Ch62 Occipitoatlantoaxial injuries (Occiput to C2)

Question 1

What is the classification system for Occipital Condylar fractures?

Answer 1

Anderson Montesano classification

Type I (comminuted), 
Type II (extension of a linear basilar skull fracture), and Type III (avulsion of a fragment)

Question 2

What is the classification system for Atlanto-occiptal dissociation?

Answer 2

Type I

Anterior dislocation of occiput relative to the atlas

Type II

Longitudinal dislocation (distraction)

Type III

Posterior dislocation of occiput

Question 3

What is the most sensitive radiological marker for Atlanto-occipital dissociation?

Answer 3

Condylar gap (Adults <2mm on XR, 1.6mm on CT)

Question 4

How do you calculate Power’s ratio?

Answer 4

Only for Anterior AOD

Basion - Posterior arch of C1 / Anterior arch C1 - Opisthion

<0.9 normal
>0.9 - < 1 Intermediate
>1 AOD

Question 5

How do you manage occipital-condylar fractures?

Answer 5

Type 1 and 2 in a collar
Type 3 in a collar or Halo
If bilateral - Halo
If evidence of ligamentous injury - Halo or fixation

Question 6

What are the types of atlanto-axial subluxation?

Answer 6

1. rotatory: usually seen in children after a fall or minor trauma
2. anterior
3. posterior: rare. Usually from erosion of odontoid. Unstable. Requires fusion

Question 7

What is Grisel syndrome?

Answer 7

rare cause of torticollis that involves subluxation of atlanto-axial joint from inflammatory ligamentous laxity following an infectious process in the head and neck, usually a retropharyngeal abscess.

Question 8

What is the classification system for degree atlanto-axial subluxation?

Answer 8

Fielding & Hawkins
1 - intact Transverse ligament, bilateral facet injury
2 - Injured transverse ligament, unilateral facet
3 - Injured transverse ligament, bilateral facet
4 - incompetent odontoid with posterior displacement

3 and 4 highly unstable

Question 9

How do you assess for transverse ligament rupture?

Answer 9

Rule of spence - overhang of C1 lateral mass over C2 combined >7mm

Atlantodental interval >3mm in adults >4mm in paeds

Question 10

What is the classification system for transverse ligament rupture?

Answer 10

Dickman classification

Type 1 Anatomic disruption - tear of the ligament itself. Rare. Requires fixation

Type 2 Physiologic disruption - detachment of the C1 tubercle from the lateral mass - Halo recommended

Question 11

When would you fix a C1 fracture

Answer 11

when the Transverse ligament is affected

Question 12

What is the classification system for Hangmans fractures?

Answer 12

Levine/Effendi classification

1- vertical pars fracture just posterior to the VB. No angulation
1A - Fracture lines on each side not parallel, fracture may pass through foramen transversarium on one side

2 - vertical pars fracture with disruption of C2/3 disc and PLL >3mm subluxation
2A oblique fracture- more angulation

3 Type 2 + C2/3 facet capsule disruption

Question 13

What is the classification system for peg fractures?

Answer 13

Anderson and D’Alonzo

Question 14

What is the fusion rate for Halo in managing peg fractures?

Answer 14

72%

Rigid collar fusion rate - 53%

Question 15

What are the 2 types of os odonoideum?

Answer 15

orthotopic: ossicle moves with the anterior arch of C1
dystopic: ossicle is functionally fused to the basion. May sublux anterior to the C1 arch