Inclusion Criteria:  All the patients diagnosed with a pelvic tumor； Underwent limb salvage surgery following type II or II+III pelvic resection； Acetabulum reconstruction using a modular, titanium hemipelvic prosthesis.  Exclusion Criteria:  A lack of postoperative CT images; Having undergone revision surgery or noninitial/primary resection; unable to calculate the hip displacement by the specific measurement method we proposed.