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Pre- and Postoperative Nuss Procedure CT Analysis for Assessing Pectus Excavatum Indices

Qi Zeng¹, Mohammad F. Obeid², Nahom Kidane², Chenghao Chen¹, Robert E. Kelly³, Frederic D. McKenzie²

¹Pediatric Thoracic Surgery, Beijing Children's Hospital, China

²Modeling, Simulation, and Visualization Eng. Dept., Old Dominion University, USA

³Pediatric Surgery, Children’s Hospital of The King’s Daughters and Eastern Virginia Medical School, USA

 

Background: Haller index (HI), introduced in 1987 and considered the gold standard for assessing pectus excavatum (PE) severity, is evaluated with computed tomography (CT) [1]. Since it is highly influenced by the chest width, some have argued that it may provide an inaccurate depiction especially for patients with nonstandard morphologies. The correction index (CI) was, therefore, introduced relying on distances of the sternum and the anterior most portion of the chest from a known fixed position [2, 3]. In this work, we investigate the robustness of HI and CI with the hypothesis that CI provides a better objective assessment for postoperative outcomes.

Patients and Methods: Although postoperative CT scanning is not routinely performed at many institutions, pre- and postoperative CT data for 30 patients who underwent the Nuss procedure was obtained from the Beijing Children's Hospital. The study included 22 males and 8 females in age groups 5 to 7, 7 to 12, and 12 to 18 (10 patients each) with mean age of  years at the time of surgery. The bar was placed for an average duration of  years and the morphologies included 19 cups, 7 trenches, and 4 saucers as classified by [4]. Haller and correction indices were calculated for both datasets for each patient.

Results: All patients showed preoperative HI () and CI () higher than the recommended severity cut-off line of 3.25 and 28% [3], respectively; justifying the need for surgical intervention. Postoperative results, however, indicate that 60% of the patients still have a HI larger than 3.25 (), whereas only 6.3% of the patients had a CI larger than 28% (). Those readings are plotted together on histograms in Figure 1 showing a bigger overlap between pre- and postoperative HI readings and a smaller overlap between those for CI.

Conclusion: Haller index is useful for preoperative evaluation of pectus excavatum. However, it can be misleading for postoperative assessment. Reviewing postoperative CT data for 30 patients showed that the correction index is a more reliable measure for that purpose. This study provided a dataset for young patients for whom surgery was recommended. Anticipated findings were confirmed suggesting that CI is a better reflection of postoperative results than HI.

Keywords: Pectus, Haller index, correction index