Fig. 3

Preoperative anteroposterior pelvic radiographs and distributions of joint contact pressure (CP) on the acetabular cartilage before and after virtual periacetabular osteotomy (PAO) in two representative cases with hip dysplasia (right dysplastic hips). A In one case, the maximum CP decreased by increasing the lateral center-edge angle (LCEA) from 30° to 40°, while (B) in the other case, the maximum CP increased. Case B had larger extrusion index (47.2 vs. 27.6) and roundness index (53.4 vs. 52.1) than case A. The reference locations of the acetabular cartilage at the standing position are denoted as anterior (Ant), superior (Sup), posterior (Pos), and inferior (Inf)