Temperature as a Causative Factor in Diabetic Foot Ulcers: A Call to Revisit Ulceration Pathomechanics

Combined impact of heat and dust on diabetes hospitalization in Kuwait

INTRODUCTION

In Kuwait, a severe diabetes and obesity epidemic coexists with intense dust storms and harsh summer heat. While, theoretically, this interplay between dust, heat, and diabetes presents a serious public health problem, the empirical understanding of the actual risks remains limited. We hypothesized that increased exposure to heat and dust, independently and jointly, exacerbates the risk of hospitalization for diabetes patients.

RESEARCH DESIGN AND METHODS

We placed custom-designed particle samplers in Kuwait to collect daily dust samples for 2 years from 2017 to 2019. Samples were analyzed for elemental concentrations to identify and quantify dust pollution days. Temperature data were collected from meteorological stations. We then collected hospitalization data for unplanned diabetic admissions in all public hospitals in Kuwait. We used a case-crossover study design and conditional quasi-Poisson models to compare hospitalization days to control days within the same subject. Finally, we fitted generalized additive models to explore the smoothed interaction between temperature and dust days on diabetes hospitalization.

RESULTS

There were 11 155 unplanned diabetes hospitalizations over the study period. We found that each year, there was an excess of 282 diabetic admissions attributed to hot days (95% CI: -14 to 473). Additionally, for every 10 µg/m3 increase in dust levels, there were about 114 excess diabetic admissions annually (95% CI: 11 to 219). Compared with mild non-dusty days (33°C (0 µg/m3)), hot-dusty days jointly increased the relative risk of diabetic admissions from 1.11 at 42°C (85 µg/m3) to 1.36 at 42°C (150 µg/m3).

CONCLUSIONS

Both heat and dust seem to contribute to the increased diabetes morbidity, with combined hot-dusty conditions exacerbating these risks even further.

The Effect of Dimple Insole Design on the Plantar Temperature and Pressure in People with Diabetes and in Healthy Individuals

An increase in plantar pressure and skin temperature is commonly associated with an increased risk of diabetic foot ulcers. However, the effect of insoles in reducing plantar temperature has not been commonly studied. The aim was to assess the effect of walking in insoles with different features on plantar temperature. Twenty-six (F/M:18/8) participants-13 with diabetes and 13 healthy, aged 55.67 ± 9.58 years-participated in this study. Skin temperature at seven plantar regions was measured using a thermal camera and reported as the difference between the temperature after walking with an insole for 20 m versus the baseline temperature. The mixed analyses of variance indicated substantial main effects for the Insole Condition, for both the right [Wilks' Lambda = 0.790, F(14, 492) = 4.393, p < 0.01, partial eta squared = 0.111] and left feet [Wilks' Lambda = 0.890, F(14, 492) = 2.103, p < 0.011, partial eta squared = 0.056]. The 2.5 mm-tall dimple insole was shown to be significantly more effective at reducing the temperature in the hallux and third met head regions compared to the 4 mm-tall dimple insole. The insoles showed to be significantly more effective in the diabetes group versus the healthy group, with large effect size for the right [Wilks' Lambda = 0.662, F(14, 492) = 8.037, p < 0.000, Partial eta-squared = 0.186] and left feet [Wilks' Lambda = 0.739, F(14, 492) = 5.727, p < 0.000, Partial eta-squared = 0.140]. This can have important practical implications for designing insoles with a view to decrease foot complications in people with diabetes.

Can thermography predict diabetic foot ulcer risk in patients with diabetes mellitus? A systematic review

BACKGROUND

There is a growing prevalence of diabetic foot ulcers (DFUs) in patients with diabetes mellitus and the use of thermography has sparked interest in a non-invasive diagnostic method for early DFU risk assessment and management.

AIM

This systematic review aims to assess the use of thermography in predicting diabetic foot ulcer risk in patients with diabetes mellitus.

