Paediatric post-traumatic osseous cystic lesion following a distal radial fracture.

Post-traumatic osseous cystic lesions are a rare complication in children. An aetiology of intramedullary fat seepage through the damaged bone cortex and its entrapment within the subperiosteum has been proposed. These lesions run a benign course and usually resolve spontaneously. The presence of fatty marrow gives it a distinct appearance which aids in its diagnosis and differentiation from other bone lesions. This case demonstrates a fat-fluid level within the subperiosteal cystic lesion in Magnetic Resonance Imaging (MRI) and this is a typical feature of post-traumatic cystic lesion in a child. Recognition of this imaging feature allows for a confident diagnosis, cutting down on unnecessary, potentially invasive investigations.