Atlantoaxial injuries

1. Atlantoaxial Injuries
NEUROSURGERY DEPARTMENT – SKUH
BY MOHAMED HESHAM – RESIDENT OF NEUROSURGERY

2. Content
 Anatomy
 Atlantoaxial Subluxation:
• Rotatory
• Anterior
• Posterior
 Atlas (C1) fractures
 Axis (C2) fractures
• odontoid fractures
• hangman’s fracture
• miscellaneous C2 fractures
 Combination C1 & C2 injuries

3. Anatomy

8. ==

12.  AKA predental space or interval. The distance between the anterior
margin of the dens and the closest point of the anterior arch of C1
(“C1 button”) on a lateral C-spine X-ray.
 The normal ranges:
• Male : ≤ 3 mm
• Female : ≤ 2.5 mm
• Pediatric : ≤ 4 mm
 An abnormally increased ADI is a surrogate marker for transverse
atlantal ligament disruption.
Posterior atlantodental interval (PADI)
 AKA the neural canal width (NCW). measured from the back of the
odontoid to the anterior aspect of the posterior C1 ring. It is more
useful than the ADI for some conditions, e.g. AAS in rheumatoid
arthritis or Down syndrome.
Anterior atlantodental interval (ADI)

13.  Anatomical variations in pediatrics:
• C1 (atlas)
o Ossification centers :
 1 (sometimes 2) for body (not ossified at birth; appears on X-ray during 1st yr)
 1 for each neural arch (appear bilaterally ≈ 7th fetal week)
o Synchondroses :
 synchondrosis of the spinous process: fuses by ≈ 3 yrs of age
 2 neurocentral synchondroses: fuse by ≈ 7 yrs of age
o The ossification centers of C1 fail to completely close in 5% of adults (usually posteriorly). When present, the rare
anterior defect is usually associated with a posterior defect.

15. • C2 (axis)
• Ossification centers : 4 primary ossification centers
o odontoid process : The two halves of the odontoid fuse together in the midline at 7 months
o vertebral body
o 2 neural arches
o A secondary ossification center (os terminale) appears at the summit of the dens between 3 and 6 years of
age, and fuses with the dens by age 12 years.
• Synchondroses :
o The posterior arches fuse together by 2–3 years of age.
o The anterior synchondroses normally fuse between 3 and 6 years of age.
o the dentocentral synchondrosis (AKA subdental synchondrosis) may be visible on X-ray until ≈ 11 years of
age.

17. Subluxation/Dislocation
 Types of Atlantoaxial Subluxation:
• Rotatory
• Anterior
• Posterior

18. Rotatory atlantoaxial subluxation
 Etiology:
• Spontaneously : with rheumatoid arthritis or congenital dens anomalies
• Major or minor trauma
• Infection of the head or neck including upper respiratory tract (known as Grisel syndrome) as a mechanical
and chemical injury to the facet capsules and/or transverse atlantal ligament
 The vertebral arteries may be compromised in excessive rotation, especially if it is combined with
anterior displacement.
 With an intact TAL, rotation occurs without anterior displacement. If the TAL is incompetent as a
result of trauma or infection, there may also be anterior displacement with more potential for
neurologic injury. Posterior displacement occurs only rarely.

19.  Clinical presentation :
• Patients are usually young.
• Neurologic deficit is rare.
• neck pain, headache,
• torticollis—characteristic “cock robin” head position with ≈ 20°lateral tilt to one side, 20°rotation to the other,
and slight (≈ 10°) flexion reduced range of motion, and facial flattening.
• Although the patient cannot reduce the dislocation, they can increase it with head rotation towards the
subluxed joint with potential injury to the high cervical cord.
• Brainstem and cerebellar infarction and even death may occur with compromise of circulation through the
Vertebral artries.

20. Fielding & Hawkins classification:

22. Radiological Evaluation:

23.  Management:
• Grisel’s syndrome:
o antibiotics + traction + immobilization, Type I: soft collar, Type II: Philadelphia collar or SOMI (Sternal Occipital
Mandibular Immobilizer), Type III or IV: halo.
o After 6–8 weeks of immobilization, check stability with flexion-extension X-rays. Surgical fusion for residual instability.
• Traction:
o within the 1st month of subluxation, the subluxation can usually be reduced with gentle traction (in children start with 7–
8 lbs and gradually increase up to 15 lbs over several days, in adults start with 15 lbs and gradually increase up to 20).
o If the subluxation is present > 1 month, traction is less successful. Active left-right neck rotation is encouraged in
traction .If reducible, immobilization in traction or halo is maintained × 3 months (range: 6–12 weeks).If not reducible,
Surgical fusion is required.

