Technology and Smart Wearables in Diabetic Foot Management
Diabetes mellitus continues to be a growing problem in the United States affecting an estimated 38.4 million people, or 11.6% of the population.1 Estimates place the lifetime risk of developing a diabetic foot ulceration (DFU) as high as 25 to 34%.2,3 Lifetime incidence of lower extremity amputation is estimated to be 20% and 5-year mortality rate after amputation can be as high as 70%.4 There is a 2-fold increased risk of death at 10 years for individuals who have had a DFU as compared to those who have not.3
Having a history of DFU is the strongest predictor of future foot ulceration, with one-year recurrence estimated at around 40% and recurrence rates of approximately 65% at 5 years.3 DFU development is multifactorial, but frequently results from factors including increased plantar pressures, foot deformity, peripheral neuropathy, and peripheral vascular disease. Peripheral neuropathy is believed to be a large driving factor in recurrence of ulceration, due to less ability to appreciate early signs of impeding skin breakdown.3 Although recommendations are in place encouraging regular podiatric evaluation for those at the highest risk of ulceration, delays can still exist in identifying DFU.5
Unfortunately, if not recognized expediently, DFUs may often become infected, potentially leading to hospitalization and lower extremity amputation. Therefore, patient education regarding the importance of daily pedal inspection and understanding of contributors to DFU is key. However, patients may face challenges in executing those daily pedal inspections due to mobility or visual impairments. Home monitoring for early signs of ulceration is one proposed way to add more data to efforts to prevent DFU development. Many encourage monitoring skin temperature, due to possible association with inflammation and local soft tissue injury, making it a potential early sign of a foot ulceration.6,7 Some then postulate that if there is a detected increase in skin temperature, then activity reduction may decrease the likelihood of ulcer development.
Initial randomized trials of home temperature monitoring studied the use of handheld infrared thermometers to measure skin temperature at 6 locations on each foot daily.8 When detecting hotspots, defined as temperature differences > 2.2oC (4oF) on two consecutive days between similar locations on both feet, study participants were instructed to decrease their walking activity. The results of these randomized trials confirmed a reduced risk of developing of DFU in those who self-monitored temperature as compared to those who did not.8 Incidence of reulceration has also diminished 3- to 10-fold when employing self-temperature monitoring as compared to standard of care treatment in randomized controlled trials.6 Despite the available data supporting the utility of regular monitoring
of skin temperature, in practice this is not commonly performed. Several concerns have been raised regarding compliance with home monitoring efforts, and individuals not adhering to self-temperature measurement and not minimizing their activity level did have increased likelihood of ulceration.6
Understanding Potential “Smart” Solutions
We can now note the emergence of several advanced smart technologies and wearables aimed at detecting changes in skin temperature to help promote ulcer-free days for those with a history of DFU. One such device is the Podimetrics SmartMat remote temperature monitoring system (Podimetrics). This device is a wireless, thermometric floor mat where the patient stands in place for approximately 20 seconds, resulting in a temperature scan or thermogram of the feet. Information from the thermogram is then sent from the mat wirelessly and securely (Health Insurance Portability and Accountability Act (HIPAA)-compliant) to a server managed by the manufacturer.9 A prospective, multicenter study of the device in a subset of patients with a history of DFU demonstrated accurate identification of 97% of DFUs using the 2.2oC threshold around 5 weeks (37 days) prior to presentation.9 A majority of participants in the initial studies of the device found the mat to be easy to use and the authors noted high adherence to device use, with 86% using the mat at least 3 times per week.9 However, one must consider the downside to measurements generally taken only once per day.
Advocates of continuous temperature monitoring cite its ability to take into account activity level and thus provide more clinically significant temperature changes over time.10 This has led to additional technologies and wearables with the ability to detect continuous temperature changes. One such device is Siren Socks (SirenCare, Inc.) These sensor-embedded socks utilize a neurofabric textile with microsensors to help measure temperature on the bottom of the feet. The sensors connect to a Bluetooth-enabled device which allows the 6 sensors (located at the hallux, first metatarsal head, third metatarsal head, fifth metatarsal head, midfoot, and heel) to register temperature readings at 10-second intervals and send this information to a mobile phone paired with the socks. A phone application can then create alerts for temperature changes, which may indicate the potential ulcer development.10 Pilot studies confirmed these smart socks’ accuracy in measuring skin temperature as well as comfort and acceptability, with participants finding the socks to feel the same as a standard sock.10 Retrospective study of the socks in patients with peripheral neuropathy has confirmed a significant difference in skin temperature in those with a foot injury suggestive of early foot ulceration as compared to those without, offering promising early results.11
While skin temperature monitoring through technology and wearables is one described method to assess for early ulcer development, several other technologies exist, designed to monitor plantar pressure. Pedobarographic/pressure mats are one such described method frequently available for use in the clinical setting, although attempts to develop more portable devices for use outside of the clinic exist.12 Studies of pedobarography in predicting DFU development showed variable sensitivity and specificity, therefore concluding that this may a less accurate method of determining ulceration risk.13
