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Table 2 Orthopedic parameters, including landmarks and definitions

From: Therapeutic effects of functional orthodontic appliances on cervical spine posture: a retrospective cephalometric study

Atlas inclination (modified) Angle from atlas plane to Frankfort horizontal plane.
Atlas plane (AT) Line drawn through the most anterior and most posterior sites of the atlas.
Chamberlain’s distance Distance from dens tip to Chamberlain’s line.
Chamberlain’s line (palato-occipital line) Line drawn from posterior edge of hard palate to posterior edge of foramen magnum.
Clivus-dens angle Angle between dorsal ends of clivus and dens axis.
Dorsal clivus boundary Dorsal end of clivus
Dorsal dens boundary Dorsal end of dens axis
McGregor’s line (palato-suboccipital line) Line from posterior edge of hard palate to most inferior point of squama occipitalis.
McRae’s line (foramen magnum line) Line between anterior and posterior edges of foramen magnum.
OPT line Line drawn against the anterior cranial base to define the craniocervical angle.
Powers ratio Ratio between distances (i) opisthion to dens tip and (ii) Ba to projection center of arcus posterior atlantis.
Ranawat’s line Distance between a line connecting the projection centers of the anterior/posterior arches of the atlas and the center of the shadow of the axis vertebra.
Redlund-Johnell/Petersson line Distance between McGregor’s line and center of inferior endplate of second cervical vertebra (mC2)
Solow/Tallgren sum (modified) Sum of angles formed by linear parameters OPT, CVT (line through spC2 und pC2), NL, NSL and ML to the Frankfort horizontal plane.