Background
Recent studies have raised again the question of the role of shear forces under the foot in the development of ulcers in individuals with diabetes. To date, accurately measuring these forces has remained a challenge. Shear force sensors, used to measure these forces, can be primarily categorized into two types: measurement plates and wearables that are sensors to be worn inside the footwear.
Measurement platforms, being stationary, offer the ability to conduct static measurements and, at best, a few steps of dynamic data. However, for a comprehensive understanding of ulcer formation, continuous monitoring over extended periods is essential. Typical force plates don’t offer a local resolution, so they measure only the total horizontal force component. However, ulcers are something local and therefore measuring local shear forces is essential.
At present, a fully reliable system for measuring shear forces inside a patient’s shoe does not exist. To address this gap, novel GmbH, a pioneer in capacitive sensor systems, is developing a novel shear force measurement system. This new solution aims to overcome the limitations of existing systems. In the scope of this project, the final product undergoes benchmark testing and evaluation with human subjects to ensure accuracy and reliability.
The primary goal of the project is to develop an advanced insole-embedded 3D sensor prototype tailored for measuring shear forces at different locations underneath the foot. Alongside the hardware, the project produces an integrated software suite for sensor adjustment and calibration, 3D data visualization, and detailed data analysis, enabling researchers and healthcare professionals to interpret and utilize the sensor data effectively.
Approach
The project consists of three studies. The first study aims to assess the validity and reliability of a novel shear force sensor system across varying applied shear forces and different insole surfaces. Validity is evaluated by comparing measurements from the sensor system to known forces applied by a reference system, with the expectation that the sensor readings match the reference values. Reliability refers to the consistency of the sensor readings when the same experiment is repeated under the same conditions. Additionally, the coefficient of friction—determined by the contact surface materials—is varied as an independent variable to observe its effect on shear force measurements across different insole surfaces.
Once the sensor system is validated through benchmark testing in the first study, the focus shifts to subject testing. The second study investigates the contributions of footwear, shear, and normal load to overall shear forces during walking in healthy participants.
Pressure-relieving interventions, such as specialized footwear, are widely used to offload plantar pressure. However, their effect on shear forces—believed to play a role in tissue damage and ulcer recurrence—remains insufficiently understood. Gaining insights into this relationship is critical for improving ulcer prevention strategies. The third study focuses on diabetic patients with previously healed foot ulcers. It examines how local shear forces change before and after footwear optimization. In particular, it explores whether shear forces respond to footwear modifications in a similar way as normal pressures do.
In summary, the overall aim of this research is to test and implement the finalized shear force measurement system in order to improve our understanding of how shear contributes to foot ulcer development.
Secondments are taking place at the German Sport University for sensor validation and subject testing in non-diabetic participants, and at Amsterdam University Medical Center for testing optimized footwear in diabetic individuals.
Our Research Team and Development Team
Novel (www.novel.de) has been focused on reliable electronics and sensor technology and smart software for biomechanical, medical and industrial application. In 1984 the German Federal Ministry for Research and Technology (BMFT) approved a significant grant to Novel for developing the first dynamic pressure distribution measurement platform system (emed®) for the early recognition of high pressure points under the neuropathic diabetic foot. Novel presented as a world-first the pedar® system (including software) for the analysis of pressure distribution inside special shoes for people with diabetes. The candidate will learn from, and collaborate with a multidisciplinary team of physicists, engineers and software engineers and another Doctoral Candidate for DIALECT, who will also focus on the development of a smart system to monitor a different aspect of the foot load (horizontal forces) – potentially causing skin damage.
German Sport University
With more than 6000 students from 93 countries, the German Sport University Cologne (GSU) is currently an outstanding university location both nationally and internationally. The GSU stands for applied and basic research with a high volume of third-party funding and state-of-the-art as well as international teaching in all social and life science sub-disciplines of sport science. The Doctoral Candidate will be working with the Neuromechanics and Musculoskeletal Biomechanics Group (Prof. Dr. Uwe G. Kersting) at the Institute of Biomechanics and Orthopaedics.
The aim of the group is to understand fundamental mechanisms of positive and negative adaptations to physical loading in sports and everyday life contexts. We join biomechanics and neurophysiologic/motor control research methods to:
- Understand acute and long-term sports injury mechanisms
- Investigate the processes of multi-layered adaptation during training, rehabilitation and return to play
- Assess the influence of equipment, training and conditioning strategies in fundamental, clinical and applied research contexts.
The German Sports University (GSU) will be the PhD awarding institute for the doctoral candidate. This also means that the doctoral candidate will follow the doctoral program of the GSU. For further information see here
Doctoral Candidate
Onur Okcu
Recruiting organisation: Novel GmbH, Ismaninger Str. 51, 81675 Munich, Germany
Hosts: Dr. Axel Kalpen; Dipl. Ing. Peter Seitz; Dr. Ahmad Dahrouj
Duration: 36 months
Secondments: GSU, Cologne, Germany (2 months); Istituto Orthopedico Rizzoli, Bologna, Italy (2 months); OIM Voetzorg / Feeture, Amersfoort, Netherlands (1 month).
Summary: The risk of developing a foot ulcer in people with diabetes increases with the presence of loss of protective sensation, biomechanical abnormalities and peripheral vascular disease. In people at high risk of ulceration, we have incomplete understanding of the pathogenesis of ulcer recurrence. Biomechanical factors are important, but there are gaps in our knowledge concerning the extent and mechanisms through which biomechanical factors contribute to ulceration and amputation. One of those gaps is regarding the role of shear in the development of foot ulcers, where general consensus is that this factor plays a significant role, but we are not able to quantify it because a system or sensor that measures shear inside a patient’s shoe is currently not available. In this DIALECT project, we aim to develop the first of its kind sensor that can measures shear inside people’s footwear, to help improve our understanding of the role that shear plays in ulcer development and in evaluating footwear for people with diabetes for shear-reducing capacity.