eComment. Is overgrowth of costal cartilages the unique cause of pectus deformities?

Does overgrowth of costal cartilage cause pectus excavatum? A study on the lengths of ribs and costal cartilages in asymmetric patients. Jr et al. Outcome analysis of minimally invasive repair of pectus excavatum: review of 251 cases. eComment. Is overgrowth of costal cartilages the unique cause of pectus deformities? In their recent article, Park and coworkers hypothesized that 'if overgrowth of the costal cartilage is the cause of the outward protrusion of the anterior chest wall seen in pectus carinatum (PCar), the costal cartilage lengths on the more protruded side would be greater than that on the opposite side'. By studying the length of three paired rib/costal cartilages in 22 patients with asymmetric PCar, Park and coworkers discovered no statistically significant differences between the two sides and concluded 'overgrowth of the costal cartilage might not be the responsible factor in PCar' [1]. This is an interesting and meticulous study, which, however, raises some issues, as they outlined in their article. First, a rather small number of patients were enrolled. Second, only three paired rib/cartilages (fourth to sixth) were measured while either the third to seven paired rib/cartilages are involved in the standard form of PCar deformities; and second to fourth/five in the upper form (pouter pigeon breast) [2]. Last, no data are provided regarding the morphology/distortion of costal cartilages. Upon reexamining Figure 1 of the article (thoracic CT, axial view of an asymmetric PCar) it appears to us that the right cartilage area (more protruded side) is convex-shaped, while the contralateral cartilage area is concave, leading to sternum rotation, volume reduction of the rib cage on the left and, consequently, asymmetric deformity. Therefore this issue impedes a clear demonstration of the authors' hypothesis. In fact, the pathogenesis of anterior chest wall deformities remains elusive so far. Apart from connective tissue disorders or severe scoliosis, the cause of pectus deformities has been thought to be abnormal elongation of the ribs [3], and then costal cartilages [4], while Park and coworkers, and others [1, 5] claim that overgrowth of costal cartilages is not responsible, since there is no significant change in the costal cartilage length/rib length ratio (C/R ratio). In our opinion, this latter finding might be suggestive of a developmental cartilage dysfunction including the growth centre at the costochondral junction, leading to proportionate over-growth of both cartilage and adjacent rib (thus with no change of C/T ratio) as shown bilaterally in …