Quantitative evaluation of thoracic flattening using a novel index in patients with pectus excavatum: a retrospective study

Pectus excavatum is a common thoracic deformity characterized by sternal depression and thoracic flattening, and can impact cardiopulmonary function. Indices like the Haller Index and Correction Index assess sternal depression, but do not specifically quantify thoracic flattening. We retrospectively analyzed 266 patients with pectus excavatum who underwent the Nuss procedure and 109 controls without thoracic deformities. A novel Thoracic Thickness Index was developed to quantify thoracic flattening using chest computed tomography. Thoracic Thickness Index was compared between patients and controls across age groups and sexes. Pre- and post-operative Thoracic Thickness Index values were also evaluated in patients with pectus excavatum. Multiple regression analysis was used to identify predictors of postoperative Thoracic Thickness Index. Thoracic Thickness Index was significantly lower in patients with pectus excavatum than in controls across most age and sex groups, indicating a flatter thorax. The overall median TTI was 56.2 in patients with pectus excavatum and 62.0 in controls ( P < 0.001). In patients, Thoracic Thickness Index decreased with age. Thoracic Thickness Index improved significantly after surgery but remained lower than control values in most age groups. Multiple regression analysis identified preoperative Thoracic Thickness Index, age, and sex as significant predictors of postoperative Thoracic Thickness Index. This is the first study to quantitatively evaluate thoracic flattening in pectus excavatum using the Thoracic Thickness Index. Patients with pectus excavatum showed significantly flatter thoraxes than the controls, and thoracic flattening progressed with age. TTI may serve as a complementary morphological index for assessing thoracic flattening in pectus excavatum. Further studies are warranted to establish its clinical utility.