Diaphyseal aneurysmal bone cysts (ABCs) of long bones in extremities: Analysis of surgical management and comparison with metaphyseal lesions

Abstract

Introduction: Aneurysmal bone cysts (ABCs) are benign lesions of long bone metaphysis affecting mostly medullary region in younger age below 20 years of life. These may be originated rarely either in the cortex or in the superficial regions of diaphysis. The study highlighted the differences of diaphyseal lesions from the usual metaphyseal ones in view of their clinical, radiological and biological behavior and also discussed their management in brief.

Material and methods: We reviewed a total of 84 aneurysmal bone cysts over the past fourteen years (2004-2017) and evaluated their surgical outcomes retrospectively. Total ten lesions were diaphyseal cortical in location (group I), while 74 lesions were conventional metaphyseal type (group II).

Results: We observed that cortical ABCs were occurred commonly in diaphysis of femur, humerus, tibia and radius while presentation was at an older age than metaphyseal type. Radiographically these were eccentric lesion and more prone for pathological fractures than conventional type. These are differentiated radiographically from other benign lesions but also mimicking malignant conditions including low grade surface osteosarcoma and telangiectatic osteosarcoma while resemble similar to these on histopathological examination (HPE).

Conclusion: Biological behavior of cortical lesions does not differ significantly than conventional type but these are more prone for pathological fractures so these eccentric cortical ABC lesions should be treated with adequate internal fixation along with curettage and bone grafting. Although incidence of cortical or surface variety of ABCs is rare but surgeons might evaluate its severity in view of aggressive benign or malignant lesions of diaphysis.

Keywords: Aneurysmal bone cyst (ABC); Cortical aneurysmal bone cyst; Curettage; Diaphyseal type; Histopathology; Internal stabilization; Metaphyseal type.

Fig. 1

1a, Radiograph showing osteolytic lesion in mid-diaphyseal cortex of radius; 1b and 1c, Radiographs and clinical picture, showing swelling in the forearm with total lysis of mid-diaphysis of radius mimicking sarcoma associated with pathological fracture and surrounding soft tissue infiltration by the lesion; 1d (excised lesion) and 1e showing total diaphyseal resection followed by free fibular grafting at excised space, healed very well radiologically; and 1f showing clinically excellent functional outcomes of limb.

Fig. 2

2a, 2b and 2c Radiographs and MRI imaging showing large eccentric cortical mid-diaphyseal lesion of femur encroaching surrounding soft tissue within compartment; 2d showing complete healing of lesion after excision and fixation with plating at 3 years follow-up; 2e showing excellent functional outcome and full range of moments.

Fig. 3

Microscopic view of cortical ABC of femoral diaphysis showing cystic serosanguinous fluid spaces bordered by fibroblastic septae, showing multinucleated osteoclast-like giant cells and strands of osteoid formation with fibro-myxoid tissue.

Fig. 4

Microscopic view of diaphyseal cortical ABC showing blood filled cysts without endothelium bordered by fibroblastic tissue and scattered osteoclast-like giant cells.