Optimizing footwear for the diabetic foot: Data-driven custom-made footwear concepts and their effect on pressure relief to prevent diabetic foot ulceration

Efficacy of auxetic lattice structured shoe sole in advancing footwear comfort-From the perspective of plantar pressure and contact area

Introduction

Designing footwear for comfort is vital for preventing foot injuries and promoting foot health. This study explores the impact of auxetic structured shoe soles on plantar biomechanics and comfort, motivated by the integration of 3D printing in footwear production and the superior mechanical properties of auxetic designs. The shoe sole designs proposed in this study are based on a three-dimensional re-entrant auxetic lattice structure, orthogonally composed of re-entrant hexagonal honeycombs with internal angles less than 90 degrees. Materials fabricated using this lattice structure exhibit the characteristic of a negative Poisson's ratio, displaying lateral expansion under tension and densification under compression.

Methods

The study conducted a comparative experiment among three different lattice structured (auxetic 60°, auxetic 75° and non-auxetic 90°) thermoplastic polyurethane (TPU) shoe soles and conventional polyurethane (PU) shoe sole through pedobarographic measurements and comfort rating under walking and running conditions. The study obtained peak plantar pressures (PPPs) and contact area across seven plantar regions of each shoe sole and analyzed the correlation between these biomechanical parameters and subjective comfort.

Results

Compared to non-auxetic shoe soles, auxetic structured shoe soles reduced PPPs across various foot regions and increased contact area. The Auxetic 60°, which had the highest comfort ratings, significantly lowered peak pressures and increased contact area compared to PU shoe sole. Correlation analysis showed that peak pressures in specific foot regions (hallux, second metatarsal head, and hindfoot when walking; second metatarsal head, third to fifth metatarsal head, midfoot, and hindfoot when running) were related to comfort. Furthermore, the contact area in all foot regions was significantly associated with comfort, regardless of the motion states.

Conclusion

The pressure-relief performance and conformability of the auxetic lattice structure in the shoe sole contribute to enhancing footwear comfort. The insights provided guide designers in developing footwear focused on foot health and comfort using auxetic structures.

Evaluation of usability, adherence, and clinical efficacy of therapeutic footwear in persons with diabetes at moderate to high risk of diabetic foot ulcers: A multicenter prospective study

OBJECTIVE

To evaluate therapeutic footwear expectations and usability of individuals with diabetes and foot complications.

DESIGN

A prospective multicenter study was conducted on participants with a high risk of developing a diabetic foot ulcer.

SETTING

Participants were enrolled in 11 different specialized diabetic foot units in Spain between March 2022 and June 2023.

SUBJECTS

Patients with diabetes at moderate to high risk of foot ulceration receiving first therapeutic footwear prescription.

INTERVENTIONS

All the patients included in the research were prescribed with their first pair of therapeutic footwear.

MAIN MEASURES

Primary outcome measures were MOS-pre and MOS-post questionnaires evaluating use and usability of prescribed therapeutic footwear. Secondary outcome measures aimed to evaluate footwear clinical efficacy as ulceration rate and self-reported perceived walking distance per day.

RESULTS

The use of therapeutic footwear exceeded the patient's pre-provision prediction of their anticipated use in 94% of people (n = 126). Based on the visual analogic satisfaction scale, the median satisfaction of daily wearing their therapeutic footwear was 7 points, Interquartile Range (IQR) [5-8.25]. During the follow-up period, 39 participants (29.1%) experienced diabetic foot ulcer. Perceived walking distance participants reported an improvement in their perceived walking ability during various daily life activities.

CONCLUSIONS

Diabetes patients at moderate to high risk of diabetic foot ulcer improved their perception of walking ability after therapeutic footwear prescription. Adherence to the therapeutic footwear prescription resulted in less ulcerations.

Prevention of foot ulcers in persons with diabetes at risk of ulceration: A systematic review and meta-analysis

AIMS

Prevention of foot ulcers in persons with diabetes is important to help reduce the substantial burden on both individual and health resources. A comprehensive analysis of reported interventions is needed to better inform healthcare professionals about effective prevention. The aim of this systematic review and meta-analysis is to assess the effectiveness of interventions to prevent foot ulcers in persons with diabetes who are at risk thereof.

