The natural history of unicameral bone cyst after steroid injection.

Ninety-five consecutive cases of unicameral bone cyst treated at the Istituto Ortopedico Rizzoli by intracystic injections of methylprednisolone acetate were retrospectively reviewed. Eighty per cent of the patients had a satisfactory result. Of the 20% failures, 13.5% had a recurrence of the cyst. Recurrence after methylprednisolone acetate treatment is a previously unrecognized entity, with recurrence risk factors associated with multiloculation, cyst size and age of the patient.