How Temperature Monitoring Can Prevent Diabetic Foot Ulcers

Diabetes prevalence has become pronounced in the United States, and treating the complications that arise from this disease has proven to be a relentless and demanding battle.

The most profound sequela is the formation of an ulceration. Approximately 15 to 25 percent of patients with diabetes develop a foot ulcer in their lifetime, while 1 to 3.5 million patients with diabetes in the U.S. already have a history of ulcerations.^1,2 These sequelae make up approximately one-third of the $176 billion spent yearly on diabetes care in the U.S., and these costs exceed the treatment cost of many common cancers.^3–6

Not only is there a high incidence of ulcerations but fighting ulcers becomes a relentless battle secondary to the high ulcer recurrence rate. An estimated 40 percent of foot ulcerations will recur within one year, 60 percent will recur in three years and 65 percent will recur in five years.⁷ Ulcerations are not only costly but also cause an increase in mortality. Diabetic ulcerations are the most common condition preceding amputations, and ulcers increase the risk of death 2.5-fold in comparison to patients with diabetes without foot ulceration.⁸ The demanding cost and life threatening nature of these wounds drive the need for focused medical intervention on ulceration prevention.  

We must understand the pathomechanics of diabetic foot ulcerations (DFU) to prevent ulcers from occuring. Repetitive traumatic stress and the subsequent inflammation that go unnoticed secondary to the commonly transpiring neuropathy are universally accepted as the cause of diabetic foot ulcerations.^9-11 The standard guidelines for ulcer prevention are customarily a combination of diabetes education, daily self foot checks, custom padded insoles, specialized diabetic shoes and routine physician follow-ups for foot inspections.

However, studies have shown poor adherence to such interventions by patients with diabetes.^12,13 Concomitant obesity, visual impairment and decreased joint mobility also serve as impediments for self-inspection in patients with diabetes, preventing an accurate assessment of feet and the potential recognition of early symptoms.^14,15 This observed inadequacy to the standard guidelines for ulceration prevention drives medicine to find new potential medical interventions.

How Temperature Changes Can Identify Incipient DFUs

As inflammation is a precipitating sign of ulceration, clinicians have sought techniques to identify inflammation using one of its most common symptoms, increased temperature. Randomized controlled trials have found that local areas of increased temperature, identified using simple infrared thermometers, indicate areas that are likely to ulcerate.^15-17 This suggests that monitoring of foot and skin temperatures, along with subsequent offloading following observed areas of increased temperatures, can dramatically reduce the occurence of ulcerations.^18-21

One identifies areas of increased temperature using asymmetry analysis, comparing temperatures between a pair of feet. The defined threshold reported in numerous studies is an asymmetrical difference of 4ºF (2.2°C).^18,20,23,24 A study conducted by Armstrong and colleagues found that one week prior to ulceration, preulcerative sites had a temperature increase 4.8 times greater than their contralateral counterpart, further exemplifying temperature spikes preceding ulceration.¹⁷

Lavery and colleagues observed the favorable use of temperature monitoring for ulceration prevention over the standard guidelines in the results of their blind, randomized, multicenter study of 173 patients.¹⁶ The study divided patients into three preventive treatment groups: group one used the standard guidelines, group two added a mirror to enhance visualization for daily plantar foot inspection, and group three used a digital infrared thermometer for temperature monitoring. There was no statistical difference between the standard and mirror approaches, solidifying the notion that even with the added instrumentation of a mirror to visualize potential inflammation and preulcerative symptoms, self-inspection is not sufficient to prevent ulcerations. Patients in the temperature monitoring groups had a significant decrease in ulceration occurence, specifically four times lower, than the two previous cohorts.

Further analyzing the temperature monitoring group, Lavery and colleagues found that patients who consistently recorded their temperatures were 50 percent less likely to develop an ulcer in comparison to the temperature monitoring patients who did not record their temperatures as frequently.¹⁶ This significant finding highlights that adequate adherence further enhances prevention.

A Closer Look At Innovative Temperature Monitoring Devices

With proven results showing that temperature monitoring significantly decreases ulcer occurrence and adherence further advances the use of temperature monitoring, the next innovational step is finding ways to improve patient adherence.

A wireless telemedicine foot mat can assist adherence with daily foot temperature monitoring. Frykberg and coworkers studied the efficacy of this technology, specifically using the Podimetrics Mat (Podimetrics), not only as a predictor of ulcerations but patient adherence in daily use.²⁵ The authors found that after directing their patients to use the mat daily, which included standing on the mat for 20 seconds once a day, over a 34 week period, roughly 86 percent of their 129 patients used the mat, on average, at least three days a week. The mat was able to correctly identify 97 percent of formed DFUs with an average lead time of 36 days using the standard asymmetrical temperature threshold difference of 4°F (2.22°C).

While the authors did not compare whether there was a significant difference in the formation of ulcerations between patients who used the mat daily and those who did not, future data could help define temperature monitoring protocol.²⁵ For example, if researchers observed a difference in temperature, guidelines could be set on the minimum numbers of days a week patients should use temperature monitoring.

Further simplifying patient adherence with temperature monitoring, with the hopes of further increasing adherence, has been the invention of temperature monitoring socks such as Smart Socks (Siren). These socks eliminate the need for patients to participate actively in temperature monitoring, as there is no need to conduct the timely use of a thermometer over multiple areas of the foot comparing one foot to the contralateral side, or even the need for patients to spend 20 seconds standing on a mat as described in the study above. Patients simply need to put on the socks in the morning in lieu of their normal socks. The socks continuously monitor the temperature of the prominent aspects of the plantar foot and notify the patient if signs of inflammation are evident through text message and the associated phone application, essentially eliminating any daily effort on the patient’s part.

Not only do the socks improve patient adherence, but another key advantage of the Smart Sock is truly its unique ability to monitor the temperature of the plantar foot continuously, unlike the static measurements offered by a thermometer or mat.

In Conclusion

Temperature monitoring has proven to be the new frontier in ulceration prevention. Whether that be through the use of the infrared thermometer, foot mat or socks, we cannot overlook the use of temperature monitoring due to the drastic decrease in ulceration occurrence. The guidelines set forth by the International Working Group on the Diabetic Foot have accepted the use of temperature monitoring, and the group included temperature monitoring in its recommendations for foot ulcer prevention.²⁶ As physicians treating patients with diabetes, a disease that has become an epidemic in the United States, temperature monitoring should become part of the gold standard for ulcer prevention in every practice.

Dr. Reyzelman is an Associate Professor at the California School of Podiatric Medicine at Samuel Merritt University. He is the Co-Director of the University of California San Francisco (UCSF) Center for Limb Preservation.

Dr. Dionisopoulos is a first-year resident in the Kaiser Permanente Foot and Ankle Residency Program in Northern California.

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