MATERIALS AND METHODS

We searched the available scientific literature in PubMed, EMBASE, CINAHL, Cochrane databases and trial registries for original research studies on preventative interventions. Both controlled and non-controlled studies were eligible for selection. Two independent reviewers assessed risk of bias of controlled studies and extracted data. A meta-analysis (using Mantel-Haenszel's statistical method and random effect models) was done when >1 RCT was available that met our criteria. Evidence statements, including the certainty of evidence, were formulated according to GRADE.

RESULTS

From the 19,349 records screened, 40 controlled studies (of which 33 were Randomised Controlled Trials [RCTs]) and 103 non-controlled studies were included. We found moderate certainty evidence that temperature monitoring (5 RCTs; risk ratio [RR]: 0.51; 95% CI: 0.31-0.84) and pressure-optimised therapeutic footwear or insoles (2 RCTs; RR: 0.62; 95% CI: 0.26-1.47) likely reduce the risk of plantar foot ulcer recurrence in people with diabetes at high risk. Further, we found low certainty evidence that structured education (5 RCTs; RR: 0.66; 95% CI: 0.37-1.19), therapeutic footwear (3 RCTs; RR: 0.53; 95% CI: 0.24-1.17), flexor tenotomy (1 RCT, 7 non-controlled studies, no meta-analysis), and integrated care (3 RCTs; RR: 0.78; 95% CI: 0.58-1.06) may reduce the risk of foot ulceration in people with diabetes at risk for foot ulceration.

CONCLUSIONS

Various interventions for persons with diabetes at risk for foot ulceration with evidence of effectiveness are available, including temperature monitoring (pressure-optimised) therapeutic footwear, structured education, flexor tenotomy, and integrated foot care. With hardly any new intervention studies published in recent years, more effort to produce high-quality RCTs is urgently needed to further improve the evidence base. This is especially relevant for educational and psychological interventions, for integrated care approaches for persons at high risk of ulceration, and for interventions specifically targeting persons at low-to-moderate risk of ulceration.

3D Printed customized diabetic foot insoles with architecture designed lattice structures - a case study

This study proposes a 3D printed, custom insole using an architectural lattice structure infill targeting diabetic patients at risk of foot ulcers. An analysis of five lattice configurations: Fluorite, Kelvin, Octet, Isotruss unit cells, and Truncated Octahedron was conducted to identify the most effective insole infill for plantar pressure and weight redistribution. The Kelvin lattice demonstrated minimal stiffness, suggesting its superiority in balancing plantar pressure and weight. Such lattice-structured insoles offer enhanced foot support and cushioning, crucial for ulcer-prone individuals. This research innovatively employs architectural lattice structures in designing insoles for diabetic patients, offering an insightful comparison of lattice designs for optimized foot care.

Improving Physical, Physiological, and Psychological Health Outcomes in Patients with Diabetic Foot Ulcers - State of the Art

Diabetic foot disease is a complex and challenging complication of diabetes mellitus, which imposes a significant burden of disease on patients, their carers, and the wider health systems. Recurrence rates are high, and current evidence indicates a high mortality associated with it. While management algorithms have primarily focused on the physical aspects of healing, there is increasing recognition of the critical role played by psychological and biomechanical factors in the development and resolution of diabetic foot disease. Therefore, in this paper, we aim to explore how diabetic foot outcomes can be improved by addressing not only the physical but also the psychological and biomechanical aspects that are integral to the development of this condition and its optimal resolution. We explore new technologies that allow for non-invasive objective assessment of the diabetic foot at risk, and we also explore the role of understanding biomechanics, which is essential to determining risk of foot disease, but also the potential for recurrence. In addition, we discuss the evidence linking depression and cognitive impairment to diabetic foot disease and offer our insight on the research direction required before implementing novel information into front-line clinics.