METHODS

A systematic search of publications using MEDLINE, CINAHL, and Cochrane databases was conducted in April 2023, and relevant articles were reviewed. Data was extracted and a narrative synthesis was undertaken. The evidence-based librarianship (EBL) checklist assessed the methodological quality of the studies included. Reviewing these articles to the primary and secondary outcomes of this literature review. The primary outcome focused on the predictive capabilities of thermography for DFU prediction, while the secondary outcome assessed the feasibility, usability, and effectiveness of thermography.

RESULTS

Eight studies were conducted from 1994 to 2021 with an emphasis on the predictability of thermography in predicting DFU risk. All eight studies focused on temperature variations associated with DFU development. Six of the included studies compared the effectiveness of DFU occurrence in diabetic patients and non-DFU use. The overall results showed that employing thermography in DFU prevention might allow for early detection and intervention, offering a non-invasive and effective means to reduce the risk of DFU development and its associated complications in patients with diabetes mellitus.

CONCLUSION

The systematic review indicates that thermography holds promise for predicting DFU risk, with studies showcasing predictive capabilities and patient benefits. Despite some challenges and limitations, the evidence suggests thermography's value in assessing DFU risk in diabetes patients, warranting further research on device types and locations.

A review of non-invasive sensors and artificial intelligence models for diabetic foot monitoring

Diabetic foot complications have multiple adverse effects in a person's quality of life. Yet, efficient monitoring schemes can mitigate or postpone any disorders, mainly by early detecting regions of interest. Nowadays, optical sensors and artificial intelligence (AI) tools can contribute efficiently to such monitoring processes. In this work, we provide information on the adopted imaging schemes and related optical sensors on this topic. The analysis considers both the physiology of the patients and the characteristics of the sensors. Currently, there are multiple approaches considering both visible and infrared bands (multiple ranges), most of them coupled with various AI tools. The source of the data (sensor type) can support different monitoring strategies and imposes restrictions on the AI tools that should be used with. This review provides a comprehensive literature review of AI-assisted DFU monitoring methods. The paper presents the outcomes of a large number of recently published scholarly articles. Furthermore, the paper discusses the highlights of these methods and the challenges for transferring these methods into a practical and trustworthy framework for sufficient remote management of the patients.

Trend and Seasonality of Diabetic Foot Amputation in South Korea: A Population-Based Nationwide Study

The number of lower extremity amputations in diabetic foot patients in Korea is increasing annually. In this nationwide population-based retrospective study, we investigated the data of 420,096 diabetes mellitus patients aged ≥18 years using the Korean Health Insurance Review and Assessment Service claim database. We aimed to study the seasonal and monthly trends in diabetic foot amputations in Korea. After applying the inclusion criteria, 8156 amputation cases were included. The analysis showed an increasing trend in monthly amputation cases. In terms of seasonality, the monthly frequency of amputation was commonly observed to be lower in February and September every year. Diabetic foot amputations frequently occurred in March, July, and November. There was no difference between the amputation frequency and mean temperature/humidity. This study is meaningful as it is the first nationwide study in Korea to analyze the seasonal and monthly trends in diabetic foot amputation in relation to climatic factors. In conclusion, we recognize an increased frequency of amputation in March, July, and November and recommend intensive educational program on foot care for all diabetes patients and their caregivers. This could improve wound management and amputation prevention guidelines for diabetic foot patients in the Far East with information on dealing with various seasonal changes.

Plantar shear stress in the diabetic foot: A systematic review and meta-analysis

AIMS

Diabetic foot ulceration (DFU) is a multifactorial process involving undetected, repetitive trauma resulting in inflammation and tissue breakdown. Shear stress forms a major part of plantar load, the aim of this review is to determine whether elevated shear stress results in ulceration.

METHODS

A systematic review of the Ovid Medline, EMBASE, CINAHL and Cochrane library databases was performed. Studies involving patients with diabetes who underwent plantar shear stress assessment were included. The primary outcome was plantar shear stress in patients with diabetes who had a current/previous DFU compared with those with no prior ulceration. Meta-analysis was performed comparing shear stress between those with a current or previous DFU and those without, and those with diabetes and healthy controls.

