Updated: 6/17/2021

Odontoid Fracture

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  • SUMMARY
    • Odontoid Fractures are relatively common fractures of the C2 (axis) dens that can be seen in low energy falls in elderly patients and high energy traumatic injuries in younger patients.
    • Diagnosis can be made with standard lateral and open-mouth odontoid radiographs. Some fractures may be difficult to visualize on Xrays and require a CT scan to diagnose. MRI is rarely indicated as these fractures are usually not associated with neurologic symptoms. 
    • Treatment may be nonoperative or operative depending on the Anderson and D'Alonzo type and risk factors for nonunion. Patient older than 80 have a high morbidity and mortality regardless of nonoperative or operative treatment. 
  • Epidemiology
    • Incidence
      • most common fracture of the axis
      • account for 10-15% of all cervical fractures
      • most common cervical spine fractures in the elderly
    • Demographics
      • occur in bimodal fashion in elderly and young patients
        • elderly
          • common, often missed, and caused by simple falls
          • associated with increased morbidity and mortality compared to younger patients with this injury
        • young patients
          • result from blunt trauma to head leading to cervical hyperflexion or hyperextension
        • children
          • rare and almost occur at site of  basilar synchondrosis 
  • Etiology
    • Pathophysiology
      • mechanism
        • displacement may be anterior (hyperflexion) or posterior (hyperextension)
          • anterior displacement
            • is associated with transverse ligament failure and atlanto-axial instability
          • posterior displacement
            • caused by direct impact from the anterior arch of atlas during hyperextension
      • biomechanics
        • a fracture through the base of the odontoid process severely compromises the stability of the upper cervical spine.
    • Associated conditions
      • Os odontoideum
        • etiology
          • previously thought to be due to failure of fusion at the base of the odontoid
          • evidence now suggests it may represent the residuals of an old traumatic process
        • imaging
          • appears like a type II odontoid fx on xray
        • treatment
          • observation
  • Anatomy
    • Osteology
      • axis has odontoid process (dens) and body
      • contains a transverse foramen which vertebral artery travels through
      • embryology
        • develops from five ossification centers
          • subdental (basilar) synchondrosis
            • is an initial cartilaginous junction between the dens and vertebral body that does not fuse until ~6 years of age
        • secondary ossification center 
          • appears at ~ age 3 and fuses to the dens at ~ age 12
    • Arthrology
      • C1-Dens
        • anterior dens articulates with anterior arch of C1
      • CI-C2 articulation
        • is a diarthrodial joint that provides
      • C2-3 joint
        • participates in subaxial (C2-C7) cervical motion 
    • Ligaments
      • occipital-C1-C2 ligamentous stability
      • provided by the odontoid process and its supporting ligaments
        • transverse ligament
          • primary stabilizer of atlantoaxial joint
          • limits anterior translation of the atlas
        • apical ligaments
          • limit rotation of the upper cervical spine
        • alar ligaments
          • limit rotation of the upper cervical spine
    • Blood Supply
      • a vascular watershed exists between the apex and the base of the odontoid
        • apex
          • supplied by branches of internal carotid artery
        • base
          • supplied from branches of vertebral artery
        • the limited blood supply in this watershed area is thought to affect healing of type II odontoid fractures.
    • Kinematics
    • Normal Cervical Kinematics
      Flexion/Extension
      Rotation
      Lateral Bend
      Occipitocervical joint (OC)
      50
      4
      8
      Atlantoaxial joint (C1-2)
      10
      50
      0
      Subaxial Spine (C3-7)
      50
      50
      60
      Total Motion (degrees)
      110
      100
      68
  • Classification
    • Anderson and D'Alonzo Classification
      Type I
      Oblique avulsion fx of tip of odontoid. Due to avulsion of alar ligament. Although rare,atlantooccipital instability should be ruled out with flexion and extension films . 
      Type II
      Fracture through waist (high nonunion rate due to interruption of blood supply).
      Type III
      Fx extends into cancellous body of C2 and involves a variable portion of the C1-C2 joint.
    • Grauer Classification of Type II Odontoid fractures
      Type IIA
      Nondisplaced/minimally displaced with no comminution. Treatment is external immobilization
      Type IIB
      Displaced fracture with fracture line from anterosuperior to posteroinferior. Treatment is with anterior odontoid screw (if adequate bone density).
      Type IIC
      Fracture from anteroinferior to posterosuperior, or with significant comminution. Treatment is with posterior stabilization.
  • Presentation
    • Symptoms
      • neck pain
        • worse with motion, especially rotation