Personalized Offloading Treatments for Healing Plantar Diabetic Foot Ulcers

BACKGROUND

Non-removable knee-high devices are the gold-standard offloading treatments to heal plantar diabetic foot ulcers (DFUs). These devices are underused in practice for a variety of reasons. Recommending these devices for all patients, regardless of their circumstances and preferences influencing their ability to tolerate the devices, does not seem a fruitful approach.

PURPOSE

The aim of this article is to explore the potential implications of a more personalized approach to offloading DFUs and suggest avenues for future research and development.

METHODS

Non-removable knee-high devices effectively heal plantar DFUs by reducing plantar pressure and shear at the DFU, reducing weight-bearing activity and enforcing high adherence. We propose that future offloading devices should be developed that aim to optimize these mechanisms according to each individual's needs. We suggest three different approaches may be developed to achieve such personalized offloading treatment. First, we suggest modular devices, where different mechanical features (rocker-bottom sole, knee-high cast walls/struts, etc.) can be added or removed from the device to accommodate different patients' needs and the evolving needs of the patient throughout the treatment period. Second, advanced manufacturing techniques and novel materials could be used to personalize the design of their devices, thereby improving common hindrances to their use, such as devices being heavy, bulky, and hot. Third, sensors could be used to provide real-time feedback to patients and clinicians on plantar pressures, shear, weight-bearing activity, and adherence.

CONCLUSIONS

By the use of these approaches, we could provide patients with personalized devices to optimize plantar tissue stress, thereby improving clinical outcomes.

Artificial Intelligence Methodologies Applied to Technologies for Screening, Diagnosis and Care of the Diabetic Foot: A Narrative Review

Diabetic foot syndrome is a multifactorial pathology with at least three main etiological factors, i.e., peripheral neuropathy, peripheral arterial disease, and infection. In addition to complexity, another distinctive trait of diabetic foot syndrome is its insidiousness, due to a frequent lack of early symptoms. In recent years, it has become clear that the prevalence of diabetic foot syndrome is increasing, and it is among the diabetes complications with a stronger impact on patient's quality of life. Considering the complex nature of this syndrome, artificial intelligence (AI) methodologies appear adequate to address aspects such as timely screening for the identification of the risk for foot ulcers (or, even worse, for amputation), based on appropriate sensor technologies. In this review, we summarize the main findings of the pertinent studies in the field, paying attention to both the AI-based methodological aspects and the main physiological/clinical study outcomes. The analyzed studies show that AI application to data derived by different technologies provides promising results, but in our opinion future studies may benefit from inclusion of quantitative measures based on simple sensors, which are still scarcely exploited.

Advances and perspective on animal models and hydrogel biomaterials for diabetic wound healing

Diabetic wounds are a common complication in diabetes patients. Due to peripheral nerve damage and vascular dysfunction, diabetic wounds are prone to progress to local ulcers, wound gangrene and even to require amputation, bringing huge psychological and economic burdens to patients. However, the current treatment methods for diabetic wounds mainly include wound accessories, negative pressure drainage, skin grafting and surgery; there is still no ideal treatment to promote diabetic wound healing at present. Appropriate animal models can simulate the physiological mechanism of diabetic wounds, providing a basis for translational research in treating diabetic wound healing. Although there are no animal models that can fully mimic the pathophysiological mechanisms of diabetic wounds in humans, it is vital to explore animal simulation models used in basic research and preclinical studies of diabetic wounds. In addition, hydrogel materials are regarded as a promising treatment for diabetic wounds because of their good antimicrobial activity, biocompatibility, biodegradation and appropriate mechanical properties. Herein, we review and discuss the different animal models used to investigate the pathological mechanisms of diabetic wounds. We further discuss the promising future application of hydrogel biomaterials in diabetic wound healing.

Nonoperative Treatment of Charcot Neuro-osteoarthropathy

Conservative treatment of Charcot neuro-osteoarthropathy (CN) aims to retain a stable, plantigrade, and ulcer-free foot, or to prevent progression of an already existing deformity. CN is treated with offloading in a total contact cast as long as CN activity is present. Transition to inactive CN is monitored by the resolution of clinical activity signs and by resolution of bony edema in MRI. Fitting of orthopedic depth insoles, orthopedic shoes, or ankle-foot orthosis should follow immediately after offloading has ended to prevent CN reactivation or ulcer development.

