modified by Canale and Kelly, consist of a vertical talar neck fracture with subluxation or dislocation of the ankle, STJ, and the talonavicular joint. Type IV fractures had a reported incidence of AVN at 100% (27,28,37).
T1-weighted MR images. In early AVN, diffuse marrow edema produces low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. In advanced stages, the diagnosis of AVN on MRI includes decreased signal intensity on both T1- and T2-weighted images indicative of areas of devascularization or necrotic bone (20,40) (Fig. 115.6). It has been recommended waiting at least 3 months, until bone healing is present, before doing an MRI (12).
Figure 115.5 Lateral radiograph left ankle: talar neck fracture pattern with high rate of associated AVN.
TABLE 115.1 Staging of Osteonecrosis of the Talus According to Ficat and Arlet (1950) (38)
Figure 115.7 Lateral clinical photograph depicting custom-fit patellar tendon weight-bearing prosthesis.