Effectiveness of various materials in reducing plantar shear forces. A pilot study.

Vertical plantar forces are known to be a major precipitating factor in the development of foot pathology. It is also postulated that shear forces are important in the pathogenesis of foot ulcers in patients with diabetes mellitus. Various materials are used in insoles designed to reduce forces on the foot. While many foam materials have been tested for their ability to dissipate vertical forces, few studies have tested the effect of these materials on shear forces. This study assessed the effectiveness of five different materials in reducing plantar shear forces and compared two new gel materials with three of the more conventional foam materials. Four subjects were tested while walking over a force platform with one of the five materials taped to the surface. Peak force, impulse, and resultant shear force data were analyzed. The gel materials were significantly better than the foam materials at reducing shear forces. Thus the use of gel materials in insoles may be indicated for the reduction of plantar shear forces on the diabetic foot.