Pelvic mass causing vesical compression after total hip arthroplasty. Case report.

A 59-year-old woman developed a histiocytic response to methylmethacrylate debris in a loose total hip arthroplasty. This reaction eroded through the medial wall of the acetabulum, producing a pelvic mass and presenting with urinary symptoms. A combination of an abdominal approach for removal of the pelvic mass and a lateral approach for revision of the total hip arthroplasty was required. This condition should be considered in the differential diagnosis of a mass adjacent to a loose prosthesis.