High Cervical Trauma

Question 1

Classification Systems for Occipitocervical Dissociations

Answer 1

Traynelis OR Harborview classifications

• Harborview based on degree of displacement
• Traynelis based on are of instability

Question 2

Powers Ratio

Answer 2

(Basion-Posterior Arch)/(Opisthion-Anterior arch)
Normal = 1
Anterior dislocation >1
Posterior dislocation <1
Odontoid fracture <1
Ring of atlas fx <1

Question 3

Harris Rule of 12

Answer 3

Basion-dens interval OR
Basion-posterior axial interval
if >12mm represents occipitocervical dissociation

as viewed on mid-sagittal CT

Question 4

Skull thickness at the external occipital protuberance

Answer 4

11-17mm

essential for Occipital fusions

Question 5

which vertebral artery is usually dominant?

Answer 5

Left

Question 6

Risks of ligating a vertebral artery injury

Answer 6

• cerebellar infarction
• hemiplegia
• cranial nerve palsies

overall risk 12%

Question 7

safe zone for occipital screw placement

Answer 7

The safe zone for screw placement in the occiput for occipitocervical fusion is in a triangular region created by connecting 2 dots 2cm lateral to the EOP and a point 2 cm inferior to the EOP

• use 8mm screws
• bicortical screws can risk the transverse sinus (at the level of the EOP)

Question 8

Unstable measurements of the anterior ADI in RA

Answer 8

> 3.5mm is unstable

>10mm is indication for surgery in RA

Question 9

Dangerous SAC in RA

Answer 9

< 14mm is indication for surgery

- higher risk of neurologic injury

Question 10

Lateral mass displacement distance

Answer 10

> 8.1mm means transverse ligament is disrupted

Question 11

Management of Os Odontoideum

Answer 11

• if asymptomatic, then cessation of contact athletics

- if neurologically symptomatic, then posterior C1-2 fusion

Question 12

Landell’s Atlas Classification System

Answer 12

1: single ring fracture
2: Jefferson burst fracture
3: Unilateral lateral mass fracture

Question 13

Treatment of Landell Type 1 Atlas Fracture:

Answer 13

stable, treat with hard collar

Question 14

Treatment of Landell Type 2 Atlas fracture

Answer 14

Jefferson burst

• look at sum of lateral mass displacement
• if <7mm then treat with hard collar
• if >7mm then unstable (transverse ligament injury) and needs Halo vest (if bony avulsion) OR C1-2 fusion (if instrasubstance tear)

Question 15

Treatment of Landell type 3 Atlas fracture

Answer 15

if stable, treat with hard collar

if unstable, halo vest

Question 16

Unstable measurements of ADI in trauma:

Answer 16

<3mm is normal in adult
3-5 means apical/alar disruption
>5 means transverse ligament disruption

Question 17

Risk factors for type II Odontoid nonunion (when treated in Halo vest)

Answer 17

• fracture gap >1mm
• posterior displacement >5mm
• delayed start of treatment >4 days
• posterior re-displacement >2mm

Question 18

Nonunion rate for Type II odontoid fractures treated in Halo vest:

Answer 18

54%

Question 19

rotation provided by C1-2 joint

Answer 19

50 degrees