The predictive value of cumulative plantar tissue stress on future plantar foot ulceration in people with diabetes—A 12-month prospective observational study

Aims: Plantar foot ulcers are a burdensome complication of diabetes caused by abnormal foot biomechanics. Predicting foot ulcers aids in their prevention, but the value of peak pressure—the most used biomechanical parameter—is only moderate. We aimed to improve prediction based on the more comprehensive load measure cumulative plantar tissue stress (CPTS). Methods: We prospectively observed 60 participants with diabetes at high foot ulcer risk for 12 months. At baseline, we assessed demographic and clinical characteristics—including plantar pre-ulcers (i.e., abundant callus, haemorrhage, blister, fissure)—and measured barefoot and in-shoe plantar pressures during walking and standing. Daily-life weight-bearing activity and adherence to prescribed footwear were assessed over 7 days after baseline. The primary outcome was plantar foot ulceration during the 12-month follow-up. CPTS was calculated (in GPa.s/day) from the above foot-loading factors and analysed for predicting foot ulcers and its association with pre-ulcers, using multivariate regression analyses. Results: Twenty-two participants (37%) developed a plantar forefoot ulcer. CPTS was not a significant predictor (odds ratio (OR) = 0.90 (95% confidence interval (CI): 0.50–1.59)) but pre-ulcers at baseline (OR = 9.97, 95%CI: 1.41–70.65) and walking speed (in m/s) (OR = 0.01, 95%CI: 0.00–0.32) were. CPTS was significantly associated with pre-ulcers (OR = 2.38, 95%CI: 1.02–5.54). Conclusions: CPTS did not predict plantar foot ulceration in our high-risk participants, but our findings support the mechanical pathway of plantar foot ulceration through pre-ulcer development and indicate lower walking speed as an important predictor. Assessing walking speed and early identifying and treating pre-ulcers will help predict and prevent plantar foot ulcers in high-risk people with diabetes.