24. SOMI (Sternal Occipital
Mandibular Immobilizer)
Halo vest

25. • Surgical fusion
o Irreducible subluxation or that recurs following immobilization should be treated by Surgical C1 to C2 fusion
after 2–3 weeks of traction to obtain maximal reduction. Unless other fractures or conditions are present.
o Fusion may be performed even if the rotation between C1 & C2 is not completely reduced. For irreducible
fixation, a staged procedure can be done with anterior transoral release of the atlantoaxial complex (the
exposure is taken laterally to expose the atlantoaxial joints, which must be done carefully to avoid injury to the
VAs, soft tissue is carefully removed from the joints and the atlantodental interval, no attempt at reduction was
made at the time of this 1st stage), followed by gradual skull traction and then a second stage posterior C1–
2 fusion.

26. Anterior atlantoaxial subluxation
 Etiology: (Flexion injury)
• 1. disruption of the transverse atlantal ligament: ADI will be increased up to 5mm, in case of
greater slippage, the alar ligaments must at least be stretched.
o a) attachment points of the TAL may be weakened in rheumatoid arthritis
o b) trauma: may cause anatomic or functional ligament disruption
• 2. incompetence of the odontoid process: ADI will be normal
o a) odontoid fracture
o b) congenital hypoplasia, e.g. Morquio syndrome

27.  Clinical presentation :
• Neck pain is common (with no specific character).
• One third of patients with AAS have neurologic deficit or die.
 Radiological Evaluation :
• CT Scan and MRI are indicated
• in extension, C1 is reduced.
• while in flexion, the atlas shifts forward, the atlantodental distance is increased, which may be normal
pediatrics.
• The key differentiating feature is whether the ADI is increased or normal.

28.  Assessing the integrity of the TAL:
• 1. Indirect assessment: (low sensitivity)
o a) rule of Spence : if the total overhang (lateral mass displacement (LMD)) of both C1 lateral masses on
C2 is ≥ 7 mm(missed 60% of TAL injuries detected on MRI )
o b) atlantodental interval (ADI) > 3-2.5 mm in adults, > 4 mm in peds (The most reliable radiological
parameter)
• 2. direct assessment: MRI may be able to directly assess TAL integrity by imaging it. Possible
findings:
o loss of continuity of the TAL,
o high signal within the TAL on gradient-echo MRI,
o blood separating the TAL from its insertion site on the medial tubercle
• 3. CT may demonstrate bony injury in the regions of TAL insertion on C1 tubercles.

30. Transverse ligament high-signal changes

31.  Dickman classification of transverse atlantal ligament disruption
• Clinical use of this classification has not been fully validated.
• Dickman Type I. Anatomic disruption. Tear of TAL itself without osseous component. Rare (the odontoid
odontoid usually fractures before the TAL tears).
• Unlikely to heal, requires surgical stabilization.
o Type IA: midsubstance TAL disruption. Possible findings:1. loss of continuity of the TAL2. high signal within the TAL.
TAL.
o Type IB: osteoperiosteal TAL disruption. Possible finding: blood separates the TAL from its insertion site on the
medial tubercle
• Dickman Type II. Physiologic disruption. Detachment of the C1 tubercle (to which TAL is attached) from
the C1 lateral mass. May occur in comminuted C1 lateral mass fractures. 74% chance of healing with
immobilization

32. Posterior atlantoaxial subluxation
 Caused by a hyperextension injury.
 The tectorial membrane as well as the alar ligaments must be torn.

33.  Management:
• TAL disruption:
o Fuse all Dickman Type I TAL injuries at diagnosis .
o Fuse Dickman Type II TAL injuries that are still unstable after 3–4 months of immobilization.
• Fusion is also recommended with irreducible subluxations.
• If C1 is intact, a C1–2 fusion is usually adequate. If C1 is fractured, occipital cervical fusion may be
needed.
• isolated C1 fractures / odontoid fractures with intact TAL will be discussed later.

