[Imaging appearances of subchondral insufficiency fracture]

A subchondral insufficiency fracture of the femoral head (SIF) is a recently proposed concept, which has generally been observed in elderly women with osteoporosis as well as in patients who have undergone a renal transplantation. In addition, this fracture is sometimes seen in young adults. Some cases of subchondral insufficiency fracture were managed by non-operative treatment, while others demonstrated disease progression until bone collapse which necessitated surgery. The low intensity band on the T1-weighted magnetic resonance images has been reported to be one of the characteristic imaging appearances in SIF, which corresponds histologically to the fracture line and associated fracture repair tissue. Therefore, the shape of the low intensity band generally tends to be irregular, disconnected, and convex to the articular surface. This finding has been considered to be useful for the differentiation with osteonecrosis.