RESULTS

The search strategy identified 1461 potentially relevant articles, 16 studies met the inclusion criteria, involving a total of 597 patients. Comparing shear stress between the current/previous DFU group and those without: Standardised mean difference (SMD) 0.62 (95% CI -0.01 to 1.25), in favour of greater shear stress within the DFU group, p = 0.05. Comparing shear stress between people with diabetes and healthy controls: 0.36 (95% CI -0.31 to 1.03), in favour of greater shear stress within the diabetes group, p = 0.29.

CONCLUSION

This review suggests that that patients with diabetes and a history of ulceration exhibit greater shear stress than their ulcer-free counterparts. This strengthens the premise that development of systems to measure shear stress may be helpful in DFU prediction and prevention.

Effect of Exercise Volume on Plantar Microcirculation and Tissue Hardness in People With Type 2 Diabetes

Objective: Exercise has been reported to be beneficial for people with type 2 diabetes (T2DM), but exercise, especially weight-bearing exercise, may increase the risk of diabetic foot ulcers (DFUs). This study aimed to explore the associations between different volumes of weight-bearing physical activities and plantar microcirculation and tissue hardness in people with T2DM.

Methods: 130 elderly people with T2DM were enrolled for this cross-sectional study. They were classified into the high exercise volume group and the low exercise volume group based on their weekly energy expenditure (metabolic equivalents per week) in the past year. Weekly energy expenditure was calculated using the International Physical Activity Questionnaire and the Compendium of Physical Activities. The plantar oxygen saturation (SO₂) and soft tissue hardness of each participant’s right foot were measured.

Results: A total of 80 participants completed the trial. The average exercise energy expenditure of the high exercise volume group and the low exercise volume group were significantly different (p < 0.05). The results showed that the SO₂ of the high exercise volume group (67.25 ± 6.12%) was significantly higher than the low exercise volume group (63.75 ± 8.02%, p < 0.05). The plantar tissue hardness of the high exercise volume group was lower than the low exercise volume group in the big toe, midfoot and hindfoot regions (p < 0.05).

Conclusion: This study demonstrates that higher volumes of exercise are associated with better plantar microcirculation and lower plantar tissue hardness in people with T2DM. The findings of this study indicate that weight-bearing exercise may not increase risk of developing diabetic foot ulcers.

Diurnal Temperature Ranges in Relation to Lower Limb Amputation Rate of Diabetic Foot in South Korea: A Population Based Nationwide Study

The evidence for the association between diurnal temperature range (DTR) and diabetic foot amputations is limited. We aimed to investigate the region-specific association between DTR and the amputation rate of diabetic foot in Korean national-wide data. Daily data on DTR and the rate of diabetic foot amputations from 16 provincial capital cities in Korea were obtained (2011-2018). In this study, the latitude ranged from 33°11' N to 38°61' N, and we classified each region according to latitude. Region 1, which was located at a relatively high latitude, included Seoul, Incheon, Gyeonggi-do, and Gangwon-do. Region 2, which was located at a relatively low latitude, included Busan, Ulsan, Gyeonsannam-do, Gwangju, Jeollanam-do, Jeollabuk-do, and Jeju-do. The region-specific DTR effects on the amputation rate were estimated based on a quasi-Poisson generalized linear model, combined with a distributed lag non-linear model based on the self-controlled case series design. The DTR impacts were generally limited to a period of nine days, while significant effects during lag days 7-14 were only found in the cities of Seoul, Incheon, and Gyeonggi-do (10th lag day: RR [95% CI]; Seoul: 1.015, [1.001-1.029]; Incheon: 1.052 [1.006-1.101]; Gyeonggi-do: 1.018 [1.002-1.034]). In the subgroup analysis (according to the latitude), an increase of 1 °C in DTR was associated with the risk of diabetic foot in relatively high latitude regions. DTR has considerable effects on the risk of diabetic foot amputation in various provinces in Korea, and it was particularly affected by latitude. The results can inform the decisions on developing programs to protect vulnerable subpopulations from adverse impacts.

