Standing radiographs of the foot and ankle are a minimum prerequisite. These include full-length, orthogonal, weight-bearing radiographs of the tibia and AP and lateral hindfoot views. Although not essential, maximal dorsiflexion and plantar-flexion views of the ankle, as well as lateral and oblique views of the foot, are optional and are useful for research. In addition, lateral dorsiflexion and plantar-flexion views of the hindfoot can help the surgeon determine the correctability of deformities, especially pes planus (Figure 1). When examining the AP radiograph, one evaluates the coronal plane talar deformity (Figure 2), ankle joint congruity, posttraumatic changes, and the orientation of the malleoli. Congruent deformities are characteristically more rigid and may require extra-articular correction such as a supramalleolar osteotomy. In talar varus deformities, the medial malleolus may be dysplastic because of long-term talar malalignment (Figure 3, A). This is important to recognize, as the medial malleolus may require a translational osteotomy or a prophylactic screw to prevent a postoperative fracture (Figure 3, B). In a talar valgus deformity, the fibula can be dysplastic because of excessive lateral directed forces from talus and calcaneus impingement or malaligned because of stress fracture (Figure 4, A). If this is significant, fibular realignment may be required, which is often a lateral opening wedge osteotomy (Figure 4, B). On the lateral weight-bearing ankle view, the position of the talus is noted. Classically, it is anteriorly translated in varus deformities (Figure 5, A) and posteriorly translated in valgus alignment (Figure 5, B).

The authors recommend a hindfoot alignment radiograph because clinical evaluation of this can be unreliable (Figure 6). This view is taken at a 20° angle to the ground, with the foot placed with its medial border parallel to the radiographic beam.⁶ This radiograph is particularly useful to predict whether additional procedures would be required to balance the TAA over a plantar-grade foot. In the presence of a talar valgus or varus deformity, the hindfoot alignment view allows assessment of the position of the calcaneus. If the axis of the calcaneus is parallel to the tibia, then there has been compensation through the subtalar joint to maintain a plantigrade foot. This influences what type of ancillary procedures are required once the ankle joint prosthesis has been inserted. For example, in a talar valgus deformity with compensation through the subtalar joint, once the TAA has been performed, ancillary procedures for a cavovarus deformity may be required to balance the hindfoot (ie, lengthening the posterior tibial tendon, talonavicular capsular release). If the longitudinal axis of the calcaneus is in line with the talar deformity, then compensation has not occurred through the subtalar joint and pes planus procedures would be required to balance the foot after the TAA (ie, medial translation osteotomy of the calcaneus, Cotton osteotomy, etc). CT is indicated when there are concerns about bone quality, cystic voids, or rotational malalignment. Special attention should be paid to large anteromedial and inferolateral talar osteophytes that can prevent reduction of the talus into the ankle mortise. In talar varus deformities, there are often large anterior fibular osteophytes that also require resection. MRI is rarely required but can be useful in assessment of cases of evaluation of osteonecrosis or ligamentous damage.