Definition
Relative translation of (typically) C2 on C3
- Physiological variant in children up to 8
Subluxation of up to 4 mm
- C2/3 in 40% children
- C3/4 14%
Reduces with extension
Aetiology
Horizontal facet joints
- flat orientation of pediatric facets and laxity of ligaments
- become more vertical with age
Diagnosis
1. Swischuk's Line
- drawn along spinolaminar line C1 & C3
- C2 should be within 1.5 - 2mm of this line
2. Pseudosubluxation will reduce with extension