Fig. 2

PI: Use the midpoint of the upper endplate of S1 as the vertical line, and the angle between the vertical line and the midpoint of the upper endplate of S1 and the center of the femoral head. If the bilateral femoral heads do not overlap, take two femoral heads The midpoint of the center line is used as the center point. SS: The angle between the upper end plate of S1 and the horizontal line. PT: The angle between the midpoint of the upper endplate of S1 and the center of the femoral head and the vertical line. TPA: The angle formed by the line between the center of the bilateral femoral head and the center of the T1 vertebral body and the line between the center of the femoral head and the midpoint of the S1 superior endplate. C7-SVA: The distance between the C7 plumb line and the upper posterior angle of the sacrum. TK: The angle between the extension line of the upper endplate of T5 and the lower endplate of T12. LL: The angle between the extension line of the upper endplate of L1 and the lower endplate of L5