior
Neck pain, myelopathy
Anterior and
posterior
24
9/F/42
Anterior
Neck pain, myelopathy
Anterior and
posterior
20
10/M/34
Posterior
Neck pain
Posterior
33
11/M/57
Anterior
Neck pain, myelopathy
Posterior
24
12/F/48
Anterior
Neck pain, myelopathy
Posterior
21
13/M/31
No
Neck pain
Posterior
20
14/F/56
Anterior
Neck pain, myelopathy
Posterior
29
15/M/55
No
Neck pain
Posterior
22
16/M/62
Anterior
Neck pain, myelopathy
Posterior
24
17/F/35
Posterior
Neck pain
Posterior
12
18/M/50
Anterior
Neck pain, myelopathy
Anterior and
posterior
22
19/F/42
Posterior
Neck pain, myelopathy
Posterior
18
20/M/24
Anterior
Neck pain
Posterior
24
21/M/66
Anterior
Neck pain, myelopathy
Posterior
20
Discussion
The odontoid process is an important
anatomic structure for maintaining the
stability of the C1-C2 joint, and odontoid fractures that do not receive timely
and appropriate treatment lead to nonunion or to old odontoid fractures, resulting in cervical spinal cord compression. Nonsurgical treatments are usually
considered first for type I or III odontoid
fractures, and surgery is considered for
patients with C1-C2 instability. However, conservative treatment of type II
fractures might lead to nonunion, even
with halo brace fixation, and the fracture healing rate is reported to be low.4,30
Therefore, most orthopedic surgeons
FEBRUARY 2015 | Volume 38 • Number 2
Table 2
Changes in Pre- and Postoperative Visual Analog Scale and
Japanese Orthopaedic Association Scores
Variable
Preoperative
Last Follow-up
t
P
Visual analog scale score
5.9±1.5
1.8±0.8
-12.4
.001
Japanese Orthopaedic Association
scorea
9.2±1.9
13.8±1.9
16.8
.001
a
Includes 14 patients with cervical spinal cord injury.
prefer surgery for the treatment of type II
odontoid fractures. The timing of surgery
for odontoid fractures is believed to be
critical, and a retrospective study report-
ed that delay of treatment by more than
4 days could result in nonunion.31 However, delayed or inappropriate treatment
of odontoid fractures is not uncommon
97
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Figure 1: Preoperative lateral radiograph (A) and
computed tomography sagittal reconstruction (B)
showing odontoid fracture of C2 and posterior dislocation of C1. Preoperative sagittal magnetic resonance imaging scan showing odontoid fracture of
C2, posterior dislocation of C1, and compression of
the spinal cord (C). Postoperative lateral radiograph
showing good reduction of C1 and satisfactory internal fixation (D). Postoperative sagittal computed
tomography reconstruction showing posterior C1C2 bony fusion 1 year after surgery (E).
and treatment is usually initiated at the
onset or progression of late neurologic
symptoms; subsequently, the nonunion
rate for delayed treatment of odontoid
fractures was found to be higher than
that for early treatment.10 In the current
study, 7 patients underwent conservative treatment that resulted in nonunion
of odontoid fractures (33.3%). Six patients had mild symptoms after trauma,
and timely and effective therapy was not
carried out until an old odontoid fracture
was diagnosed when neurologic symptoms occurred after a secondary trauma
or simply after progression of C1-C2 instability.
The biomechanical strength of C1
and C2 pedicle screw fixation is simi-
98
lar to the strength of Magerl screws,32
providing reliable biomechanical stability of C1 and C2. The binding wire at
the posterior edge of C1 is not needed;
therefore, C1 and C2 pedicle screw fixation is suitable for patients who have
a defect on the posterior arch of C1 or
those who need extra pressure from the
posterior arch of C1. Compared with
Magerl screws, C2 pedicle screws are
inserted with an interior angle of 20°
to 25°, which effectively avoids injury
to the vertebral artery, even if the vertebral artery foramen is enlarged. In addition, C2 pedicle screws enable better
direct vision during surgery, making C2
pedicle screw fixation safer than the use
of Magerl screws.12,33,34 Although it was
reported that C2 pedicle screws penetrated into the vertebral arterial foramen in
5.4% of patients because of the limited
experience of the surgeon, no obvious
clinical symptoms occurred.12 In addition, 4 of 160 patients had hemorrhage
during C2 pedicle screw placement35;
however, no abnormality was shown by
postoperative angiography and no relevant symptoms occurred. In the current
study, C2 pedicle screws penetrated into
the interior wall of the vertebral arterial
foramen by less than 1 mm in 7 patients.
