Diabetic foot ulceration is linked to high amputation and mortality rates, with the substantial associated annual spend on the at-risk diabetic foot reflecting the intensive time and labour involved in treatment. Assessing plantar interactions and developing improved understanding of the formation pathways of diabetic ulceration is important to orthotic interventions and patient outcomes. Plantar skin surrogates which emulate the mechanical and tribological characteristics can help improve physical models of ulceration, reduce reliance on cadaveric use and inform more complex computational modelling approaches. The information available from existing studies to characterise plantar skin is limited, typically featuring ex-vivo representations of skin and subcutaneous tissue combined and given focus to shear studies with time dependency. The aim of this study is to improve understanding of plantar tissue mechanics by assessing the mechanical characteristics of plantar skin in two groups; (1) non-diabetic and (2) diabetic donors without the subcutaneous tissue attachment of previous work in this field. Digital image correlation was used to assess inherent skin pre-tension of the plantar rearfoot prior to dissection. Young's modulus, storage and loss moduli were tested for using tensile stress-strain failure analysis and tensile and compressive dynamic mechanical analysis, which was conducted on excised plantar rearfoot donor specimens for both disease state cohorts at frequencies reflecting those achieved in activities of daily living. Plantar skin thickness for donor specimens were comparable to values obtained using ultrasound acquired in vivo values. Median tensile storage and loss moduli, along with Young's modulus, was higher in the diabetic cohort. With a mean Young's modulus of 0.83 ± 0.49 MPa and 1.33 ± 0.43 MPa for non-diabetic and diabetic specimens respectively. Compressive studies showed consistency between cohorts for median storage and loss moduli. The outcomes from this study show mechanical characteristics of plantar skin without the involvement of subcuteanous tissues under reflective daily achieved loading regimes, showing differences in the non-diabetic and diabetic specimens trialled to support improved understanding of plantar tissue response under tribological interactions.

The formation of diabetic foot ulcers (DFU) is consequential of peripheral neuropathy, peripheral arterial disease and foot deformity, leading to altered foot biomechanics and plantar loads. Plantar load comprises of normal pressure and shear stress, however, there are currently no in-shoe devices capable of measuring both components. The STrain Analysis and Mapping of the Plantar Surface (STAMPS) system, developed at the University of Leeds, utilises Digital Image Correlation (DIC) to measure the strain captured by a plastically deformable insole, as a method to understand plantar load during gait. A 2D DIC software was used to capture cumulative plantar strain and displacement pointwise data, however this method was limited to the analysis of planar surfaces. To address this, 3D instrumentation and DIC methods have been developed and implemented into the STAMPS3D system, used as a tool to capture data that is representative of the non-planar nature of plantar surfaces of the foot. A case-study is used to demonstrate how STAMPS3D can measure multi-dimensional strain, bringing potential to improve clinical screening of DFU risk.

Introduction: Diabetes-related foot disease including foot ulcers (DFU) are a growing concern with a huge associated socio-economic impact. Bespoke contoured orthoses are a common clinical intervention used to help prevent DFU formation in regions at risk through offloading, by implementing various design features such as arch support, cuts-outs, metatarsal pads and variable density materials. Research surrounding contoured orthoses has been limited to measuring plantar pressure to assess effectiveness and guide insole modifications necessary for individual patients. However, there is currently no in-shoe measurement tool capable of measuring all components of plantar load (plantar pressure and shear stresses). Methods: The STAMPS3D system has been developed to address this gap and has been successfully shown to measure the cumulative effect of plantar strain indicative of pressure and shear stresses that arise at the plantar interface. In this work, the STAMPS3D system has been used in a proof-of-concept study to explore the efficacy of capturing 3D strain data across a non-planar surface of different contoured orthoses. Results: Plantar strain patterns were shown to vary across anatomical regions of the foot, with statistically significant increases in plantar strain found for contoured conditions across the midfoot due to offloading associated with contoured orthoses. Differences in plantar strain were also observed across the toe and forefoot regions as a result of changing the material stiffness of the orthoses. Discussion: This work demonstrates the utility of employing 3D measurement to improve our understanding of plantar load under the influence of design features implemented in contoured orthoses and their ability to offload regions at risk of DFU formation. In doing so, improvements in management and prevention of diabetes-related ulceration can be made, tackling the social and financial costs associated.

