Fig 1.
Case and control groups inclusion flowchart.
Fig 2.
The definition of the xiphisternal angle.
A: A line connecting the midpoint of the cranial end and the midpoint of the caudal end of the sternal body. B: A tangent line to the midline of the base of the xiphoid process (excluding the xiphisternal joint). C: A tangent line to the midline at the maximum ventral curvature of the xiphoid process. D: A tangent line at the tip of the xiphoid process. XSBA: The angle between line A and line C, with line A as the baseline. XXBA: The angle between line B and line C, with line B as the baseline. XTSBA: The angle between line A and line D, with line A as the baseline. TBAXP: The angle between line B and line D, with line B as the baseline.
Fig 3.
Illustration of a CT sagittal image around the xiphoid process and descriptions of soft tissue compression signs and anatomical features of the xiphoid tip.
The xiphoid process compresses the rectus abdominis and skin ventrally, leading to positive signs for ASRA and ASSS (a). While the xiphoid tip protrudes into the rectus abdominis, resulting in a positive PXTRA sign, there’s no rectus abdominis thickening, hence a negative HRA sign (b). Subcutaneous tissue thins due to xiphoid pressure, resulting in a positive TST sign (c).
Fig 4.
Examples of the xiphoid process shape, soft tissue compression signs, and anatomical findings of the xiphoid tip (exclude CXT).
The shape of the xiphoid process is defined by noting any bends from its base, using ‘F’ for forward bends and ‘B’ for backward bends. If it is straight, we denote it as ‘S’.
Fig 5.
Characteristics of case and control groups.
Fig 6.
Comparison of CT signs between case and control groups.
* We excluded cases where all four angles couldn’t be measured due to the xiphoid process base not being within the imaging range in 21 controls. Additionally, 175 controls were excluded from XSBA and XSTBA measurements because the sternum wasn’t adequately imaged. ** We omitted one case of xiphoid process absence from the description but included it in the denominator for probability calculations.
Fig 7.
A scatter plot depicting the correlation between age and the length of the xiphoid process, as well as the correlation between age and the xiphisternal angle.