Atlanto-axial Rotatory Instability

 

Atlantoaxial 3D CT

 

Definition

 

Acute dislocation of the atlanto-axial facet joint

Present with acute torticollis

 

Etiology

 

Children

1.  Post trauma - can be minor

- due to horizontal orientation of facet joints

- ligamentous laxity

- weak neck muscles

- relatively large head

2.  Grisel's syndrome

- non traumatic

- post nasopharyngeal inflammation / infection

- hypothesised to be due to lymphatic swelling

3.  Post ear / nose / throat surgery

 

Adults involved in trauma

- low incidence of neurological injury

 

Ruf et al J Neursurg 2021

- 44 children, mean age 9

- 21 (48%) related to previous infection / Grisel's sydrome

- 19 (43%) related to minor trauma

- 4 (9%) unknown cause

- delayed diagnosis common (mean presentation 178 days)

 

Examination

 

Cock Robin position

- the chin tilted to one side

the neck flexed laterally to the other

 

Torticollis

 

Myelopathy - gait disturbance, neurological deficits

 

DDx

 

Fibrosis sternocleidomastoid - chronic torticollis

Ondontoid fracture

Os ondontoid

 

Xray

 

Open mouth xray

 

Lateral mass C1 rotated & asymmetric

Wink Sign - C1 facet locked over C2

 

Atlanto-axial open mouth

 

CT Scan

 

Atlanto-axial CT 1Atlanto-axial CT 2

 

Atlanto-axial CT 4Atlanto-axial CT 3

Atlanto-axial rotatory instability

 

Atlantoaxial 3D CTCT rotatory AAI

 

Classification Fielding & Hawkins

 

Type I

Unilateral facet subluxation / dislocation

ADI < 3 mm

Transverse ligament intact Most common
Type II

Unilateral facet subluxation / dislocation

Anterior displacement of the atlas by 3–5 mm

ADI 3 - 5 mm

Transverse ligament injury  
Type III

Bilateral facet subluxation / dislocation

Anterior displacement of atlas by more than 5 mm

ADI > 5 mm

Alar and tranverse ligament deficient

Both lateral masses displaced anteriorly

 
Type IV Posterior displacement of atlas Ondontoid process deficient or fractured

Rare

Highest risk of neurological injury

 

Management

 

Closed reduction

 

Admit

- bed rest

- NSAIDS / muscle relaxants

 

Options

- hard collar

- halter traction

- cervical traction

- reduction under GA

 

Halter traction

Halter traction

 

Results

 

Ishii et al Spine 2011

- 7 patients with torticollis > 5 months duration

- closed reduction under GA then Halo-Thoracic Brace (HTB) 3 months

- no failures

 

Beier et al J Neurosurg Pediatr 2012

- 40 cases average age 8

- range of time periods since onset torticollis

- half successfully reduced with cervical collar

- remainder treated with halter traction or HTB

- 3 cases required operative fusion

 

Yeung et al JBJS Am 2022

- 43 patients mean age 8 average 3 months post onset of symptoms

- halter traction successful in 42/43 (98%) with average treatment 18 days

- 1 recurrence successfully treated with repeat halter traction

 

Open reduction

 

Indication

- failed closed reduction

- bony fusion / anatomical changes

 

Open reduction and posterior fusion

- cervical traction

- neurological monitoring

- care with vertebral artery

- reduction via anterior (trans-oral) or posterior approach

- posterior C1-C2 fusion

 

Posterior C1-C2 arthrodesis

 

1. Sublaminar wires - Gallie / Brooks

 

2.  Pedicle screws

- C1 lateral mass C2 pedicle screws (Goel-Harms)

- trans-articular screws C1 C2 (Magerl)

 

Results

 

Wang et al. Spine 2016

- 32 children with AARI > 6 weeks

- average 6 months of torticollis

- 8/32 (25%) had neurological symptoms

- half reducible with traction, posterior fusion

- half required trans-oral reduction and posterior fusion

- 31/32 (97%) had solid fusion

- 1 required revision due to recurrent torticollis