Modern concepts of primary aneurysmal bone cyst

Introduction Despite the long experience of radiologists, pathologists and orthopaedists with aneurysmal bone cysts (ABC), there is limited knowledge regarding the cause of the lesion and the optimal treatment. The pathogenesis of ABC remains unclear with theories ranging from a post-traumatic, reactive vascular malformation to genetically predisposed bone tumours. Recent genetic and immunohistochemical studies proposed that primary ABC is a tumour and not a reactive tumour-simulating lesion. The chromosomal analyses and some reported familial cases of this osteolytic bone lesion propose a hereditary factor in a presumably multifactorial pathogenesis. Materials and methods The imaging studies, even CT scan and MRI sometimes do not provide clearly diagnostic criteria for the diagnosis of ABC. The radio-graphically differential diagnosis between ABC and unicameral bone cyst (UBC) is sometimes not clear. Double density fluid level, septation, low signal on T1 images and high intensity on T2 images strongly suggest the bone cyst is an ABC, rather than a UBC. Conclusion Common methods of treatment vary considerably in the literature. The usual methods of treatment are curettage, resection, intracystic injections and embolization. Biopsy is imperative before any treatment. Ethibloc (R) treatment remains highly controversial. For some authors Ethibloc (R) injection can be recommended as the first-choice treatment excluding spinal lesions. A minimally invasive method by introduction of demineralized bone and autogenous bone marrow is able to promote the self-healing of a primary ABC.