Movement Analysis Laboratory, IRCCS Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136, Bologna, Italy.
J Foot Ankle Res. 2021 Mar 17;14(1):18. doi: 10.1186/s13047-021-00461-z.
Foot 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.
A 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.
The 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).
The 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.
足部保健研究越来越关注个性化的矫形和假肢设备，以解决患者特定的形态和疾病问题。定制需要先进的 3D 图像处理工具来评估足部和腿部的几何参数和变化。本研究的目的是介绍一种从足底 3D 扫描测量足部形状的新软件。
使用基于 Kinect 的扫描设备获取 44 名健康受试者的 3D 足部形状。在 Matlab 中开发了一个软件，用于从足部扫描中测量足部主要形态参数。使用主成分分析将足部扫描相对于同一参考系进行定向。通过百分比误差和 Bland-Altman 图评估软件测量值的准确性，并评估与手动测量值的相关性。提出了归一化拱容积指数（nAVI）并与传统拱指数相关联。使用组内相关系数（ICC）评估足部测量的跨会话重复性。
软件与手动测量之间的平均百分比误差分别为足部长度 1.2%±0.8%、足部宽度 9.1%±3.7%、足弓高度 22.3%±13.5%和足弓深度 23.1%±12.7%。足部长度（R=0.97）和足部宽度（R=0.83）的相关性非常强，而足弓高度（R=0.62）和足弓深度（R=0.74）的相关性较强。nAVI 与拱指数呈负相关（R=-0.54）。软件与手动测量的足部长度差异较小（Δ=0.92mm），软件对足部宽度的测量值存在高估（Δ=8.6mm），对足弓高度（Δ=-1.4%）和足弓深度（Δ=-11%）的测量值存在低估。所有测量值的重复性均为中等至极好（0.67-0.99）。
本软件无需皮肤标记或识别解剖标志，即可估计足部主要形态参数。此外，测量结果不受足部在扫描设备上的方向影响。测量的准确性和重复性较好，使该软件成为一种潜在有用的、无需操作人员干预的工具，可用于评估足部形态变化和矫形定制。当有 3D 足部图像时，nAVI 可用于更真实地分类足部类型。
