Atlanto-axial instability
Definition
Loss of ligamentous stability between atlas and axis
Can cause impingement of the spinal cord
Etiology
Loss of ligamentous stability between atlas and axis
Can cause impingement of the spinal cord
RA
OA
AVN
Infection
Charcot
Paralysis of deltoid
Torn rotator cuff
Insufficient glenoid bone stock
Usually after 50-60 years of age
Primary 90% of cases
Secondary
- AVN
- trauma
- instability
Coronal plane fracture of distal femoral condyle
- intra-articular
- often only attachment is posterior capsule
Rare
Usually a severe valgus trauma
Uncommon
< 1% Primary bone tumour
Young boys
- second decade
Similar to OO
Spine 30%
- especially posterior elements
Long bones 35%
Back or limb pain
- pain less severe than OO
Fracture distal to articular surface & proximal to intertrochanteric region
On average 4 years younger than intertrochanteric fracture
One year mortality as high as 36%
Only 1/3 will return to pre-fracture living environment
Bilateral Pars Fracture C2
- traumatic axis spondylolisthesis
Neurological injury uncommon
- fragments separate and decompress
Different to judicial hanging where spinal cord is severed
Rare
- unilateral
- bilateral
Compression
Lateral Compression
Rotation
Skull base pain
Cock Robin
Cranial nerve injury
Type I
Impaction of a condyle
Facet joint dislocations secondary flexion distraction injury
10%
1. Unifacet subluxation - interspinous process widening
2. Unifacet dislocation - 25% anterolisthesis
3. Bifacet dislocation - 50% anterolisthesis
4. Complete vertebral translation - 100% anterolisthesis
Burst fractures
- injury to anterior and middle columns +/- posterior column
Vertical compression
10% cervical fractures
Most commonly C5/6
Anterior & middle columns fail
- if severe, posterior ligament complex fails