The footprint ratio as a predictor of pes planus: a study of indigenous Malawians.

The footprint ratio or arch index is the ratio of the middle third of the toeless footprint to the total toeless footprint area. This ratio was determined in an indigenous Malawian population to classify the foot arch type and the incidence of pes planus. The dynamic footprints of 305 able-bodied subjects, free from foot pain, comprising 139 males and 166 females aged between 13 and 17 years, were studied from randomly selected secondary schools in the city of Blantyre. Males had higher arch index than female, but this was not statistically significant (p > .5). The incidence of pes planus was 242.6/1000 using the arch index method. This incidence was higher when it was compared to other methods. Furthermore, the index was found to be statistically higher in Malawians than Caucasian Americans (p < .001) and Europeans (p < .01) previously studied using similar methods. The study has shown probably for the first time the arch index of an African population, and it shows racial variations between Caucasians and Africans. Also the reliability and reproducibility of the arch index method in determining the incidence of pes planus in a given population has been confirmed.