Stress reduction in the residual limb of a transfemoral amputee varying the coefficient of friction

Abstract

ABSTRACT: A finite element computer model was used to validate the relationship between coefficient of friction (COF) and the shear stresses and pressures obtained at the socket/residual limb interface for four individuals with transfemoral amputation. This model simulated the process of donning the socket and application of loads during the stance phase of gait cycle. The residual limb was modeled as a solid multilayer (skin, fat and muscle) with hyperelastic properties. An experimental design was made to calculate the significance of hairiness, sweating, and texture factors in measuring the COF between polypropylene and skin with the help of a sclerometer; values were obtained from 0.188 to 0.545. It was demonstrated that the surface texture is significant when measuring the COF. On the results of the simulation, a horizontal strip where the greatest stresses and pressures occurred was identified; in this strip, the COF was varied from 0.2 to 0.6 to observe its effect on the distribution of stresses. The average shear decreased up to 25%, whereas the pressures did not vary significantly and the results do not exceed the value of 70 kPa, from which values are potentially harmful to the skin. Key indexing terms: socket-limb residual interface, finite element analysis, dynamic simulation, stress distribution.