Remote Patient Monitoring Utilization of a Smart Sock Among Patients with Peripheral Neuropathy – Real-World Registry Findings (Preprint)

Background

Remote patient monitoring (RPM) devices are increasingly being used in caring for patients to reduce risks of complications. Temperature monitoring specifically has been shown in previous studies to provide a useful signal of inflammation that may help prevent foot ulcers.

Objective

In this cross-sectional study, we evaluated utilization data for patients who were prescribed smart socks as remote temperature monitoring devices.

Methods

This study evaluated data from a patient registry from January to July 2021. The utilization data, which were collected starting from the first full month since patients were prescribed the smart socks, were evaluated along with retention over time, the average time that the socks were worn, and the number of days that the socks were worn per month and per week.

Results

A total of 160 patients wore the smart sock RPM device for 22 to 25 days per month on average. The retention rate was 91.9% (147/160) at the end of the 7-month period; a total of 13 patients were lost to follow-up during this period. The average number of days that the socks were worn per week was 5.8. The percentage of patients with a utilization rate of >15 days ranged from 79.7% (106/133) to 91.9% (125/136) each month.

Conclusions

This study shows a high level of utilization for a smart sock RPM device and a high compliance rate. A future prospective study on the clinical outcomes after the use of the smart socks may further solidify the idea of conducting temperature monitoring for foot ulcer prevention.

Evaluation of Real-World Smart Sock-Based Temperature Monitoring Data as a Physiological Indicator of Early Diabetic Foot Injury: Case-Control Study (Preprint)

Background

Lower extremity complications of diabetes represent major health care complications both in terms of cost and impact to quality of life for patients with diabetic peripheral neuropathy. Temperature monitoring has been shown in previous studies to provide a useful signal of inflammation that may indicate the early presence of a foot injury.

Objective

In this study, we evaluated the temperature data for patients that presented with a diabetic foot injury while using a sock-based remote temperature monitoring device.

Methods

The study abstracted data from patients who were enrolled in a remote temperature monitoring program (2020-2021) using a smart sock (Siren Care). In the study cohort, a total of 5 participants with a diabetes-related lower extremity injury during the study period were identified. In the second comparison cohort, a total of 26 patients met the criteria for monitoring by the same methods but did not present with a diabetes-related podiatric lower extremity injury during the same period. The 15-day temperature differential between 6 defined locations on each foot was the primary outcome measure among subjects who presented with a diagnosed foot injury. Paired t tests were used to compare the differences between the two groups.

Results

A significant difference in temperature differential (temperature measured in °F) was observed in the group that presented with a podiatric injury over the course of evaluation versus the comparator group that did not present with a podiatric injury. The average difference from all 6 measured points was 1.4 °F between the injury group (mean 3.6, SD 3.0) and the comparator group (mean 2.2, SD 2.5, t=–71.4, df=39; P<.001).

Conclusions

The results of this study suggest temperature monitoring in a sock form factor could be used to predict a developing foot injury. The continuous temperature monitoring system employed has implications for further algorithm development to enable early detection. The study was limited by a nonrandomized, observational design with limited injuries present in the study period. We look forward to further studies that will refine the predictive potential and confirm or refute the current promising data.

Mobile Health-Based Thermometer for Monitoring Wound Healing After Endovascular Therapy in Patients With Chronic Foot Ulcer: Prospective Cohort Study

BACKGROUND

Foot temperature may increase after endovascular therapy, but the relationship between foot temperature and wound healing is unclear.

OBJECTIVE

This study was performed to evaluate the feasibility of a mobile health (mHealth)-based thermometer for foot temperature monitoring in patients with chronic foot ulcer before and after endovascular therapy and to determine the association between temperature change and wound healing time.

METHODS

This was a prospective cohort study. Patients who had a chronic foot ulcer (>3 months) and underwent endovascular therapy between June 2019 and December 2019 were included. The participants received standard medical care and endovascular therapy for revascularization. The mHealth-based thermometer, composed of 4 temperature-sensing chips, was put on the foot before and after endovascular therapy. Data from the chips were transferred to an associated mobile phone app via Bluetooth. Wound healing time was estimated using the Kaplan-Meier method, and the associations between baseline characteristics and clinical outcomes were evaluated using a Cox proportional hazard model.

