Sensory insole system for diabetic patients achieves reduction in recurrent ulcers

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Breanne everett Acwhtr
Breanne Everett

Improvements that enable better miniaturisation of technology leads to higher-quality wearable health solutions, including digital devices that were “never before possible’, said Breanne Everett (Orpyx Medical Technologies, Calgary, Canada) at the American College of Wound Healing and Tissue Repair (ACWHTR; 11-12 October 2019, Chicago, USA).

Furthermore, new directions in reimbursement toward remote physiologic monitoring are enabling alignment of patient, provider and payer incentives, she revealed. “With the right tools, providers can now be paid to deliver sustained, prevention-based wound management.” Everett, a medical doctor and resident in plastic and reconstructive surgery at the University of Calgary, was delivering a presentation entitled, “Foot pressure dynamic management: changing the game,” in which she outlined the diabetes epidemic among North Americans and its impact on diabetic peripheral neuropathy.

In her talk, Everett drew attention to the findings of a study on a sensory insole system developed by Orpyx—called SurroSense Rx—where she is CEO and president. Researchers had sought to determine the device’s efficacy in reducing foot ulcer recurrence in high-risk patients, hypothesising that such a system would be effective in achieving a decrease. The trial, “Innovative intelligent insole system reduces diabetic foot ulcer recurrence at plantar sites: a prospective, randomized, proof-of-concept study”, was carried out by Caroline Abbott et al and published in the October issue of The Lancet Digital Health.

During her presentation at ACWHTR, Everett set the scene: One in three North Americans are either diabetic or pre-diabetic; there are 1.7 million ulcers per year in the United States; 25% of people with diabetes develop ulcers during their lifetime; and there are 120,000 lower extremity amputations per year. In terms of cost, she emphasised that the direct cost of diabetes care is US$176 billion, with around US$60 billion related to limb care. Diabetic foot ulcers result in costs up to US$70,000 per event, with a median of US$15,200.

The five-year mortality rate of a patient with a diabetic foot ulcer is 45%, which is higher than breast cancer and colon cancer rates. “Current standard of care has not significantly improved DFU recurrence rates over time,” Everett went on to say. “Once a patient’s wound has healed, there is a 49% chance they will re-ulcerate in the first year, which jumps to 65% within five years and by year 10 almost all patients will have at least one additional ulcer in their lifetime. Because of this, we need to shift our thinking. Often, once the wound is closed, we consider the patient healed and send them back to their normal activities. Instead, we need to consider these patients in remission and provide sustained, preventative care.”

The study aimed to investigate the effect of a sensory insole system in a real-life situation over 18 months. The technology would provide feedback when sustained low-magnitude plantar pressure occurs during harmful physical activities like prolonged sitting and standing in order to guide regular offloading, the authors of the trial noted.

Researchers recruited patients with diabetes, peripheral neuropathy and a recent history of plantar foot ulceration from two multidisciplinary outpatient diabetic foot clinics in the UK, randomly assigning them to either an intervention or control group. “All patients received an insole system, which measured plantar pressure continuously during daily life,” the authors wrote. “The intervention group received audiovisual alerts via a smartwatch linked to the insole system and offloading instructions when aberrant pressures were detected; the control group did not receive any alerts.”

The primary outcome was plantar foot ulcer occurrence within 18 months, while a secondary outcome was adherence to wearing the device, along with exploratory outcomes of time to ulceration and callus severity.

Between March 2014 and December 2016, some 90 patients signed up to take part, with 58 going on to complete the study. At follow-up, 10 ulcers from 8,638 person-days were recorded in the control group and four ulcers from 11,835 person-days in the intervention group, the researchers found. Ultimately, there was “a 71% reduction in ulcer incidence in the intervention group compared with the control group [IR: 0.29, 95% CI: 0.09–0∙93; p=0.037].”

Everett continued: “The number of patients who ulcerated was similar between groups (six of 26 [control group] vs. four of 32 [intervention group]; p=0.29); however, individual plantar sites ulcerated more often in the control group (10 of 416) than in the intervention group (four of 512; p=0.047). In an exploratory analysis of good compliers (n=40), {defined as those that wore the system for at least 4.5 hours a day}, ulcer incidence was reduced by 86% in the intervention group versus control group [IR: 0.14, 95% CI: 0.03–0.63; p=0.011].”

In the exploratory analysis, plantar callus severity—measuring the change from baseline to six months—was greater in re-ulcerating patients (callus severity score: 6.5, IQR 4.0–8.3) than non-re-ulcerating patients (2, 0.0–4.8; p=0.040).

Funding for the study was provided by Diabetes UK for the first three years, with Orpyx funding year four, as well as acting as the overall provider of the insole systems and associated technical support. Neither backer had any input on the trial, the researchers wrote. The authors concluded: “To our knowledge, this study is the first to show that continuous plantar pressure monitoring and dynamic offloading guidance, provided by an innovative intelligent insole system, can lead to a reduction in diabetic foot ulcer site recurrence.” They further recommended that future randomized controlled trials probe the efficacy and cost-effective of the system in the wider diabetic at-risk neuropathic community for ulcer prevention.

In a follow up interview with Everett she elaborated on her work in preventing diabetic foot ulcer recurrence. “Since the study completion, we have focused on improving the functionality of the device to make it easier for the wearer by imbedding the sensors into a high-quality, custom insole”, stated Everett. “In addition to pressure sensing, the device can also monitor temperature which is a late stage indicator of potential diabetic foot ulcer formation. We are excited to announce Orpyx SI Sensory Insoles will be commercially available in the US and Canada in late 2019.”

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