| Abstract|| |
Back ground: Aneurysmal bone cysts have raised intra-cystic pressures which are dynamic and diagnostic in nature. Aneurysmal bone cysts could be diagnosed from other benign cystic lesions of bone by recording their intra-cystic pressures with a spinal manometer. Raised intra-cystic pressures in aneurysmal bone cysts are maintained as long as the periosteum over the cyst is intact even in those with pathological fractures. Even though its pathology is definite its aetio-pathology is not clear
Method: Fourteen out of 16 radiologically benign cystic lesions of bone were subjected to intra-cystic pressure recordings with spinal manometer. Other two cysts had displaced unimpacted pathological fractures and so their intra-cystic pressures could not be recorded. All 16 cysts were subjected to histo-pathological examination to confirm their diagnosis and to find out for any preexisting benign pathology. All the cysts were surgically treated.
Results: Fourteen benign cystic lesions of bone were diagnosed as aneurysmal bone cysts preoperatively by recording raised intra-cystic pressures and confirmed by histo-pathology. In addition, histo-pathology revealed pre-existing benign pathology. All cysts were successfully treated surgically.
Conclusions: Since, there is appreciable rise in intra-cystic dynamic pressures, the aneurysmal bone cyst is considered to be due to either sudden venous obstruction or arterio-venous shunt. Pre-operative intra-cystic pressure recordings help not only to diagnose aneurysmal bone cysts but also to assess the quantum of blood loss and its replacement during surgery.
Keywords: Aneurysmal bone cyst; Raised intra-cystic pressures; Associated pathology.
|How to cite this article:|
Rangachari P. Aneurysmal bone cysts. Indian J Orthop 2005;39:174-8
| Introduction|| |
The term aneurysmal bone cyst was coined by Jaffe and Lichtenestein  . Aneurysmal bone cysts are considered to be tumour like bony lesions consisting of large blood filled aneurysmal spaces without endothelial lining. Its pathology is definite and characteristic but its aetio-pathology is quite uncertain. In addition this cystic lesion has raised intra-cystic pressure which is dynamic in nature with oscillations.
There is steady increase in number of scientific papers dealings with typical radiological, clinico-pathological features and treatment of aneurysmal bone cysts ,,,,,,,,,,,,,,,, . But there are a few with controversial hypothesis regarding the aetiology and diagnostic relevance and nature of raised intracystic pressures in these cystic lesions.
| Method and Material|| |
The author had an opportunity of studying 16 cases of aneurysmal bone cysts during a period of 25 years from 1981 to 1996. The study consisted of detailed clinical, radiological, surgical and histo-pathological findings and pre-operative intra-cystic pressure recordings where possible.
Five patients were over 20 years and the other 11 patients were 20 years and less. Both sexes are equally involved. Ten patients including the one having lesion in iliac bone, had lesions on left side and six had the right side. Nine aneurysmal bone cysts (Four in humerus, three in femur and one each in fibula and radius) were in long tubular bones, three in short tubular bones (one each in fourth metacarpal, fourth metatarsal and clavicle) and four in other bones (three in talus and one in ileum)
Pain with or without swelling was present in all patients. Pain and wasting of muscles were present in cysts of long tubular bone of upper limb. Three cases, having lesion in talus, not only had pain and wasting of leg muscles but also limitation of ankle movements. Two patients presented with displaced unimpacted pathological fractures of the femoral bone. Four other patients, presented with swelling and painful restricted movements of the limbs. Skiagrams showed cystic lesions with impacted pathological fractures. All of them gave history of injury following fall while playing.
Percutaneous intra-cystic pressures were studied preoperatively in 14 patients. The pressures were studied using a spinal manometer and an 18 gauge needle. The needle was inserted while the patient was lying supine under aseptic conditions and local analgesia, into each radiologically diagnosed benign cyst horizontally through one or two easily accessible regions and connected to vertically held spinal manometer [Figure - 1]. The colour (blood or wine coloured), the type of rise (gradually rising with oscillations or suddenly with static rise) and final height in centimeters of the oscillating liquid column in manometer tubes, were recorded. Pressure could not be measured in two patients with displaced fractures.
| Results|| |
Radiological features: The lesions in 14 patients were central and in two others (one each in talus and superior margin of the acetabulum) were eccentric. All cystic lesions were well circumscribed lytic lesions mostly with trabeculations giving multicystic appearance [Figure - 2],[Figure - 3]. The cystic wall in most of the cases was very thin due to marked expansion and in two such lesions involving the entire talar bone resulted in collapse of its body due to weight bearing. Six cases had pathological fractures, two without impaction (one each in sub-trochantric region and in distal half of humerus and one each in proximal shaft of radius and distal end of femur). In children the aneurysmal bone cyst could involve the diaphyseal and metaphyseal parts of tubular bones but not the epiphysis [Figure - 4]a.