34. Atlas (C1) fractures
 Usually from axial loading (a “blow-out” fracture).
 Acute C1 fractures account for 3–13% of cervical spine fractures
 56% of patients had isolated C1 fractures; 44% had combination C1–2 fractures; 9% had
additional non-contiguous C-spine fractures. 21% had associated head injuries.
 In pediatrics, it is critical to differentiate a C1 fracture from the normal synchondroses (a
fracture may also occur through unfused synchondroses) and from pseudospread of the
atlas.

35.  Clinical presentation :
• Neurologic deficit is rare with isolated C1 fractures
• Possible clinical findings :
1. neck pain is common and the patient will often guard against movement
2. prevertebral swelling may impinge on the esophagus and cause swallowing difficulties
3. pain in the distribution of the greater occipital nerve may occur from C2 root involvement
4. associated vertebral artery dissection) may produce symptoms of posterior circulation
ischemia (diplopia, altered level of consciousness, lateral medullary syndrome…)
5. lower cranial nerve (IX-XII) palsies have also been reported

36.  Radiological Evaluation :
• Thin cut high-resolution CT is the diagnostic test of choice.
• It is critical to evaluate from C1 through C3 .
• MRI may be able to directly evaluate the integrity of the TAL.
• The stability of the occipitoatlantoaxial complex is primarily due to ligaments, with little
contribution from bony articulations. Integrity of the transverse atlantal ligament is the
most important determinant of stability in C1 fractures.

37.  Classification:
• Sir Geoffrey Jefferson described a four-point (burst) fracture of the C1
ring in 1920. The term now includes any burst fracture of C1 (3 or 2-
point fractures are more common the latter usually through the C1
arches (thinnest part)).
• Jefferson type III is the classic 4-point Jefferson fracture
• The practice guidelines are based on the Landells classification

38. (A) Jefferson type I (B) Jefferson type II
Landells: Type I posterior arch alone or anterior arch alone (single arch)
45% of C1 fractures

39. (C) Jefferson type III
(The classic 4-point Jefferson fracture)
Landells: Type II anterior AND posterior arch (“burst fracture”) 37–51%

40. (D) Jefferson type IV
Landells: Type III lateral mass fractures (comminuted) 13-37%

41.  Management:
• Treatment of an isolated C1 fracture is based on the integrity of the transverse atlantal ligament.
• Non-surgical treatment :
o A stable isolated type I, type II fractures with intact transverse ligament, and type III fractures can be effectively
treated with external immobilization devices for 2 or 3 months, with successful union/healing rates > 96%.
o There is insufficient evidence to recommend any of the following cervical immobilization devices over the other: soft
collar, rigid collar, SOMI, halo-vest.
o At the end of nonsurgical treatment, surgical fusion is recommended for late instability e.g. on flexion/extension C-
spine X-rays.
o Even with a satisfactory X-ray result, 20–40% of patients have neck pain after rigid immobilization.
o Immobilization or attempted reduction in halo traction followed by a halo vest are treatment options that are
reasonable as long as there is no evidence of sagittal atlantoaxial instability, ie, widening of the ADI, even those that
meet the radiographic criteria of instability (rule of Spence/ boney avulsion).

43. • Surgical treatment :
o In most cases, reduction of the lateral dislocation of the lateral mass
of C1 by halo traction only is not possible.
o Type II fractures with evidence of transverse ligament disruption are
considered unstable, although some patients can be effectively
treated with either rigid immobilization alone (halo vest) for a
period of 3 months or with posterior surgical stabilization (C1-2
Fusion / Occipital-cervical Fusion).
o Some authors promote early surgical treatment of unstable atlas
fractures due to the discomfort of prolonged treatment in halo
vests and healing rates. this is done at the cost of reducing mobility.

44. Axis (C2) fractures
 20% of cervical spine fractures.
 Types:
• odontoid fractures :type II odontoid fracture is the most common injury of the axis
• hangman’s fracture
• miscellaneous C2 fractures

45. Hangman’s fracture “traumatic
spondylolisthesis of the axis”
 bilateral fracture through the pars interarticularis (isthmus) of the pedicle of C2, with disruption
of the C2-3 junction.
 7% of all cervical spinal injuries,
 Rare in children < 8 years old where the forces tend to fracture the incompletely fused
odontoid.
 Infrequently associated with spinal cord injury (5.5%).
 Usually stable. Nonunion is rare. 90% heal with immobilization only.
 The basic mechanism of injury is hyperextension with vertical compression of the posterior
column with translation of C2 and C3.

