Mineralized area of the human rib cross-sections from early puberty until adulthood

Ribs undergo numerous changes during growth and development. Although they occur both externally and internally, the latter are not as extensively documented during the transition from puberty to adulthood. Therefore, it is unknown how rib cross-sectional mineralized area changes during this period. To shed light on this issue, we micro-CT scanned ribs from each costal level belonging to 21 individuals equally distributed into three developmental groups: pre-pubescents, post-pubescents, and adults. Then we selected the cross section at the midshaft of each rib and measured its percentage of mineralized area. Our results show that adults have lower mineralized area in their rib cross sections than both pre- and post-pubescents, which is consistent with previous research. Between pre- and post-pubescents, mineralized area is greater in the latter from costal levels 1-8. We propose that this might respond to a peak of mineralized area happening during late puberty. Regarding the tendency of the data, the three groups show a U-shaped trend with two maximum values at costal levels 1 and 12 and a minimum value at levels 4-5. We suggest that greater values are located at the beginning and the end of the costal series due to the mechanical stress produced in these areas by the scalene muscles (ribs 1-2) and diaphragm (ribs 7-12) during breathing. Interestingly, the U-shaped trend is less pronounced in pubescents, whose central costal levels have relatively more mineralized area than that of adults due to ongoing maturation from the external to central costal levels.