RESULTS

A total of 163 patients with chronic foot ulcer who underwent endovascular therapy were enrolled and followed up until wound healing was complete or for 180 days. The mean foot temperature before endovascular therapy was 30.6 (SD 2.8 °C). Foot temperature increased significantly (mean 32.1 °C, SD 2.8 °C; P=.01) after the procedure. Wound healing time was significantly different in the Kaplan-Meier curves of the patient group with temperature changes ≥2 °C and the group with temperature changes ≤2 °C (log-rank P<.001). A foot temperature increase ≥2 °C after endovascular therapy was associated with increased wound healing in univariate analysis (hazard ratio [HR] 1.78, 95% CI 1.24-2.76, P=.02), and the association remained significant in multivariate analysis (HR 1.69, 95% CI 1.21-2.67, P=.03).

CONCLUSIONS

The mHealth-based thermometer was feasible and useful for foot temperature monitoring, which may provide health care professionals with a new endpoint for endovascular therapy. Foot temperature increases ≥2 °C after endovascular therapy were associated with faster wound healing in patients with chronic foot ulcer. Further studies are needed, however, to confirm these findings.

Temperature- and Pressure-Regulating Insoles for Prevention of Diabetic Foot Ulcers

Diabetic foot ulcers (DFUs) pose a major threat to the United States healthcare system as well as patients and their families. High ulcer recurrence rates indicate that existing preventive measures are not effective. A new generation of multimodal preventive devices may reduce ulceration and amputation rates. Because previous research has revealed that tissue maintained at cooler temperatures is more resistant to breaking down, the evaluated technology may prevent foot ulceration. The purpose of this study was to test previously designed Temperature and Pressure Monitoring and Regulating Insoles (TAPMARI) in diabetic neuropathic and healthy subjects. A cooling unit, a mini-water pump, a battery pack, and a microcontroller (or simply thermostat) were placed inside a box attached to the subjects' calf, which provided cooling inside the shoe. The microcontroller was set at 28°C. Eight subjects provided informed consent, 3 of whom had diabetic neuropathy. Subjects used the instrumented shoe on the right foot and the matching control shoe on the left and walked on a treadmill for 5 minutes at self-selected speeds. Baseline and postwalking thermographs were obtained with a thermal camera. At the 2-hour midpoint, subjects again walked on the treadmill for 5 minutes at self-selected speeds. Second baseline and postwalking thermographs were captured. Plantar pressure distributions were also quantified. The TAPMARI successfully regulated foot temperatures at or below the target temperature. The mean baseline temperature of the right (regulated) and left (control) feet were 28.1 ± 1.9°C (mean ± standard deviation) for all subjects. The mean temperatures at the end of the study were 25.9 ± 2.5°C (right) and 31.7 ± 1.6°C (left) in all subjects. In the diabetic neuropathy group, the final mean temperatures were 27.5 ± 2.4°C (right) and 31.6 ± 0.8°C (left), which indicated that the temperature goal was met inside the instrumented shoe. By regulating temperatures, TAPMARI may reduce the metabolic demands in the foot and prevent cell autolysis by eliminating the imbalance between oxygen demand and supply. This study warrants further development and testing of TAPMARI as well as investigating the clinical effectiveness in preventing DFUs.

Describing Normative Foot Temperatures in Patients With Diabetes-Related Peripheral Neuropathy

BACKGROUND

Prior research shows increased foot temperatures are predictive of diabetes-related foot complications. Our aim was to describe normative skin foot temperatures for individuals with diabetic peripheral neuropathy to better inform new technologies. We also explored for potential risk factors which correlate with changes in foot temperatures.

