Rapidly destructive coxopathy after subchondral insufficiency fracture of the femoral head.

Rapidly destructive coxopathy (RDC) is a rare disorder, and its pathophysiology is unknown. Here, we report a case of RDC evaluated by roentgenography and magnetic resonance imaging, from the onset of hip pain without changes on roentgenograms, to the terminal stage with collapse of the femoral head. Our serial radiological findings clearly illustrate the entire process of RDC, especially the initial stage. Subchondral insufficiency fracture of the femoral head seems to be an important preliminary event in the development of RDC.