Prediction of clinical foot characteristics using quantitative features from different measurement set-ups

We measured 77 healthy subjects without major foot deformities. They were all clinically assessed by 10 experts (orthopedic technologists, podiatrists, and one orthopedic surgeon), hence a total of 770 assessments. Furthermore, an anamnesis was conducted, and gait of all subjects was quantitatively measured using three-dimensional (3D) motion analysis (Codamotion), dynamic pressure plate (RSScan International), a dynamic 3D scanner (ViALUX), and a force plate (AMTI). To identify those clinical characteristics, which are robust over the different experts, we conducted a 2agreement weighted kappa analysis which is an extension of Cohen’s kappa for multiple raters (Warrens, 2012). Furthermore, we included both the popularity and the discriminative power of a characteristic (i.e. how many experts scored it and how diverse are the scores, respectively.). We included these last two elements because if either popularity or discriminative power are low, we cannot say much about a certain feature, e.g. if it is evaluated by only one or two experts, or if all subjects get the same score. In a second part, we used the quantitatively extracted features (from the pressure plate, 3D motion analysis, dynamic 3D scanner, and force plate) to predict the average expert scores, for each clinical characteristic individually. To determine the best feature subset, we carried out a feature selection using the Lasso technique in a 10-fold cross validation. The feature subset was then fed to a support vector machine (SVM) classifier which trained a prediction model using a leave-one-out crossvalidation. Finally, from these data we can give an indication which hardware is best to predict foot characteristics. To this end, we built the SVM model only including features from one or a limited set of measurement equipment. In this abstract, we highlight three cases: prediction of the resting calcaneal stance position (RCSP), pressure of the midfoot during stance, and the ratio of the forefoot/heel width.