Regional differences in the biological variability of plantar pressure as a basis for refining diagnostic gait analysis

Abstract

The variability of movement plays a crucial role in shaping individual's gait pattern and could, therefore, potentially serve diagnostic purposes. Nevertheless, existing concepts for the use of variability in diagnosing gait present a challenge due to the lack of adequate benchmarks and methods for comparison. We assessed the individuality of contribution of foot parts that directly mediate the transmission of forces between the foot and the ground in body weight shifting during walking based on 200 pedobarometric measurements corresponding to the analysed foot parts for each of 19 individuals in a homogeneous study group. Our results show a degree of individualisation of the contribution of particular foot parts in the weight-shift high enough to justify the need to consider it in the diagnostic analysis. Furthermore they reveal noticeable, functionally driven differences between plantar areas most apparent between the lowest individuality for the first foot ray and the highest for second one and metatarsus. The diagnostic reference standard in pedobarometry should describe the contribution in the shift of body weight during walking for each area of the foot separately and include information on the intra-individual variation and individualisation of descriptors of the contribution. Such a comprehensive standard has the potential to increase the diagnostic value of pedobarometry through enrichment of the assessment description.

Figure 1

Scheme of the measurement system.

Figure 2

Intraindividual variation (CV) in relation to mean value of pmp index across foot areas (1: heel, 2: midfoot, 3–7: the five metatarsal heads, 8: hallux (first toe), 9: second toe and 10: third to fifth toes). Grey points symbolise the pairs of mean value and intraindividual CV for each mask of each participant. The centres of the ellipses describe pairs of the mean of both the average value (A) and the intra-individual variation (V^intra) of the datasets for each mask, while the ellipses themselves describe the 1 SD distance from these centres.

Figure 3

Biological variability in the contribution of particular foot parts to body weight shift during walking, assessed by analysis of pmp index values. (A) Highlighs a linear relationship (regression line: V = mean(V^inter/V^intra)⋅V^intra) between the intra- and inter-individual variation as well as the diversity of their ratios between the masks independent of this relationship; the whiskers around each point represent 95% confidence intervals. (B) Illustrates the differences between the IxI for each mask and their mean value. The most obvious differences are between 1MTH (3) and 2MTH (4); the area of 1MTH (3) is the least, whereas 2MTH (4) is the most individualised. (C) The result of the k-means classification of these differences in terms of intra-individual CV, with the variation between 1MTH (3) and 2MTH (4) here reflecting the difference in their IxI values presented in (B). (D) Spatial illustration of the classification result, and shows the relationship of the variability and the individualised functioning of the different parts of the foot to their functional role in the body weight transfer process during walking. The Labelling of individual masks represents anatomical and functional foot plantar areas: 1: heel, 2: midfoot, 3–7: five metatarsal heads, 8: hallux (first toe), 9: second toe and 10: third to fifth toes.

Figure 4

Individuality of the contribution of foot parts during body weight shifting, based on the pmp index. The red and yellow lines refer to thresholds that affect the decision of how to proceed with diagnostic assessment. None of the foot plantar areas has an individuality index that falls within the area perceived as strongly preferencing the use of a population reference interval. Foot plantar areas: 1—heel, 2—midfoot, 3–7—five metatarsal heads, 8—hallux (first toe), 9—second toe and 10—third to fifth toes.