Aim: To evaluate a new approach to the differentiation of the right and left ribs, the vertical displacement sign, and to compare its efficacy with the big rib sign.
Materials and methods: One hundred and nine lateral chest radiographs that clearly showed both the gastric air bubble sign and the cardiac silhouette sign were retrospectively reviewed by two radiologists. Each study was evaluated by consensus. Each radiograph was assessed for suitability of reading with each technique. Suitable radiographs were then reviewed using both the big rib sign and vertical displacement sign independently.
Results: Applicability of the vertical displacement sign [107 of 109 (98%)] was greater than that of the big rib sign [95 of 109 (87%)] (P = 0.0017). The accuracy of the vertical displacement sign [105 of 107 (98%)] was higher than that of the big rib sign [74 of 95 (78%)] (P < 0.001).
Conclusion: The vertical displacement sign seems to be a reliable technique for the differentiation of right and left ribs on the lateral chest radiograph and can be used as a complementary technique when the big rib sign is not applicable.