Non-invasive Clinical Pectus Index as a Measurement of Severity in Pectus

Overview

Pectus excavatum (PE), the most common congenital chest wall deformity, requires surgical repair when the degree of deformity is severe. Currently, the Pectus Index (PI) is used to classify PE severity. Calculation of the PI requires cross-sectional imaging of the chest, usually with computed tomography (CT) or Magnetic Resonance Imaging (MRI), to obtain the necessary measurements. However, CT delivers a high dose of ionizing radiation, which carries cumulative long-term risks of malignancy and MRI can be costly. The purpose of this study is to develop a method whereby accurate chest wall measurements can be obtained to quantify PE severity without the need for cross-sectional imaging.

This is a prospective study. The study population will consist of 2 groups. The first group (PE Group) will consist of patients presenting to the Johns Hopkins All Children's Hospital (JHACH) Pediatric Surgery or Cardiac Surgery Clinics and the outpatient clinic system at Johns Hopkins Hospital for evaluation of pectus excavatum. The second group (Control Group) will be age and gender matched patients presenting to the Radiology department of JHACH undergoing CT chest for indications other than chest wall deformity. Clinical caliper measurements will be taken and used to calculate the Clinical PI. The steps to obtain the clinical caliper measurements are as follows: With the subject lying down, a ruler will be placed across the chest and a second ruler will be used to measure the depth at the deepest point of the sternum. The 2nd ruler will then be used to measure the height of the horizontal ruler to the bed on both sides. All measurements will be made on end expiration. With the subject standing, a measuring tape will be placed around the chest at the point of the deepest sternal depression. The sternum, spine and the bilateral lateral chest locations will be marked with temporary ink. The tape will be kept as level as possible. Chest calipers will be used to measure from deepest point of sternum to posterior midline, posterior midline to anterior chest and the transverse chest diameter. Each measurement will be taken at end expiration. The circumference of the chest will be recorded. Each set of measurements will be taken by 2 independent members of the research team. Attempts will be made to record the amount of time it takes to obtain the measurements. Consent will be obtained to photograph the process for illustrative purposes. Every attempt will be made to conceal the patient's identity by excluding the face from the photograph. In instances where the face is not able to be excluded, the facial features will be blurred. Clinical measurements may be recorded during routine medical care at the provider's discretion. However, these measurements will be considered research procedures for the purposes of this trial. A copy of the measurements will be placed in the medical chart of subjects evaluated for PE for the provider's future reference. Measurements obtained in the Control group will be strictly for the purposes of the research protocol. All subjects, regardless of group, will be provided standard of care for all other medical conditions. All CT and MRI performed for both PE and Control groups will be reviewed and the PI will be determined by a single, blinded radiologist. The radiologist determining the PI may not be the interpreting radiologist and will have no responsibility to provide a comprehensive interpretation of the study. The PI as determined by the research radiologist will be recorded separately from the subject's EMR in a research file. Having a single, blinded radiologist determine the PI for the entire research cohort will allow for consistency in determining the PI, as this is the gold standard to which we are comparing our clinical measurements.