Purpose: The NUSS procedure is one of the most popular surgeries for correcting pectus excavatum. However, little is known regarding stress and strain oil the deformed ribs after inserting the pectus bar, We used ultrasonography to investigate costochondral changes before and after the NUSS procedure. Methods: Ninety-five patients underwent the Nuss procedure between July 2007 and February 2008 at 2 institutions. Chest ultrasonography, specifically of the bones and cartilage, was pet-formed I clay before and I week after the operation. Results: Postoperatively, all patients showed various degree, of deformation from the second to sixth cartilages bilaterally. The cartilages were not fractured. Of these patients, 28 (29.5%) had significant changes, including acute angulation of the costochondral junction and rib fractures near the pectus bar. These changes were associated with increased age (P < .01) and the degree of postoperative sternum elevation (P < .01). The pectus index and sex were not significant predictors of rib damage. Conclusions: The NUSS procedure created significant stress and strain over the deformed cartilages. Approximately 29% of the patients showed localized, self-limited costochondral changes via chest ultrasonography. (C) 2008 Elsevier Inc. All rights reserved.