In addition to pressure mats, pressure-sensing socks and wearables have also been developed. One such device is the Sensoria Smart Sock (Sensoria Health). This sock has textile sensors capable of detecting changes in plantar pressure and force as well as gait parameters. The information measured by the sensors then transmit from the sensors to a Bluetooth-enabled core which subsequently communicates this information to a mobile application.14 Furthermore, this information also transmits to a cloud-based HIPAA-compliant system for remote monitoring. Initial studies of this device demonstrated its ability to accurately measure pressure as well as other parameters of gait.14,15
Other areas of study have included investigation of pressure sensing insoles, recognizing therapeutic inserts and accommodative footwear as a means of offloading. One such study looked at the SurroSense Rx System (Orpyx Medical Technologies) in 2019. That system includes a pressure sensing insole and smart watch system aimed at preventing DFUs. Eight sensors measure plantar pressure at a rate of 8 Hz, taking real-time data on plantar pressures that exceed capillary perfusion pressure (>35 mmHg).16 Subjects with a history of DFU and peripheral neuropathy were given the Surrosense Rx system (insoles and smartwatch). In the intervention group, audiovisual and vibrational alerts transmitted to the user’s smartwatch to encourage offloading when detecting pressures above threshold. These alerts included feedback with suggestions such as sitting down, removing or decreasing weight from the affected foot, or checking shoe gear, allowing for resumption of normal activities once pressure reductions occurred.16 Authors noted a reduction in DFU recurrence in 71% of those in the intervention group over an 18-month follow-up and further analysis of those adhering to daily use of the system demonstrated 86% ulcer reduction.16
Other devices have been described to detect both changes in skin temperature and plantar pressures such as SmartSox (Novinoor), which employs flexible, thin fiber optic sensors to detect temperature and pressure in the plantar foot under the hallux, first metatarsal head, fifth metatarsal head, midfoot, and hindfoot.17 Although excellent agreement in temperature and pressure measurement has been noted in in vitro laboratory testing as well as basic human subjects testing, there have been no large volume clinical studies to date to validate its ability to prevent DFU. Other described technologies for those with diabetic neuropathy include Temperature and Pressure Monitoring and Regulating Insoles (TAPMARI), which use a multilayer insole with a cooling mini water pump and microcontroller (thermostat) to maintain a set temperature to cool the shoe. A 2020 study of the TAPMARI demonstrated its ability to maintain and regulate temperature. One belief contends that temperature maintenance below a set threshold may help lessen metabolic oxygen demand and prevent cell autolysis, thus helping prevent ulceration, although additional study of the clinical effectiveness of the device is necessary.18
Although much of the existing technology focuses using smart wearables for DFU prevention, some smart wearables aim to assist in active DFU treatment. These technologies monitor continuous pressure, as continuously high plantar pressure is known to be detrimental to DFU healing.19 These continuous pressure monitoring systems have the ability to collect real-time data, then sent via Bluetooth to a mobile application and additionally to a web dashboard available to a clinician for review.19 Patient adherence to the use of recommended offloading devices in DFU treatment has long been a concern, with previous studies suggesting offloading devices are only used for approximately 28% of daily activity.20 New technologies may offer advantageous opportunities to monitor offloading adherence. A Smart boot (Sensoria Health) has been developed and designed for the offloading treatment of diabetic foot ulcerations. This removable walking boot is equipped with a microelectronics system consisting of an inertial measurement unit, accelerometer, a gyroscope, and a Bluetooth Low Energy (BTLE) communication module to communicate with a smartwatch and patient monitoring application.21 With this technology, the clinician can remotely monitor patient adherence to boot use as well as activity level. Real-time alerts may also be provided to the patient based on this data. Preliminary studies demonstrated the ability of the boot to accurately monitor activity and use, paving the way for further clinical study.21 In addition, Najafi and team developed a smart tag called PAMTag which monitors activity levels and compliance with offloading devices.22 The smart tag can be placed on the offloading device and communicates with a smart watch, detecting if the offloading device is being used during activity and providing feedback if not worn.22
In Summary
With the Internet of medical things (IoMT) allowing for the development of wearable smart technologies and sensor-based technologies to connect the patient, a cloud-based network, and the clinician, this has opened many opportunities in the realm of DFU treatment and prevention.23 While development of such wearable devices is still in its early phases, these technologies offer exciting possibilities regarding longstanding diabetic foot management and overcoming challenges in DFU prevention and treatment. Given the burden of the diabetic foot to both the individual and the healthcare system, these technologies are much needed and offer the ability to bridge a gap in outside of the clinic or hospital. It will be exciting to continue to see how these emerging technologies evolve and change in the coming years.
Dr. Skolnik is a podiatrist at Massachusetts General Hospital in Boston. She is an Instructor in Orthopedic Surgery at Harvard Medical School and a Diplomate of the American Board of Podiatric Medicine.
Dr. Skolnik has submitted for NIH grant funding with Sensoria Health Inc. for the development of new smart wearable technologies.
Editor’s Note: All products mentioned are specifically from the literature cited. The products, their exact trade names, manufacturers, and other details may have evolved since the time of that publication. Please consult manufacturer websites and materials for full information on the current status of these products.
References
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