      • dysphagia
        • may be present when associated with a large retropharyngeal hematoma
    • Physical exam
      • neurologic deficits
        • very rare due to large cross-section area of spinal canal at this level
  • Imaging
    • Radiographs
      • required views
        • AP, lateral, open-mouth odontoid view of cervical spine
      • optional views
        • flexion-extension radiographs are important to diagnose occipitocervical instability in Type I fractures and Os odontoideum
          • instability defined as
            • atlanto-dens-interval (ADI)
              • > 10mm
            • space available for cord (SAC)
              • < 13mm 
      • findings
        • fx pattern best seen on open-mouth odontoid
    • CT
      • study of choice for fracture delineation and to assess stability of fracture pattern
    • CT angiogram
      • required to determine location of vertebral artery prior to posterior instrumentation procedures
    • MRI
      • indicated if neurologic symptoms present
  • Treatment
    • Treatment Overview Table
      Type I
      Collar
      Type II (age < 40)
      Halo Vest
      Type II (40-80)
      Surgery
      Type II (> 80 years)
      Collar
      Type III
      Collar
    • Nonoperative
      • observation alone
        • indications
          • Os odontoideum
            • assuming no neurologic symptoms or instability
      • hard cervical orthosis
        • indications
          • Type I
          • Type II in elderly who are not surgical candidates
            • union is unlikely, however a fibrous union should provide sufficient stability except in the case of major trauma
            • no evidence to support Halo over hard collar 
        • technique
          • typically worn for 6-12 weeks
      • halo immobilization
        • indications
          • Type II young patient with no risk factors for nonunion 
        • contraindications
          • elderly patients
            • do not tolerate halo (may lead to aspiration, pneumonia, and death)
        • technique
          • typically work for 6-12 weeks
    • Operative
      • posterior C1-C2 fusion
        • indications
          • Type II fractures with risk factors for nonunion
            • indicated in patient 50-80 
          • Type II/III fracture nonunions
          • Os odontoideum with neurologic deficits or instability
      • anterior odontoid screw
        • indications
          • Type II fractures with risk factors for nonunion AND
            • acceptable alignment and minimal displacement (reduction obtained) 
            • anterior oblique fracture pattern 
              • fracture line is perpendicular to screw trajectory
            • patient body habitus must allow proper screw trajectory
        • outcomes
          • associated with higher failure rates than posterior C1-2 fusion
      • transoral odontoidectomy
        • indications
          • severe posterior displacement of dens with spinal cord compression and neurologic deficits
          • rarely performed due to high complication rate
            • C1 laminectomy typically provides sufficient decompression of the spinal canal and is preferred
  • Techniques
    • Halo immobilization
      • complications
        • pin site infection
          • initial superficial pin infection can be treated with tightening and oral antibiotics 
    • C1-C2 posterior fusion
      • approach
        • posterior midline cervical approach
      • stabilization technique
        • sublaminar wiring techniques (Gallie or Brooks)
          • require postoperative halo immobilization and rarely used
        • posterior C1-C2 segmental fixation
          • C1 lateral mass screws
            • 10 degrees medial, 22 degrees cephalad
            • avoid perforation of anterior cortex of C1 lateral mass due to potential internal carotid arteryinjury 
          • C2 fixation options include
            • C2 laminar screws 
            • C2 pedicle screws
            • C2 pars scews (most common)
        • posterior C1-C2 transarticular screws construct
          • contraindicated in patients with an aberrant vertebral artery
      • outcomes
        • C1-C2 fusion will lead to 50% loss of neck motion
        • Higher fusion rate in elderly compared to anterior fusion
    • Anterior odontoid screw
      • approach
        • anterior approach to cervical spine
      • technique
        • single screw adequate
      • pros & cons
        • associated with higher failure rate than posterior C1-2 fusion
        • advantage is preservation of atlantoaxial motion
    • Transoral odontoidectomy
      • technique
        • usually combined with posterior stabilization procedure
  • Complications
    • Nonunion
      • overall incidence
        • 33% (up to as high as 88% in some studies)
      • risk factors
        • Type II fractures with 
          • posterior displacement ( > 2 mm) 
            • strongest predictor of nonunion
          • age > 40 years 
          • ≥ 5 mm displacement (>50% nonunion rate)
          • delay in treatment ( > 4 days)
          • angulations > 10°
          • smoker
    • Mortality
      • overall patient > 80 year of age do poorly with operative or nonoperative treatment 
        • especially with halo orthosis

