Radiography versus computed tomography for displacement assessment in calcaneal fractures

Coronal computed tomography (CT) scans are commonly used in fracture classification systems for calcaneus fractures. However, they may not accurately reflect the amount of fracture displacement. The purpose of this paper was to determine whether lateral radiographs provide superior assessment of the displacement of the posterior facet compared to coronal CT scans.

Lateral radiographs of calcaneus fractures were compared with CT coronal images of the posterior facet in 30 displaced intra-articular calcaneus fractures. The average patient age was 39 years old. Using a Picture Archiving and Communication System (PACS), measurements were obtained to quantify the amount of displacement on the lateral radiograph and compared with the amount of depression on corresponding coronal CT scans.

On lateral radiographs, the angle of the depressed portion of the posterior facet relative to the undersurface of the calcaneus averaged 28.2 degrees; Bohler's angle averaged 12.7 degrees. These numbers were poorly correlated (r = 0.25). In corresponding CT images from posterior to anterior, the difference in the amount of displacement of the lateral portion of the displaced articular facet versus the nondisplaced medial, constant fragment, was minimal and consistently underestimated the amount of displacement.

Underestimation of the amount of depression and rotation of the posterior facet fragment was seen on the coronal CT scan. We attribute this finding to the combined rotation and depression of the posterior facet which may not be measured accurately with the typical semicoronal CT orientation. While sagittal reconstructed images would show this depression better, if they are unavailable we recommend using lateral radiographs to better gauge the amount of fracture displacement.