Against the Overgrowth Hypothesis: Shorter Costal Cartilage Lengths in Pectus Excavatum

Background: Pectus excavatum is a common chest wall deformity with no known cause. A common hypothesis is that in patients with pectus excavatum, there is an overgrowth of costal cartilage relative to healthy individuals. Materials and methods: We obtained radiological curvilinear three-dimensional measurements of the fourth to eighth costal cartilage and associated ribs in 16 patients with pectus excavatum and 16 age- and gender-matched controls between the ages of 6 and 32 y. An analysis of variance was used to compare bone length, cartilage length, and their ratios between patients and controls. Results: Relative to bone length, patients with pectus excavatum overall had shorter costal cartilage lengths (P < 0.001), especially on the left side (P < 0.05). We were unable to localize this observation to specific ribs during post hoc analysis. Conclusions: This is the first study to empirically test the overgrowth hypothesis of pectus excavatum for ribs 4 through 8. Although we and others have found no evidence to support this hypothesis, we surprisingly found the alternate hypothesis to be true: patients with pectus excavatum tend to have shorter costal cartilages. Future studies should expand on these results with larger sample sizes and consider volumetric measurements longitudinally during thoracic development.