Smart insoles: Assessing their clinical potential

Athletes have been quick to embrace smart insoles and the biomechanical data generated by the devices’ embedded sensors. But experts believe smart insoles may also have potential clinical applications for patients with foot health problems, such as diabetic neuropathy.

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By Shalmali Pal, Lower Extremity Review March 2016

Wearable devices to track exercise and fitness have become ubiquitous in the workout environment, but more often than not, these are basically fancy pedometers. Enter smart insoles, or footwear inserts with embedded sensors, whose developers claim they produce enough legitimate data on the user’s biomechanics to fill a medical file.

Although not as sophisticated (or as expensive) as in-shoe measurement systems used for research, the new generation of smart insoles can measure location, foot pressure, stride length, and more in real time. The data are then sent via wireless technology to a mobile computing platform—tablet, smart phone, smart watch—that allows the user to interact with the information through the software.

“These kinds of tools are going to be a new measure of quality of life, and of how people move through their world,” said David Armstrong DPM MD PhD, a professor of surgery at the University of Arizona College of Medicine and director of the Southern Arizona Limb Salvage Alliance (SALSA), both in Tucson.

Many of these devices have been adopted by athletes—runners, in particular—who are keen on self-management and, not surprisingly, interested in the nitty-gritty details of their performance. But do smart insoles have a part to play in helping people with foot health problems, such as diabetic neuropathy? LER: Foot Health spoke with an international group of biomechanical experts to get their take on how “smart” these insoles really are.

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What’s out there?
A 2014 white paper on smart textiles, garments, and fabrics, including wearable technology, noted the global market for these products is expected to be worth $1.5 million by 2020. The main growth sector since 2011 has been in the protection and military clothing sector, but sports and fitness applications, following by health and medical, are expected to see major advances.

The personalized feedback smart insoles deliver can help clinicians maintain contact with patients without extra in-person visits or waiting until an emergency arises.

Just doing a Google search for “smart insoles” yields more than 800,000 results. In many cases, these are products that are currently on the market; in others, they are links to crowd-sourcing pages to fund development of experimental products.

One example is Feetme’s smart inner insoles, each with 80 pressure sensors, which provide real-time gait analysis via a smart phone, and may prove useful for patients with diabetes to monitor foot pressure and potentially prevent ulcers.

Alexis Mathieu, cofounder and chief executive officer of the Paris, France-based company, said the main target for the insoles are runners and patients with diabetes. Mathieu said the company has conducted one clinical trial with its smart insole, and is in the process of setting up another, but declined to share study details or results.

Made by Orpyx Medical Technologies of Calgary, Canada, Surrosense Rx is a sensor-embedded insert that captures pressure data from feet. The data are sent wirelessly to a smart watch device (which is packaged with the insoles). According to the company, the “smart watch alerts you when dangerous time and pressure levels are detected, so you can modify behavior and avoid damage.”

The market for Surrosense Rx is patients with diabetes. Bijan Najafi PhD, director of clinical research in the Division of Vascular Surgery and Endovascular Therapy at Baylor College of Medicine in Houston, and colleagues recently conducted a pilot study to test the recurrence of diabetic foot ulcers in patients using the device, which is considered a class I medical device and therefore is exempt from FDA 510(k) premarket review.

The study included 21 patients with diabetic neuropathy and recently healed ulcers. The participants received an average of 3.38 daily alerts per day, of which nearly 44% were successfully managed, Najafi said. In addition, the majority of the alerts (45.8%) were related to pressure changes under the metatarsal heads, which is one of the plantar surfaces that is most prone to ulceration.

The preliminary data, presented at the 2015 International Symposium on the Diabetic Foot, showed no serious adverse events with the device, and more importantly, no re-ulceration or foot problems during active use of the device or during the three-month follow-up period after discontinuing use of the device. However, when self-reported utilization was compared to sensor-based wear time, results showed patients tended to overestimate their time spent using the device, leading the authors to caution that “patient adherence to [mobile health] technology is highly dependent on user interface, number of false alarms, and level of comfort.”

Real-time feedback and a “user-friendly” interface are two factors that can make a smart insole stand out, said Najafi, who is also director of Interdisciplinary Consortium on Advanced Motion Performance (iCAMP) at the University of Arizona, where the pilot study was conducted. The study was partially funded by Orpyx.

“The big challenge is still how to visualize or feed back key information to patients for assisting them to take care of their own health,” Najafi said. “Another key challenge is how to engage patients to continue wearing these insoles.”

For Armstrong, a coauthor on the study, smart insoles like Surrosense Rx that rely on sensory substitution technology—or the use of one sensory modality to supply environmental information normally gathered by another sense while still preserving some of the key functions of the original sense—will have the longest staying power in the market.

“There are other kinds of insoles that measure pressure or temperature, but most of them haven’t reached the same level of sophistication as the sensory substitution devices,” he said.

And, even the devices that are driven by more sophisticated software still contend with the challenge of being user-friendly and comfortable.

