Epiphyseal involvement of simple bone cysts.

Epiphyseal involvement of a simple bone cyst (SBC) is uncommon. Eight patients are reported in whom an SBC was found to cross the growth plate, involving the epiphysis in seven patients and the apophysis in one. All patients had more than two pathologic fractures. In seven patients growth disturbance was found. Functional impairment did not develop in any patient. Radiographically, all lesions presented a characteristic involvement of the epiphysis and metaphysis in various proportions. Only one of four cysts treated with methylprednisolone acetate injections showed incomplete healing; the others failed to respond. After percutaneous grafting of autologous bone marrow, three of seven cysts healed and the others attained incomplete healing. Epiphyseal involvement of SBC should be considered a more aggressive form of an active lesion.