Table 1.

Spinopelvic radiographic parameters, performed on lateral pelvic radiographs

Angle	How to measure	Normal values (Lazennec)	Normal values (Dorr)
Pelvic tilt (PT)	Angle from center of femoral head; one arm goes vertical and the other arm goes towards center of S1 sacral endplate
Sacral slope (SS) or sacral tilt (ST)	Angle from anterior S1 end plate; one arm travels along the tangent of the end plate and the other arm goes horizontal	40° standing, 20° sitting	40° ± 10° standing, 20° ± 9° sitting
Pelvic incidence (PI)	Fixed angle from middle of S1 endplate; one arm goes towards center of femoral head and the other arm goes perpendicular to slope of S1 end plate	56–58°	53° ± 11° standing or sitting
Ante-inclination (AI) or sagittal tilt	Angle from posterior inferior edge of acetabulum; one arm goes horizontal and the other arm travels to anterior edge. This measures the cup opening angle.	36–47° standing, 51–58° sitting	35° ± 10° standing, 52° ± 11° sitting
Sagittal acetabular angle (SAA)	Fixed angle created from slope of S1 end plate and line from posterior inferior acetabulum to anterior edge of acetabulum	69°	75° ± 15°
Anterior pelvic plane (APP)	Angle from pubic tubercle; one arm goes towards ASIS and the other arm travels directly vertically. Surrogate for pelvic tilt using computer navigation
Lumbar lordosis (LL)	Angle between superior L1 endplate and inferior L5 endplate
Pelvic femoral angle (PFA)	Angle centered over femoral head; one arm goes towards middle of S1 endplate and the other arm travels parallel to proximal femur.		180° ± 15° standing, 132° ± 12° sitting

Values from Lazennec JY, Brusson A, Rousseau MA. Hip-spine relations and sagittal balance clinical consequences Eur Spine J. 2011;20 Suppl 5(Suppl 5):686–98 and Ike H, Dorr LD, Trasolini N, Stefl M, McKnight B, Heckmann N. Spine-pelvis-hip relationship in the functioning of a total hip replacement. J Bone Joint Surg Am. 2018 Sep 19;100(18):1606–1615