Site- and sex-differences in morphological and mechanical properties of the plantar fascia: A supersonic shear imaging study

The purpose of this study was to investigate the site- and sex-differences in the morphological and mechanical properties of the plantar fascia (PF) in humans. The thickness and shear wave velocity (SWV) of PF at five different sites between the medial calcaneal tubercle and the second toe were measured for 40 healthy young participants (20 males and 20 females) using supersonic shear imaging (SSI). The thickness and SWV measurements were highly repeatable (ICC ≥ 0.93). The proximal sites of PF around the calcaneal attachment were significantly thicker and stiffer (higher SWV values) than the middle and distal sites (p < 0.05). In addition, females had significantly thinner PF in proximal and middle sites than males, while being significantly stiffer in regardless of the sites, compared with males (p < 0.05). The results of the present study partly support previous findings on the site- and sex-differences in PF morphology, and further reveal inhomogeneity and sex-specificity of PF stiffness. The present study widely opens the possibility of evaluating PF functions in vivo.