Avascular Necrosis

Lack of blood supply can lead to avascular necrosis of a carpal bone. Carpal bones are rarely affected, with the exception of two carpal bones: the lunate and scaphoid are the most susceptible to AVN because of their unique blood supply, their position in the carpus, and their large cartilage surface area. In the case of scaphoid fracture, the risk of AVN is highest for fractures close to the proximal pole. Caffey’s disease should be considered if multiple carpal bones are involved in a young child. The different signal changes in the affected carpal bone vary depending on the stage of AVN. A table summarises a practical MRI approach to the different stages, based on the original Lichtman classification on standard views. A fracture may resemble an AVN. Evaluation of postoperative status remains a problem. MRI signals of marrow and soft tissue generally remain disrupted up to 6 months after surgery, CE may be present or absent, and residual metal artefacts may interfere with images. The evolution towards eventual collapse and/or fragmentation can be illustrated on MRI.