Imaging of postoperative avascular necrosis of the ankle and foot.

Avascular necrosis (AVN) of the ankle and foot is an uncommon and often unexpected postoperative complication in patients with persistent pain and disability postprocedure. Artifacts from metallic implants may obscure characteristic imaging signs of AVN, and radiography and computer tomography are the mainstay imaging modalities of the postoperative ankle and foot. MRI and nuclear medicine imaging play an important complementary role in problem solving and excluding differential diagnostic considerations including infection, nonunion, occult fracture, and secondary osteoarthritis.This review article evaluates different imaging modalities and discusses characteristic sites of AVN of the ankle and foot in the postoperative setting including the distal tibia, talus, navicular, and first and lesser metatarsals. Radiologists play a key role in the initial diagnosis of postoperative AVN and the surveillance of temporal evolution and complications including articular collapse and fragmentation, thus influencing orthopedic management.