Foot deformities, function in the lower extremities, and plantar pressure in patients with diabetes at high risk to develop foot ulcers

Abstract

Objective: Foot deformities, neuropathy, and dysfunction in the lower extremities are known risk factors that increase plantar peak pressure (PP) and, as a result, the risk of developing foot ulcers in patients with diabetes. However, knowledge about the prevalence of these factors is still limited. The aim of the present study was to describe the prevalence of risk factors observed in patients with diabetes without foot ulcers and to explore possible connections between the risk factors and high plantar pressure.

Patients and methods: Patients diagnosed with type 1 (n=27) or type 2 (n=47) diabetes (mean age 60.0±15.0 years) were included in this cross-sectional study. Assessments included the registration of foot deformities; test of gross function at the hip, knee, and ankle joints; a stratification of the risk of developing foot ulcers according to the Swedish National Diabetes Register; a walking test; and self-reported questionnaires including the SF-36 health survey. In-shoe PP was measured in seven regions of interests on the sole of the foot using F-Scan(®). An exploratory analysis of the association of risk factors with PP was performed.

Results: Neuropathy was present in 28 (38%), and 39 (53%) had callosities in the heel region. Low forefoot arch was present in 57 (77%). Gait-related parameters, such as the ability to walk on the forefoot or heel, were normal in all patients. Eighty percent had normal function at the hip and ankle joints. Gait velocity was 1.2±0.2 m/s. All patients were stratified to risk group 3. Hallux valgus and hallux rigidus were associated with an increase in the PP in the medial forefoot. A higher body mass index (BMI) was found to increase the PP at metatarsal heads 4 and 5. Pes planus was associated with a decrease in PP at metatarsal head 1. Neuropathy did not have a high association with PP.

Conclusions: This study identified several potential risk factors for the onset of diabetic foot ulcers (DFU). Hallux valgus and hallux rigidus appeared to increase the PP under the medial forefoot and a high BMI appeared to increase the PP under the lateral forefoot. There is a need to construct a simple, valid, and reliable assessment routine to detect potential risk factors for the onset of DFU.

Keywords: diabetic foot; foot anthropometrics; foot deformities; neuropathy; plantar pressure; prevention; risk factors.

Fig. 1

Results of the SF-36 with bars (mean±SD) showing the eight domains of the SF-36 Version 1 Scale Scores for the 74 patients. PF, physical functioning; RP, role physical; BP, bodily pain; GP, general health; VT, vitality; SF, social role functioning; RE, emotional role functioning; MH, mental health. The two summary scores are presented on the right: the Physical Component Score (PCS) and the Mental Component Score (MCS). These results are normalised against a Swedish population (n=8,000) with a mean of 50 SD 10.

Fig. 2

Illustration of variables associated with peak pressure (PP). The foot on the left represents the variables selected based on logarithmic PP, and the foot on the right illustrates the variables selected based on untransformed PP. The threshold value for a factor to be presented from the list was set at >0.70 (Appendix 1). In Appendices 2 and 3, the complete factor list and the direction and magnitude of their association can be found. The ranking procedure was performed for each separate region of interest (ROI). The seven ROI that were analysed were the hallux, metatarsal heads (1, 2, 4 and 5), the midfoot and the heel. The variable ‘Custom-made insoles’ is the effect this variable has on PP as compared with prefabricated insoles. The variable ‘Man’ is the effect this variable has on PP as compared with women. +, Factors that were shown to increase PP. –, Factors that were shown to decrease PP.