Comparing plantar shear strain in patients with a previous diabetes‐related foot ulcer and those at low risk for ulceration using the STrain Analysis and Mapping of the Plantar Surface ( STAMPS ) system

Background STrain Analysis and Mapping of the Plantar Surface (STAMPS) is an innovative system using a plastically deformable insole with a stochastic speckle pattern, developed to measure peak plantar shear strain (S MAG ) in people with diabetes. The aim was to determine whether patients with a prior DFU exhibit higher S MAG than low‐risk patients. Methods Participants walked 20 steps with the STAMPS insole within a standardised shoe and 10 m with the Pedar‐X™ (Novel, Inc.) measurement insole. S MAG was compared in participants with either a recently healed diabetic foot ulcer (Prior DFU group) or diabetes and low risk for ulceration (NICE NG‐19). Measurements were repeated three times. Images were analysed using the DIC software ‘GOM correlate’ (Zeiss, Inc.) and post‐processed using MATLAB. Outcomes were overall and regional peak S MAG and peak plantar pressure (PPP). Consenting prior DFU participants subsequently repeated the walking assessments wearing a diabetic below‐knee walker‐boot. Overall and regional peak S MAG and PPP were compared between the standard shoe and walker‐boot. Results Twenty participants with prior DFU and 14 at low risk were recruited. Overall peak S MAG within the prior DFU and low‐risk groups was 27.9% (IQR – 17.3–37.5%) and 11.5% (IQR 9.6–20.3%) respectively, p = 0.003. Within the prior DFU group, S MAG was elevated at DFU sites compared with non‐DFU sites; peak S MAG was 11.7% (IQR 7.6–25.6%) and 7.70% (4.4–13.1%). Sixteen participants completed the offloading assessments. Peak S MAG within the standard shoe and walker‐boot was 27.4% (IQR 17.2–32.7) and 8.03% (IQR 6.3–12.2). Conclusion Participants with a recently healed DFU exhibited elevated strain characteristics compared with the low‐risk group. Furthermore, prospective work will explore the relationship between S MAG and DFU formation.