http://upload.orthobullets.com/topic/2015/images/xray_jefferson_fx.jpg
http://upload.orthobullets.com/topic/2015/images/type 3 atlas.jpg
http://upload.orthobullets.com/topic/2015/images/incomplete c1.jpg
http://upload.orthobullets.com/topic/2015/images/ligaments.jpg
http://upload.orthobullets.com/topic/2015/images/atlas fxx.jpg
Introduction
  • Epidemiology
    • make up ~7% of cervical spine fractures
    • risk of neurologic injury is low
    • commonly missed due to inadequate imaging of occipitocervical junction
  • Pathophysiology
    • mechanism
      • includes hyperextension, lateral compression, and axial compression
  • Associated conditions
    • spine fracture
      • 50% have an associated spine injury
      • 40% associated with axis fx
  • Prognosis
    • stability dependent on degree of injury and healing potential of transverse ligament
Anatomy
  • Bony anatomy
    Atlas osteology
    • atlas (C1) is a ring containing two articular lateral masses
      • it lacks a vertebral body or a spinous process
      • embryology
        • forms from 3 ossification centers  
      • anatomic variation
        • incomplete formation of the posterior arch is a relatively common anatomic variant and does not represent a traumatic injury 
  • Ligamentous anatomy
    • occipital-cervical junction and atlantoaxial junction are coupled
    • intrinsic ligaments are located within the spinal canal, provide most of the ligamentous stability. They include
      • transverse ligament  
        • primary stabilizer of atlantoaxial junction
        • connects the posterior odontoid to the anterior atlas arch, inserting laterally on bony tubercles. 
      •  paired alar ligaments  
        • connect the odontoid to the occipital condyles
        • relatively strong and contributes to occipitalcervical stability
      • apical ligament  
        • relatively weak midline structure
        • runs vertically between the odontoid and foramen magnum.
      • tectorial membrane 
        • connects the posterior body of the axis to the anterior foramen magnum and is the cephalad continuation of the PLL
  • atlas (C1) is a ring containing two articular lateral masses
    it lacks a vertebral body or a spinous process
    anatomic variation
    incomplete formation of the posterior arch is a relatively common anatomic variant and does not represent a traumatic injury
    Ligamentous anatomy
    intrinsic ligaments are located within the spinal canal, provide most of the ligamentous stability. They include
    tectorial membrane (most dorsal layer) 
    connects the posterior body of the axis to the anterior foramen magnum and is the cephalad continuation of the PLL
     transverse ligament is the strongest component 
    connects the posterior odontoid to the anterior atlas arch, inserting laterally on bony tubercles.  
     paired alar ligaments 
    connect the odontoid to the occipital condyles
    relatively strong
    apical ligament
Classification
 
 Atlas Fractures Classification
Type I Isolated anterior or posterior arch fracture. A "plough fracture is an isolated anterior arch fracture caused by a force driving the odontoid through the anterior arch.
Type II Jefferson burst fracture with bilateral fractures of anterior and posterior arch resulting from axial load. Stability determined by integrity of transverse ligament.
Type III Unilateral lateral mass fx. Stability determined by integrity of transverse ligament.  
 
Transverse Ligament Injuries Classification
Type I Intersubstance tear
Type II Bony avulsion
 
Imaging
  • Radiographs 
    • lateral radiographs
      • atlantodens interval (ADI)
        • < 3 mm = normal in adult (< 5mm normal in child) 
        • 3-5 mm = injury to transverse ligament with intact alar and apical ligaments 
        •  > 5 mm = injury to transverse, alar ligament, and tectorial membrane 
    • open-mouth odontoid
      • open-mouth odontoid view important to identify atlas fractures
      • sum of lateral mass displacement 
        • if sum of lateral mass displacement is > 7 mm (8.1mm with radiographic magnification) then a transverse ligament rupture is assured and the injury pattern is considered unstable q q
  • CT
    • study of choice to delineate fracture pattern and identify associated injuries in the cervical spine 
  • MRI
    • more sensitive at detecting injury to transverse ligament 
Treatment
  • Nonoperative
    • hard cervical orthosis vs. halo immobilization for 6-12 weeks 
      • indications 
        • stable Type I fx (intact transverse ligament)
        • stable Jefferson fx (Type II) (intact transverse ligament)
        • stable Type III (intact transverse ligament)
      • technique
        • controversy exists around optimal form of immobilization
  • Operative
    • posterior C1-C2 fusion vs. occipitocervical fusion 
      • indications
        • unstable Type II (controversial)    
        • unstable Type III  (controversial)
      • technique
        • may consider preoperative traction to reduce displaced lateral masses
Techniques
  • Posterior C1-C2 fusion
    • preserves motion compared to occipitocervical fusion
    • fixation
      • C1 lateral mass / C2 pedicle screw construct
        • may be sufficient if adequate purchase with C1 lateral mass screws
      • C1-2 transarticular screw placement
  • Occipitocervical fusion
    • uses when unable to obtain adequate purchase of C1
    • leads to significant loss of motion 
Complications
  • Delayed C-spine clearance
    • higher rate of complications in patients with delayed C-spine clearance so it is important to clear expeditiously
 

Please rate topic.

