THE INFLUENCE OF GENETIC DIFFERENCES, NUTRITION AND SEX ON THE RADIOLOGICAL APPEARANCES OF THE LOWER LIMB OSSIFICATION CENTRES IN NEWBORN TWINS

Radiographs of the knee and ankle of 41 twin-pairs were taken within 72 hours of birth enabling the calcaneal, taloid, cuboid, upper tibial and lower femoral ossification centres to be measured when present. The twins were classified on the basis of placental morphology and blood groups into the following three types: Uniovular (12 pairs), binovular of the same sex (15 pairs) and binovular of different sex (14 pairs). The measurements were analysed in such a way as to give information about the effect of intra-uterine nutrition, genetic factors and sex upon osseous development. It is concluded that intra-uterine nutrition plays an important part in determining the age at which ossification centres become visible on a radiograph. It also affects greatly the actual size of the centres at birth. This latter effect is evident in all the centres studied, but appears to be more marked in a late developing centre (lower femur) than in the early developing ones (talus and calcaneum). Genetic differences and to a lesser extent sex differences also affect the size of the centres at birth.