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

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.

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.

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.

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.