The diabetic foot syndrome (DFS) is linked to loss of neuron functions, implying that the patients do not feel their feet and may unknowingly injure themselves or apply excessive plantar pressure. Such patients are at 17-40 times higher risk of foot amputation than non-diabetics. Sensor-equipped insoles are being developed to warn diabetics against inadverted excessive pressure. For the successful use of such technology, it is essential to understand how patients distribute plantar pressure load and to identify common pressure patterns, to be later used as basis for recognizing abnormalities. In this study, we propose a mining workflow for the discovery of pressure patterns among DFS patients. Our approach encompasses different ways of modeling pressure distribution among foot regions, and workpaths for the computation of similarity between patients and the construction of clusters of patients who apply pressure on their feet the same way. We report on our findings from a dataset of experiment participants who wore sensor-equipped insoles and were asked to apply and release pressure repeatedly over a time period of several minutes. We elaborate on the pressure patterns thus identified and juxtapose them to findings from the literature.

In diabetic patients, excessive peak plantar pressure has been identified as major risk factor for ulceration. Analyzing plantar pressure distributions potentially improves the identification of patients with a high risk for foot ulceration development. The goal of this study was to classify regional plantar pressure distributions. By means of a sensor-equipped insole, pressure recordings of healthy controls (n = 18) and diabetics with severe polyneuropathy (n = 25) were captured across eight foot regions. The study involved a controlled experimental protocol with multiple sessions, where a session contained several cycles of pressure exposure. Clustering was used to identify subgroups of study participants that are characterized by similar pressure distributions. For both analyzed groups, the number of clusters to best describe the pressure profiles was four. When both groups were combined, analysis again led to four distinct clusters. While three clusters did not separate between healthy and diabetic volunteers the fourth cluster was only represented by diabetics. Here the pressure distribution pattern is characterized by a focal point of pressure application on the forefoot and low pressure on the lateral region. Our data suggest that pressure clustering is a feasible means to identify inappropriate biomechanical plantar stress.