Presentation
A patient presenting with gonalgia after a sports injury incidentally found a lesion in the distal region of the femur. He had a history of sickle cell anemia.
Patient Data
An irregular geographic area of abnormal signal intensity in the medullary cavity of the distal femoral diaphysis and also at the level of the lateral tibial shelf which is compatible with a medullary infarction. Of note are the low intensity serpiginous borders and the high-intensity of the fatty signal within the lesion.
Case Discussion
Bone infarction is a term used to refer to bone necrosis within the metaphysis or diaphysis of a bone. It is the result of ischemia, which can lead to destruction, alteration of bone architecture, loss of function, and pain.
The FEGNOMASHIC mnemonic establishes a place for bone lesions.
Bone/medullary infarction is classically located in the metaphysis and diaphysis. While osteonecrosis is usually located in the epiphysis and subarticular region.
It typically presents as serpentiginous or amorphous sclerosis on radiography or as the double line sign on MRI. The outer border of low signal, usually serpentine (border between living and necrotic bone). The inner margin of the bright line (granulation tissue) and the inner signal are usually composed of fat.
The causes are variable: trauma, embolic phenomena produced by hemoglobinopathies (as in this patient's case), fat embolism, vasculitis, and radiotherapy. Increased spinal cord pressure is caused by exogenous or endogenous corticosteroids. Osteomyelitis, Gaucher's disease.
Although the serpentiform pattern of sclerosis is the classic finding, other radiographic appearances of infarction occur frequently and may mimic other diseases such as enchondroma, bone marrow edema, and marrow replacement processes, diffuse or focal.
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