Fig. 7

a. Pelvic parameters. The red line represents the anterior and superior border of the S1 body. Line A is the horizontal axis of the body. Line B is the vertical axis of the body. Line S is the continuation of the upper border of S1. Line E is the line perpendicular to line S. Point C is the center of the hip joint. Point D is the center of the upper border of S1. ∠BCD is a pelvic tilt (PT). ∠CDE is pelvic incidence. The angle between lines A and S is the sacral slope (SS). The decrease of SS and the increase of PT are shown to be associated with the global sagittal imbalance and degenerative lumbar kyphosis. PT is 40°, SS is 15°, and PI (pelvic incidence) is 55°. b. Lumbar lordosis and sagittal balance. SVA (sagittal vertical axis; C7 plumb line) traverses nine cm anterior to the posterosuperior corner of S1, and the L1-S1 Cobb’s angle is 2.6°