Examination of the Effect of Suitable Size of Shoes under the Second Metatarsal Head and Width of Shoes under the Fifth Metatarsal Head for the Prevention of Callus Formation in Healthy Young Women.

Excessive pressure and shear stress while walking cause a risk of callus formation, which eventually causes foot ulcers in patients with diabetes mellitus. Callus under the second metatarsal head (MTH) has been associated with increased shear stress/pressure ratios (SPR). Callus under the fifth MTH has been associated with increased peak shear stress (PSS). The purpose of this study is to examine whether the effect of the suitable size and width of shoes prevents diabetic foot ulcers under the second and fifth MTH. We measured the pressure and shear stress by testing three kinds of sizes and two types of width of shoes. Significant difference was not observed in the SPR under the second MTH among different sizes of shoes. However, the pressure and shear stress were significantly lower when putting on shoes of fit size compared with larger sizes. The PSS under the fifth MTH was significantly smaller when putting on shoes of fit width compared with those of narrow width. Wearing shoes of fit size and width has the potential to prevent callus formation by reducing the pressure and shear stress constituting SPR under the second MTH and PSS under the fifth MTH.

The external force associated with callus formation under the first metatarsal head is reduced by wearing rocker sole shoes.

INTRODUCTION: Callus is one of the main causes of diabetic foot ulcers. Therefore, preventing callus formation is very important. In a previous study, it was clarified that callus formation under the first metatarsal head (MTH) is associated with high shear stress time integral/pressure time integral (SPR-i). another study, it was clarified that rocker sole shoes are effective in reducing peak pressure under the first MTH. Therefore, we hypothesized that rocker sole shoes reduce SPR-i under the first MTH. This study aimed to clarify the effect of rocker sole shoes for external forces and leg motions in comparison with that of the normal sole shoes. METHODS: In-shoe external forces and leg motions were measured during walking wearing the normal sole shoes or the rocker sole shoes in healthy participants. As the external forces, the peak plantar pressure (PP), pressure time integral (PI), peak shear stress (PSS), and shear stress integral (SSI) of each gait cycle were calculated. Additionally, shear stress-pressure ratios (SPR) were calculated by dividing shear stress by pressure; concretely, peak values (SPR-p) and time integral values (SPR-i). As the leg motion, hip and knee joint motions were analyzed for the axis of flexion- extension. Three axes of ankle joint motion (inversion-eversion, plantar flexion-dorsiflexion, and adduction-abduction) were analyzed. RESULTS AND DISCUSSION: Six participants attended, and twelve feet were analyzed. When wearing the rocker sole shoes, the SPR-i under the first MTH was significantly smaller than when wearing the normal sole shoes. The SPR-i higher than 0.60 is associated with callus formation under the first MTH. In three of five feet with callus, SPR-i exceeded 0.60 in the normal sole shoes. The SPR-i of all three feet became smaller than 0.60 when wearing the rocker sole shoes. Although the knee (flexion-extension) and ankle (plantar flexion-dorsiflexion) joint motion became smaller when wearing the rocker sole shoes, there was no significant difference in walking speed. It is considered that propulsion was maintained by the push-off support provided by rocker sole shoes. CONCLUSION: It was suggested that rocker sole shoes are effective preventing callus formation under the first MTH.