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

Sternum length norms in Han youngsters in central China

The sternum is one of the most important components of the chest wall. However, to the best of our knowledge, at present there is no reference value of the sternum length in normal Han Chinese children that has been published in the literature. The aim of the present study was therefore to establish the reference value of sternum length in a normal Han Chinese population of different ages and sex groups. Chest computed tomography scans and three-dimensional reconstruction images of 1,080 individuals who were younger than 18 years old and without congenital or acquired structural anomalies or congenital metabolic diseases were retrospectively reviewed. The length of the sternum was measured for each individual and comparisons of the sternum length according to sex were conducted using the Mann-Whitney test. Age or region group comparisons were performed using the ANOVA test, and the association between the length of the sternum and age was assessed by regression analysis. A significant association between the age (x) of the individual and the length of the sternum (y) was confirmed, although different regression patterns were identified for the sexes (the regression equation for males was y=5.616x+60.408; P<0.001; R²=0.890, whereas that for females was y=-0.134x²+6.543x+56.805; P<0.001, R²=0.890). No significant differences in sternum length were identified between the sexes for subjects aged 1-13 years old, whereas significant differences were observed comparing the sexes of the subjects aged 14-18 years old. In conclusion, the present study revealed that the length of the sternum in normal Han Chinese children can be precisely estimated by the age of the child using our formulae for the different sexes (where the most-fit formulae for the two sexes are different). This knowledge can be applied clinically in chest wall deformity assessment, and in surgery planning.

Current Concepts in the Etiology and Pathogenesis of Pectus Excavatum in Humans-A Systematic Review

Pectus excavatum (PE) is the most common deformity of the chest wall and is characterized by the posterior depression of the sternum and the lower costal cartilages. To date, the etiology of PE in humans remains enigmatic. Several etiologic hypotheses have been proposed over the past two centuries. However, most of them have been scientifically dismissed and now have only historic value. In this systematic review, we assess scientific publications of the past two centuries addressing the issue of the origin of PE in humans. We present and discuss the histologic, genetic, biomechanical, and experimental scientific achievements that contributed to the clarification of its etiology and pathogenesis. With no clear consensus over the exact mechanism, most recent studies agree that the primordial defect leading the deformation of the anterior chest wall in PE is related to the costal hyaline cartilage structure and function. Further studies on this subject must be carried out. Genetic studies seem to be the most promising way to understand the exact mechanism of PE's origin and pathogenesis.

The costochondral length in patients with pectus excavatum is longer than that of the normal thorax

PURPOSE

Recently, several investigators reported that costal cartilage does not overgrow in pectus excavatum (PE). We wished to clarify whether costochondral length is longer in PE than the normal thorax and we tried to clarify the change of the shape of precordial concavity according to the growth in PE.

METHODS

We evaluated 243 CT axial images of patients with PE and 246 CT axial images of patients without thoracic deformity. We divided the fifth costal cartilage into several lengths. We considered each part to be a straight line and calculated the length of the lines. We compared the approximate costochondral length between PE and normal thorax. We analyzed the distance between both anterior tips of fifth rib, and the ratio of the width and the depth of concavity to thoracic diameter in PE.

CONCLUSIONS

The costochondral length in patients with PE is highly likely to be longer than that of the normal thorax. The length of costal cartilage may be longer in asymmetric PE than symmetric PE. It may start in infantile period in PE that the thoracic shape turns into asymmetry from symmetry. The precordial concavity of PE may be shaped by overgrowth of both costal cartilages and ribs.