The Pectus Severity Index (PSI) can be used to describe the severity of a pectus deformity of the chest wall.
Requirement: imaging study of the chest, preferably a CT scan or MRI
Parameters:
(1) distance in cm between the posterior surface of the sternum and the anterior surface of the spine in a horizontal plane
(2) interior width of the chest at its widest point in cm
pectus severity index =
= (width of chest) / (distance between sternum and spine)
Interpretation:
• The PSI in a normal person is approximately 2.5.
• The PSI in increased in patients with pectus excavatum.
• The PSI for pectus carinatum is decreased (less than 2).
