Foot and ankle mechanics in individuals with diabetes mellitus and neuropathy

Abstract

With over 7% (20 million) people in the United States affected by diabetes mellitus (DM), DM has emerged as a significant health problem. The hallmark of DM is multi-system involvement and the lower limbs are frequently involved in the form of foot ulcers. Inability to heal foot ulcers and maintain healing contributes to the high rate of amputation seen in individuals with DM. The development of foot ulcers has been strongly linked with mechanical stress. Changes in muscle characteristics and segmental foot mobility have been postulated to limit forward progression of the leg on the fixed foot during walking. This in turn may result in prolonged and excessive loading on the ball of the foot. However the extent and site of the impairments and their functional consequences are not well understood. The purpose of this work is to examine determinants of dynamic foot function and plantar loading in individuals with DM. Our results revealed that in spite of differences in passive ankle dorsiflexion and stiffness, subjects with DM demonstrated ankle motion, stiffness and plantar pressures, similar to control subjects, while walking at the identical speed, 0.89 m/s (2 mph). In terms of segmental mobility, reductions were particularly dramatic in the calcaneus (20%) compared to the forefoot and first metatarsal. Decreases in frontal plane calcaneal motion were accompanied by reduced midfoot mobility. Sagittal motion of the first metatarsal and forefoot, and frontal motion of the calcaneus, in subjects with DM, was negatively associated with the magnitude of plantar loading under the respective segment. This information is important because it may help elucidate underlying mechanisms and add to our understanding of the disease process and its effects. In addition, these results may help develop more focused intervention strategies.