Researchers at the Cleveland Clinic did a small pilot study looking at shear reducing diabetic insoles worn by healthy subjects. Their hypothesis was that if shear reduction works with these insoles, step length should be shortened. Matassini et al. Do shear reducing diabetic insoles really reduce plantar shear? The paper is being presented on October, 2010, at the conference: A Team Approach, Diabetic Limb Salvage, Georgetown University Hospital. Presumably, step length decreases if plantar shear is reduced because gait is less efficient. In their pilot study, the investigators found, however, that the shear reducing insoles did not reduce step length.
The results from this pilot don’t surprise us. The shear reducing insoles presently on the market attempt to reduce shear over large areas of the plantar surface. If they truly were effective at reducing shear, they also would make gait inefficient because the foot would be sliding around in the shoe.
The best way to reduce shear on the plantar surface is to use targeted friction management. Not all friction and shear are bad. In order to have efficient gait, friction and shear are necessary. By targeting friction and shear reduction just to problem areas, gait efficiency can be maintained while still protecting the foot. This is the advantage of a product like ShearBan®. The ShearBan patch can be placed by the clinician at the location of shear trauma.
How does one know where to target friction relief? For both the diabetic foot and the healthy foot the answer is pretty straightforward: look for locations of heavy callusing. Friction and shear cause the callusing, and research shows that the locations of heavy callusing are where diabetic foot ulcers typically occur. Murray et al. 1996. Therefore, put the ShearBan patch on the footwear opposite the areas of heavy callusing.