A new methodology to estimate flat foot in skeletal remains - the example of Mediterranean collections

Flat feet (pes planus) are considered a postural defect caused by the collapse of the longitudinal arch, producing complete or near-complete contact of the sole of the foot with the ground. Pes planus has been well-studied in clinical literature and paleoanthropology but has not been approached extensively in bioarchaeology. The main difficulty is related to the diagnosis of this pathology based exclusively on bone remains. In this work, we propose a metric and morphological method to discriminate flat foot in dry bones. Thus, we studied 390 pairs of adult feet in a fair state of preservation from archaeological contexts from Spain, Italy, and Oman. Morphological variability, angles, and dimensions of both the normal bones and the bones displaying flat foot characteristics were analyzed. We found a correlation between the presence of flat foot and some morphological and metric features, mainly in the subtalar and Chopart joints. These results are expressed through a combination of morphological and metric variables, which are useful to discriminate between these two groups. No markedly significant differences of flat foot frequencies between the Spanish and Italian series were found across centuries. However, we noticed a notable increase of the prevalence of flat foot in the contemporary collection, possibly due to the consequences of a rise in life expectancy and modern styles of footwear.