Pressure thresholds and stiffness on the plantar surface of the human foot.

A methodology to assess Pressure Discomfort Thresholds (PDT), Pressure Pain Thresholds (PPT) and tissue stiffness on the plantar surface of the foot was developed. Ten male and 10 female participants volunteered for the study. Foot landmarks were used to create a standardised grid-type template of 95 points. For each test point, PPT and PDT values were obtained, and stiffness was calculated for each of the 20 participants. Cluster analyses were performed to determine the regions of similarity for the three dependent variables, PPT, PDT and stiffness. Moran's-I-index was used to determine the spatial auto correlations. The use of k-means clustering showed five distinct clusters while the three dependent variables showed strong correlations to each other. Morisita's similarity index was used to check the similarity of the grid among all participants. Both male and female participants showed a Morisita's index greater than 0.7 confirming the reliability of the foot template. Practitioner Summary: Pressure Discomfort thresholds (PPT), Pressure pain thresholds (PPT) and tissue stiffness were evaluated at 95 points on the plantar surface of the foot. The PPT and related PDT map are useful to design the footbeds of shoes. Based on the data collected, five distinct clusters of locations were identified.

Foot arch characterization: a review, a new metric, and a comparison.

BACKGROUND: The medial longitudinal arch of the foot is important because it helps protect the foot from injury. Researchers have developed many measures to quantify the characteristics of the arch, and there is ongoing debate about the suitability of these different metrics. This article compares the various measures related to the foot arch, including a new metric, the midfoot dorsal angle, and then investigates the differences in the dimensional measures among various foot types. METHODS: The right feet of 48 healthy individuals (24 men and 24 women) were measured, and various metrics, including the arch height index, the navicular height to arch length ratio, the arch index, the footprint index, the subjective ranking, the modified arch index, the malleolar valgus index, and the midfoot dorsal angle, were determined. RESULTS: Correlation analyses showed that the arch index obtained from the inked footprint has a moderate to high correlation (Pearson correlation coefficients >0.50) with all measured foot-type metrics except for the malleolar valgus index. There were no differences in participant age, stature, weight, body mass index, foot length, foot width, and midfoot height among high, normal, and low foot arches. However, the high-arched group had significantly shorter arch lengths but larger navicular heights and higher midfoot dorsal angles compared with the low-arched group. There were differences in force distributions and peak pressures as well. The rearfoot had more loading and greater peak pressure whereas the midfoot had less load in the high-arched group compared with the low-arched group. CONCLUSIONS: The midfoot dorsal angle may be an appropriate metric for characterizing the foot arch because it is quick and easy to measure, without the tedious procedures associated with area calculations and dimension measurements.