Insoles to ease plantar pressure in people with diabetes and peripheral neuropathy: a feasibility randomised controlled study with embedded qualitative component
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Collings, R. Insoles to ease plantar pressure in people with diabetes and peripheral neuropathy: a feasibility randomised controlled study with embedded qualitative component. Background: Diabetic foot ulceration is a devastating complication of diabetic foot disease. Therapeutic footwear and insoles are one preventative strategy to reduce elevated plantar pressures associated with foot ulcer risk. However, their effectiveness is variable, difficult to predict and evaluated by the high-risk strategy of observing foot health and tissue integrity over time. Aim: To develop and test, in a feasibility randomised controlled trial (fRCT), an insole prescription and fabrication intervention appropriate for chairside delivery to reduce plantar foot pressures and consequent foot ulceration risk in people with diabetes. Methods: The Medical Research Council’s framework for developing and evaluating complex interventions was adopted. The first phase developed the novel optimised insole intervention, informed by stakeholder and patient/public involvement and a systematic review with three meta-analyses. The second phase involved conducting a double-blinded multicentre fRCT with an embedded qualitative study. In addition to usual care, participants were randomised to either an optimised insole group or an active control group. Participants were assessed at baseline and then again at 3, 6 and 12 months with clinical outcomes of mean peak plantar pressure (MPPP) reduction for identified regions-of-interest and ulcer incidence. The embedded qualitative study involved semi-structured interviews with 12 study participants and three podiatrists to explore their experiences of the intervention and trial procedures. Data were analysed using descriptive statistics (quantitative data) and thematic analysis (qualitative data). Results: The systematic review identified the best footwear and insole design features for offloading the plantar surface of the foot to prevent foot ulceration in people with diabetic peripheral neuropathy. The review involved 54 studies, with random-effects modelling finding plantar pressure reductions with an arch profile (37kPa), metatarsal addition (36kPa) and with pressure informed design (75kPa). An optimised insole algorithm based on real-time temporal load and pressure profiles was created to underpin the optimised insole intervention. The fRCT screened 142 participants from which 61 participants were recruited; 30 randomised to the optimised insole group and 31 to the active control insole group. Forty-two participants completed the study and at 12-months, 69% of patient-reported questionnaires were returned and 68% of clinical outcomes were collected. There were seven incidences of foot ulceration in the active control group and 10 in the optimised insole group. Mean difference in MPPP between the optimised insole and active control insole for all regions-of-interest combined favoured the optimised insole, with increases from 87kPa at postrandomisation to 255kPa at 12-months. Thematic analysis revealed three themes; accepting the study, behaviour and support during study procedures, and impact from study participation. Conclusion: An optimised insole intervention has been developed to reduce the risk of foot ulceration in people with diabetic peripheral neuropathy. The feasibility study results suggest that the optimised insole holds promise as an intervention and that a full RCT to evaluate the clinical and cost-effectiveness of this intervention is feasible and warranted for people with diabetic peripheral neuropathy.