Odontoid_Fractures

Question 1

Axis Embryology

Answer 1

4 primary ossification centers and 1 secondary ossification center
Odontoid
Neural arch(2)
C2 body
Secondary is at apex of odontoid

subdental(basilar) synchondrosis does not fuse until age 6
Secondary ossification center appears ~3 years and does not fuse until ~12

Question 2

Anderson & D’Alonzo Classification of Odontoid Fractures

Answer 2

Type I - oblique alar ligament avulsion fracture tip of dens
Rule out instability with flexion-extension views
Type II - waist fxr with high nonunion rate
Type III - body of C2 and involves variable portion of C1-2 joint

Question 3

Grader Classification of Type II Odontoid Fractures

Answer 3

Type IIA - non/minimally displaced with no communition
Rx is external immobilization
Type IIB - Displaced with fxr line anterosuperior to posteroinferior
Rx is odontoid screw if adequate bone density
Type IIC - Displaced with fxr line anteroinferior to posterosuperior or significant
comminution.
Rx is posterior surgical stabilization

Question 4

Os odontoideum instability

Answer 4

ADI > 10mm

SAC < 13mm

Question 5

Treatment Odontoid Fxrs and Os Odontoideum

Answer 5

Os odontoideum - observation
Type I - cervical Orthofix (stable)
Type II Young - Halo if no risk factors for nonunion
Surgery if risk factors for nonunion
Type II Elderly - Cervical orthosis if not a surgical candidate
Surgery if surgical candidate
Type III Cervical orthosis

Question 6

Risk Factors for Type II Odontoid Nonunion (8)

Answer 6

> 6mm displacement (>50% nonunion rate) 
          strongest reason to opt for surgery
Age > 50
Fxr comminution
Fxr gap > 1mm
Angulations > 10 degrees
Delay in treatment > 4 days
Posterior re-displacement > 2mm
Smoker