Genetic and Environmental Factors of Two-phalanged Fifth Toe in Korean / 체질인류학회지

Anatomically, we have known that the first toe is composed of 2 phalangeal bones (proximal and distal phalanx) and the second, third, fourth, fifth toe are composed of 3 phalangeal bones (proximal, middle, and distal phalanx). But in Korean the 5th toe is commonly seen as 2 phalangeal bones in foot plain X-ray. In this study, we observed the numbers of phalangeal bones of fifth toe in Korean and analyzed the relation with several environmental factors and genetic factor. The data of occupation, age, body weight and foot length as well as the foot radiograph were obtained in 175 persons without any foot lesion. With the coorperative persons among them showing triphalangeal 5th toe as the index cases, radiograph of 12 family were studied to analyse the pedigree. As result, total frequency of the 5th toe symphalangism was 74.29% (male 74.2%, female 73.36%). There was no statistical difference between male and female. The bilaterality of the symphalangism was 98.46%. The occupation group were farmer, labor, self-support, white collar, student, housewife, there was no correlation between the kind of occupation and the frequency of the symphalangism. Also there was no correlation between body weight or foot length and the symphalangism. In conlusion, the two-phalanged fifth toe might be related with genetic factor rather than several environmental factors such as sex, age, occupation, body weight and length of foot. From the pedigree study we concluded the genetic trait of the triphalangism might be the autosomal recessive.

Two-phalanged Fifth Toe in Korean Children / 체질인류학회지

Radiographic research was performed to know the frequency of two-phalanged fifth toe and its relation to presence of the ossification centers in normal Korean children. Previous study showed more than 74% of the incidence in adulthood and less than 30% in childhood. Fifty children (33 male and 17 female, aged 2 to 15; mean age 9.6) were studied by plain foot radiographs focused on the fifth toe. In the 3~8 yr old 20 subjects, secondary ossification center of distal phalangeal bone was seen as a ossicle (small bone) placed at proximal to the distal phalanx. Secondary ossification center of middle phalangeal bone and the bony shaft of the phalanx was hard to distinguish. So keeping up the objectivity, regardless of distinguishable ossification center or the bony shaft of phalanges, ossicles seen on the 5th toe was counted to classify the presumptive type of the toe. Epiphyseal ossification center of proximal phalanx was excluded from the count. There were three types of the fifth toe which has 2 ossicles to 4 ossicles. Overall incidence of the type of 2 ossicles was 24% (12/50). Above 12 yr old group the incidence was 61% (11/18), and above 13 yr old group the incidence was 75% (9/12). The incidence of biphalangism came closer to the adult's after late childhood. This finding represent that progress of biphalangealization completed after late childhood. It seems that the progress starts earlier than 3 yr old. We made the hypothesis by the incidence of 30% (6/20) of the type which has 4 ossicles on the fifth toe at 3~8 yr old group. Four ossicles might be a secondary ossification center of distal phalanx and the bony shaft of distal, middle and proximal phalanx. They might form a distal interphalageal joint and the triphalangeal toe. To know more about the morphogenesis of biphalalngeal 5th toe, further progressive study in childhood is needed.