BERLIN – Smart insoles that warn diabetic individuals of high plantar pressures could be a simple solution to help them avoid recurrent foot ulcers, according to the results of a randomized trial.
Study participants with a history of diabetic foot ulcers wore the plantar pressure–sensing insoles (SurroSense Rx) and received feedback via sensor linked to a smart watch worn and were 71% less likely to experience a recurrent foot ulceration than were those who wore the insoles but did not get the pressure feedback (incidence rate ratio, 0.29; 95% confidence interval, 0.09-0.93; P = .037). The device has been cleared by the Food and Drug Administration.
Overall, there were few ulcers that occurred in the study, with 10 ulcers from 8,638 person-days from six patients reported in the control group and four ulcers from 11,835 person-days from four patients in the intervention group.
“Diabetic foot ulcers are a major global health and economic burden, but, in theory at least, they are ultimately preventable,” said study investigator Neil Reeves, PhD,, who presented the findings at the annual meeting of the European Association for the Study of Diabetes.
Data suggest that recurrence rates for ulceration are as high as 65% at 6 years, he said, with up to a quarter of ulcers progressing to the point where some form of amputation is needed.
“In the laboratory, we can measure plantar pressures, and these are considered as a relatively accurate proxy for diabetic foot ulcer risk. So we can discriminate between those with diabetic neuropathy, and those without, and also those with a previous history of ulceration,” Dr. Reeves said.
Dr. Reeves, who is professor of musculoskeletal biomechanics at Manchester (England) Metropolitan University, observed that the rationale behind the development of the smart insoles was to move plantar pressure measurement out of the laboratory and into the real world.
The smart insoles incorporate eight discreet pressure sensors that are connected to pod worn on the front of the participant’s own shoe and that wirelessly relay pressure information to a smartwatch. Both the control and the intervention groups received the same device, Dr. Reeves pointed out, but the difference was that the only the intervention group got any pressure feedback from the sensors to the smartwatch.
“When high pressure was experienced in the intervention group on any of these sensors, the patient was alerted both by an auditory alarm and also by being able to see this on the smartwatch,” Dr. Reeves explained.
“The patient would be alerted as to where the pressure was high on the foot and that would be a trigger to offload this high pressure.” Patients would then be instructed via the smartwatch to try to offload the pressure by either walking around for 2 minutes, actively taking the weight off the foot, or removing the shoe to check for any foreign bodies.
In all, there were 58 study participants – 32 randomized to the intervention group and 26 to the control group – who had a history of diabetic foot ulcers and peripheral neuropathy but who were able to walk independently for at least 30 steps. The mean age of patients in the intervention group was 59 years, 88% were male, 72% had type 2 diabetes mellitus, with the mean duration of diabetes was 22 years. Corresponding data in the control group were 67 years, 89% male, 85% had type 2 diabetes, and 21 years’ diabetes duration.
Patients were reviewed monthly over a period of 18 months or until plantar ulceration occurred. Information on diabetic foot ulcers was collected and standardized using a previously developed mobile app (Diabetes Sci Technol. 2018;12[1]:169-73) and then confirmed via blinded assessment by two experts.
Dr. Reeves noted that there was no significant difference in the time to ulceration between the groups, with 77.5% and 68.4% of the intervention and control group remaining ulcer free at 18 months (P = .30). When the data were adjusted for compliance, there was an 86% reduction in the risk of reulceration in the intervention versus the control group (IRR, 0.14; 95% CI, 0.03-0.63; P = .011). This analysis took into account only those study participants who had 4.5 hours or more of daily wear of the smart insoles (n = 40). On average, the insoles were worn for 6.1 hours in the control group and by 6.9 hours in the intervention group.
“We suggest that the mechanism for this beneficial effect in the present study is likely pressure offloading, which has been afforded by providing patients in the intervention group with this plantar-pressure feedback,” said Dr. Reeves.
“That’s feedback that they’ve lost naturally many years ago due to diabetic peripheral neuropathy,” he added. “So, in that respect, we would suggest that patients have really been empowered here to take control of their foot health in a way that they haven’t been able to since the onset of significant diabetic peripheral neuropathy.”
Diabetes UK provided the primary funding for the study (years 1-3), with Orpyx Medical Technologies, Canada, providing funding during the study extension (year 4). Dr. Reeves did not have any disclosures.