A study of in-shoe plantar shear in normals

Objective. To quantify features of in-shoe plantar shear in asymptomatic ad ult gait. Design. In order to standardize footwear conditions and facilitate later co mparison to patient groups, measurement is made in a group of adults walkin g freely in stock orthopaedic footwear. Background. Better data on plantar shear is required to complement well-doc umented pressure data for an overall picture of plantar stress. Methods. Measurements were made locally beneath the medial four metatarsal heads and heel using biaxial. transducers mounted flush into an inlay. Pres sure distribution was also measured. Results. The shear data revealed common features in the shear pattern occur ring at defined phases of gait, with good inter-step reliability. For the f ive sites of interest, these values ranged from 24 kPa to 70.4 kPa, and 31 kPa to 86.5 kPa for individuals wearing nylon hose or hose-free respectivel y. Maximum shear occurred more laterally than maximum pressure. Conclusions. Features of plantar shear were not always as expected; for exa mple the forward thrust at gush-off was not reflected in the anteroposterio r shear stress. Because of the inter-subject variability, study of a larger group is indicated.