Predictive value of forefoot plantar pressure to predict reulceration in patients at high risk

AIMS

To analyze a plantar pressure cut-off point for diabetic foot reulceration beneath the metatarsal heads in patients with previous forefoot amputation.

METHODS

A one-year prospective study was conducted in a total of 105 patients at high risk for foot ulceration. Peak plantar pressure (PPP) and pressure-time integral (PTI) in the entire foot, the forefoot region, and each metatarsal head separately were registered. ROC curves were used to select the optimal diagnostic pressure cut-off points. Patients were follow-up monthly or until the development of an ulcer event.

RESULTS

A total of 52 (49.5%) patients developed a reulceration. Using ROC analyses for PPP in the full-foot and in the forefoot, did not predict reulceration beneath the metatarsal heads. Analyzing separately each metatarsal head all patients with values greater than or equal to 20.8 N/cm² at the 1st, 18.62 N/cm² for the 2nd, 18.85 at the 3rd, 17.88 at the 4th, and 12.2 at the 5th metatarsal heads will suffer a reulceration despite the use of orthopedic treatment with optimum values of sensitivity (from 100 to 87.5) and specificity (from 83.2 to 62.8).

CONCLUSION

Barefoot pressures beneath the metatarsal heads should be analyzed separately to predict the region at risk of reulceration.

Effects of wear and tear of therapeutic footwear in patients remission. A 5-year follow-up study

AIMS

To assesses the relationship between the wear and tear of therapeutic footwear (TF) and the risk of recurrence in diabetes remission patients.

METHODS

Remission patients (N = 115) participated in this 5-year prospective study in a specialized Diabetic Foot Unit between October 2016 and January 2022. Patients' TF was assessed in a three-month interval from Day 0 until ulcer recurrence was found. Primary outcome measure was based on the recurrent event in the forefoot.

RESULTS

A total of 82 patients (71.3%) renewed their TF, and 33 patients (28.7%) did not renew their TF during the follow-up period. Patients who failed to renew their TF group experienced more recurrent events (22 vs 14, p <.001, CI [0.04-0.259]) and minor amputations (11 vs 8, p =.002, CI [0.07-0.6]). Both groups showed different recurrence-free survival median times of 205.5 [Interquartile range (IQR) - 188-222] weeks and 89.9 [IQR - 53-126] weeks. Patients who did not renew their TF increased their risk of suffering from a recurrent event in the Cox regression model (p <.001, CI [0.03-0.38], Hazzard Ratio 0.147).

CONCLUSIONS

Patients who renewed their TF because of wear and tear experienced lower recurrences and minor amputations.

Analysis of Plantar Pressure Pattern after Metatarsal Head Resection. Can Plantar Pressure Predict Diabetic Foot Reulceration?

To evaluate the metatarsal head that was associated with the highest plantar pressure after metatarsal head resection (MHR) and the relations with reulceration at one year, a prospective was conducted with a total of sixty-five patients with diabetes who suffered from the first MHR and with an inactive ulcer at the moment of inclusion. Peak plantar pressure and pressure time integral were recorded at five specific locations in the forefoot: first, second, third, fourth, and fifth metatarsal heads. The highest value of the four remaining metatarsals was selected. After resection of the first metatarsal head, there is a displacement of the pressure beneath the second metatarsal head (p < 0.001). Following the resection of the minor metatarsal bones, there was a medial displacement of the plantar pressure. In this way, plantar pressure was displaced under the first metatarsal head following resection of the second or third head (p = 0.001) and under the central heads after resection of the fourth or fifth metatarsal head (p < 0.009 and p < 0.001 respectively). During the one-year follow-up, patients who underwent a metatarsal head resection in the first and second metatarsal heads suffered transfer lesion in the location with the highest pressure. Patients who underwent a minor metatarsal head resection (second–fifth metatarsal heads) showed a medial transference of pressure. Additionally, following the resection of the first metatarsal head there was a transference of pressure beneath the second metatarsal head. Increase of pressure was found to be a predictor of reulceration in cases of resection of the first and second metatarsal heads.