46.  Clinical presentation :
• Cervical pain.
• Most (≈ 95%) are neurologically intact
• Those few with deficits are usually minor (paresthesias, monoparesis…) and many recover
within one month.
• Occipital neuralgia is common.
• 30% of patients have associated head injury and there will be other associated C-spine
injuries.

47.  Classification:
 Levine/Effendi classification
• The system of Effendi as modified by Levine
• is widely used in grading adult HF (not applicable to peds).
• Angulation is measured as the angle between the inferior endplates of C2
and C3.
• Anterior subluxation of C2 on C3 > 3 mm (Type II) is a surrogate marker
for C2–3 disc disruption, which can be evaluated more directly with
cervical MRI.

49.  Type I
• Vertical pars fracture just posterior to the vertebral body
• Radiological findings :
o ≤ 3 mm subluxation of C2 on C3
o No angulation
• Mechanism : Hyperextension + axial loading
• stable on flexion/extension X-rays.
• Neurologic deficit rare

50.  Type IA
• “atypical hangman’s fracture”
• Radiological findings :
o Anterior C2 VB may be subluxed 2-3 mm
o Fracture line may not be visible on X-ray
o Fracture lines on each side are not parallel and may pass through foramen transversarium on one
side
o VB may appear elongated
• Mechanism : hyperextension + lateral bending
• 33% incidence of paralysis
• vertebral arteries could be injuried.

51.  Type II
• A vertical fracture through pars, disruption of C2–3 disc & posterior
longitudinal ligament
• Radiological findings :
o > 3 mm subluxation of C2 on C3
o > 10° angulation
o Slight anterior compression of C3 possible
• Mechanism : axial loading + extension with rebound flexion
• Early instability is suspected.
• Neurologic deficit rare.

52.  Type IIa
• Oblique fracture (usually anterior-inferior to posterior superior)
• Radiological findings :
o usually little (≤ 3 mm) subluxation of C2 on C3
o more angulation (> 15°)
• Mechanism : flexion distraction
• Unstable.
• ******Traction → increased angulation & widening of disc space ∴
do not use traction

53.  Type III
• Type II + bilateral C2–3 facet capsule disruption.
• C2 posterior arch is free floating.
• Anterior longitudinal ligament may be disrupted
• Radiological findings :
o > 3 mm subluxation of C2 on C3
o > 10° angulation
o facets of C2/C3 may be subluxed or locked
• Mechanism : flexion (capsule disruption) followed by compression (isthmus
fracture)
• Highly unstable pattern.
• Neurologic deficit may occur & may be fatal.
• Facet dislocation usually irreducable ∴ do not use traction

54.  An additional group of injuries may also be described as traumatic spondylolisthesis of C2-3 with:
• bilateral laminar fractures (type IV)
• bilateral facet fractures of the inferior articular processes of C2 (type V)
 Grading system of Frances:

55.  Radiological Evaluation :
• Cervical CT: with sagittal & coronal reconstructions should be done to fully assess the fracture.
• CTA: should be done to evaluate the vertebral arteries if fracture extends through foramen transversarium
(especially Levine Type IA) and in patients with symptoms suggestive of stroke.
• MRI: to look for C2–3 disc disruption marker for instability (Levine grade II).
• X-rays: lateral X-rays show the fracture in 95% of cases,
• Instability can usually be identified as
o marked anterior displacement of C2 on C3 (exceeds 50% of the AP diameter of C3 vertebral body),
o excessive angulation of C2 on C3 (> 11° angulation)
o excessive motion on flexion-extension films.
o Patients suspected of having Levine Type I fractures and are neurologically intact should have physician-supervised
flexion-extension X-rays to rule out a reduced type II fracture.

56.  Management:
• The three most important actions to improve survival in patients who suffer an injury of the
CCJ:
o Early diagnosis
o Prompt intubation (if needed)
o Immobilization of the head and neck which produces adequate reduction in 97–100% and results in
a fusion rate of 93–100%
• Stable fractures (Levine Types I or IA, or Francis Grades I or II)
o Treat with immobilization (Philadelphia collar or SOMI) for × 3 months.
o Halo-vest may be needed in unreliable patients or for combination C1–2 fractures.

