Massive intrapelvic synovial cyst as a complication of total hip replacement arthroplasty: a case report.

The authors report a case of massive intrapelvic synovial cyst complicating total hip arthroplasty in a 35-year-old woman with rheumatoid arthritis. The clinical presentation raised the possibility of a coincidental soft-tissue malignant tumour. This was ruled out by ultrasonography, computed tomography, fine-needle aspiration with examination of cells and culture and, ultimately, by image intensification in the operating room during aspiration of the cyst and injection of the adjacent hip joint with Hypaque. The authors conclude that perforation of the acetabular floor at total hip arthroplasty was likely the precipitating event. After 1 year there was no indication for surgical excision of the cyst.