Fig. 2. Measurement of the sagittal plane and the turn angle (At the level of first cervical vertebra). The patient’s sagittal plane was taken to be a straight line (  A ) drawn between the center of the vertebral body and was perpendicular to the surface on which the patient was lying. The turn angle is the angle (  B ) between this line and a line (  C ) drawn passing through the midline of the palate and the center of the body of cervical vertebra.