## Guided Mark-Up: Cervical Spine Measurements

**Atlas Angle:** The angle that the major axis of C1 (from this aspect) makes with the horizontal.

**Atlas/Axis Angle:** The perpendicular to the posterior side of the C2 body is constructed, and the angle between this constructed line and the major axis of C1.

**Atlas/Skull Angle:** The angle between a line at the base of the skull (at the level of the foramen magnum) and the major axis of C1.

**Occiput Angle:** The angle between a line at the base of the skull (at the level of the foramen magnum) and the horizontal.

**Jackson’s Angle:** The angle between two constructed lines: one at the posterior of the body of C2, and the other at the posterior of the body of C7.

**Cervical Lordosis:** The angle between two constructed lines: one along the major axisof C1, and the other along the inferior side of the body of C7. Some literature argues
the ideal value is 42 degrees.

**George’s Deviation:** George’s line is the curve created by connection points chosen on the posterior sides of all vertebral bodies. According to some literature, in the ideal
casethese points lie on a circular arc. Metron’s “George’s Deviation” parameter is a sum of all the offsets from this perfect circular arc. A perfect value would be zero ( 0.0 ) meaning that all
points lie on a perfect circular arc. The higher the value of this parameter, the more deviation there is from a circular arc.

**C1-T1 Offset:** Construct a line from the inferior posterior corner of the T1 body vertically in the image, and then measure horizontal displacement of the superior posterior
corner of the C1 body. Some literature suggests this value be “small”.

**C2-C7 Offset:** Construct a line from the inferior posterior corner of the C7 body vertically in the image, and then measure horizontal displacement of the superior posterior
corner of the C2 body. Some literature suggests this value be “small”.

**Gravity Line Offset:** Some literature suggests that a point at the anterior lip of the sella turcica serves as a good reference of the center of mass of the head, and further
that a line dropped vertically from that point should pass “near” the disc space between C4 and C5. This parameter gives this measure.