Foot Type Classification Research Articles

Automated plantar contact area estimation in a dynamic state using K-Means clustering

BackgroundEstimation of plantar contact area (PCA) can be used for a variety of purposes such as classification of foot types and diagnosis of foot abnormalities. While some techniques have been developed for assessing static PCA, understanding dynamic PCA may improve understanding of gait biomechanics. This study aims (1) to develop an approach to estimate PCA from video images of footprints during walking and (2) to assess the accuracy and generalizability of this method. MethodsA sample of 41 ambulatory, young adults (age = 24.3 ± 3.2 years, mass = 67.2 ± 16.9 kg, height = 1.63 ± 0.08 m) completed 10 trials walking on a raised transparent plexiglass platform. Foot contact during walking was recorded using a video camera placed under the platform. An image processing algorithm, Clustering Segmentation, was developed based on identifying color intensity between the PCA and the rest of the foot and plantar contact morphology. ResultsThe proposed approach was compared to manual hand tracing, which is widely accepted as the Gold Standard, as well as with an earlier automated approach (Lidstone et al., 2019). Results showed that Clustering Segmentation followed the Gold Standard closely in all phases of gait. The maximum PCA and the maximum PCA length and width generally increased with foot size, indicating that the algorithm could successfully estimate the PCA across a wide range of foot sizes. Results also showed that the proposed approach for obtaining the PCA may be used to characterize various foot types in a dynamic state. ConclusionClustering Segmentation algorithm eliminates the need for subjective interpretation of the PCA. The results showed that the algorithm was considerably faster and more accurate than the earlier automated method. The proposed algorithm will be appropriate for assessment of foot abnormalities and provides complementary information to gait analysis.

Semi-automatic measurements of foot morphological parameters from 3D plantar foot scans

BackgroundFoot healthcare research is focusing increasingly on personalized orthotic and prosthetic devices to address patient-specific morphology and ailments. Customization requires advanced 3D image processing tools to assess foot and leg geometrical parameters and alterations. The aim of this study is to present a new software for the measurement of the foot shape from 3D scans of the foot plantar surface.MethodsA Kinect-based scanning device was used to acquire the 3D foot shape of 44 healthy subjects. A software was developed in Matlab to measure the foot main morphological parameters from foot scans. Principal Component Analysis was used to orientate the foot scans with respect to the same reference system. Accuracy, via percentage errors and Bland-Altman plots, and correlation of the software-based foot parameters were assessed against manual measurements. A normalized Arch Volume Index (nAVI) was proposed and correlated to the traditional Arch Index. Test-retest Intraclass Correlation Coefficient was used to assess the inter-session repeatability of foot measurements.ResultsThe average percentage error between software and manual measurements was 1.2 ± 0.8% for foot length, 9.1 ± 3.7% for foot width, 22.3 ± 13.5% for arch height and 23.1 ± 12.7% for arch depth. Very strong correlations were observed for foot length (R = 0.97) and foot width (R = 0.83), and strong correlations for arch height (R = 0.62) and arch depth (R = 0.74). nAVI was negatively correlated to the Arch Index (R = -0.54). A small difference was found between software and manual measurements of foot length (Δ = 0.92 mm), a software overestimation of foot width (Δ = 8.6 mm) and underestimation of arch height (Δ = -1.4%) and arch depth (Δ = -11%). Moderate to excellent repeatability was observed for all measurements (0.67–0.99).ConclusionsThe present software appears capable to estimate the foot main morphological parameters without the need for skin markers or for identification of anatomical landmarks. Moreover, measurements are not affected by the foot orientation on the scanning device. The good accuracy and repeatability of measurements make the software a potentially useful operator-independent tool for the assessment of foot morphological alterations and for orthotics customization. nAVI may be used for a more realistic classification of foot types when 3D foot images are available.

A data-driven classification of 3D foot types by archetypal shapes based on landmarks.

The taxonomy of foot shapes or other parts of the body is important, especially for design purposes. We propose a methodology based on archetypoid analysis (ADA) that overcomes the weaknesses of previous methodologies used to establish typologies. ADA is an objective, data-driven methodology that seeks extreme patterns, the archetypal profiles in the data. ADA also explains the data as percentages of the archetypal patterns, which makes this technique understandable and accessible even for non-experts. Clustering techniques are usually considered for establishing taxonomies, but we will show that finding the purest or most extreme patterns is more appropriate than using the central points returned by clustering techniques. We apply the methodology to an anthropometric database of 775 3D right foot scans representing the Spanish adult female and male population for footwear design. Each foot is described by a 5626 × 3 configuration matrix of landmarks. No multivariate features are used for establishing the taxonomy, but all the information gathered from the 3D scanning is employed. We use ADA for shapes described by landmarks. Women’s and men’s feet are analyzed separately. We have analyzed 3 archetypal feet for both men and women. These archetypal feet could not have been recovered using multivariate techniques.

