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Calcaneal aneurysmal bone cyst

Case contributed by Suman Bandhu
Diagnosis probable

Presentation

Severe heel pain. Unable to weight bear for one day.

Patient Data

Age: 9 years
Gender: Male
x-ray

Lateral radiograph of ankle shows a well defined lucent lesion with a narrow zone of transition in the calcaneum. Likely benign.

The intraosseous calcaneal lesion is sharply marginated, cystic and shows fluid-fluid levels.

Differentials in this age group include aneurysmal bone cyst or hemorrhage within a simple bone cyst.

Case Discussion

Fluid-fluid levels within a bone or soft tissue lesion appear due to presence of fluids of differing density/signal, like blood and clear fluid in the same cavity/compartment. Their demonstration needs the fluid to settle by gravity and  the plane of imaging to be gravity-dependent and perpendicular to the fluid level. This can be separation of blood and serum in a cavernous space containing blood, hemorrhage and separation of serum and blood products or separation of cells and fluid in necrosis.

They occur in a wide variety of lesions. These include aneurysmal bone cyst, simple bone cyst with hemorrhage, telangiectatic osteosarcoma, chondromyxoid fibroma. Amongst these, the possibilities can be narrowed down, as in this case, by other factors such as age, history, location of lesion and other imaging features.

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