“Right now, the form factor of smart insoles is like the early days of the cell phones, when the phones were large and clunky,” Armstrong explained. “That form factor was good, but it was uncomfortable. Eventually, we evolved to the smart phone, which is much smaller in comparison. There are some insoles right now that are good products, but they are unwieldy and not necessarily practical.”

Rob Conenello DPM, immediate past president of the American Academy of Podiatric Sports Medicine, and a podiatrist with Orangetown Podiatry in New York, said he does not currently use smart insoles in his practice, though he is interested in doing so.

“I’ll go to a show, see a smart insole that interests me, and then six months later at another show, the device is that much better,” Conenello said. “My biggest concern is that… I don’t want to invest in a product that is basically going to become obsolete before I’ve really had a chance to use it.”

In addition, he said, many smart insoles offer quantitative data (eg, step counts), which isn’t necessarily what he’s looking for.

“I’d like more qualitative analysis from these devices, and I think that’s where they are headed,” he said.

All about smart insoles.
Wearable technology.Clinical value
Experts say the personalized feedback smart insoles can deliver to users and clinicians makes them a worthwhile consideration for practitioners looking to maintain contact with patients without extra in-person visits or waiting until an emergent situation arises.

Smart insoles can also help patients with self-management, Armstrong said. For instance, the smart insoles may alert a user with a healed diabetic foot ulcer that her activity level is outside the norm for her on a given day, and that this has led to pressure and temperature changes in the feet.

“This may make the patient realize that she’s been on her feet, running errands or something similar, for longer than she realized,” Armstrong said. “That perhaps it’s time to take a break.”

But, in terms of clinical applications, two major questions remain: What to do with all the data these insoles have the potential to generate, and how to get users to pay attention to it?

One drawback of these devices is the potential for “analysis paralysis,” Armstrong noted.

“When you start hitting people with reams of data, then that becomes something they will ultimately ignore,” he said. “How many apps do we have on our phone right now that are constantly sending us alerts or updates? And how many times do we actually access that information, or simply ignore it, over the course of a day?”

In fact, feedback received when patients are not experiencing symptoms can lead them to simply stop using the device.

“People don’t necessarily change their behavior unless something ‘breaks,’” he said. “They tend to distance themselves from their issues unless there’s a problem.”

Conenello said he likes the idea of getting complete information on how a person’s gait changes over time, in a real-world setting.

A sampling of smart insoles
Lechal (Hyderabad, India) manufactures smart insoles that feature haptic, or kinesthetic, feedback to provide the wearer with navigation via their smart phone in addition to tracking steps and calories.
Digitsole (Nancy, France) has developed a smart insole with customizable temperature available via a smart phone interface that tracks steps and warms the feet./
The FootLogger insole (Seoul, South Korea) features a three-axis accelerometer along with eight pressure sensors that collect, transmit, and store data related to the weight distribution of each step.
Wiiv Wearables (Vancouver, Canada) makes biomechanically optimized custom insoles that are 3D-printed based on scans taken with a user’s smart phone. The insoles aren’t smart yet, but the company hopes to incorporate into the orthoses electronic sensors that collect and record dynamic data.
HCi Viocare Technologies (Glasgow, UK) has a smart insole that can measure pressure exerted and shear across the sole, as well as determining weight, balance, calories burned, and distance traveled.
Moticon (Munich, Germany) manufactures OpenGo smart insoles that come with 13 pressure sensors and 3D acceleration sensors to determine the direction and speed of movement. Data are communicated to a Bluetooth-enabled smart phone or tablet.
ReTiSense (Bengaluru, India) has developed the Stridalyzer for runners. Sensors embedded in the insoles measure impact and pressure experienced in the foot and knees and sends real-time data on running form and style and foot and knee stress points to the user’s smart phone.
Kinematix (Porto, Portugal) is in the process of bringing its Tune device to market. The 2-mm sensors fit underneath an insole and track running activity information. These data are combined with GPS-based assessments of the runner’s speed, pace, distance, and time.
Feetme (Paris, France) has smart inner insoles that provide real-time gait analysis via a smart phone, and may prove useful for patients with diabetes to monitor foot pressure and potentially prevent ulcers.
Surrosense Rx insoles from Orpyx (Calgary, Canada) collect pressure data and send it to a smart watch, which alerts the user when dangerous time and pressure levels are detected.

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A review of wearable sensors and systems with application in rehabilitation, Patel S, Park H, Bonato P, Chan L, Rodgers M. J Neuroeng Rehabil. 2012 Apr 20;9:21. doi: 10.1186/1743-0003-9-21.

Also see
Wearable Movement Analysis System for Children with Movement Disorders – Lower Extremities Assessment System, Chong Yu Zheng, Jasmy Yunus. The 15th International Conference on Biomedical Engineering, Volume 43 of the series IFMBE Proceedings pp 395-398
Fitness Trackers Move to Earphones, Socks and Basketballs in The New York Times

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