Figure 1. Examples illustrating the rib cage measurements.

(A) Rib cage measurements were taken at three anatomical levels as follows: 1) sternal articulation of the first rib (upper level), 2) manubrio-sternal joint (middle level), and 3) xiphisternal joint (lower level). The areas burdens were manually traced by using a freehand electronic caliper (green line) along the inner surface of the rib cage. (B) For each hemithorax, several rib cage diameters (D) were measured by using the electronic caliper. To better display them, the diameters are shown separately. On the left side: D1 (from the most dorsal point of the rib and the apex of the vertebral spinous process); D2 (from the most ventral point of the rib cage to the sternal midpoint); D3 (from the most lateral point of the rib cage to the most lateral point of D4). On the right side: D4 (from the apex of vertebral spinous process to the lowest point of D3); D5 (from the most ventral point to the most dorsal point of the rib cage) diameters. (C) Haller's index was obtained by assessing the ratio between the mid-antero-posterior diameter (from the inner surface of the sternum to ventral surface of the vertebral body) and the global transverse diameter (from the most external mid-point of the rib of one side to the opposite one).