Abstract
Diabetic peripheral neuropathy (DPN) is associated with peripheral sensory and motor nerve damage that affects up to half of diabetes patients and is an independent risk factor for falls. Clinical implications of DPN-related falls include injury, psychological distress and physical activity curtailment. This review describes how the sensory and motor deficits associated with DPN underpin biomechanical alterations to the pattern of walking (gait), which contribute to balance impairments underpinning falls. Changes to gait with diabetes occur even before the onset of measurable DPN, but changes become much more marked with DPN. Gait impairments with diabetes and DPN include alterations to walking speed, step length, step width and joint ranges of motion. These alterations also impact the rotational forces around joints known as joint moments, which are reduced as part of a natural strategy to lower the muscular demands of gait to compensate for lower strength capacities due to diabetes and DPN. Muscle weakness and atrophy are most striking in patients with DPN, but also present in non-neuropathic diabetes patients, affecting not only distal muscles of the foot and ankle, but also proximal thigh muscles. Insensate feet with DPN cause a delayed neuromuscular response immediately following foot–ground contact during gait and this is a major factor contributing to increased falls risk. Pronounced balance impairments measured in the gait laboratory are only seen in DPN patients and not non-neuropathic diabetes patients. Self-perception of unsteadiness matches gait laboratory measures and can distinguish between patients with and without DPN. Diabetic foot ulcers and their associated risk factors including insensate feet with DPN and offloading devices further increase falls risk. Falls prevention strategies based on sensory and motor mechanisms should target those most at risk of falls with DPN, with further research needed to optimise interventions.
Highlights
Exercise Sciences, Faculty of Science and Engineering, Manchester Metropolitan University, Manchester M1 5GD, Academic Editor: Nikolaos Papanas
Sensory and motor deficits caused by Diabetic peripheral neuropathy (DPN) underpin changes to gait that cause balance impairment and increase falls risk
Muscle weakness and atrophy are prevalent in diabetes patients, but most marked in those with DPN compared to their non-neuropathic counterparts and evident in both distal and proximal regions of the lower limb
Summary
Alterations to the natural walking strategy including a slower walking speed, reduced joint range of movement and lower joint moments have been shown to occur even before the onset of measurable DPN [47,48,49,50]. Despite no differences in foot length between the groups studied (DPN, non-neuropathic diabetes and controls), patients with DPN altered how the ground reaction force was applied on their foot, reducing the external leverage around the ankle joint centre and minimising forces developed by the ankle plantar flexor muscles [64] This can be regarded as a natural gait strategy (regardless of whether this was conscious) to minimise these muscular forces while walking, compensating for marked muscular weakness in this cohort. Despite the generation of lower ankle and knee joint moments during overground and stair walking, non-neuropathic diabetes patients and patients with DPN have been shown to have higher ‘operating strength’, meaning their muscles are operating closer to their maximum capacity [49,50] This brings with it potential risks, as people need to have some level of ‘strength reserve capacity’ to call upon for any unexpected situations such as a trip or perturbation to balance. Gait alterations in non-neuropathic diabetes patients have been reported in other gait-related variables including impaired visual gaze behaviour during gait [68], reduced stepping accuracy [68], reduced speed of strength generation [18], a higher metabolic energy cost of walking [69] and altered Achilles tendon function during walking [63]
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