Effect of a carbon reinforcement for maximizing shoe outsole bending stiffness on plantar pressure and walking comfort in people with diabetes at high risk of foot ulceration

BACKGROUND

Different shoe design features can reduce peak plantar pressure to help prevent foot ulcers in people with diabetes. A carbon reinforcement of the shoe outsole to maximize bending stiffness is commonly applied in footwear practice, but its effect has not been studied to date.

RESEARCH QUESTION

What is the effect of a carbon shoe-outsole reinforcement on peak plantar pressure and walking comfort in people with diabetes at high risk of foot ulceration?

METHODS

In 24 high-risk people with diabetes, in-shoe regional peak pressures were measured during walking at a comfortable speed in two different shoe conditions: an extra-depth diabetes-specific shoe with a non-reinforced outsole and the same type of shoe with a 3-mm-thick full-length carbon reinforcement of the outsole. The same custom-made insole was worn in both shoe conditions. Walking comfort was assessed using a Visual Analogue Scale (0-10, 10 being highest possible comfort).

RESULTS

Significantly lower metatarsal head peak pressures (by a median 10-22 kPa) were found with the reinforced shoe compared to the non-reinforced shoe (p < .001). In >83% of cases with the reinforced shoe and >71% with the non-reinforced shoe metatarsal head peak pressures were <200 kPa. At the hindfoot, peak pressures were significantly higher (by a median 24 kPa) with the reinforced shoe (p = .001). No significant shoe effects were found for the toes. No significant shoe effects were found for walking comfort: median 6.1 for the reinforced shoe versus 5.6 for the non-reinforced shoe.

SIGNIFICANCE

Adding a full-length carbon reinforcement to the outsole of a diabetes-specific shoe significantly reduces peak pressures at the metatarsal heads, where ulcers often occur, in high-risk people with diabetes, and this does not occur at the expense of patient-perceived walking comfort.

Data-driven CAD-CAM vs traditional total contact custom insoles: A novel quantitative-statistical framework for the evaluation of insoles offloading performance in diabetic foot

Background

Elevated plantar pressures represent a significant risk factor for neuropathic diabetic foot (NDF) ulceration. Foot offloading, through custom-made insoles, is essential for prevention and healing of NDF ulcerations. Objective quantitative evaluation to design custom-made insoles is not a standard method. Aims: 1) to develop a novel quantitative-statistical framework (QSF) for the evaluation and design of the insoles’ offloading performance through in-shoe pressure measurement; 2) to compare the pressure-relieving efficiency of traditional shape-based total contact customised insoles (TCCI) with a novel CAD-CAM approach by the QSF.

Methods

We recruited 30 neuropathic diabetic patients in cross-sectional study design. The risk-regions of interest (R-ROIs) and their areas with in-shoe peak pressure statistically ≥200kPa were identified for each patients’ foot as determined on the average of peak pressure maps ascertained per each stance phase. Repeated measures Friedman test compared R-ROIs’ areas in three different walking condition: flat insole (FI); TCCI and CAD-CAM insoles.

Results

As compared with FI (20.6±12.9 cm²), both the TCCI (7±8.7 cm²) and the CAD-CAM (5.5±7.3 cm²) approaches provided a reduction of R-ROIs mean areas (p<0.0001). The CAD-CAM approach performed better than the TCCI with a mean pressure reduction of 37.3 kPa (15.6%) vs FI.

Conclusions

The CAD-CAM strategy achieves better offloading performance than the traditional shape-only based approach. The introduced QSF provides a more rigorous method to the direct 200kPa cut-off approach outlined in the literature. It provides a statistically sound methodology to evaluate the offloading insoles design and subsequent monitoring steps. QSF allows the analysis of the whole foot’s plantar surface, independently from a predetermined anatomical identification/masking. QSF can provide a detailed description about how and where custom-made insole redistributes the underfoot pressure respect to the FI. Thus, its usefulness extends to the design step, helping to guide the modifications necessary to achieve optimal offloading insole performances.