ABSTRACT
Many uncemented acetabular components use transfixation screws to stabilize the acetabular component until ingrowth of bone occurs. But the use of transacetabular screw fixation in total hip arthroplasty could increase the incidence of intrapelvic complications including neurovascular injury, extrinsic compression and erosion of intrapelvic organs. Metal debris was attributed to corrosion or fretting between screw and metal shell may lead to pelvic osteolysis. A foreign body reaction to metal and polyethylene wear debris in a loose acetahular component eroded the medial wall of the acetabulum and produced an intrapelvic mass. We experienced a case of intrapelvic pseudocyst in a failed total hip arthroplasty. The cyst communicated with hip joint through the transacetabular fixation screw which was placed near the center of the acetahulum.