Manometric study: In all 14 patients there was gradual rise of blood column with oscillations in manometer. The oscillations of blood column were synchronous with peripheral pulsations. This proves to show that raised intracystic pressures is due to obstruction to venous system. The degree of rise depends upon the types of arteries supplying the cyst. The intra-cystic pressures ranged from 1 cm.H 2 O to 45 cm.H 2 O. All these cysts were proved to be aneurysmal bone cysts histopathologically. In one patient with cystic lesion in mid-shaft of humerus the intra-cystic pressure recorded was as low as 1 cm. H 2 O following diagnostic open biopsy done elsewhere three weeks before. In three other cases, one each in mid shaft of humerus, lower end of femur and proximal shaft of radius with impacted pathological fractures, the intra-cystic pressures were still found to be high with 40 cm. H 2 O, 20 cm. H 2 O and 30 cm. H 2 O respectively. Thus it could be surmised that the intra-cystic pressures would be very low following open biopsy and would be high as long as the periosteum is intact even the cysts are associated with pathological fractures. Preoperative percutaneous intra-cystic pressure recording procedure was introduced by the author not only as a diagnostic clinical test to differentiate aneurysmal bone cysts from other benign osseous cystic lesions, but also to have an idea of the degree of bleeding during surgery and amount of blood to be replaced, if necessary. It was found that aneurysmal bone cysts with 20 cm. H 2 O and less did not require any blood transfusion. But those having pressures over 20 cm. H 2 O did require one unit of blood for every 10 cm. H 2 O rise.
Treatment: Curettage and autogenous iliac bone grafting was done in four cases. In seven other cases the entire cyst was excised enbloc and the gap was bridged with fibular graft. In three of these cysts the fibular graft was strengthened with K-wire passed through its medullary canal in order to prevent fracture of the fibular graft during revascularisation. In another case the fibular graft without K-wire was reinforced with thoroughly boiled cubes of homogenous cancellous bone graft harvested from femoral heads. In case No.13 with aneurysmal bone cyst having impacted supra-condylar fracture with about 15 0 anterior angulation, the cyst was thoroughly curetted and grafted with struts of fibular (to prevent collapse of subchondral cartilage), autogenous iliac cancellous bone and thoroughly boiled cancellous bone from femoral heads.
Operative findings: In 10 cases with aneurysmal bone cysts there was single blood filled cavity with thin outer shell of bone. On opening the cysts there was sudden welling or gushing of blood. In the rest of the six cysts the cavity was crossed with solid soft tissue septa, dividing the cavity into several loculi. In three of them some of the loculi were filled with reddish fleshy soft tissue which when subjected to histological examination, proved to be osteoclastoma. In eight cysts, while nibbling the cyst wall and its junction with normal bone the feel and sound was like biting a piece of sugarcane and all of them on histological examination found to be fibrous dysphasia.
Histopathology findings: Histopathologically the striking feature was numerous irregular dilated non-endotheliated blood spaces, diagnostic of aneurysmal bone cyst. The wall of blood spaces showed loose fibroblastic cellular tissue with variable number of osteoclasts. In eleven patients there was evidence of benign pre-existing pathology in the cyst wall and in intra-cystic fibro-cellular septa [Figure - 5]a,b such as fibrous dysplasia in eight cysts and osteoclastoma in three other cysts.
Follow Up: Fifteen patients1 were followed up for periods ranging from one year to ten years. Only one patient with lesion in meta-carpal bone was lost for follow up after surgery. In two patients recurrence of aneurysmal bone cyst was observed in well taken fibular grafts, one with the lesion in mid-shaft of humerus [Figure - 2]c and the other in distal end of fibula [Figure - 4]b, an year and half and ten months after radical excision of the lesion and bone grafting respectively. The recurred cystic lesion in the humerus was excised enbloc and the gap was bridged with iliac dowel graft and fixed with plate and screws [Figure - 2]d. Eleven years after, skiagrams showed good take up of the graft with proper moulding without recurrence [Figure - 2]e. In another case with recurred lesion in distal end of fibula, since lesion was small and eccentrically situated towards the periphery, it was curetted and filled with cancellous iliac bone graft. This too healed well with no recurrence. Both the recurred cystic lesions histologically proved to be aneurysmal bone cysts.