Average 4.0 of 37 Ratings

Questions (4)

(OBQ12.255) A 35-year-old patient sustains a bilateral anterior and posterior arch (C1) injury with an intact transverse ligament. Which of the following treatment options is most appropriate? Review Topic

QID:4615
1

Observation alone

1%

(19/2366)

2

Soft collar orthosis for 4-6 weeks

3%

(79/2366)

3

Occipitocervical fusion

8%

(200/2366)

4

Rigid collar orthosis for 6-12 weeks

80%

(1886/2366)

5

Posterior C1-C2 fusion

7%

(177/2366)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

The patient has sustained a Jefferson fracture of the C1 arch. Given that the transverse ligament is intact, of the options listed, a rigid collar orthosis for 6-12 weeks would be the most appropriate treatment.

Fractures of the atlas are often the result of hyperextension, lateral compression and axial compression. Type 2 atlas fractures (Jefferson burst) involve the anterior and posterior arches as a result of axial loading. The stability and treatment of these fractures depends on the integrity of the transverse ligament.

Dickman et al. reviewed 39 patients with injury to the transverse ligament or its bony origins. They recommend that ligamentous (Type 1) injuries be treated with early surgery where as bony ligamentous avulsion (Type 2) injuries be treated initially with a hard cervical orthosis. Type 2 injuries had a 74% success rate of healing with conservative measures.

Spence et al. report a case of an atlas fracture with an associated injury to the transverse ligament. They indicate that lateral mass displacement greater than 6.9 mm is likely indicative of a tear in the transverse ligament. They recommend use of radiographs to delineate the integrity of the transverse ligament, as this will help guide treatment.

Illustration A shows an axial CT cut of a Jefferson fracture. The posterior arches are bilaterally fractured with unilateral involvement of the anterior arch.

Incorrect Answers
Answer 1: Observation is not indicated in this situation.
Answers 2, 3: In a Jefferson type injury, a soft collar orthosis is not indicated
Answer 5: Given the integrity of the transverse ligament, a posterior cervical fusion is not indicated at this time.

ILLUSTRATIONS:

Please rate question.

Average 4.0 of 15 Ratings

Question COMMENTS (3)

(OBQ10.71) Figure A shows the coronal and axial CT images of a 27-year-old male that suffered a fall from a significant height. Which of the following radiographic measurements would best indicate disruption of the transverse ligament? Review Topic

QID:3159
FIGURES:
1

Atlantodental interval (ADI) of 2mm

6%

(135/2271)

2

Posterior atlanto-dens interval (PADI) of 16mm

9%

(204/2271)

3

C2 pars horizontal displacement of 3 mm

3%

(70/2271)

4

Combined lateral mass displacement of 8.2mm

78%

(1781/2271)

5

A Power's ratio of 1.2

3%

(71/2271)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

The clinical presentation is consistent with a Jefferson fracture. A combined lateral mass displacement of 8.2mm or greater would indicate injury to the tranverse ligament.

A Jefferson fracture (Type II Atlas Fracture) is characterized by bilateral fractures of both the anterior and posterior arch. They are considered unstable when the transverse ligament is no longer intact. Radiographically, an atlanto-dens-interval (ADI) of >3mm or a sum of lateral mass displacement of >8.2mm both indicate a ruptured transverse ligament. Treatment of Jefferson fractures remain controversial. A stable injury (intact transverse ligament) can be treated with a cervical orthosis.

Spence et al., in a historic anatomic study, showed that lateral mass separation of > 6.9 mm implied rupture of the transverse ligament.

Heller et al. built radiographic magnification into Spence's findings, and argues that a transverse ligament rupture should not be inferred unless lateral mass separation is > 8.1 mm on open mouth odontoid views.

Haus et al. published a case report of a single patient with a lateral mass displacement of 14mm that was treated successfully with a cervical orthosis only.

Illustration A shows. Illustration shows the radiographic parameters that indicated a rupture of the transverse ligament.

