Growth of Long-bones of Human Fetus as Illustrated by the Tibia.

Abstract

The growth in length of the human tibia in the latter part of prenatal life has been studied quantitatively from observations, made chiefly by Corrado 1 and by Tamassia, 2 on a series of 152 fetuses. The data include the total body-length, the total length of the tibia, the length of the tibial diaphysis, and the combined lengths of the superior and inferior (cartilagenous) tibial epiphyses. Regression formulae have been computed for certain relationships between these values and are given, with other data, in Table I. Fig. 1 shows the distributions of these observations and their regressive lines.

These formulae indicate that, in the period under consideration, the growth in length of the tibia and the lineal growth of its various parts are directly proportional to the growth in total or crown-heel length. The empirical formulae for the total length of the tibia and for the length of the tibial diaphysis, with respect to total body-length, are characterized by negative second constants, as are the various empirical formulae which have been developed for the external dimensions of the lower extremities (Calkins and Scammon 3 ). The empirical formulae for the epiphyses, on the other hand, show positive second constants. Therefore, while the lengths of the tibia as a whole and of its diaphysis are becoming relatively, as well as absolutely, greater, the epiphyses are becoming relatively shorter, although absolutely longer.

Fig. 2 shows the calculated growth in length of the tibia and its several parts in the last trimester of prenatal life. The relation of the lengths of these structures to age, in fetal or lunar months, has been computed by the use of the empirical formula of Scammon and Calkins 4 for the relation between time and total body-length in the fetal period.