57.  Unstable fractures
 Levine Type II (≤ 5 mm of subluxation and angulation <10°)
• Vaccaro and colleagues reported excellent results with early halo
immobilization and reduction for type II or IIA hangman’s fractures.
1. Reduction + gentle traction (X-ray monitoring to prevent
“iatrogenic hanging”)within 1st 24 hrs
2. halo vest × 2-3 months
3. Follow up serial X-rays
4. Stabilize surgically if fracture moves
5. After 8–12 weeks, change to Philadelphia collar or cervicothoracic
orthosis/brace until fusion is definitely complete (usually 34
months).

58.  Levine Type II (> 5 mm of subluxation and angulation ≥10°)
• Surgical fusion is recommended as:
1. Risk of settling if immediately mobilized in halo-vest
2. Decreased fusion rates with an angulation of ≥12°, requiring an extended period of traction.
3. Healing with significant angulation may result in chronic pain
• Conservative:
1. Cervical traction can be maintained for 4 weeks
2. Reduction should be reassessed 1 hour after removing weight from traction,
3. if stable, reassess again 24 hours after mobilizing in a halo vest.
4. If unstable, return to traction and repeat trial at 5 & 6 weeks.
5. If still unstable at 6 weeks, surgical fusion is recommended.

59.  Levine Type IIa
• Traction will accentuate the deformity.
• Reduced by immediate placement in halo vest (bypassing traction) with extension and axial loading
applied.
• Halo-vest immobilization × 3 months produces ≈ 95% union rate.
 Levine Type III
• Closed reduction of such a lesion is usually not possible and dangerous since all the structures of C2/3
are destroyed and manipulation of the head does not have any effect on the C2/3 joint
• Posterior open reduction is necessary to reduce the dislocation at C2/3.
• At the same time, posterior/anterior fusion to prevent redislocation of C2/3 is mandatory.

60.  Surgical managment:
• Indications of surgery:
o Irreducible fractures (includes most Levine Type III & some Type II)
o failure of external immobilization to prevent movement at fracture site
o traumatic C2–3 disc herniation with compromise of the spinal cord
o established non-union: evidenced by movement on flexion-extension film; all failures of nonoperative treatment
had displacement > 4 mm, angulation of ≥12°
• Hangman’s fractures likely to need surgery :
o Levine Type II or III (irreducible)
o Francis grade II, IV, or V (angulation of ≥12° or disk disruption)
o anterior displacement of C2 VB > 50% of the AP diameter of the C3 (> 4 mm)
o angulation produces widening of either the anterior or posterior borders of the C2–3 disc space > the height of the
normal C3–4 disc below (angulation of ≥12° or disk disruption)

61.  Surgical options:
• Fusion techniques:
o posterior approach: C1–2 posterior wiring and fusion, C1–3 fusion using C1-3 lateral mass screws (skipping C2)
or occiput-C3 fusion: may be used if C1 is also damaged (skipping C1 & C2)
o Anterior approach: C2-3 ACDF.
• Fixation techniques:
screw placement from posterior approach through the C2 pedicle across the fracture fragment.
 Treatment endpoint
• Plain X-rays should show trabeculation across the fracture site or interbody fusion of C2 to C3.
• Dynamic X-ray : should show no movement at the fracture site.

62. Odontoid fractures
 Odontoid fractures comprise ≈ 10–20% of all cervical spine fractures and 60% of atlas fractures
 They are easily missed on initial evaluation, especially since significant associated injuries are frequent and
may mask symptoms.
 Although conservative management should be considered, given the high rate of nonunion associated with
these lesions, surgery is the gold standard of treatment.
 Etiology:
• Significant force is required to produce an odontoid fracture in a young individual (FFH/RTA)
• In patients > 70 years of age, simple ground level falls (GLF)
• Pathologic fractures can also occur, e.g. with metastatic involvement.
 Mechanism of injury:
• Flexion is the most common mechanism of injury, with resultant anterior displacement of C1 on C2 (atlantoaxial
subluxation).
• Extension only occasionally produces odontoid fractures, usually associated with posterior displacement.

