On the assessment of the growth patterns in human fetal limbs: longitudinal measurements and allometric analysis

The total length (TL) and length of the ossified part (OL) of some long bones of the upper (humerus, ulna, radius) and lower limb (femur, tibia, fibula) were evaluated in 58 aborted human fetuses (crown-rump length, CRL, between 38 and 116 mm, developmental age from 8 to 14 weeks). The specimens, without any detectable malformation, were cleared and double-stained with alcian blue and alizarin red S to obtain a differential detection of the ossified part within the comprehensive outline between the cartilaginous epiphyses. The correlation between the values of TL and OL and those of CRL emphasized that the systematic OL measurement in limb long bones correlated better than TL with development age, since OL increased faster than TL. TL and OL also correlated with the CRL by bivariate allometry (ln y = ln a + b ln x) and the data obtained showed that they grew with positive allometry. The comparison between the cumulative values of the bones examined in each limb showed that both TL and OL grew relatively faster in the lower limb than the upper; the greatest growth rate was found for OL in the lower limb. These results many provide a tool for a comprehensive assessment of long bone growth patterns and may be useful in determining fetal growth even in incomplete specimens, in which one or some long bones can still be measured.