METHODS

We conducted a retrospective chart review of adult patients >18 years of age with diabetes mellitus and clinically diagnosed diabetic peripheral neuropathy with pedal digital thermometry performed between 2009 and 2018. A total of 58 patients met these criteria. Univariate modeling was based on covariates that may affect foot temperature including age, peripheral arterial disease, toe pressure, seasonality of measurement, smoking pack-years, caffeine use, insulin use, and calcium channel blocker use.

RESULTS

In patients with diabetic peripheral neuropathy, mean toe temperatures of 27.67°C (6.300°C), forefoot of 28.58°C (5.36°C), midfoot of 29.21°C (3.81°C), and rearfoot of 29.88°C(3.83°C) were demonstrated. A modest negative correlation between seasonality and toe and metatarsal temperatures (r = -0.38, P < .05; r = -0.43 P < .01, respectively) was demonstrated. Midfoot temperatures were modestly and positively correlated to the presence of small fiber symptoms (r = 0.33, P = .03). Positive modest correlation with rearfoot temperatures and amount of pack-year history (r = 0.30, P = .03) was seen.

CONCLUSION

Normative foot temperatures in neuropathic patients were found to be inversely associated with seasonality at the toe and metatarsal level. Smoking and pack-year history demonstrate modest correlation previously unseen in temperature analyses and warrant further exploration. Normative temperatures in neuropathic patients can better inform new technologies for the prevention of diabetic foot ulcer and Charcot neuroarthropathy.

Prediction of Diabetic Foot Ulceration: The Value of Using Microclimate Sensor Arrays

BACKGROUND

Accurately predicting the risk of diabetic foot ulceration (DFU) could dramatically reduce the enormous burden of chronic wound management and amputation. Yet, the current prognostic models are unable to precisely predict DFU events. Typically, efforts have focused on individual factors like temperature, pressure, or shear rather than the overall foot microclimate.

METHODS

A systematic review was conducted by searching PubMed reports with no restrictions on start date covering the literature published until February 20, 2019 using relevant keywords, including temperature, pressure, shear, and relative humidity. We review the use of these variables as predictors of DFU, highlighting gaps in our current understanding and suggesting which specific features should be combined to develop a real-time microclimate prognostic model.

RESULTS

The current prognostic models rely either solely on contralateral temperature, pressure, or shear measurement; these parameters, however, rarely reach 50% specificity in relation to DFU. There is also considerable variation in methodological investigation, anatomical sensor configuration, and resting time prior to temperature measurements (5-20 minutes). Few studies have considered relative humidity and mean skin resistance.

CONCLUSION

Very limited evidence supports the use of single clinical parameters in predicting the risk of DFU. We suggest that the microclimate as a whole should be considered to predict DFU more effectively and suggest nine specific features which appear to be implicated for further investigation. Technology supports real-time in-shoe data collection and wireless transmission, providing a potentially rich source of data to better predict the risk of DFU.

Vehicle ergonomics contributing to a diabetic foot ulcer

Background

Diabetes mellitus continues to be a rising concern in the United States. It affects an estimated 9.4% of the population and approximately 1.5 million Americans are diagnosed annually. Approximately 85% of diabetic foot ulcers are associated with diabetic peripheral neuropathy and an infected diabetic foot ulcer is often the first sign of diabetes. There are countless studies within the literature that investigate how insensate feet and the manifestation of a foot ulcer further decrease quality of life and increase risk for mortality. Literature focuses on gait and kinematics that contribute to the formation of a diabetic foot ulcer. While pressure and shear forces are etiologic factors that may lead to the formation of diabetic foot ulcers, the position of the foot while driving an automobile has been ignored as a possible risk factor.

Case presentation

The clinical case will describe the events of healing a neuropathic diabetic foot ulcer beyond the standard of care treatment plan. It is one of the first case reports to describe vehicle ergonomics as an etiologic factor contributing to a diabetic foot ulcer. Once the patient becomes aware of the unnecessary source of pressure, education and care is provided to manage this likely source of daily pressure to the neuropathic foot.

Conclusion

The article emphasizes the importance of a complete assessment, including nontraditional factors, which may lead to diabetic complications.