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(SBQ18SP.6) An active 79-year-old male fell from standing height and noticed immediate neck pain. Examination in the emergency department reveals 5/5 motor in bilateral upper and lower extremities. Current imaging is shown in Figures A-C. The patient undergoes treatment that included closed reduction under anesthesia immediately followed by a posterior C1-2 fusion utilizing lateral mass screws at C1 and pedicle screws at C2. Which of the following statements is true regarding this treatment approach?

QID: 211168
FIGURES:
1

It will increase the rate of nonunion compared to nonoperative treatment.

2%

(39/1768)

2

It will increase the rate of dysphasia compared to treatment in a halo immobilization.

6%

(100/1768)

3

It will decrease mortality compared to nonoperative treatment.

79%

(1389/1768)

4

It has a decreased fusion rate compared to an anterior surgical approach

8%

(143/1768)

5

It will lead to a lower SF-36 score.

5%

(82/1768)

L 2 A

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(SBQ12SP.12) An 72-year-old man falls down the stairs and strikes his forehead. He presents to the emergency room with neck pain and a normal neurological exam. He is an active smoker. His past medical history includes chronic obstructive pulmonary disease, atrial fibrillation, and insulin-dependent diabetes mellitus. Coronal and sagittal images from a CT scan of his cervical spine are shown in Figure A. Which treatment option is most appropriate?

QID: 3710
FIGURES:
1

Figure B

8%

(377/4442)

2

Figure C

10%

(428/4442)

3

Figure D

3%

(125/4442)

4

Figure E

67%

(2988/4442)

5

Figure F

11%

(497/4442)

L 4 B

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(OBQ12.103) A young boy is involved in a motor vehicle accident and presents with neck pain. A CT scan is performed and is negative for fractures. Based on the presence of the ossification center shown in Figure A, what is the most likely age bracket of this patient.

QID: 4463
FIGURES:
1

< 1 years of age

0%

(10/3592)

2

1-3 years of age

7%

(246/3592)

3

3-6 years of age

33%

(1181/3592)

4

8-10 years of age

50%

(1802/3592)

5

> 12 years of age

9%

(328/3592)

L 4 C

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(OBQ12.116) A 67-year-old male smoker was involved in a motor vehicle accident and presents with neck pain. On initial presentation his neurologic exam was intact. Injury films are shown in Figure A and B. The patient was evaluated and surgical treatment was recommended. The patient left the hospital against medical advice. Seven months later he returns with continued neck pain. His current neurologic exam shows no deficits. A current CT scan and MRI is performed and shown in Figure C and D. What is the most appropriate treatment at this time?

QID: 4476
FIGURES:
1

Physical therapy and NSAIDS

15%

(677/4565)

2

Hard Cervical Orthosis

3%

(130/4565)

3

Halo Immobilization

2%

(75/4565)

4

Anterior screw osteosynthesis

7%

(337/4565)

5

Posterior C1-C2 fusion

72%

(3305/4565)

L 2 B

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(OBQ12.65) A 45-year old male is involved in a motor vehicle accident and presents to the emergency room with complaints of neck pain. Physical exam shows he is an ASIA E. An open-mouth cervical radiograph is shown in Figure A. A sagittal CT scan is shown in Figure B. A CT axial angiogram is shown in Figure C. Which of the following treatment options is contraindicated in this patient.

