Bone infarcts
Bone infarct refers to ischemic death of the cellular elements of the bone and marrow. A considerable lack of uniformity exists in the use of terminology for bone infarct. At present, the term osteonecrosis is accepted and used widely. In general, bone infarct refers to lesions occurring in the metaphysis and diaphysis of bone. Lesions in the epiphysis are called avascular necrosis (AVN).
Causes include trauma, collagen vascular disorders such as (systemic lupus erythematosus (SLE), rheumatoid arthritis, and scleroderma), Hemoglobinopathies, Hemophilia ,Gaucher disease, Fabry disease, Dysbaric osteonecrosis, Radiation therapy, Infection , Pancreatitis , Pregnancy , Gout andhyperuricemia , Diabetes and drugs(steroids, indomethacin, and phenylbutazone).
Imaging Findings:
Plain radiography
Epiphyseal region: An arclike, subchondral, lucent lesion may be associated with areas of patchy loss of bone opacity intermingled with sclerotic areas and bone collapse.
Diametaphyseal region: A sheetlike lucency of varying size is usually surrounded by shell-like sclerosis and/or calcification and periostitis.
In flat or complex bones, patchy lucencies and sclerosis are often associated with bone collapse or fractures.
CT scans
CT scans demonstrate central or peripheral areas of reduced attenuation. Reformatted sagittal and coronal images show subchondral fractures and collapse of the articular surface.
CT findings may show subtle trabecular irregularity associated with bone necrosis when plain radiographic findings are normal.
MRI
T1WI:
a. Serpiginous lines of decreased signal intensity.
b. Edema; moderate decrease in signal intensity.
T2WI:
a. Double line sign of decreased signal intensity periphery with adjacent hyperintense inner boarder.
b. Double lines may form pseudomass in chronic cases and internal marrow fat is preserved distinguishing infarct from tumour.
c. Acute infarct as a less well-defined area of edema within cancellous bone.
d. Variable degrees of collapse of articular surface.
MR of the above patient reveal bilateral extensive medullary infarction in the femoral and tibial shafts.
Bone Scan:
a. “Cold spot†(no uptake) in the region in region of disturbed blood supply
b. Uptake in acute cases where revascularization has occurred