Normal and five-fingered hand: comparative X-ray morphometry in the post-natal age

Five-fingered hand (5-FH) with complete developed phalanges is a rare phenotype observed so far only in humans and characterized by three phalanges of the 1st ray. A long-lasting, debated question is if the missing element of the normal hand 1st ray is the metacarpal or the phalanx. In this study, comparative X-rays morphometry of long bones in normal and 5-FH is carried out with the aim to face this question through homology analysis of long bone segments in the transverse and longitudinal line of normal hand and 5-FH.