Optimization of the visco-elastic parameters describing the heel-region of a prosthesis

Although compliance (visco-elasticity) of a prosthesis has the potential to affect clinically relevant aspects of a lower extremity amputee's gait, it is currently unknown what the compliant parameter values should be. Here, a simple dynamical model is used to approximate walking with a compliant prosthesis. An exhaustive search is used to identify the optimal compliant element parameter set in terms of the model's stability as measured by the reciprocal of the gait sensitivity norm (rGSN). We identified a parameter set yielding a 17% larger rGSN than the best commercially available prosthesis; however, this is unlikely to be the global optimum for the physically realizable visco-elastic parameter space. Due to the nonlinear effects of the compliant elements, it is difficult to make generalizations about speed and step length, such difficulties are not present with simpler contact models. However, there is some evidence to support a possible trade-off between efficiency and stability.