Unicameral bone cysts.

Unicameral, or solitary, bone cysts are unusual tumors seen in the ends of long bones in skeletally immature persons. The etiology of these lesions is poorly understood. Various hypotheses have included dysplastic processes, synovial cysts, and abnormalities in the local circulation. Most patients present with a nondisplaced pathologic fracture, but occasionally cysts are found incidentally. Plain radiographs typically show a symmetric lesion with cortical thinning and expansion of the cortical boundaries. Once diagnosed, unicameral bone cysts continue to be a treatment dilemma. Traditional methods, such as prednisolone therapy, usually involve multiple anesthetics and injections and are associated with high recurrence rates. Major surgical procedures, such as wide exposure, curettage, and bone grafting, may be somewhat more effective, but still carry with them significant morbidity and recurrence rates. Newer techniques involving percutaneous grafting with allograft or bone substitutes or a combination of the two are promising in light of their low complication rate and lower reoperation rate.