Introduction: Diabetes‐related foot ulcers (DFU) are growing in prevalence, driven by the global rise in diabetes. Plantar callus has been identified as a risk factor for DFU formation, with its presence considered highly predictive for ulceration. Preventative strategies, such as debridement and offloading aim to reduce the thickness of localised hard skin formed through repetitive high pressure and shear stress. Although several studies have looked at the quantitative effects of callus and its removal in the neuropathic foot, assessments have relied solely on pressure measurements, neglecting the contribution of shear stress. A lack of in‐shoe measurement devices capable of measuring shear, either independently or alongside pressure, limits our understanding of how the foot behaves in the presence of callus or responds as a result of debridement. Methods: This proof‐of‐concept study investigates the use of the STAMPS3D system to capture cumulative 3D plantar strain data across the foot in the presence of simulated callus in healthy participants. By introducing multi‐layer silicone inserts that replicate key mechanical features of callus at the 1 ^st metatarsal head and heel regions, this study explores plantar strain responses in healthy participants. Results: The simulated callus produced subtle redistribution of strain across the foot with distinct local changes at the callus sites. Conclusion: Findings may inform future approaches to objective callus assessment, guide debridement practices and contribute to DFU prevention strategies.

Diabetic Foot Ulcers (DFUs) pose a serious health risk to people with diabetes, with a high risk of recurrence following the first DFU and a risk of foot amputation or death. It greatly impacts patient quality of life and costs the NHS up to 0.7% of its annual budget. Over the last 20 years, work has highlighted the link between DFU formation and normal forces. More recently, work has highlighted the importance of strain/shear forces, which are inherently coupled with normal forces. While limited lab-based in-shoe systems have been produced to detect shear, they alter the shoe–foot interface and are not commercially available. Additionally, consultation with people with diabetes highlighted that they may not wear shoes around the house, leaving long periods where in-shoe solutions cannot track forces. We, therefore, present the development of a novel plantar shear measuring system, the Shear Tracking for Enhanced Prevention Sock (STEPS), an instrumented garment to provide an accessible tool for people at risk of DFUs. Integrating sensors within the sock provides a solution that seamlessly integrates within the foot–shoe environment, is suitable for shoeless use, and helps mitigate adherence issues. A prototype STEPS was produced, successfully integrating printed resistive strain sensors (proxy for shear) within custom-designed socks with flexible connectivity to a welt-mounted data acquisition unit. Proof-of-concept testing characterised the system’s ability to measure plantar strain. A single-participant pilot study demonstrated that STEPS captures repeatable, gait-synchronised strain signals during walking, with a stationary noise floor below 10% of the typical per-cycle resistance response and between-repeat correlations of R = 0.41 and 0.78 for Sensor 1 and 2 respectively, supporting its potential to detect strain (as proxy for shear) during daily activity.

Diabetic Foot Ulcers (DFUs) pose a serious health risk to people with diabetes, with a high risk of recurrence following the first DFU and a risk of foot amputation or death. It greatly impacts patient quality of life and costs the NHS up to 1% of its annual budget. Over the last 20 years, work has highlighted the link between DFU formation and normal forces. More recently, work has highlighted the importance of strain/shear forces, which are inherently coupled with normal forces. While limited lab-based in-shoe systems have been produced to detect shear, they alter the shoe-foot interface and are not commercially available. Additionally, consultation with people with diabetes highlighted that they may not wear shoes around the house, leaving long periods where in-shoe solutions cannot track forces. We, therefore, present the development of a novel plantar shear measuring system, the Shear Tracking for Enhanced Prevention Sock (STEPS), an instrumented garment to provide an accessible tool for people at risk with DFU. Integrating sensors within the sock provides a solution that seamlessly integrates within the foot-shoe environment, is suitable for shoeless use, and helps mitigate adherence issues. A prototype STEPS was produced, successfully integrating printed resistive strain sensors (proxy for shear) within custom-designed socks using conductive embroidery for flexible connectivity. The strain sensor has a low profile (<0.5 mm thickness) and remains unobtrusive. Preliminary testing shows the capacity for strain measurement of 12+%, with a resolution of 0.013 Ω across a 20 Ω range, demonstrating good sensitivity over 90 cycles. Proof-of-concept testing characterised the system’s ability to measure plantar strain. A single-participant pilot study demonstrated that STEPS captures repeatable, gait-synchronised strain signals during walking, with a signal-to-noise ratio exceeding 30 dB and between-repeat correlations of up to R=0.77, supporting its potential to detect strain (as proxy for shear) during daily activity.