Crescent sign

Crescent sign


Crescent sign in radiology refers to a thin, curvilinear lucent line parallel and inverted to the cortical margin of a bone. It represents the margin of a disk of articular cartilage and underlying subchondral bone, that has fractured. This is a medical sign of osteochondritis dissecans, a consequence of avascular necrosis.

This sign commonly occurs on the femur, both in the hip joint on the femoral head,[1] and in the knee joint. Interruption of the blood supply to the bone leads to ischemic necrosis of the marrow and bone that it supplies. Eventually, the bone infarcts and insufficiency fractures may ensue. Fractures that occur in the subchondral bone may be recognized by a crescentic lucent zone that separates the fragment from the remainder of the bone. Usually indicates stage III osteonecrosis per Enneking's criteria.

The treatment is immobilization, to prevent the joint collapse.

References

  1. ^ Norman A, Bullough P (1963). "The radiolucent crescent line: An early diagnostic sign of avascular necrosis of the femoral head". Bull Hosp Joint Dis 24: 99–104. PMID 14048829. 
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