Fig.2 Case 1. a. Anteromedial view of the left pelvis in 3D CT angiography. The external iliac artery（yellow arrowhead）was displaced superiorly due to compression of the migrated cup. b. Anterior view of the left abdomen and groin on a traction table. An oblique skin incision line parallel to the inguinal ligament was marked at the left lower abdomen, starting from the midpoint between the umbilicus and pubic symphysis. c. Operative view through the retroperitoneal approach. A tape was passed around the mobilized external iliac artery located medially on the iliopsoas muscle belly（white star）. d. Postoperative anteroposterior radiograph showing the reconstructed left hip using a Kerboull cross-plate, structural allograft, and cemented cup.