Diabetes: Sensor sole warns of foot ulcers

People with long-term diabetes often struggle with pressure sores and chronic wounds on their feet. These occur due to circulatory and sensory disorders. Careful monitoring of one's own feet is necessary for prevention. A newly developed insole with sensors, in combination with telemedicine, is intended to prevent the formation of foot ulcers.

In an interview with MEDICA-tradefair.com, Prof. Peter R. Mertens describes the functionality, development, and advantages of the new technology, which was developed at Otto von Guericke University Magdeburg.

Prof. Mertens, what is the functionality of the sensor sole based on?

Prof. Peter R. Mertens: Quite often, I see patients with sensory disorders and inflammation of the feet. We wanted to develop a system for prevention that is based on temperature measurements; where there is inflammation, the temperature rises.

We developed the temperature sensor technology for an insole with the Magdeburg-based company Thorsis and included 280 participants with nerve damage in our study. They were no longer able to judge whether they felt warmth or coldness at their feet; they had a general sensory disorder. Half of the participants received the insole and a smartphone and were asked to measure the temperature of their feet for three minutes in the morning and three minutes in the evening.

What advantages does the insole offer?

Mertens: If the temperature was elevated for 72 hours and there was no evidence of gout, we asked the participants to send us a photo of their feet. After reviewing the pictures, we recommended that they take the weight off their feet. 134 of the 140 participants completed the study and no one developed an ulcer in more than two years. There were five ulcers in the control group. We had expected around 30 ulcers and attributed the good result to the intensive care we provided within the study. Thanks to the telemedicine system we developed, people in the trial group were able to communicate more closely with doctors.

What specifically caused the improvements?

Mertens: The only intervention was the request to put the feet up when the temperature rose. This enabled us to reduce physical activity so that the temperature dropped again. As it is difficult to measure in a closed shoe, we used slippers for this study to prevent temperature build-up, for example due to rubbing surfaces.

We deliberately refrained from taking continuous temperature measurements. We wanted to motivate people to take the temperature regularly. If there is more than one alarm per week, participants become restless and no longer like using the system.

How important was your own telemedicine infrastructure?

Mertens: We designed the app so that you can photograph the feet using a visual template. Relatives can do this or the patient can use a selfie stick. More than 80 percent of patients did this. So there was temperature data, photos and a questionnaire. Participants were also able to send us information.

On our side, the procedure was quick because we standardized everything. This was the only way we could get a good overview of the development of 140 participants in half an hour a day. However, it must of course be ensured in future that our time resources for monitoring are also reflected financially.

What are the next steps towards market maturity?

Mertens: The approval process in Germany is complex and expensive. We estimate at least 18 months. There is no telemedicine application in our healthcare system yet. But we did not want patients to be left alone and have to interpret their data themselves.

If we can prevent two thirds of ulcers, we will have a major impact. There are around 35,000 amputations per year in Germany, 75 percent of which are caused by diabetes and sensory disorders.

We are exploring opportunities for cooperation, including the development of a digitalization platform. Cooperation with one of the big players that already has the prerequisites for a telemedicine platform would be helpful. The question regarding the exchange of data is: who owns the data? This has not yet been defined, and politicians would have to set the rules here.

An orthopaedic shoemaker was also involved, and we found interest and support from the podiatry profession. They are closest to the patients and could use the system almost like a professional tool.