A classification of foot types of high school girls in South Korea

Wearing uncomfortable shoes for a long time may cause pains by blisters or corns in the foot. It may lead to weaken ligaments and muscles of lower limbs and feet. The previous researchers claimed that a pain in the foot may be prone to a backache [1]. High school girls feel discomfort in their foot for wearing shoes, especially the heel, toes, or sole, caused by the shape, height of heel, or ball girth of the shoe [2]. The aim of this study was to analyze characteristics according to the forms of the foot that would be applied to make well-fitted shoes for female South Korean youths. This study classified foot types of South Korean high school girls of 17 and 18 years. The three-dimensional foot scan data were collected with a 3D foot scanner. 201 subjects were participated in the experiment. Twenty-four dimensions were measured on the right foot: 6 lengths, 9 heights, 4 girths, 2 widths and 3 angles. The results of this study were follows; First, five factors were extracted by factor analysis. They were foot length, foot girth and width, lateral foot height, medial foot height, and toe flexure factors. Second, four foot types were classified by cluster analysis. Cluster 1 (n=55, 27.4%) referred to the wide and float foot with a long foot length and low heights, and have a little prominent metatarsale fibulare. Cluster 2 (n=59, S.D.=29.3%) represented the small foot with the shortest foot length, the smallest foot girth, and gentle curves on the forefoot. Cluster 3 (n=41, S.D.=20.4%) represented thick foot with open toes compared to the other types. Cluster 4 (M=46, S.D.=22.9%) explained the slant foot to the lateral side that has a flat sole and a little prominent metatarsale tibiale. The findings of this study show that female high school girls in South Korea have diverse shapes and measurements of the foot. The results of this study may be applied for making shoes with the proper fitness for female South Korean youths.

The Comparison of Clinical Assessment Tools for the Foot Posture

It is important to assess foot posture when investigating the relationship between lower extremity dysfunctions and foot types. Although several measurements of static foot posture have been used, there is no consensus regarding clinical measurements for foot posture. The aim of this study is to explore the differences among navicular drift (NDt), foot posture index (FPI), arch index (AI), dorsal arch height ratio (DAHR), normal navicular height truncated (NNHt) and to discover the most effective measurement. After foot types were classified by navicular drop test (NDp), clinical measurements of NDt, FPI, AI, DAHR, and NNHt were performed on 64 subjects' feet. ANOVA analysis was used for the variance of the difference between the NDp and the five kinds of clinical measurements, and the level of significance was set at <TEX>${\alpha}$</TEX>=.05. The results showed that all five clinical measurements demonstrated significant differences with navicular drop. In post-hoc, FPI and NNHt showed significant differences in all foot types. The five clinical measurements are suitable the classification of foot types through the NDp. Therefore, it could be possible to assess correct and objective foot posture by using FPI and NNHt.

Classification of Foot Types for a Shoes Size System for Women in Their 20～30s according to a Survey of Hand-Made Shoes Companies

The purpose of this study was to determine the fundamental foot measurement data that is essential for a shoes size system of women in their 20~30s according to a survey of Korean hand-made shoes companies. This research on the current situation of shoes companies was done by interviewing and surveying employees of these companies. The subjects for this study were 407 women in their 20s~30s who lived in a metropolitan area, and who wanted to enhance their foot health and prevent injury with a proper shoes size system. They were measured with the 3D scan method in use of 6th Size Korea. The result of this study showed that there is considerable dissatisfaction related to women's shoes and the current foot size system using foot length. The Korean hand-made shoes companies assessed here did not use the KS system, but they recognized the necessity of measuring the foot width and circumference, understanding that doing so properly can decrease the return and repair rate. And current target age for shoes bye the hand-made shoes companies was reported to be approximately 5 years. There were significant results according to ANOVA, factor and cluster analyses according to the age range pertaining to the foot length, circumference and height. Each element was significantly correlated with user's satisfaction. There were 5 factors and 3 clusters represented, and foot circumstance and width were as important as foot length with a range of 5 years.

A footprint-based approach for the rational classification of foot types in young schoolchildren

Background Discrepancy in the classification criteria among footprint parameters complicates attempts for rational classification of feet. Objective To develop a footprint-based classification technique for the rational classification of foot types by allowing simultaneous use of several parameters (co-classification). Method Static standing footprints were recorded from 132 schoolchildren. The Arch Index (AI), Martirosov's K Index (KI), Footprint Angle (FPA) and Chippaux-Smirak Index (CSI) were determined. k-means cluster analysis was applied to obtain individual classifications and co-classifications. Results Identification across classified foot types coincided with all parameters for 0.8–3.5% of the sample. Values ranged from 2.3 to 10.6% when classification coincided with three out of four parameters. The inconsistency between every initial individual classification and co-classifications corresponded to 15.2% for AI, 49.2% for KI, 41.7% for FPA and 48.5% for CSI. Conclusions The co-classification process indicated low percentages of correctly identified foot types from all parameters that suggest the dependence of the classification on the parameter of choice used to assess arch configuration. The AI gave the lowest percentages of misclassified cases during the co-classification process. The co-classification model with the 4-cluster solution is proposed and confidence limits are reported for a rational classification of feet in young schoolchildren.

Serial measurement of calcaneal pitch during midstance.

Although emerging evidence suggests a causal relationship between arch structure and musculoskeletal injury, few investigations have adequately assessed arch function during gait. In this study, digitized videofluoroscopy was used to evaluate the sagittal plane motion of the calcaneus during gait. Nine female subjects requiring diagnostic foot radiographs underwent videofluoroscopy. The calcaneal inclination angle, arch height ratio, and tarsal index were digitally analyzed for all radiographic images. Calcaneal pitch was correlated to both the arch height ratio and the tarsal index. Repeated measures analysis of variance helped to identify a significant reduction in the mean calcaneal pitch during the midstance and early propulsive periods of gait. These findings suggest that although calcaneal pitch may be used as an indicator of rearfoot position, biomechanical classification of foot types based on radiographs may result in erroneous conclusions concerning foot function.