Relative growth of the human metacarpals in the prenatal period: anatomic basis of preventive surgery for congenital deformities of the hand.

Twenty right metacarpal bones of Brazilian fetuses (ranging from 17 to 35 weeks post-conception) were studied by the allometric method to define the pattern of metacarpal growth. The metacarpal measurements analysed were their maximum length (ML), ossified shaft length (OSL) and midshaft breadth (MSB). These data were related to crown-rump length and the metacarpal weight to fetal weight. The increase in metacarpal measurements showed an allometric positive coefficient (kappa), highest in the OSL. The ML growth followed an axo-marginal pattern. The 3rd metacarpal showed the highest MSB kappa coefficient. The metacarpal weight showed the highest correlation coefficient (r) to the fetal data. These findings are important to the knowledge of human hand growth and are the basis of preventive surgery for congenital deformities of the hand.