The relationship between the mechanical properties of heel-pad and common clinical measures associated with foot ulcers in patients with diabetes

Aim: The present study aims at investigating the correlation between the mechanical properties of the heel-pad of people with type-2 diabetes and the clinical parameters used to monitor their health and ulceration risk. Methods: A new device for the in-vivo testing of plantar soft tissues was built and pilot-tested. This device consists of an ultrasound probe connected in series with a dynamometer. Loading is applied manually using a ball-screw actuator. A total of 35 volunteers with type-2 diabetes were recruited and the thickness, stiffness of their heel-pads as well as the energy absorbed during loading were assessed. The participants with diabetes also underwent blood tests and measurements of Ankle Brachial Index and Vibration Perception Threshold. Results: Pearson correlation analysis revealed strong correlations between triglycerides and heel-pad stiffness (r = 0.675, N = 27, p < 0.001) and between triglycerides and energy (r = -0.598, N = 27, p = 0.002). A correlation of medium strength was found between Fasting Blood Sugar (FBS) and stiffness (r = 0.408, N = 29, p = 0.043). Conclusions: People with type-2 diabetes and high levels of triglycerides and FBS are more likely to have stiffer heel-pads. Increased stiffness could limit the tissues' ability to evenly distribute loads making them more vulnerable to trauma and ulceration. (C) 2014 Elsevier Inc. All rights reserved.