Learning Radiology xray montage
 
 
 
 
 
 

Bone Infarct
Medullary Bone Infarct, Osteonecrosis

General Considerations

  • Usually found within the intramedullary cavity of the metaphysis or diaphysis of bone
    • When osteonecrosis occurs in the epiphysis, it is called avascular necrosis
  • In long bones, their calcification is similar to an intramedullary bone infarct
    • Bone infarcts tend to have a well-circumscribed, sclerotic margin
  • Due to interruption of the blood supply from numerous causes including:
    • Sickle cell disease
    • Polycythemia
    • Arteritis, as in connective tissue diseases
    • Trauma
    • Idiopathic
    • Excessive exogenous or endogenous steroids
    • Alcoholism and pancreatitis

Imaging Findings

  • Intramedullary calcification will be seen on conventional radiographs after months or years
  • Frequently has a well-defined “membrane” or “shell” surrounding it (unlike enchondromas)
  • There may be associated periostitis
  • MRI is much more sensitive to ischemic changes and may show findings in 6-12 hours
    • On MRI, the signal in the center of  a chronic bone infarct is similar to normal marrow; in acute infraction, the T1 signal is decreased
  • “Double line sign” on T2-weighted MRI is due to hyperintense central ring of granulation tissue and hypointense peripheral ring that is sclerotic

Differential Diagnosis

  • Enchondroma

Prognosis

  • Very rarely may de-differentiate into a malignancy such as osteosarcoma or fibrosarcoma

 Bone Infarct

Chronic Bone Infarct. There is a well-defined, intramedullary calcification in the meta-diaphysis of the distal tibia with a "shell-like" outer calcified membrane characteristic of an old bone infarct.

 

bone infarcts

Densities in both proximal tibias an distal femurs represent areas of avascular necrosis in a patient with sickle cell disease.