63.  Clinical presentation :
 Fatality: the frequency of fatality resulting directly from odontoid fractures is unknown due to other associated
injuries , estimated as being between 25–40%.
 Neurological deficit:
• 82% of patients with Type II were neurologically intact,
• 8% had minor deficits of scalp or limb sensation,
• 10% had significant deficit (ranging from monoparesis to quadriplegia).
• Type III fractures are rarely associated with neurologic injury.
 High posterior cervical pain: associated by paraspinal muscle spasm, reduced range of motion of the neck,
tenderness, and may radiate to the distribution of the greater occipital nerve (occipital neuralgia).
 Paresthesias in the upper extremities and slight hyperreflexia may also occur.
 Myelopathy may develop in patients with nonunion.

64.  Classification & Radiological evaluation: (Anderson and
D’Alonzo System)
 Type I
• through tip (above transverse ligament), rare
• Due to a shear injury when the tip of the dens comes into contact with
the rim of the foramen magnum, however, it can also represent:
o an avulsion of the alar ligament and must t be seen as part of an
atlantooccipital dislocation.
o an avulsion of the transverse ligament, and must t be seen as part of an atlanto-axial
dislocation. (less likely)
• It is usually believed to be stable and may be treated with external
orthosis; however, one report suggests otherwise, and dynamic imaging
may be used to assess stability.

65.  Type II
• the most common
• through base of neck the most common dens fracture
• The fracture surface is small and the fracture has a high nonunion rate when treated
conservatively.
• The fracture may be oblique and the dens may be dislocated anteriorly or posteriorly.

66.  Nonunion:
• A wide range of nonunion rates with immobilization alone (5–76%) is quoted: 30% is probably a reasonable
estimate for overall nonunion rate, with 10% nonunion rate for those with displacement < 6 mm.
• Symptoms:
o The most common is continued high posterior cervical pain beyond the time that the brace is removed.
o Late myelopathy can develop in as many as 77% of mobile nonunions as a result of motion and soft tissue proliferation
around the unstable fracture site.
• Radiographic criteria :
• defect in the dens with contiguous sclerosis of both fragments (vascular pseudarthrosis)
• defect in the dens with contiguous resorption of both fragments (rarefying osteitis or atrophic pseudarthrosis)
• defect in the dens with definite loss of cortical continuity
• Dynamic X-ray: movement of dens fragment

67. Odontoid pseudarthrosis
Neglected neck trauma about 20 years ago.

68.  Type IIa
• similar to type II, but with large bone chips at fracture site.(comminuted)
• comprise ≈ 3% of type II odontoid fractures.

69.  Type III
• through body of C2 .
• The fracture is in cancellous bone and therefore has a better healing
potential with a nonunion rate of only 7% when treated conservatively.
• The fracture often enters the lateral atlantoaxial joint involving the
superior articular surface on one or both sides and may create an
intraarticular step.

70.  Management:
• Isolated Type II odontoid fractures in adults ≥ 50 years of age should be considered for surgical
stabilization & fusion
• Nondisplaced type I, II & III fractures may be managed initially with external cervical immobilization,
(recognizing that type II odontoid fractures have a higher rate of nonunion)
• Indications surgical fixation for: (Type II & III: )
o dens displacement ≥ 5 mm
o Type IIA fracture (comminution of fracture)
o inability to maintain or achieve alignment with external immobilization

71.  Immobilization:
• 10–12 weeks of immobilization
• Halo vest: fusion rate = 72%, appears superior to an SOMI. If a halo is used, obtain supine and upright lateral C-spine X-
rays in the halo. If there is movement at the fracture site, then surgical stabilization is recommended.
• Rigid collar: fusion rate = 53%.
• Cervicothoracic orthosis provides better immobilization against flexion and rotation than a collar or an SOMI
• For poor surgical candidates: there is theoretical and anecdotal rationale to consider calcitonin therapy with a rigid cervical
cervical orthosis.

