Avascular Necrosis of the Talus: A Pictorial Essay

Abstract

The talus is predisposed to avascular necrosis (AVN), or bone death due to ischemia, owing to its unique structure, characteristic extraosseous arterial sources, and variable intraosseous blood supply. Both traumatic and atraumatic causes have been implicated in talar AVN. The risk of posttraumatic AVN can be predicted using the Hawkins classification system. In addition, the "Hawkins sign" can be used as a radiographic marker that excludes the development of AVN. At radiography, talar AVN typically manifests as an increase in talar dome opacity (sclerosis), followed by deformity and, in severe cases, articular collapse and bone fragmentation. At any stage of this sequence, the radiographic findings can vary depending on differences in the vascular status of the talus and the degree of bone repair. Magnetic resonance imaging is the most sensitive technique for detecting talar AVN and can be used when AVN is strongly suspected clinically despite normal radiographic findings. Computed tomography (CT) also demonstrates typical patterns and can be used to confirm radiographic findings. Coronal CT is required for viewing the articular surface of the talar dome to rule out subtle depression, collapse, and fragmentation. Nevertheless, radiography remains the mainstay of the diagnosis and temporal observation of talar AVN.

The Foot and Ankle: Acquired Disorders

“…Hawkins sign, which is fi rst seen from 6 to 8 weeks after injury, indicates that there is adequate blood supply to the talar dome and low probability of osteonecrosis [ 20 ]. This sign appears as subchondral lucency that parallels the talar dome, and it results from imbalanced bone resorption relative to bone formation in the setting of hyperemia [ 21 ].…”

Imaging of Postoperative Avascular Necrosis of the Ankle and Foot

“…There are no tendinous attachments or muscle origins and $60% of the talar surface is covered by articular cartilage, leaving little area for vascular perforation. 3,7 Major extraosseous arterial supply comes from branches of the posterior tibial artery, anterior tibial artery, dorsalis pedis artery, and perforating peroneal artery with a key anastomosis in the sinus tarsi between the artery of the tarsal canal and tarsal sinus artery.…”

“…A partial Hawkins sign indicative of incomplete AVN is more commonly observed in the medial talus, indicating susceptibility to AVN of the lateral talar dome or inferior articular surface of the body. 7 Complete revascularization after surgery may take between 6 months and 3 years. During this time fractures may heal as progressive sclerosis and cystic changes of AVN either resolve or lead to osseous collapse.…”

“…2,3,7 Systemic causes including sickle cell disease, SLE, corticosteroids, and ischemia due to diabetes may cause multifocal infarctions of the foot and ankle and have a predilection for the talus and calcaneus. 8 Some authors limit the definition of AVN to include only systemic causes, arguing that bone necrosis is a histological end point of many disease processes including severe osteoarthritis, fractures, infections, and tumors.…”

Talar Revascularization After a Complete Talar Extrusion

“…MRI is the most sensitive diagnostic method for detecting talar avascular necrosis and has been shown to identify pathologic bone changes earlier than other imagining modalities. 9 The purpose of this case report is to emphasize and introduce two important aspects in the management and followup of this extremely rare and controversial injury. First, in accordance with recent literature recommendations, we used reimplantation rather than primary excision with fusion.…”