Effects of worn and new footwear on plantar pressure in people with gout

BACKGROUND In clinical trials, good quality athletic shoes offer short-term improvements (two-months) in foot pain and disability in people with gout, but these improvements are not sustained over time. This may be due to wear and subsequent changes to the structural integrity of the shoe. The aim of this study was to examine the effects of wear on plantar pressures and footwear characteristics in shoes over six-months in people with gout. METHODS Forty people with gout participated in a cross-sectional repeated measures study. Participants wore a pair of commercially available athletic footwear for six-months. Participants then attended a study visit where the worn footwear was compared with a new pair of the same model and size of footwear. Wear characteristics (upper, midsole, outsole) and plantar pressure were measured in the two footwear conditions. Wear characteristics were analysed using paired t-tests and Fisher's exact tests. Plantar pressure data were analysed using linear mixed models. RESULTS Increases in medial midsole (P < 0.001), lateral midsole (P < 0.001) and heel midsole (P < 0.001) hardness were observed in the worn shoes. Normal upper wear patterns (P < 0.001) and outsole wear patterns (P < 0.001) were observed in most of the worn shoes. No differences in peak plantar pressures (P < 0.007) were observed between the two footwear conditions. Reduced pressure time integrals at the first metatarsophalangeal joint (P < 0.001), second metatarsophalangeal joint (P < 0.001) and hallux (P = 0.003) were seen in the worn shoes. CONCLUSIONS The study found signs of wear were observed at the upper, midsole and outsole in the worn footwear after six-months. These changes to the structural properties of the footwear may affect forefoot loading patterns in people with gout.