72.  Type I:
 So rare that meaningful analysis is difficult. If there is associated atlanto-axial instability, surgical fusion may at times be
necessary.
 Type II:
 Patients < 7 years old almost always heal with immobilization only
 Patients ≥ 7 years old Surgical treatment is recommended with any of the following:
• displacement ≥ 5 mm (some use ≥ 6 mm as the cutoff, citing a 70% nonunion rate for these regardless of age or direction of
displacement)
• instability at the fracture site in the halo vest
• age ≥ 50 years: increases nonunion rate (with halo) 21-fold
• nonunion including firm fibrous union,especially if accompanied by myelopathy
• disruption of the transverse ligament: associated with delayed instability
 Surgical options
• odontoid compression screw appropriate for acute type II fractures with transverse ligament intact and attached
• C1–2 fusion: for options including wiring/fusion, transarticular screws.

73.  Type IIa:
• Early surgery is recommended
 Type III:
• ≈ 90% heal with external immobilization (and analgesics) if adequately maintained for 8–14
weeks.
o Halo-vest brace is probably best (fusion rate ≈ 100%).
o Rigid collar (fusion rate = 50–70%); monitor the patient with frequent C-spine X-rays to rule out
nonunion.
• Surgical treatment: Atlantoaxial fusion and Anterior odontoid screw fixation

74. Os odontoideum
 is defined as an ossicle of cortical bone in the position of the odontoid process often attached to the
C2 body by a cartilaginous segment. occasionally may fuse with the clivus. May mimic Type 1 or 2
odontoid fracture.
 Etiologic theories: (True os odontoideum is rare)
• congenital: developmental anomaly (nonunion of dens to body of axis). However, does not follow known
ossification centers(there is no site of fusion where the axis meets the body)
• acquired: postulated to represent an old nonunion fracture or injury to vascular supply of developing odontoid
 Ossiculum terminale: nonunion of the apex at the secondary ossification center, is more common.
 anatomic types:
• 1. orthotopic: ossicle moves with the anterior arch of C1
• 2. dystopic: ossicle is functionally fused to the basion. May sublux anterior to the C1 arch

75.  Clinical presentation :
• Most patients are neurologically intact and present with atlantoaxial instability, which may be
discovered incidentally.
• Occipitocervical/neck pain
• Myelopathy: further subdivided
o a) transient myelopathy: common following trauma
o b) static myelopathy
o c) progressive myelopathy
• intracranial signs or symptoms: from vertebrobasilar ischemia
 Many symptomatic and asymptomatic patients have been reported with no new problems over
years of follow-up.

76.  Evaluation
 It is critical to R/O C1–2 instability. However, myelopathy does not correlate with the degree of C1–2 instability. (An AP canal
diameter < 13 mm does correlate with the presence of myelopathy.)
 the following plain C-spine X-rays: AP, open-mouth odontoid, lateral (static & flexion-extension) with or without tomography
(CT or plain) and/or MRI of craniocervical junction
 Treatment
 immobilization is unlikely to result in fusion.
 patients without neurologic signs or symptoms:
• may be followed with clinical & radiographic surveillance
• or posterior C1–2 fusion may be done
 patients with neurologic signs or symptoms or C1–2 instability: posterior C1–2 internal fixation and fusion
 if surgery is done: post-op halo immobilization is recommended (e.g. following posterior wiring & fusion) unless rigid internal
instrumentation is used
 for patients with irreducible cervicomedullary compression and/or evidence of associated occipitoatlantal instability: occipital-
occipital-cervical fusion ± C1 laminectomy
 for patients with irreducible cervicomedullary compression, consider ventral decompression

77. Miscellaneous C2 fractures
 Comprise ≈ 20% of C2 fractures.
 Includes fractures of spinous process, lamina, facets, lateral mass or C2 vertebral body.
 Fractures of spinous process or lamina may be treated with Philadelphia collar or cervicothoracic orthosis
(CTO).
 Fractures which compromise the anterior or middle columns (i.e., fractures of facets, C2 body, or lateral
mass) require
• Nondisplaced : CTO or halo-vest
• Displaced : halo-vest.
 Management of fractures of the axis (C2) body:
• fractures initially managed with external immobilization in most cases (halo or collar)
• surgical stabilization should be considered in cases of:
• a) severe ligamentous instability
• b) inability to establish or maintain alignment with external immobilization
• evaluate for vertebral artery injury in cases of comminuted fracture of the axis body

78. Combination C1 & C2 injuries
 They are relatively common and may imply more significant mechanical injury than isolated C1 or C2
fractures.
 Base treatment primarily on the type of C2 injury