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bone infarcts are often thought to be in the same spectrum of disease as osteonecrosis
occurs within the metaphysis or diaphysis of long bone
Epidemiology & Incidence
similar risk factors as those seen in osteonecrosis
trauma, sickle cell disease, connective tissue disorders, Gaucher's disease, steroid use
interruption of blood supply by intrinsic or extrinsic factors
often found when imaging the extremities for other reasons
medullary lesion of sheet-like central lucency surrounded by sclerosis with a serpiginous border
"smoke up the chimney"
key feature is that central signal remains of normal marrow
T1 weighted images
peripheral low signal due to grannulation tissue and to lesser extent sclerosis
periphery may enhance post gadolinium
T2 weighted images
acute infarct may show ill-defined non-specific area of high signal
intense inner ring of granulation tissue and a hypointense outer ring of sclerosis
cold in ear
hot in late resorptive and revascularisation phase
usually asymptomatic and do not require treatment
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Qbank (1 Questions)
A 45-year-old female twists her knee suddenly while playing tennis. She denies any history of knee pain in the past. Radiographs are shown in Figure A. What is the diagnosis?
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PREFERRED RESPONSE ▶
Idiopathic bone infarcts often occur in the metaphysis of long bones such as the femur and tibia. They are often asymptomatic and found on imaging studies for other reasons. The infarcted area undergoes progressive, but incomplete resorptive replacement. The bone infarct becomes surrounded by a thick and calcified fibro-osseous wall in a healing attempt. This accounts for the blotchy medullary and linear peripheral shadows seen in radiographs of old bone infarcts resembling “smoke up the chimney”.
Bone scans are cold in the early stages and hot as revascularisation occurs. The etiology is thought to be related to intrinsic/extrinsic vascular compromise such as atherosclerosis, arteritis, and thrombosis. Biopsy (usually unnecessary) shows mineralization of necrotic marrow elements. Bone infarcts usually are asymptomatic, and no treatment is required. If a patient presents with pain, another etiology should be sought. Rarely, malignancy, such as a malignant fibrous histiocytoma, can occur at the site of a bone infarct
Jan Szatkowski MD
Michael Hughes MD
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Transient Osteoporosis of the Knee / AVN Femoral Condyle (C1803)
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