No uncontrollable hemorrhage occurred,
and no symptoms were observed during follow-up. Therefore, penetration
of the screw by less than 1 mm should
not injure the vertebral artery. Because
preoperative complete repositioning of
C1 was not a prerequisite for posterior
surgery, the screws, titanium plate, or
rod used for internal fixation could help
in repositioning, which is an apparent
advantage over other posterior instruments. In the current study, incomplete
repositioning of C1 dislocation before
posterior surgery was observed in 9 patients and these patients required further
fixation with posterior surgery.
ORTHOPEDICS | Healio.com/Orthopedics
n Feature Article
The C1 and C2 pedicle screw placement should be individualized; screw
position, length, and insertion direction
should be planned with detailed preoperative imaging. In addition, CT reconstruction can help to determine the thickness
of the C1 posterior arch and the possibility of performing pedicle screw placement
and to estimate the possible influence of
the location and size of the vertebral artery foramen. Screw placement is finally
determined with the use of a nerve dissector to intraoperatively detect the interior
edge of the C1 pedicle, the posterior edge
of the C1 lateral mass, and the interior
and upper edges of the C2 pedicle. Some
patients had a narrowed posterior arch of
C1, and 3.5-mm screws should penetrate
through the pedicle, without the need for
special treatment. In the current study, 9
of 42 screws penetrated the pedicle. No
effect on the stability of internal fixation was observed, and stability was still
better than that achieved with C1 lateral
mass screws.25 The nerve root and venous
plexus between the C1 and C2 vertebral
laminae do not need deliberate exposure,
but sometimes there is unavoidable hemorrhage of the venous plexus that can be
stopped with electrocoagulation. Sponge
compression hemostasis is usually used
for massive hemorrhage.
In the current study, neck pain and
symptoms of cervical spinal cord injury
were significantly improved as a result
of satisfactory repositioning and timely
C1 and C2 pedicle screw fixation. Few
postoperative complications occurred.
No vertebral artery or spinal cord injury
occurred, although 3 patients had occipital pain that might be associated with C2
nerve root irritation. This irritation might
also be caused by sponge compression hemostasis for vein bleeding between the C1
and C2 vertebral laminae, by bone particle
stimulation during bone graft, or by penetration of the C1 pedicle screw through
the posterior arch. These complications
could be effectively avoided by careful
manipulation during operation. Patients
FEBRUARY 2015 | Volume 38 • Number 2
recovered promptly with postoperative
symptomatic treatment. Limitations of the
current study included the small sample Figure 2: Preoperative lateral radiograph showing
size, the short follow-up period, and the odontoid fracture of C2 and anterior dislocation of
C1 (A). Sagittal magnetic resonance imaging scan
lack of a control group.
Conclusion
The findings showed that C1 and C2
pedicle screw fixation can be directly
used for repositioning of C1-C2 dislocation with firm fixation and a high rate of
bone graft fusion. Few complications such
as vertebral artery and spinal cord injury
occurred in this study, and C1 and C2 pedicle screw fixation could be a safe and effective surgical treatment for old odontoid
fractures associated with C1-C2 dislocation or instability.
showing odontoid fracture of C2, anterior dislocation
of C1, compression of the spinal cord, and hyperintense magnetic resonance imaging signal within
the spinal cord (B). Postoperative lateral radiograph
showing good reduction of C1 and satisfactory internal fixation (C). Postoperative sagittal computed tomography reconstruction showing posterior C1-C2
bony fusion 1 year after surgery (D).
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