Spinal balance

Pelvic Incidence (PI)

Angle between the perpendicular line drawn from the center of the S1 endplate and the line that joins the center of the femoral heads to the center of the S1 endplate.

Pelvic Tilt (PT)

Angle between the line that joins the center of the femoral heads to the center of the S1 endplate and the vertical line through the center of the femoral heads.

Lumbar Lordosis (LL)

Angle between the superior L1 endplate and the S1 endplate.

Thoracic Kyphosis (TK)

Angle between the superior T1 endplate and the superior T12 endplate.

SVA (sagittal translation of C7 plumb line)

Sagittal distance between the vertical line through the center of C7 body (C7 plumbline) and the vertical line through the posterosuperior corner of the S1 endplate.