The posteroanterior chest radiograph in depressed sternum.

The posteroanterior and lateral chest radiographs of 72 consecutive patients with sternal depression, together with 72 age- and sex-matched controls, have been reviewed. We assessed size and position of the cardiac silhouette, mediastinal contour, radio-opacity in the right lower zone and rib configuration. The degree of depression was determined from the lateral radiograph. The most significant signs of sternal depression on the posteroanterior chest radiograph are a straight left heart border, displacement of the cardiac silhouette to the left and an indistinct right heart border. These three signs have a high specificity for sternal depression and are significantly more commonly seen with increasing severity of depression. The presence of any three, or of more than three, of the described signs was 95.5% specific. However, despite this high specificity, the sensitivity and positive predictive value even for a combination of signs are low. Sternal depression is a relatively common chest deformity and the radiologist should be aware of the changes on the posteroanterior chest radiograph to avoid pitfalls in diagnosis.