11 Aug

University of Hull Students are Improving Steeper Insole Prescription for Diabetic Patients

Since its introduction in 2023, Steeper has been continually making strides to improve the prescription of 3D-printed insoles throughout our orthotic clinics up and down the country. Collaboration is key to this project, and our work with the University of Hull continues to prove fruitful as the results of their latest study have revealed the most effective insole top cover materials for reducing friction and pressure in diabetic patients.

In April 2024, a pilot study led by Dr Harriet Talbott, Medical Engineering Programme Director at the University of Hull, concluded that 3D-printed insoles were a suitable treatment option for Diabetic Insensate Patients. We wanted to know more about how we could improve this product even further to help this particular patient group, so a further study was initiated; An experimental and computational approach to understanding the mechanical and tribological behaviours of insole materials.

This study, carried out by Dr Sarah Crossland, Dr Harriet Talbott and the University of Hull students Callistus Ezenwaka and Chiedozie Okefienam, noted that 40% of diabetic patients who develop an ulceration will be given a life expectancy of up to 5 years (Jupiter et al 2016). Therefore, improving our treatment methods to prevent this potentially life-threatening outcome is vital. Tribology - the science of interacting surfaces in relative motion would be used to determine the outcomes of this study.

Chiedozie completed his undergraduate in the field of Prosthetics and Orthotics before practising in Nigeria for 2 years. Having seen the effects of living with diabetes first-hand, he knew what kind of impact research like this could have, commenting, "In the UK, over 60% of lower limb amputations are caused by diabetes. If we're able to reduce the amount of shear that leads to these ulcers, it can have a positive impact on the lives of these patients, so this was a key reason for me to get involved in this project."

Callistus graduated as a Biomechanical Engineer in 2017 before switching to a career in IT in 2020 and was extremely intrigued by the computational modelling aspects of this project. During the data analysis stage of the project, he commented, "For me to do an accurate and repeatable computerised model, I had to specify the properties of each material. Upon analysing them, I found that when you increased the thickness, you would increase the stress on the foot - it was linear. But for pressure, there was no linear relationship.

Using a simulated skin interface, they tested the pressure and friction response of insole materials including Leather, Chamois, Poron, Neosorb Bamboo, Plastizote and Sponge Rubber, each at different thicknesses. A tribometer recreated the loading profile of the 1st met head of the foot, taking 4500 steps to gauge an average response on each material. Significant testing went into each sample; 22 different material samples were each tested three times individually, and then again in a combination of top cover and mid-layer material options to create as many accurate profiles as possible. This data would then be used to carry out Finite Element Modelling and create computational results.

While friction isn’t a definite value, it is subjective based on the surfaces that are analysed and how they interact with one another, many factors were considered when recreating environmental characteristics. To meet the intended 'ideal conditions' friction had to be measured (µ) below 0.3 (Derler et al , 2009), while input loading pressure was set to 140 kPa (Pataky, et al 2005), representative of the average met head loading profile of a Type 2 diabetic patient. The results found that 1mm Blue Pearl Leather in combination with 6mm Lunairmed and Sponge Rubber fell into the ‘ideal conditions’ category for lowest friction and lowest pressure. The study also found that combinations such as 1.5 mm Grey Poron with 1mm Blue Pearl Leather, 3mm Pink Poron with 1mm Blue Pearl Leather, and 6mm Pink Poron with 1mm Blue Pearl Leather returned balanced friction and pressure-relieving results.

Alex Callaghan, Head of Orthotic Clinical Quality at Steeper said, “Our collaboration with The University of Hull has been instrumental in advancing our understanding of how insole materials can be optimised for diabetic patients. The recent study conducted by their academic team and students demonstrates that specific material combinations, such as 1mm Blue Pearl Leather with a 3-6mm poron or Lunairmed mid-layer, not only reduce friction but also lower pressure at critical points on the foot. These two properties are essential in preventing ulceration, and the findings are already influencing our prescribing practices. Working with The University of Hull has enabled us to base clinical decisions on rigorous experimental and computational evidence, ensuring that we continue to improve outcomes for patients at risk of diabetic foot complications.”

We are pleased to report that the findings of this study have directly impacted our prescribing practices. By leveraging strong collaborations, such as the one with the University of Hull, we aim to continuously enhance patient outcomes. Students Callistus and Chiedozie are already considering the next steps in their research, focusing on questions such as: What types of friction cause ulcerations to form in the first place? How do these findings apply to different loading profiles across the foot? We look forward to continuing our support for universities across the country in helping students answer these vital questions and ultimately improve patients' lives.

University of Hull Students are Improving Steeper Insole Prescription for Diabetic Patients

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