25 3 Age (years) Fig. 1 Age distribution of eighty-one patients with aneurysmal bone cysts showing that this is a condition mainly affecting teenagers. 40 6 THE JOURNAL OF BONE AND JOINT SURGERY ANEURYSMAL BONE CYSTS OF THE PINE MALCOLM C. HAY, DENNIS PATERSON, ThOMAS K. F. TAYLOR From The Princess Margaret Hospital for Children, Perth, The Adelaide Children ‘s Hospital, Adelaide, and The Royal North Shore Hospital, Sydney Aneurysmal bone cysts are uncommon lesions, especially in the spine. Seventy-eight cases have been previously documented in the English literature an d an additional fourteen cases are now reported. There is a definite predilection for the lumbar region and the neural arch is the part of the vertebra most commonly ffected. It is r commended that treatment should consist of total excision or when this is not possible, curettage. Radiotherapy should be reserved for those few cases wh re operation is inadvisable. In 192 Jaffe and Lichtenstein described two cases of a peculiar blood cyst which they termed an aneurysm l bone cyst. They recognised that the nature of the lesion was not clear, but they were of the opinion “that the blood filled cavi y should be regarded as simply a large venous pool” . The term aneurysmal was used to denote the “ blow out” radiographic appearance which resembles the saccular protrusion of the walls of an aneurysm and also because cystic blood-filled spaces are encountereded at operation. The name has been generally accepted, though indeed it is neither an aneurysm nor a bone cyst. Aneurysmal bone cysts are uncommon and Dahlin (1967) found twenty-six (1.4 per cent) in 2000 primary bone tumours at the Mayo Clinic. The lesion has been reported in almost every bone, with a high incidence in th spine. This has been variously recorded from 3 p r cent of sixty-six cases (Biesecker et al. 1970) to 20 per cent of ninety-five cases (Tillman et al. 1968). The aetiology of this condition is unknown and much debated. In the spine these lesions often presen problems in diagnosis and management, and there is frequen ly a neurological nvolvement. Because of the rarity of this condition and the small siz of any one series, it was decided to analyse the clinical features of all adequately documented cases of aneurysmal bone cyst f the spine in the English literature. Twenty-seven authors have reported seventy-eight cases. To these we add fourteen cases of our own, a total of ninety-two. The details of the latter are summarised in Table I. In certain respects a proportion of the previously reported cases are incom- pletely docum ented. DIAGNOSIS C linical features S ex incidence. In all large series of aneurysmal bone cysts from the whole skeleton there is a slight predominance of female patients. Among our own patients with aneur smal bone cyst of the spine, and also those in the literature, 57 per cent were female and 43 per cent male. Age. Aneu ysmal bone cyst is primaril a condition of the second decade. The incidence in the spine is the same as in the appendicular skeleton. In eighty-one patients with spinal lesions for whom there was ufficient information, the average age was 16.6 years (Fig. 1). Site. Aneurysmal bone cysts have been described at every level of the spinal column except the coccyx (Fig. 2). Jaffe 1958) considered there was no bias in spinal distribution but in thi series, taking into account the number of vertebrae in each region, there was a definite predilection for the lumbar spine (Fig. 2) . These lesions are often not confined to one vertebra and six of our Malcolm C. Hay, F.R.C.S.(Ed.), F.R.A.C.S., The Princess Margaret Hospital for Children, Subiaco, estern Australia 6005, Australia. Sir Dennis Paterson, F.R.C.S., F.R.A.C.S., The Adelaide Children’s Hospital, 72 King W illiam Road, orth Adelaide 5006, Australia. Professor Thomas K. F. Taylor, D.Phil., F.R.C.S., Royal North Shore Hospital of Sydney, St Leonards, New South Wales 2065, Australia. Requests for reprints should be sent to Dr Malcolm C. Hay, 26 Cohn Street, West Perth 6005, Western Australia.
