Determinants of plantar pressures in the diabetic foot

The aim of this study was to determine, by the use of regression analysis, the factors that are associated with the increased plantar pressure in the diabetic foot. In-shoe plantar pressure measurements using the Novel Pedar were carried out on 50 subjects with diabetes. Variables measured were age, body weight, duration of diabetes, a number of selected structural radiographic angles, soft tissue thickness, plantarflexion, and dorsiflexion strength at the ankle and first metatarsophalangeal joint, Neuropathy Symptom Score, and the Michigan Neuropathy Disability Score. Stepwise regression modelling indicates that 28% of the variability in hallux peak pressure could be explained by the first metatarsophalangeal joint range of motion and the Michigan Neuropathy Disability Score (P=.0004). The Michigan Neuropathy Disability Score explained 17% of the peak pressure under the first metatarsal head (P=.002). None of the measured variables could explain any of the variation in peak pressure plantar to the lateral forefoot. Thirty-two percent (32%) of the variability in peak pressure under the heel was explained by the Michigan Neuropathy Disability Score and age (P<.0001). Very little of the variation in the pressure time integrals could be explained by the measured variables except for 10.3% of the variation in the pressure time integral for the heel being explained by body weight. This study has shown that neuropathy-related variables play an important role in the plantar pressure under the diabetic foot. The range of motion of the first metatarsophalangeal joint is also important in determining pressures under the hallux.