Traumatic Atlanto-Axial Rotatory SubluxationShashank Gandhi, MDDepartment of Neurosurgery

Case

64M, s/p fall down stairs while intoxicated 3 days ago. No LOC. P/w persistent neck pain & right shoulder pain.

PMH: EtOH abuse

Neuro: AA&Ox3, FC, MAE 5/5, SILT

CT C Spine

Hospital Course

• CTA neg• MRI – posterior interspinous ligament edema; non-specific fluid

in C1-2 lateral mass articulations• Discharged home with Miami J collar for 6wks

• 4wk office f/u• Inconsistent Miami J use• Continued neck pain• Neuro intact

4wk F/U

Fielding Type IIIWhite & Panjabi Type C

Traction & Reduction in MayfieldC1-3 Fusion

Immediate Post-Op 4wk Post-Op

12wks Post Op

Pathology Usually traumatic (adults) or infection/inflammation (Grisel’s Syndrome) Mechanism: forced rotation with an element of lateral tilt C1-2 facet is more horizontal than other levels Other reports of rotatory deformities caused by:

Ankylosing spondylitis Rheumatoid arthritis Metastatic tumors, eosinophilic granulomas Down Syndrome (25% patients) After sub occipital craniectomy and C1-3 laminectomy Klippel feil syndrome (congenital failure of segmentation of

cervical spine- short neck , low hairline and decreased motion) Os odonteum

Presentation “Cock-Robin” position: Head is rotated toward the anteriorly displaced

C1-2 joint and tilted away from the involved side C2 joint spinous process may be prominent and deviated to the side to

which the chin is pointed- Result of lateral tilt of the head or possibly counter rotation of C2

Stability of AA jointAlar ligaments

- prevents excessive rotation- attaches to sides of dens and inserts at base

of the occiput

Transverse ligament – most important - prevents excessive anterior shift- attaches to anterior arch of C1 bilaterally via

tubercles- confines the odontoid process within the

articular notch on the anterior arch of C1- Allows 47 degrees rotation- Non-elastic; fails suddenly with rapid force- Rupture centrally or laterally at insertion site

on tubercles

Steele's Rule of ThirdsCanal of the atlas is about 3 cm in AP diameterSpinal cord, odontoid and the free space are each approximately 1 cm in diameterAnterior displacement of the atlas > 1 cm may jeopardize the adjacent segment of the spinal cord

Atlantodental Interval (ADI)

• Atlantoaxial joint may be incompetent when the TL is disrupted- Widened ADI seen on lateral plain films or CT scan- ADI >5mm – failure of alar ligaments- Normal ADI is <3mm in males and < 2.5mm in females- Normal ADI is pediatrics is <4 mm (kids < 15 yo)

Imaging

ADI Lateral atlantoaxial space surrounding dens may be asymmetrical Dens may be displaced in any direction Rotational angle

Imaging: plain film/waters view

Asymmetry between dens & lateral mass C1

Lateral mass that appears wider and closer to midline is rotated anteriorly

C1-2 joint spaces are asymmetrical

Flexsion / Extension Films

Rotation on CT scan Able to visualizing rotation and associated fractures Dynamic CT scans are not advocated

- Risk of inducing neurological injury secondary to instability Standard measurement technique for rotational angle

MRI – Ligament Integrity

Shape of the transverse ligament is convex toward the dura Tears: loss of anatomical continuity with regions of high signal

Translational AA subluxation and alar ligament disruption

White & Panjabi Classification

Atlantoaxial injury algorithm

Fusion Options

• Doral Wiring Techniques• Gallie Fusion• Brooks-Jenkins Fusion• Locksley Intersegmental tie-bar technique

• Screw Fixation• Magerl Transrticular Screws• C1-2 Rod Cantilever Technique• C2 Laminar Screws

Gallie Fusion Limitation: single, midline point of fixation - susceptible to rotational forces Concern exists when more than one spinal segment is spanned using

sublaminar wires increased risk of encroachment on neural elements

Brooks-Jenkins Fusion• Overcomes rotational deficiencies of Gallie fusion w/ bilateral,

interlaminar bone grafts • Limitation: requiring multisegment sublaminar wires; also requires

postop orthosis (Halo)

Locksley Intersegmental tie-bar technique

grafts are secured with sublaminar wires addition of a posterior stabilization plate,

secured by wires to spinous processes Three-point fixation with immediate rigidity

and resistance to all axes of movement. The rib, by its natural contour, is an ideal

graft selection. An iliac autograft can also be used.

Transarticular Screws

• Increased rotational stability• Not require stable posterior arch• High fusion rate; immediate stabilization • Risk of injury to vertebral arteries

Transarticular C1-2 screws with a posterior wiring (modified Brooks)

C1-2 Rod Cantilever • C1 lateral mass &

C2 pedicle screws

C2 Laminar Screws• C1 lateral mass & C2 laminar screws• Avoid VA injury• Requires intact posterior elements• Outcomes equal to Magerl’s & C2 pedicle screws• Higher rate of revision when used in subaxial constructs

References The Evolution of Posterior Cervical and Occipitocervical Fusion: Atlantoaxial Fusion, John

R. Vender, MD, Andy J. Rekito, MS, Steven J. Harrison, MS, and Dennis E. Mcdonnell, MD, Department of Neurosurgery and Medical Illustration Graduate Program, Medical College of Georgia; and Department of Neurosurgery, Gunderson-Lutheran Clinic, La Crosse, Wisconsin

Handboook of Neurosurgery: Greenberg Youmans Post-Traumatic Atlantoaxial Rotatory Fixation in an Adult: A Case Report; Yeon-Seong et al,

Spine Vol 32, Number 23, ppE682-687, 2007