Fig. 2

The load conditions of finite element analysis. The superior segment of S1 of the models was fixed. The compression (A) and torsion (B) were applied in all models. The relative displacement and rotational angle of the pubic symphysis were determined to display regional stability. The horizontal variation of distance between two reference (point E and F) points in bilateral pubic bones under compressive load was defined as regional compressive stability (C). The angular increment formed by two reference points (point G and H) in bilateral pubic bones and the center point of sacral endplate (point S) under torsional load was defined as regional torsional stability (D)