Schematic diagram of spinopelvic and lumbar indicators measurement. PI: angle between sacral plate and vertical line, PT: angle between femoral head-sacral plate midpoint line and longitudinal axis, SS: angle between sacral plate and the horizontal axis. LL: angle between L1 and sacral plate, DLL: L4 superior endplate to S1, DA: L5 lower endplate to S1, and ∆PI-LL is calculated as the difference between PI minus LL.