QID: 4425
FIGURES:
1

Anterior screw osteosynthesis with single cannulated screw

12%

(576/4972)

2

Halo immobilization

15%

(752/4972)

3

Anterior screw osteosynthesis with two cannulated screws

10%

(477/4972)

4

C1-C2 transarticular screws

50%

(2482/4972)

5

Posterior C1-C2 wiring with autograft

13%

(637/4972)

L 4 B

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(OBQ11.263) In Figures A-E, which of the following fracture patterns is at greatest risk for nonunion with nonoperative treatment?

QID: 3686
FIGURES:
1

Figure A

2%

(60/3495)

2

Figure B

54%

(1886/3495)

3

Figure C

3%

(96/3495)

4

Figure D

19%

(663/3495)

5

Figure E

22%

(771/3495)

L 3 B

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(OBQ10.130) In patients who are neurologically intact, all of the following cervical spine injuries can be appropriately managed with external immobilization in a rigid cervical orthosis EXCEPT

QID: 3223
FIGURES:
1

Figure A

1%

(27/4049)

2

Figure B

1%

(55/4049)

3

Figure C

5%

(199/4049)

4

Figure D

4%

(168/4049)

5

Figure E

89%

(3586/4049)

L 1 C

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(OBQ10.185) In elderly patients with type II odontoid fractures, which of the following treatment modalities has the highest morbidity and mortality?

QID: 3278
1

Hard cervical collar

2%

(56/2731)

2

Anterior screw osteosynthesis

7%

(184/2731)

3

Halo vest immobilzation

80%

(2182/2731)

4

Posterior cervical stabilization

4%

(114/2731)

5

Soft cervical orthosis

7%

(180/2731)

L 2 B

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(SBQ09SN.26.2) A 65-year-old diabetic male with a 30-pack-year smoking history and COPD presents to the ED with severe axial neck pain after a fall from standing while attempting to use the restroom in the middle of the night. He is neurologically intact and denies any radicular symptoms. Figures A through D are the current radiographs and CT scans. What is the most appropriate management at this time?

QID: 214189
FIGURES:
1

Continued immobilization in a semi-rigid cervical orthosis for 6 to 8 weeks

8%

(117/1513)

2

Reduction and posterior instrumented C1-C2 fusion

58%

(872/1513)

3

Open reduction and internal fixation of the odontoid process with an anterior odontoid screw

32%

(483/1513)

4

Resection of the odontoid process through a transoral approach

1%

(11/1513)

5

Reduction with Gardner-Wells tong traction and 6 weeks of skeletal traction

1%

(19/1513)

L 4 B

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(OBQ08.78) A 37-year-old male was involved in a motorcycle accident. He is neurologically intact. A coronal and sagittal CT scan is shown in Figure A. What is the most appropriate management?

QID: 464
FIGURES:
1

Posterior C1-C2 fusion

6%

(182/3259)

2

Anterior odontoid screw fixation

20%

(647/3259)

3

Transoral anterior odontoid resection

0%

(8/3259)

4

Cervical immobilization for 6-8 week in an external orthosis

72%

(2361/3259)

5

Treatment in a soft cervical orthosis for two weeks followed by range of motion exercises

2%

(52/3259)

L 2 B

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(OBQ06.263) A 36-year-old male falls while intoxicated two weeks ago and has had persistent neck pain ever since. For unclear reasons he did not seek medical attention. He now reports persistent neck pain, but denies symptoms in his upper and lower extremities. On physical exam he has Grade 5 motor strength in his upper and lower extremities, normal reflexes, and his sensory exam is normal. A CT scan is shown in Figure A. All of the following place this patient at an increased risk of nonunion EXCEPT:

QID: 274
FIGURES:
1

Fracture gap of 2 mm

3%

(102/3525)

2

Posterior displacement of > 5mm

2%

(71/3525)

3

Delay in treatment of 2 weeks

4%

(128/3525)

4

Age < 40 years

89%

(3141/3525)

5

Posterior angulation

2%

(72/3525)

L 2 B

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