Thesis

125 Review of the role of bone-SPECT/CT in tarsal coalitions For plain radiographs in suspected TCC, the x-ray beam needs to be angled between 35 and 45 degrees as the patient stands on the cassette, also called the Harris projection [9]. Even then, the TCCs may be hard to visualize using plain radiographs. Sensitivity of plain radiographs for the most specific findings for TCC vary considerably in literature [3, 7, 9-11]. The C-sign, a C-shaped line formed by the outline of the talar dome and the inferior margin of the sustentaculum tali on lateral projections (see Figures 2 and 3, blue arrows on the lateral view), has reported sensitivity ranging from 40% to 97% and mediocre sensitivity for the talar beak of 53% (see Figures 2 and 3, red circle on the lateral view and a narrowed irregular joint space on the 45o view) [3]. Other studies found a 20% incidence of C-sign in patients who had a flatfoot deformity but no tarsal coalition [7, 11]. Therefore, especially in suspected TCC, additional advanced imaging would logically have incremental value over plain radiographs. Figure 3. Plain radiographs: strongly suggestive of TCC in the left foot with a C-sign (blue arrows) and a prominent talar beak (i.e. a superior projection of the distal aspect of the talus, red circle) on the lateral view and a narrowed irregular talocalcaneal joint space on the 45° view. TCC, talocalcaneal coalitions. Computed tomography (CT) displays the anatomical changes in TCs of especially bone, with straightforward abnormal osseous continuity in osseous coalitions and more subtle changes in fibrous and cartilaginous coalitions by using cross-sectional 5

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