Foot ulcers are a prevalent complication in the diabetic population, and despite that, the exact causation of plantar ulcers is still unknown. Research suggests that vertical pressure and horizontal shear play an integral role, but the pressure and shear distributions must be precisely measured on the entire plantar surface. Unfortunately, only pressure distribution measurement systems are commercially available. Several shear stress distribution measurement systems have been developed in universities in the past, but the systems are limited in their resolution, accuracy, and size. To address this need, Bertec Corporation is proposing to collaborate with Innovative Scientific Solutions Inc. and the Cleveland Clinic Foundation to develop a measurement tool where the continuous distributions of pressure and shear over the entire plantar foot can be quantified for approximately the cost of existing commercially available tools that are capable of only measuring pressure. This tool will be a force plate developed by Bertec with an elastic surface stress sensitive film (S3F) coating the top developed by ISSI. The device will be tested with diabetics and age-matched controls at the Cleveland Clinic in order to better refine the system and its software. It will be capable of measuring the ground reaction forces and the continuous pressure and shear distributions as a subject walks across the plate. The final product will be of great interest to biomechanists, podiatrists, physical therapists, and doctors specializing in the treatment of diabetes and diabetic foot complications. But in order to reach that goal, the following specific aims must be accomplished:
Aim 1, Phase I) Integrate an elastic polymeric film sensitive to pressure and shear with a 6-component force plate in order to obtain a prototype instrument that will yield ground reaction forces plus a true pressure and shear deformation distribution in the polymeric film, due to plantar loading;
Aim 2, Phase II) Capture precise foot landmark positions on the prototype product of Aim 1, so that the measured quantities can be accurately mapped to the physical location on the foot;
Aim 3, Phase II) Utilizing the finite element analysis model, as independently established by Innovative Science Solutions Inc., for the surface stress sensitive film, and the synchronously measured shear forces from the force plate, convert the shear deformation distribution of the prototype product to shear stress distribution. Then integrate this analysis module into Bertec's digital data acquisition software allowing auto-calculation of shear stresses;
Aim 4, Phase II) Incorporate the pressure deformation distribution and foot marker position data from Phase I and Aim 2 into the data acquisition software. Using the finite element analysis model and the synchronously measured vertical force by the force plate, calibrate the pressure deformation model to auto-calculate true pressure distribution;
and Aim 5, Phase II) Evaluate the clinical utility of the prototype system, including the acquisition software measuring shear stress and pressure distribution acting upon the plantar foot, from a functional as well as a research point of view through clinical trials of patients with and without diabetes.

Public Health Relevance

Nearly 10% of the US population has diabetes, and foot ulcers are one of the most common complications - often resulting in amputation. Pressure and shear stress acting on the sole of the foot may be responsible for ulcer formation, but no tool is commercially available that can measure pressure and shear distributions. Bertec's S3F-force plate system is capable of measuring and displaying the distributions and forces acting upon sole of the diabetic's foot.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Small Business Innovation Research Grants (SBIR) - Phase II (R44)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-MOSS-F (15))
Program Officer
Jones, Teresa L Z
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Bertec Corporation
United States
Zip Code
Berki, Visar; Boswell, Melissa A; Ciltea, Daniela et al. (2015) Expanded butterfly plots: A new method to analyze simultaneous pressure and shear on the plantar skin surface during gait. J Biomech 48:2214-6
Stucke, Samantha; McFarland, Daniel; Goss, Larry et al. (2012) Spatial relationships between shearing stresses and pressure on the plantar skin surface during gait. J Biomech 45:619-22