Intrapelvic cyst formation after hip arthroplasty with a carbon fibre-reinforced polyethylene socket.

Carbon fibre-reinforced polyethylene cups were inserted in total hip arthroplasties for both hips of a male patient. Ten years after the arthroplasty of the right hip, an intrapelvic cyst was observed. The cyst was connected to the inner acetabular wall. The endoprosthetic cup showed gross loosening with a marked osteolysis of the acetabulum. Revision arthroplasty with allograft bone and an uncemented endoprosthesis was successfully performed. The fibrotic tissue at the bone-cement interface showed numerous histiocytic cells with cytoplasmic infiltrates of carbon and polyethylene particles. The left hip was also later revised for loosening, but no cyst formation was observed on that side.