Spino-cranial angle (SCA), the angle is defined between the C7 slope and the straight line joining the middle of the C7 end plate and the middle of the sella turcica. T1-slope (T1s), angle between a horizontal line and the superior endplate of T1 or C7. C2-C7 lordosis (CA), angle between the lower plate of C2 and the lower plate of C7. C2-C7 SVA (cSVA), the distance from the posterior, superior corner of C7 to the plumbline from the centroid of C2