C. W. Snyder1, P. D. Danielson1, S. Farach1, N. M. Chandler1 1All Children’s Hospital – Johns Hopkins Medicine,Department Of Surgery,St. Petersburg, FL, USA
Introduction: Pectus excavatum requires surgical correction when the chest wall deformity, measured by the Haller Index (HI), is severe. Currently, the HI is calculated by cross-sectional imaging with computed tomography, which involves ionizing radiation, or magnetic resonance imaging, which is time-consuming and costly. The purpose of this study was to determine if clinical measurements could accurately determine the severity of the chest wall deformity and the need for surgical repair.
Methods: Patients undergoing surgical repair of pectus excavatum between 2010 and 2014 were included. HI was obtained from radiologist reports. External anterior-posterior (AP), lateral, and right and left chest distances were measured directly from the images by surgeon reviewers. The AP distance was measured at the deepest point of the sternum, from the anterior midline skin surface to the posterior midline skin surface. The lateral distance (LD) was measured at the same level, from the left to right lateral mid-axillary line skin surface. The estimated clinical pectus index (eCPI) was calculated as the LD divided by the AP. The right and left chest distances were measured from the posterior midline skin to the right and left anterior chest wall at the mid-clavicular line. The percent depth (%depth) was calculated as the difference between the right or left chest distance and the AP divided by the chest distance. If the right or left %depth differed due to asymmetry, the larger %depth was used. On a subset of patients, physical measurements were obtained prospectively using chest calipers (clinical pectus index, CPI). Descriptive statistics were calculated for the HI, eCPI, and CPI. The HI and eCPI measurements were compared using Pearson’s correlation coefficient and linear regression.
Results:A total of 41 patients were included, 31 with radiologic measurements and 10 with both radiologic and clinical measurements. The median HI was 4.4 (range, 3.0-8.7). The median (range) eCPI was 1.9 (1.5-2.2) and CPI was 1.9 (1.6-2.3). The median (range) %depth was 18% (17-39%) on caliper measurement. All patients had eCPI and CPI greater than 1.5 and %depth greater than 17%. The HI and eCPI measurements demonstrated excellent correlation (r=0.75, p<0.0001). On linear regression, the eCPI predicted the HI accurately (Adjusted R2 = 0.54, p<0.0001)(Fig1).
Conclusion:Severity of pectus excavatum can be measured with a simple, inexpensive, non-invasive bedside caliper technique. The eCPI calculated by external measurements correlates well with the HI. A CPI greater than 1.5 and percent depth greater than 17% corresponds to a severe defect requiring surgical correction. Further study is needed to verify accuracy and reproducibility of this technique.
