[A rare entity: intraosseous synovial cyst of the calcaneus].

The authors report a rare case of a histologically proven intraosseous ganglion found in the calcaneus. A 59 year old carpenter was referred to our institution because of progressive talalgia with swelling of the hindfoot, increasing with prolonged standing and walking at job. X rays showed a multilobular radiolucent cyst developed in the anterior part of the left calcaneus, outlined by a rim of sclerotic bone. A lateral cortical split revealed by CT was deemed to be a traumatic communication with the soft tissue. At biopsy, a gelatinous and hematic content was noted but pathologic examination of the cyst walls failed to reveal the diagnosis; there were no malignant cells. 5 weeks later, the cyst and its contents were excised through lateral approach and the defect filled with cancellous bone graft. At pathological examination, a final diagnosis of ganglion cyst was determined. One year after surgery, the patient was asymptomatic; no sign of recurrence was observed. Intraosseous ganglia are benign subchondral cysts which rarely involve foot bones. When pain becomes consistent and swelling occurs because of overlooked fracture, malignant bone tumors should be ruled out. Histological examination is mandatory to confirm the diagnosis. Excision of the cyst and bone grafting are effective; recurrence is infrequent.