Fig. 2.

Radiographs are shown of a 42-year-old woman with dysplastic right hip. a She preoperatively presented with a negative impingement test, even if the alpha angle was 60°. b During the operation, the impingement test converted to positive following the rotation and fixation of the acetabular fragment. However, the impingement test returned to negative after osteochondroplasty of the femoral head-neck junction by which the postoperative alpha angle was improved to 41°. Letters α and α’ refer to alpha angle, which was described by Notzli et al. [12]