Fig. 1

A 64-year-old woman with left hip osteoarthritis (after total hip arthroplasty). Anteroposterior pelvic radiographs taken after left total hip arthroplasty (THA) are shown. In the supine position (a), cup inclination is 45°, and cup anteversion is 25°. However, in the standing position, the pelvis markedly tilts backward; cup inclination is 59°, and cup anteversion is 42° (b). Although this case is not included in the present study, the case, in which the hip joint was anteriorly dislocated 2 weeks after THA (c), triggered the initiation of the study