Definition
Also known as metaphyseal fibrous defect.
Fibrous cortical defects are the same pathological lesion but smaller in size. The arbitrary cut off is 2cm.
Non-ossifying fibromas may be seen with café-au-lait spots, and this is known as Jaffe-Campanacci syndrome
Epidemiology
Extremely common, found in around 1/3 of patients 4-8 years old.
Multiple in more than 50%.
Site
Metaphysis of long bones of lower limb, especially the distal end of the femur.
Aetiology
Muscular pull or periosteal injury may predispose.
Clinical
Usually asymptomatic, picked up on routine XR.
May sustain pathological fracture if more than 50% of the bone is involved.
Radiology
The lesions usually lie in the long axis of the bone and are eccentrically located. They often produce some bulging of the cortex and may cause thinning of the cortex.
The boundary is sclerotic and there may be trabeculae.
MRI: intermediate signal intensity T1 and T2.
Pathology
Grossly, has a yellowish appearance caused by the foam cells.
Consists of proliferation of spindle cells, in a swirling pattern. Haemosiderin is seen, as are giant cells and foam cells.
Treatment
Asymptomatic lesions do not need treatment. Large lesions with impending fracture may require curettage and bone grafting. Lesions located in close proximity to an active physis may be best managed non-operatively until the lesion is no longer adjacent to the physis in order to minimize the risk of surgical injury to the growth plate.
Prognosis
Most regress.