A radiographic study of the longitudinal growth of primary ossification centers in limb long bones of the human fetus.

This paper describes an extensive study of the growth of ossification centers in limb long bones of the human fetus from 8 to 26 weeks of conceptual age. Longitudinal measurements were made of the femur, tibia, fibula, humerus, radius, and ulna. Comparisons were made between bones on the left and right sides of the body and between the sexes. Standards are presented for the growth of these centers. They compare well with previous studies, any differences being accounted for by different methods of aging and measurement. A complicated picture of growth of the two sides of the fetal body is presented. Growth of the humerus, tibia, and fibula appears to be dominant on the left side of the body while growth in the femur is dominant on the right. At present, no explanation is available, but it is possible that factors such as manual dominance may be related. Evidence also is presented which suggests that the female fetus is in advance of the male in terms of ossification but only ater 21 weeks gestation.