Figure 9a. AVN of the talus in a 42-year-old man who was receiving prednisone for inflammatory bowel disease. (a) Lateral radiograph of the ankle shows a large, curvilinear radiolucent cleft extending from the talar dome into the talar body (arrowheads). In addition, there is serpiginous sclerosis within the distal tibia, calcaneus, and navicular bone (arrows). (b) Corresponding sagittal reconstructed image of the ankle from CT data shows a hypoattenuating area (arrowheads) surrounding a collapsed fragment of the talar dome. Areas of serpiginous sclerosis within the distal tibia, calcaneus, navicular bone, and base of the first metatarsal bone are again evident (arrows), findings that are consistent with medullary infarcts.