Comparison of physical activity and cumulative plantar tissue stress among subjects with and without diabetes mellitus and a history of recurrent plantar ulcers

Objectives. To compare the amount of weight-bearing activity and estimates of cumulative plantar tissue stress between subjects with and without diabetes mellitus and a history of recurrent plantar ulcers. Design. Cross-sectional study with matched groups. Background. Weight-bearing activity among individuals with diabetes is likely to influence the amount of mechanical trauma accumulated by plantar tissues, yet activity levels have not been accounted for in previous measurements of plantar tissue stress or predictions of plantar tissue injury. Methods. Study groups included subjects with diabetes mellitus and peripheral neuropathy, either with or without a history of recurrent plantar ulcers, and non-diabetic control subjects (n=10 per group). Pressure on the plantar foot was assessed as subjects walked at their preferred speed in the shoes they reported wearing most often each day. Physical activity was monitored over seven consecutive days using an accelerometer. The product of mean daily strides and forefoot pressure-time integral was used to estimate daily cumulative stress on the plantar forefoot. Results. Subjects with diabetes and a history of recurrent plantar ulcers were 46% less active than subjects without diabetes (mean (SD)=2727 (1345) versus 5037 (2624) strides/day, P=0.04), and accumulated 41% less daily stress on the forefoot than non-diabetic and diabetic control subjects without a history of plantar ulcers (mean (SD)= 210 (134) versus 354 (118) and 354 (148) MPa s/day respectively, P=0.03). Conclusions. Subjects with diabetes and a history a previous ulcers may be susceptible to plantar tissue injury even at relatively low levels of cumulative tissue stress.