Pelvic rotation and tilt can cause misinterpretation of the acetabular index measured on radiographs
van der Bom, M.J., Groote, M.E., Vincken, K.L., Beek, F.J.A., Bartels, L.W.
Clinical Orthopaedics and Related Research 469 (6), p. 1743-1749
Clinical Orthopaedics and Related Research 469 (6), p. 1743-1749