Local shear stress measurements in the normal and diabetic foot patients during walking

The purpose of this study is to determine distributions of local plantar shear stress and pressure in diabetic foot patients during walking. Twelve normal subjects who have no surgical history of foot problems in foot and three diabetic foot patients with diabetic neuropathy in the lateral heel participated in the study. An insole-type local shear stress sensor was developed, and both mediolateral and anteroposterior components of local shear stress were measured during level walking. Results showed that shear stress in the lateral heel for diabetic foot patients was relatively smaller than that in the normal. For diabetic foot patients, significantly larger shear stress in the medial direction was observed at the 2nd metatarsal head in pre-swing, comparing with the normal. Anteroposterior shear stress in diabetic foot patients became significantly smaller at the 4th metatarsal head in pre-swing than that in the normal. For patients who had diabetic neuropathy in the lateral heel, the center of pressure started from the medial heel and then moved linearly toward 1st or 2nd metatarsal head. Diabetic foot patients showed relatively smaller pressure in the 2nd metatasal head and the hallux in pre-swing than the normal subjects. Results showed that local shear stress distribution correlated very well with the pressure distribution. Further study with patients of different foot problems would be very helpful to design corresponding foot orthoses.