Two patients, one with lesion involving the entire talus with collapse of its body due to weight bearing and other with lesion in distal end of femur having displaced impacted supra condylar fracture had painless restricted movements of the ankle and the knee respectively following surgery.
| Discussion|| |
Till 1974 only 26 cases of aneurysmal bone cysts were reported from India. Further 20 cases were reported by the author from the state of Andhra Pradesh, . During 40 year period, 66 cases were seen in Memorial Hospital, New York  . Till 1968 only 12 cases were reported from Bristol Bone Registry  . Dahlin et al  found 26 cases of aneurysmal bone cysts in a series of 2000 primary bone lesions, forming 1.3%. In 1988 Martines and Sissons  reviewed 123 aneurysmal bone cysts with and without secondary bone pathology. Between 1973 and 1998, 100 cases of aneurysmal bone cysts were recorded in Semmelweis University of Medicine, Budapest, Hungary  .
There was no sex predilection. High incidence was observed is 2nd and 3rd decade of life. Even though aneurysmal bone cysts were described in all parts of skeleton, its incidence was reported in descending order as 34% in lower limbs; 27% in vertebral column; 18% in upper limb; 9% in pelvis and 3% in skull and mandible bones  . In this series 50% cases were seen in lower limbs and 37.5% in upper limbs and 6.25% each in thorax and pelvis. The radiological findings  and histological features ,,,, were very characteristic and well described. The pathogenesis of aneurysmal bone cyst is not clear. Lichenstein , considered it to be due to either vascular disturbance in the form of sudden venous occlusion or developmental formation of an arterio-venous shunt and this postulation is supported by many others ,,,,. This vascular disturbance could take place either in normal bone as primary lesion or in pre-existing pathological lesions ,,9],,,, . Bieseckar et al  proposed a theory, after studying 66 aneurysmal bone cysts, that the primary bone lesion initiates an osseous arterio-venous fistula and thus creating a secondary vascular reactive lesion resulting in aneurysmal bone cyst.
Szendroi et al  with the help of angio-graphic, immuno histo-chemical and electron microscopic studies proved that the trigger point for the aetiology of aneurysmal bone cysts is presumably on the venous side of the cysts resulting in high increase in intra-cystic pressures. However they did not confirm increased intra-cystic pressures in aneurysmal bone cysts by taking manometric pressures. In order to prove that aneurysmal bone cysts are due to arterio-venous shunt or venous obstruction resulting in increased intra-cystic pressures, Bieseckar et al  tried to record the raised intra cystic pressures using spinal manometer and 18 gauge needle after histological diagnosis following open biopsy. They could succeed in recording raised intra-cystic pressures, though very low, in three out of six histologically diagnosed aneurysmal bone cysts. But the author has introduced this method of recording raised intra-cystic pressures as a clinical diagnostic test to diagnose and differentiate aneurysmal bone cysts from other benign osseous cystic lesions which could be real or solid cystic. The periosteum should be intact to record high intra-cystic pressures even though associated with pathological fractures. Besides the presence of gradually rising column of blood with oscillations that correspond with peripheral arterial pulsation in spinal manometer, is diagnostic of aneurysmal bone cyst  . This confirms the vascular involvement aneurysmal bone cyst is on the venous side.
Interestingly in a few osseous benign cystic lesions, sudden static rise of wine coloured liquid column in spinal manometer without oscillations was seen. These cysts on histological examinations proved to be simple bone cysts.
There was significant oozing of blood in aneurysmal bone cysts with 30 cm H 2 O and above intra-cystic pressures. Preoperative intra-cystic pressure recordings would give an idea of quantity of blood loss and its replacement, if necessary, with blood transfusion.
Quite often other benign bony lesions are present either within the cyst or in cyst wall or adjacent to it. They are a few reports of aneurysmal bone cysts associated with other benign bony lesions, the most common being fibrous dysplasia, osteoclastoma, non-ossifying fibroma and chondroblastoma ,,,, . In this series of 16 cases of aneurysmal bone cysts, 11 of them (68.8%) had associated benign lesions, such as, fibrous dysplasia in eight and osteoclastoma in three. Complete excision of the cystic lesion and filling the gap with fibular bone graft or iliac dowel bone graft is ideal , . If this is not possible, then thorough curettage and autogenous cancellous iliac bone grafting is advised. Radiotherapy is indicated in those not accessable for surgery or when recurred aggressively.
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307, Prashanth Toweres, Musheerabad, Hyderabad
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]