Morphological characteristics of the heel fat pad in the dominant and non-dominant feet under varying loads.

[Purpose] Morphological changes in the dual-layered structure of the heel fat pad under varying loads, differences between the dominant and non-dominant feet, and changes over one month are not understood. This study aimed to examine these factors, as understanding normal conditions provides insights into identifying abnormal conditions. [Participants and Methods] Forty healthy Japanese adults (80 feet) participated in this study. The heel fat pad was divided into a macrochamber layer (extending from the calcaneal tuberosity to the fibrous septum, including the macrochambers) and a microchamber layer (extending from the microchambers to the skin). The thickness of each layer in the dominant and non-dominant feet was measured under four conditions: non-load, sitting, 50% load, and 80% load. The compressibility indices were calculated and compared. The same investigations were performed one month later. [Results] Changes in thickness from non-load to 80% load mainly occurred in the macrochamber layer (compressibility index=0.40), with minimal changes observed in the microchamber layer (compressibility index=0.76). No significant differences were observed, although a difference of a few millimeters was observed. Similar results were obtained in the second examination, which was conducted after one month. [Conclusion] These results likely represent the morphological changes in the normal heel fat pad under varying loads.