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Fig. 2 | BMC Musculoskeletal Disorders

Fig. 2

From: Relations between the Crowe classification and the 3D femoral head displacement in patients with developmental dysplasia of the hip

Fig. 2

a The anterior pelvic plane (APP) was used for the pelvic coordinates, based on the anatomic bony landmarks, including the right anterior superior iliac spine (R-ASIS), the left anterior superior iliac spine (L-ASIS) and the midpoint of the pubic tubercles (MPT). The origin of the pelvic coordinate system was at the mid-point between two ASISs in the X-axis running from the R-ASIS to the L-ASIS. The Y-axis was parallel to the normal vector of the plane formed by two ASISs and the mid-point of PSISs and passing through the origin and the middle of pubic tubercles. The Z-axis was the cross product of the X and Y axes. The pelvic width (PW) and the pelvic height (PH) were noted. b The center of rotation (COR) was defined as the centroid of the best sphere (red-covered surface) to the surface of the femoral head (the average of standard deviations (STD) of the best-fit sphere of all femoral heads is < 0.4 mm). c Bony landmarks of the pelvis including anterior-superior iliac spines (ASIS), pubic tubercles (PT) and posterior-superior iliac spine (PSIS) were digitized. The pelvic depth (PD) was shown

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