Instructions to reviewers Reference lines Anterior axial line (AAL) - - PowerPoint PPT Presentation

Instructions to reviewers

• Reference lines

– Anterior axial line (AAL)

• Quantitative assessment

– Atlanto-axial interval (AAI) – Condyle-axial interval (CAI)

Reference line

• Drawn with arrow tool

at 100% magnification

– Anterior axial line (AAL)

• Line along the anterior

border of the C2 body and dens extending into the cranial space. If the bone curves or scallops, draw the most easily reproducible line possible

Measurements

• Performed with length tool at

300% magnification

– AAI: Linear distance between the ALL

and the posterior border of the anterior C1 arch. If the posterior cortex of the anterior arch of C1 is irregular in contour, then choose the smallest distance available based on a single reproducible landmark

– CAI: Linear perpendicular distance

between cephalad extension of the anterior axial line and the anterior border

• f the occipital condyle (the same point

must be seen between each x-ray). Positive value when condyle is anterior to the AAL, negative value when condyle is posterior to the AAL.

AAI CAI

CAI: 2.0mm AAI: 4.8mm

CAI: -3.1mm AAI: 3.8mm

Movement calculations

• C0-2: CAIflexion- CAIextension

C0-2 = 2.0mm – (-3.1mm) = 5.1mm

• C1-2: AAIflexion- AAIextension

C1-2 = 4.8mm – 3.8mm = 1.0mm

• C0-1: |C0-2| – |C1-2| (these are abs value)

C0-1 = 5.1mm – 1.0mm = 4.1mm