Early MRI findings of rapidly destructive coxarthrosis.

Rapidly destructive coxarthrosis (RDC) is known to affect elderly women, but its etiology is unknown. This is the first report to our knowledge, based on a search of the English literature, that reveals the entire process of hip destruction from the onset to the terminal stage of RDC, in an 80-year-old woman. Radiographic evaluation showed subchondral insufficiency fracture of the femoral head at an early stage of this disease. An MRI examination within a month of the onset of hip pain showed the entire femoral head with low intensity on T1-weighted images and high intensity on T2-weighted images, and a small low-intensity band at the subchondral area of the lateral weight-bearing portion of the head. These findings are consistent with subchondral insufficiency fracture and associated bone marrow edema. The lesion developed into a deep and large erosion at the superolateral portion of the femoral head, the process being observed on both roentgenograms and MRI. These findings were confirmed during total hip arthroplasty. This case suggests that subchondral insufficiency fracture of the femoral head may be a preceding sign of destruction of the femoral head.