Fig. 2

Four observation points in the FE model. Points 1 and 4 were located at the upper and lower ends of the sacrum, respectively. Point 2 was located at the intersection of the horizontal midline between S1 and S2 posterior sacral foramen and the fracture line. Point 3 was located at the intersection of the horizontal midline between S2 and S3 posterior sacral foramen and the fracture line