Incorrect Answers:
Answer 1: An Atlantodental interval (ADI) of 2mm is normal and would not indicated an injury to the transverse ligament. An ADI of >3mm indicates injury to the transverse ligament.
Answer 2. A Posterior atlanto-dens interval (PADI) of 16mm is a normal finding. A Posterior atlanto-dens interval (PADI) of < 14mm would indicated a injury to the tranverse ligament. Keep in mind diameter of the spinal canal at C1 = PADI + diameter of dens + ADI.
Answer 3: C2 pars horizontal displacement is used to evaluate traumatic spondylolithesis of axis (Hangman's fracture).
Answer 4: The Power's ratio is used to evaluate occipitocervical instability.

ILLUSTRATIONS:

Please rate question.

Average 4.0 of 31 Ratings

Question COMMENTS (10)

(OBQ05.67) A Gallie C1-2 fusion with sublaminar wiring of C1 to the spinous process of C2 is a valid treatment option for which of the following injury patterns? Review Topic

QID:953
1

occipital-cervical dissociation

4%

(25/654)

2

comminuted C1 burst fracture

9%

(60/654)

3

type I odontoid fracture

4%

(29/654)

4

type III odontoid fracture

13%

(83/654)

5

transverse ligament disruption

70%

(455/654)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

A C1-2 fusion with sublaminar wiring or modern screw-rod constructs is indicated in transverse ligament injuries.

Gallie et al reports “Recurrence of the [atlanto-axial] displacement following disruption of the transverse ligament can be prevented by fastening the two vertebrae together by fine steel wire passed around the laminae or spines. And the risk of late recurrence can be eliminated by bone grafts laid in the spines or on the laminae and articular facets."

Of note, this technique is somewhat dated, although one can still use it with successful results. Other C1-C2 fusion technique currently used include C1/2 transarticular screws or C1 lateral mass/C2 pedicle screw-rod construct.

Illustration A shows the anatomy of the tranverse ligament, which is an important stabilizer of the C1-2 motion segment.

Incorrect Answers:
Answer 1: C1-2 fusion is not valid for occipital-cervical dissociation because fusion to the occiput is needed and not addressed.
Answer 2: Comminuted C1 burst fracture also needs fusion to the occiput because comminution will compromise your fixation at C1.
Answer 3 & 4: Types I and III odontoid fractures are treated nonoperatively.

ILLUSTRATIONS:

Please rate question.

Average 4.0 of 21 Ratings

Question COMMENTS (2)

(OBQ04.176) Biomechanical studies have shown that an atlanto-dens interval of >7mm is likely associated with? Review Topic

QID:1281
1

an intact transverse ligament, with ruptured alar and apical ligaments

6%

(104/1706)

2

a ruptured transverse ligament, with intact alar and apical ligaments

20%

(336/1706)

3

a ruptured transverse and apical ligament, with an intact alar ligaments

8%

(135/1706)

4

a ruptured transverse and alar ligament, with an intact apical ligaments

19%

(321/1706)

5

a ruptured transverse and alar ligament, and a ruptured tectorial membrane

47%

(801/1706)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

The intrinsic ligaments, located within the spinal canal, provide most of the ligamentous stability. These ligaments form three layers anterior to the dura. From dorsal to ventral, they include the tectorial membrane, the cruciate ligament, and the odontoid ligaments. The tectorial membrane connects the posterior body of the axis to the anterior foramen magnum and is the cephalad continuation of the posterior longitudinal ligament. The cruciate ligament lies anterior to the tectorial membrane, behind the odontoid process. The transverse atlantal ligament is the strongest component, connecting the posterior odontoid to the anterior atlas arch, inserting laterally on bony tubercles. The odontoid ligaments (alar and apical ligaments) are the most ventral ligamentous structures. The paired alar ligaments connect the odontoid to the occipital condyles. They measure 5 to 6 mm in diameter and are relatively strong, in contrast with the small apical ligament that runs vertically between the odontoid and foramen magnum. In normal adults the ADI is < 3mm and < 5mm in children. Experimentally produced transverse ligament insufficiency with intact alar and apical ligaments results in a maximal translation of 5 mm, as shown by Fielding et al. Displacement >7 mm was associated with loss of integrity of the alar ligament and tectorial membrane.

ILLUSTRATIONS:

Please rate question.

Average 3.0 of 30 Ratings

Question COMMENTS (4)
Sorry, this question is available to Virtual Curriculum members only.

Click HERE to learn more and purchase the Virtual Curriculum today!


CASES (2)
VIDEOS (1)
GROUPS (1)
EVIDENCE & REFERENCES (12)
Topic COMMENTS (18)